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robertg
08-02-2017, 07:51 AM
I bought a pair of D.A.S. lenses and horns which are the same size as a 2395. I am thinking of building a 4350 box and replacing the mid with the D-401 and using a 2402 for the high. Would this work? I would have to use woofers that go up to 800 Hz. What woofer would work, and would the port size have to be changed?

allen mueller
08-02-2017, 09:27 AM
Nice did you just get those off eBay? I have the same horns. D.A.S had those and another model that was a very similar to the smaller Jbl lense. Spec sheets are on the web if you search. The horn as far as I know is identical to the shape of the jbl horn. There are some pics somewhere on the web with dims comparing the horns with dims. Gary Stewart tipped me off on the D.A.S horns awhile back. If you don't end up building enclosures at the very least you want to cover up the backs. I did mine by replacing some of the spacers with small wood blocks which gave me something to attach to. I used some 1/8 thick wood that I lined with felt. I'm not home now but I'll snap a pic when I can.

Al

RMC
08-02-2017, 09:56 AM
Hi Robert,

2395 and 4530 are short-throw devices (up to 75 feet for 4530) whereas 2402 (40° conical dispersion) is a long-throw tweeter... You'd be better off using the 2405 type tweeter for better balance, dispersion and similar "reach". The original compression driver for 2395 horn/lens assembly was the JBL 2440. The original recommended drivers for the 4530 boxes were JBL 2205H (replaced by 2225H) and E-140 15" which may be difficult to find in original state or with original recones... So, then look-up Thiele/Small parameters on JBL's Web site for the best drivers (2205H/E-140) and try to find a new driver with as close as possible T/S to those to load your 4530 boxes, as well as with response > 800hz for x-over purpose. The 2225H was not recommended by JBL for 4530 use (see T/S) but some people did use it with success they said, and it was the only "suitable" (closest) one left at that time in the JBL catalog.

There is no port in a 4530 but rather a rear-loaded folded horn (scoop). No need to change the dimensions of that. If you did it may not work correctly (according to specs).

Richard

robertg
08-02-2017, 10:01 AM
I got them on ebay a couple of weeks ago for $300.00. They have a bit of road rash on one corner, I might have to round all of the corners to match, or find a good welder. I found the spec sheet and it says they are good from 800 hz to 4000 hz. Hopefully I can find plans for a cabinet that has enough room for them and two 15 woofers. I really don't want to try to design my own cabinet.

RMC
08-02-2017, 10:06 AM
Two woofers is not a 4530 but rather a 4520 cabinet...

Richard

robertg
08-02-2017, 10:06 AM
Hi Robert,

2395 and 4530 are short-throw devices (up to 75 feet for 4530) whereas 2402 (40° conical dispersion) is a long-throw tweeter... You'd be better off using the 2405 type tweeter for better balance, dispersion and similar "reach". The original compression driver for 2395 horn/lens assembly was the JBL 2440. The original recommended drivers for the 4530 boxes were JBL 2205H (replaced by 2225H) and E-140 15" which may be difficult to find in original state or with original recones... So, then look-up Thiele/Small parameters on JBL's Web site for the best drivers (2205H/E-140) and try to find a new driver with as close as possible T/S to those to load your 4530 boxes, as well as with response > 800hz for x-over purpose. The 2225H was not recommended by JBL for 4530 use (see T/S) but some people did use it with success they said, and it was the only "suitable" (closest) one left at that time in the JBL catalog.

There is no port in a 4530 but rather a rear-loaded folded horn (scoop). No need to change the dimensions of that. If you did it may not work correctly (according to specs).

Richard
I changed the original post to 4350, I'm dislexic at times.

allen mueller
08-02-2017, 10:27 AM
Forgot to mention I use mine with a bms
coax so I don't use a uhf driver. I agree with RMC a 2405 or a 2404 would be a better match.

robertg
08-03-2017, 06:50 AM
So what drivers would work if I built this cabinet? The 4350 came with dual 2331 drivers, but I believe they were use only to 200 Hz. They probably are difficult to find also. I have a couple of E145, but the next two might take a while to find.

The cabinet should be approximately 12 cubic feet with six 3" ports.

RMC
08-03-2017, 10:53 AM
So what drivers would work if I built this cabinet? The 4350 came with dual 2331 drivers, but I believe they were use only to 200 Hz. They probably are difficult to find also. I have a couple of E145, but the next two might take a while to find.

The cabinet should be approximately 12 cubic feet with six 3" ports.

Hi Robert,

Since the 4350 came with 2231H you may want to try to find that driver's successors which are 2234H and 2235H, the latter being easier to find. But there's a wrench in the wheel if you want to build a pair of boxes: you have a pair of E-145 (musical instrument driver) and the 15" 2235H is more of a studio monitor/Hi-Fi driver with different specs than E-145. That would mean different low-frequency sound from the two boxes..., even supposing both drivers would be a good match for the box you plan to build (which may not be the case) !

Maybe you'd be better off looking for two more E-145 to minimize costs ? (vs 4 x 2235H), since logically you need four of the same thing for a pair of 4350 type boxes. Then you have to run driver data in speaker design software to see what proper box you can make with each pair. Box volume and port number/dimensions may or may not be as you had planned, specially if they are not the original 2231H...

An even better/cheaper solution would be to build boxes for a single E-145 along with your horn/lens and tweeter devices. Simpler/cheaper all the way.

Richard

robertg
08-03-2017, 12:58 PM
I was thinking about going to a single driver, but I like the symmetrical look of two 15" drivers in such a wide cabinet. Mounting a 36" wide horn on a narrow cabinet doesn't look right to me.

After doing a bit more of research, it looks like the 4508 cabinet will work with dual E145s and the more common 2225. I could build a cabinet based on it.

RMC
08-03-2017, 04:50 PM
I was thinking about going to a single driver, but I like the symmetrical look of two 15" drivers in such a wide cabinet. Mounting a 36" wide horn on a narrow cabinet doesn't look right to me.

After doing a bit more of research, it looks like the 4508 cabinet will work with dual E145s and the more common 2225. I could build a cabinet based on it.

You are right about 4508 cabinet being suitable for both E-145 and 2225H drivers as per JBL. But you still have two issues remaining: Your lens at 36" wide are still much wider than a 4508 at 26.5" wide and the sound differences between one cab with 2 x E-145 and the other cab with 2 x 2225H...

BTW there's a small difference (1 db) in sensitivity re each driver (times two drivers = 2 db, which is noticeable) and different response curves for the drivers... Also 4508 dimensions have varied berween 1980 and 1982 as per JBL depending where you looked at them (Compare JBL "Low frequency Enclosures" 05/80 brochure vs the JBL 1982 Pro catalog). Also have a look at JBL Pro Enclosure Guide for other alternative boxes.

Richard

robertg
08-03-2017, 05:05 PM
I would turn them sideways and mount the horn and tweeter on top, probably end up with a cabinet thats 35" x 41". I would also use four matching woofers, preferably E-145. If I could find a deal on 4-2225 woofers, that would work also.

The top section of the cabinet would be wasted space, just housing the horn and tweeter.


Model 4508 Bass Reflex Dual Driver
The 4508 is a slim-profile, vented enclosure that offersoutstanding low frequency reproduction in a very compactpackage. Frequency response is uniform to 45 Hz withusable response to 35 Hz. Net weight, less drivers, is 49 kg(108% lb). 1060 mm x 667 mm x464 mm deep (41in x26
in x l8 in deep).

Lee in Montreal
08-03-2017, 07:36 PM
Hey Robert

Perhaps of inspiration. If I were in your shoes, I'd go this way. ;-) But not with a bullet but a 2405 tweeter crossed at 8Khz
Make the cab as deep as your horns.

https://s-media-cache-ak0.pinimg.com/originals/21/6c/2a/216c2a0e10b6b07c874edbd83c20d583.jpg

robertg
08-03-2017, 08:23 PM
I've seen that picture before, I think it's on Pinterest. I still like the look of the bullet, but I'll have to try a pair of 2405 tweeters one day. I think they have the same mounting pattern as a 2402, however if I use my 2482 mid drivers, I have to use something that crosses over at 4k. My horns and drivers are 17.5" deep, so most of the cabinets are 18" deep or more. I wasn't planning on having the horn in the same space as the woofers anyway so the backs will be open.



Hey Robert

Perhaps of inspiration. If I were in your shoes, I'd go this way. ;-) But not with a bullet but a 2405 tweeter crossed at 8Khz
Make the cab as deep as your horns.

https://s-media-cache-ak0.pinimg.com/originals/21/6c/2a/216c2a0e10b6b07c874edbd83c20d583.jpg

berga12
08-04-2017, 07:18 AM
If you want a good "Modern" alternative you can use 4x2226h, much lighter than 2225h, suitable also for some horn loaded cabinet, easier to find, modern technology and nice sound.

I used 4 in place of the 2235h in the meantime I was waiting to get them, and they are able to produce until 38-40hz flat on a 4350 cabinet (with shorter port) with a big punch and clean sound.

Ofcourse if you have enough money the market is full of alternative, for example TAD1601 :bouncy:

RMC
08-05-2017, 08:16 PM
Hi Robert

You're right re 2482 compression driver, its response curve shows it is flat (± 3 db) to 5khz then drops rapidly. So 4khz x-over is about as high as you can get anyway considering the horn/lens 4khz limit you indicated.

LIKELY CORRECTION: In posts # 4 (and 14), you indicated having found the DAS spec sheet for the horn/lens (I don't have it) and that it is good for 800-4,000 hz. The upper limit seems low compared to an original 2395 horn/lens (up to about 7-8khz with 2441, good for 2405), but if indeed yours is limited to 4Khz, then you can't use the 2405 with a JBL stated x-over of 7,000 hz or higher (not lower) as I suggested initially. Therefore, the bullet 2402 remains in the race. However, you should also consider the 2404 tweeter with a x-over at 3,000 hz or higher (similar to 2402 at 2,500+ hz), but it has much wider coverage angles (100° X 100°) than the 2402 (40° conical) to probably better "match" your lens coverage. You can also look elsewhere for a proper tweeter. As for coverage of the original 2395 its rated at 140° horizontal X 45° vertical, which is quite wide horizontally (DAS lens coverage I don't have).

There's also an issue with regards to a side-effect of mutual coupling of drivers in a box (e.g. 2 X 15") that people rarely consider nor mention around here, which you should be aware of about the drivers' sound dispersion : BEAMING. This is a directional property occuring when multiple cone drivers are close to each other, such as 2 x 15" in a cab. After showing - 6 db beamwidth curves for three sizes (10", 12", 15") of dual low frequency drivers, JME adds:" The assumption is made that the drivers are arrayed in a vertical line, so that maximum coverage will be obtained horizontally." (John M. Eargle (JBL), Loudspeaker Handbook, Chapman & Hall, 1997, P. 80). No, there's no typo error in that statement. Vertical driver alignment leads to increased vertical driver beaming ("focus") and maximum horizontal coverage. Horizontal driver alignment leads to increased horizontal driver beaming and maximum vertical coverage! Further explanations of this below.

In your post # 8 you mentioned the 4350 woofers being used only to 200 hz which seems about right, since the 4350b version data sheet mentions a 250 hz x-over to a 12" 2202H up to 1.1khz. It would probably take a whole book to explain each of the Design Engineer's choices made for that complex loudspeaker. Just remember these are large control room monitors, with that environment in mind, not exactly home hi-fi speakers. But I'm pretty sure the 200-250 hz x-over to a 12" driver is in good part for reasons related to avoiding or reducing horizontal beaming effect that comes from having two 15" drivers side-by-side if they were used up to 800 hz for example. Meaning the 200-800 hz or so range might have been too directional horizontally (narrow listening window).

This is where the intended application/purpose of your boxes becomes important: Home "Hi-Fi", Sound reinforcement indoors or outdoors, Studio monitoring, Disco Club use, etc. ?? My feeling is that it may be for Home sound. Then, horizontal sound dispersion is usually priviledged in such situation, having enhanced stereo effect (that was ONE of the reasons for my initial 2405 tweeter suggestion, another one being slant plates dispersion patterns mentioned above). An exception to wide horizontal sound dispersion in home use is Multi-channels Home Theatre sound application, because of the desirable localization of some sounds (e.g. dialogue). J. Eargle wrote a small article about that (Home theatre sound) in Audio Magazine long ago, considering his vast knowledge and experience in Cinema Sound, among his many other Audio fields of expertise: Bible!

Electro-Voice also has an interesting explanation of the beaming side-effect related to the use of dual woofers in their model TL 770D data sheet of 1996 (this is a two-woofer in a vented box similar to a 4508 for example). In the section dealing with "Use in multiples": "Cone loudspeakers may be stacked for greater acoustic ouput and a narrower beamwidth. (...) This principle is already employed in the dual-woofer TL770D, and is responsible for the higher sensitivity and narrower vertical beamwidth (with the system long axis vertical) relative to similar single-woofer systems. (...) At relatively low frequencies, below about 150 hz for typical TL series dimensions, stacking produces additional acoustic output without altering dispersion." (P. 3)

The last phrase from that quote is based on the fact that low frequencies are mostly omnidirectional, so no altering of sound dispersion there. But higher than the low frequencies, beaming starts to kick-in with dual-driver boxes... Since your proposed box is NOT a duplicate or real 4350 it will be impacted, more on horizontal woofer dispersion if the box is placed longer side down as you mentioned for a 4508 type of box.

By analogy, a similar situation of beaming also happens with mid/high frequency horns combined. In his "Handbook of Sound System Design", ELAR, 1989, in section "Directional properties of combined radiators", sub-section "Techniques for narrowing coverage", John Eargle of JBL states "In-line vertical stacks of horns have long been used for producing narrower vertical coverage that can be provided by a single horn. (...) Note that the horizontal pattern of these arrays is the same as for a single horn. If horns are placed side by side, horizontal coverage will be narrowed, again at the expense of considerable lobing. (...) Note here that the vertical pattern of the horizontal array is the same as that of a single horn." (P. 90-91). Read horn = woofer.

Moral: your intended boxes (as per your indications) don't seem like a good idea sonically and you may regret their sound after all the work is done... In my view, It's better to know ahead of time to minimize the number of banana peels on your way. Its your time and money so YOU decide what YOU want to do, for me it doesn't change anything, but I hate seeing an audiophile colleague heading for the wall, then having to re-do the job afterwards... Don't build boxes because of impressive looking double woofers, just to minimize appearance of too wide a horn on a narrower cabinet or for the nice looking 2402, but rather make some that are technically sound with what you have or find within budget, for your enhanced musical enjoyment ! If you continue as is, there's good chance you'll have omnidirectional bass, then narrower double woofer coverage up to 800 hz, then slant plates wide dispersion 800-4,000 hz, and finally narrow coverage from 2402 tweeter. Sounds good ??

My suggestions: Since you already have the compression drivers/horns/slant plates with wide dispersion, then find a suitable tweeter with wide dispersion and with an acceptable x-over point for tweeter/horn . If double woofers are a must, then have the box/woofers vertically aligned for improved woofer horizontal dispersion up to 800 hz, improved stereo effect, and better match with horn/tweeter dispersion patterns. In your shoes, I would still strongly consider a pair of boxes with one E-145 in each since you already have those ("free" gear). Even used alone, the E-145 are quite capable fellows if they are in good shape (original, reconed as such or with good aftermarket kit). Their intended application such as bass, organ, LF reinforcement, plus an Xmax of 7 mm (twice that of E-140! according to JBL's spec sheet), are such that you can pump some pretty good bass output from these. Finally, I've seen a reasonably uniform frequency response for a Musical Instrument driver.

RE your post # 12: Your quote regarding "Model 4508 Bass reflex dual driver" enclosure appears to come from JBL's "Low Frequency Enclosures, 05/80. Those dimensions for 4508 have varied a little over time from 41.75 X26.5 X 18.25" to 39.75 X 26.5 X 17.25" (JBL, 1982, Pro Catalog). If you build such boxes, make sure you have correct dimensions to work with. JBL Pro Enclosure Guide also gives other box suggestions.

RE Berga 12 post # 15: 2226H may turn-out to be expensive, plus a "waste" of your E-145, and not necessarily a good idea "with a big punch". Though In sound reinforcement for Disco application it may make sense... Regards,

Richard

ivica
08-06-2017, 02:29 AM
Hi Robert

You're right re 2482 compression driver, its response curve shows it is flat (± 3 db) to 5khz then drops rapidly. So 4khz x-over is about as high as you can get anyway considering the horn/lens 4khz limit you indicated.

LIKELY CORRECTION: In posts # 4 (and 14), you indicated having found the DAS spec sheet for the horn/lens (I don't have it) and that it is good for 800-4,000 hz. The upper limit seems low compared to an original 2395 horn/lens (up to about 7-8khz with 2441, good for 2405), but if indeed yours is limited to 4Khz, then you can't use the 2405 with a JBL stated x-over of 7,000 hz or higher (not lower) as I suggested initially. Therefore, the bullet 2402 remains in the race. However, you should also consider the 2404 tweeter with a x-over at 3,000 hz or higher (similar to 2402 at 2,500+ hz), but it has much wider coverage angles (100° X 100°) than the 2402 (40° conical) to probably better "match" your lens coverage. You can also look elsewhere for a proper tweeter. As for coverage of the original 2395 its rated at 140° horizontal X 45° vertical, which is quite wide horizontally (DAS lens coverage I don't have).

There's also an issue with regards to a side-effect of mutual coupling of drivers in a box (e.g. 2 X 15") that people rarely consider nor mention around here, which you should be aware of about the drivers' sound dispersion : BEAMING. This is a directional property occuring when multiple cone drivers are close to each other, such as 2 x 15" in a cab. After showing - 6 db beamwidth curves for three sizes (10", 12", 15") of dual low frequency drivers, JME adds:" The assumption is made that the drivers are arrayed in a vertical line, so that maximum coverage will be obtained horizontally." (John M. Eargle (JBL), Loudspeaker Handbook, Chapman & Hall, 1997, P. 80). No, there's no typo error in that statement. Vertical driver alignment leads to increased vertical driver beaming ("focus") and maximum horizontal coverage. Horizontal driver alignment leads to increased horizontal driver beaming and maximum vertical coverage! Further explanations of this below.

In your post # 8 you mentioned the 4350 woofers being used only to 200 hz which seems about right, since the 4350b version data sheet mentions a 250 hz x-over to a 12" 2202H up to 1.1khz. It would probably take a whole book to explain each of the Design Engineer's choices made for that complex loudspeaker. Just remember these are large control room monitors, with that environment in mind, not exactly home hi-fi speakers. But I'm pretty sure the 200-250 hz x-over to a 12" driver is in good part for reasons related to avoiding or reducing horizontal beaming effect that comes from having two 15" drivers side-by-side if they were used up to 800 hz for example. Meaning the 200-800 hz or so range might have been too directional horizontally (narrow listening window).

This is where the intended application/purpose of your boxes becomes important: Home "Hi-Fi", Sound reinforcement indoors or outdoors, Studio monitoring, Disco Club use, etc. ?? My feeling is that it may be for Home sound. Then, horizontal sound dispersion is usually priviledged in such situation, having enhanced stereo effect (that was ONE of the reasons for my initial 2405 tweeter suggestion, another one being slant plates dispersion patterns mentioned above). An exception to wide horizontal sound dispersion in home use is Multi-channels Home Theatre sound application, because of the desirable localization of some sounds (e.g. dialogue). J. Eargle wrote a small article about that (Home theatre sound) in Audio Magazine long ago, considering his vast knowledge and experience in Cinema Sound, among his many other Audio fields of expertise: Bible!

Electro-Voice also has an interesting explanation of the beaming side-effect related to the use of dual woofers in their model TL 770D data sheet of 1996 (this is a two-woofer in a vented box similar to a 4508 for example). In the section dealing with "Use in multiples": "Cone loudspeakers may be stacked for greater acoustic ouput and a narrower beamwidth. (...) This principle is already employed in the dual-woofer TL770D, and is responsible for the higher sensitivity and narrower vertical beamwidth (with the system long axis vertical) relative to similar single-woofer systems. (...) At relatively low frequencies, below about 150 hz for typical TL series dimensions, stacking produces additional acoustic output without altering dispersion." (P. 3)

The last phrase from that quote is based on the fact that low frequencies are mostly omnidirectional, so no altering of sound dispersion there. But higher than the low frequencies, beaming starts to kick-in with dual-driver boxes... Since your proposed box is NOT a duplicate or real 4350 it will be impacted, more on horizontal woofer dispersion if the box is placed longer side down as you mentioned for a 4508 type of box.

By analogy, a similar situation of beaming also happens with mid/high frequency horns combined. In his "Handbook of Sound System Design", ELAR, 1989, in section "Directional properties of combined radiators", sub-section "Techniques for narrowing coverage", John Eargle of JBL states "In-line vertical stacks of horns have long been used for producing narrower vertical coverage that can be provided by a single horn. (...) Note that the horizontal pattern of these arrays is the same as for a single horn. If horns are placed side by side, horizontal coverage will be narrowed, again at the expense of considerable lobing. (...) Note here that the vertical pattern of the horizontal array is the same as that of a single horn." (P. 90-91). Read horn = woofer.

Moral: your intended boxes (as per your indications) don't seem like a good idea sonically and you may regret their sound after all the work is done... In my view, It's better to know ahead of time to minimize the number of banana peels on your way. Its your time and money so YOU decide what YOU want to do, for me it doesn't change anything, but I hate seeing an audiophile colleague heading for the wall, then having to re-do the job afterwards... Don't build boxes because of impressive looking double woofers, just to minimize appearance of too wide a horn on a narrower cabinet or for the nice looking 2402, but rather make some that are technically sound with what you have or find within budget, for your enhanced musical enjoyment ! If you continue as is, there's good chance you'll have omnidirectional bass, then narrower double woofer coverage up to 800 hz, then slant plates wide dispersion 800-4,000 hz, and finally narrow coverage from 2402 tweeter. Sounds good ??

My suggestions: Since you already have the compression drivers/horns/slant plates with wide dispersion, then find a suitable tweeter with wide dispersion and with an acceptable x-over point for tweeter/horn . If double woofers are a must, then have the box/woofers vertically aligned for improved woofer horizontal dispersion up to 800 hz, improved stereo effect, and better match with horn/tweeter dispersion patterns. In your shoes, I would still strongly consider a pair of boxes with one E-145 in each since you already have those ("free" gear). Even used alone, the E-145 are quite capable fellows if they are in good shape (original, reconed as such or with good aftermarket kit). Their intended application such as bass, organ, LF reinforcement, plus an Xmax of 7 mm (twice that of E-140! according to JBL's spec sheet), are such that you can pump some pretty good bass output from these. Finally, I've seen a reasonably uniform frequency response for a Musical Instrument driver.

RE your post # 12: Your quote regarding "Model 4508 Bass reflex dual driver" enclosure appears to come from JBL's "Low Frequency Enclosures, 05/80. Those dimensions for 4508 have varied a little over time from 41.75 X26.5 X 18.25" to 39.75 X 26.5 X 17.25" (JBL, 1982, Pro Catalog). If you build such boxes, make sure you have correct dimensions to work with. JBL Pro Enclosure Guide also gives other box suggestions.

RE Berga 12 post # 15: 2226H may turn-out to be expensive, plus a "waste" of your E-145, and not necessarily a good idea "with a big punch". Though In sound reinforcement for Disco application it may make sense... Regards,

Richard


Hi RMC,

Very instructive explanation about drivers mutual coupling.
In some of my older post I have shown the influence of the drivers mutual coupling relative to the frequency while their center to center distance is about 50cm (20") what can be expected for 15" drivers combination
.
http://www.audioheritage.org/vbulletin/showthread.php?39103-Dual-drivers-One-or-Two-chambers-in-enclosure&p=399606&viewfull=1#post399606


http://www.zainea.com/mutualcoupling.htm


May be some more "help" would be welcome if
1.drivers dispersion 'curves' has to be included, as for 15" drivers over 800Hz they start to "beam" ( +/- 45 deg-off-axis), so
2.tilting bass baffles horizontally off-axis about 15 to 20 degs (as DD66000/67000)
would improve upper bass section dispersion in the horizontal plane while divers would be mounted side by side horizontally
3.in the smaller rooms, tilting the speaker towards the listeners by 15 ~ 30 degs would help too

http://libinst.com/PublicArticles/Setup%20of%20WG%20Speakers.pdf

4.but after all, we have to be aware about the influences of the listening room large surfaces ( floore , ceiling, walls ), even in stereo reproduction left-right channals bass section mutual drivers coupling, so in the "open-field" opperation relative to the "in-room" different expectations has to be aware off.


regards
ivica

RMC
08-06-2017, 03:48 PM
Hi Ivica,

Some good points you raised here.

For direct sound to the listener, the beaming problem isn't a big thing if you are always listening on-axis and not too close. If you move around however or are located off-axis, then it would be noticeable. As for reflected sound in a room, well there's a good chance the imbalances would be heard with very different low/mid/high coverage patterns from each driver used. My point here is simply why build a box with more "flaws", or repeating some errors of others, when you can easily build one with less issues?

RE "drivers dispersion 'curves' has to be included, as for 15" drivers over 800Hz they start to "beam" It seems dispersion curves for 15" drivers above 800 hz don't present much interest since MOST of these are crossed over at that frequency anyway(except for the few ones that do up to 1,200 hz). I think double 15" close together start to beam way before 800 hz.

RE "tilting bass baffles horizontally off-axis about 15 to 20 degs (as DD66000/67000)" This example is quite good, I had forgotten about these boxes that I can't afford anyway... Very clever idea from the Design Engineer, though much more difficult to build for us, and knowing the exact angles to use on the baffle if different driver used. Again, I'm pretty sure this is for minimizing horizontal double woofer beaming, and I agree with you this should improve upper bass section dispersion in the horizontal plane.

RE "tilting the speaker towards the listeners by 15 ~ 30 degs would help too" Agreed. Above I wrote about listening on-axis which basically leads to the same thing. To "toe-in" the boxes as they say is done so the listener can be more on-axis and also to hear more depth. Personnaly, I don't like having to be always on-axis for proper sound. If you can only get well-balanced sound in a very narrow window it gets annoying.

TWO ADDITIONS TO MY PREVIOUS POST:

1) The old saying, too often seen around here, "If some is good, then more will be better", doesn't always apply, specially in Audio. Example, this time related to directional properties of combined MF/HF radiators: "Simpler arrays are usually better behaved than larger ones, and there should always be logical reasons for combining two or more HF elements in an array." (J. Eargle, Handbook of Sound System Design, P. 88).

2) In my last post # 16 where I mentioned the E-145 had an Xmax of 7mm (twice that of E-140!) I forgot to mention this 7mm is also 2mm more than the 2225H considered at 5mm. Not bad for such an older device.

BTW Ivica there's two other issues about mutual coupling that I have not mentioned yet since the opportunity has not presented itself: diminishing returns with too many boxes stacked and box alignment shifts when mutually coupling loaded vented boxes (not drivers by themselves). Both from J. Eargle's books mentioned here. Other illustrations that "If some is good, then more will be better", doesn't always apply!

Richard

robertg
08-06-2017, 08:08 PM
Thanks for the detailed reply, It would take me a day to write something like that.

So if I use one E145 and I wanted to make the box at least 36.5" wide, I would end up with a 9-10 cubic foot box. Is using something that large going to cause issues? I do have a couple pairs of 2404 tweeters also.

RMC
08-07-2017, 09:30 AM
Hi Robert,

I've checked some box volumes and made a quick simulation in speaker design software for you re E-145. I'll be back tonight with that, no time right now..

Richard

Ian Mackenzie
08-07-2017, 10:53 AM
What are you going to be using this system for?

If you are using it as "large" domestic hifi here are my thoughts.

Acquire 4 2234H woofer build by Edgewound.

The dual 2234H form the bass and mid up to 800 Hz.

Use the 4435 mode of driving the 2234H.

One woofer is a helper below 100 Hz. The system is flat to 30 hertz and full power to 26

System sensitivity is around 96 Db 1 watt 1 metre.

The single woofer above 100 Hz will image better than two woofers.

The concept is proven by JBL so you don't need to engineer anything.

Just biamp @800 Hz

The 2234 is a 2335 without the mass ring. It's a significant improvement over the stock 2235 in the midrange due to the lower MMS and provides extended bass in the 4435 box.

If your budget permits buy two 2 inch Jbl compression drivers and load with Truexent Berilyum diaphragms.

The 2405 may be redundant.

I think it would win in several areas with extended bass, mid range clarity, high resolution highs and dynamics.

robertg
08-07-2017, 03:36 PM
What are you going to be using this system for?

If you are using it as "large" domestic hifi here are my thoughts.

Acquire 4 2234H woofer build by Edgewound.

The dual 2234H form the bass and mid up to 800 Hz.

Use the 4435 mode of driving the 2234H.

One woofer is a helper below 100 Hz. The system is flat to 30 hertz and full power to 26

System sensitivity is around 96 Db 1 watt 1 metre.

The single woofer above 100 Hz will image better than two woofers.

The concept is proven by JBL so you don't need to engineer anything.

Just biamp @800 Hz

The 2234 is a 2335 without the mass ring. It's a significant improvement over the stock 2235 in the midrange due to the lower MMS and provides extended bass in the 4435 box.

If your budget permits buy two 2 inch Jbl compression drivers and load with Truexent Berilyum diaphragms.

The 2405 may be redundant.

I think it would win in several areas with extended bass, mid range clarity, high resolution highs and dynamics.
I was reading about the 4435 yesterday. The two chambers are divided horizontally, so my mid range would have to go above the cabinet because the divider would hit it. The 36" lens would have to be centered in the cabinet. Possible, but wasted cabinet space. Also the 2234 and 2235 are difficult to find.

Would it make sense if I built a 15 cubic foot enclosure with two chambers. I could use an 18" 224x series driver up to 80-100 hz and use my E-145 above that? This enclosure is going to be at least 38" wide, so making it a foot taller isn't a big deal.

Im running a DBX Driverack PA2 with a McIntosh MC2500 for the bottom end and two small amps for the minds and highs. I'm not sure if I want to throw another amp in there. I'm assuming I can throw a passive crossover in there and use the MC2500 for both the 15" and 18"?

Ian Mackenzie
08-07-2017, 04:19 PM
I was reading about the 4435 yesterday. The two chambers are divided horizontally, so my mid range would have to go above the cabinet because the divider would hit it. The 36" lens would have to be centered in the cabinet. Possible, but wasted cabinet space. Also the 2234 and 2235 are difficult to find.

Would it make sense if I built a 15 cubic foot enclosure with two chambers. I could use an 18" 224x series driver up to 80-100 hz and use my E-145 above that? This enclosure is going to be at least 38" wide, so making it a foot taller isn't a big deal.

Im running a DBX Driverack PA2 with a McIntosh MC2500 for the bottom end and two small amps for the minds and highs. I'm not sure if I want to throw another amp in there. I'm assuming I can throw a passive crossover in there and use the MC2500 for both the 15" and 18"?

My recommendation is that you make the system modular until you have auditioned what ever you propose to use.

Nothing ever works quite like you think it might when it comes to loudspeakers

Attempting to integrate the system in one box at concept stage is fraught with risk.

Just mount the slant plate horn on the recommended baffle and sit atop your proposed bass box

Incidentally the Everest 66000 only had one active woofer on one side and the wave guide above it.

You might also consider stacking two woofers vertically depending on the size of your room and listening distance.

A reconer like Edgewound can help you build a 2234.

If you want to scale up look at Drew Daniels creation in the Library.

Another proven design is two 18 inch 2241/2240 stacked vertically, four E110/K110 stacked vertically next to the 2241 and the horn atop and the 2405. Louder, lower distortion and more robust.

The E110 run from somewhere around 200 to 1000 Hz but you can try out other options.

I have heard this design with a 2397. It was crisp and smooth as a vintage studio monitor.

This is much like a Clair Bros design used in the 80's.

The down side of scaling up is you start to loose the tight driver integration of monitor series and you end up with a wall of sound as opposed to realistic sound stage width and depth.

RMC
08-07-2017, 08:35 PM
Hi Robert,

The JBL recommended enclosure volumes for a single E-145 is in the range of 3-8 Cu. Ft. or 85-227 liters net(see JBL, E-series, Instruction Manual, 02/81, P. 5). So a box of 9-10 cu. ft. is too large in JBL's view for proper performance. In order to help you "fit" on box top the compression driver/horn/lens assembly, I took the largest proposed volume (8 cu. ft.) and ran a quick computer simulation in Winspeakerz v. 2.5.2 speaker design software.

The T/S parameters used were those of JBL from the E-series brochure (Fs 35hz, Qts .25, Vas 275L./9.7 cu. ft, etc.). In such a box, tuning at 40 hz leads to an about flat response in the bass range. But this woofer has a rising response in the mid-bass like many other Musical Instrument drivers.

After testing a few, my preference would go to a 45 hz tuning (Fb) for two reasons. First, tuning lower usually puts more strain on a woofer (Increased excursion) and you therefore reach X max faster and at a lower output level. Second, the little higher tuning here creates a small bump in response of about 1.5 db at 50 hz which will about match the mid-bass sound level since that driver has a rising response of + 2 db or so from about 200 hz and up. At a flat response tuning of 40 hz, the mid-bass level will be about 2 db higher than the bass level. Giving more emphasis to a mid-bassy sounding speakers. I hate that. The small bass bump would then be usefull to "match, equalize or balance" perceived bass and mid-bass sound levels.

With an F3 (3 db down point) at 40 hz (with 45 hz tuning) this is still lower bass than MOST Sound Reinforcement cabinets sold. To achieve that tuning frequency, the software suggested two ducted ports of 6" dia. and 3.25" long. I think four ducted ports of 4" dia. and 2.55" long might do the job, but I have to check that again since I was in a rush to leave for an appointment today when looking at alternative port dimensions...

Personnaly, I would use a steep (18-24 db/oct.) high-pass filter for below 40 hz. Then, if you wish, you may beat the crap out of it... Although, at the JBL rated 300 watts input (program material), with NO high-pass filter in the lows, Winspeakers indicates you would reach Xmax (7.11mm) at about 37 hz! (111 db) and from about 45 hz and up close to 123 db. Sounds like enough to rattle the silver, as they say. BTW the cone excursion curve shows that the usual bump (here at 55-60 hz) in this curve, just above the 45 hz tuning frequency (Fb), represents about 4.75 mm of excursion at 300 watts out of 7.11 mm... I'm getting excited compared to my 2205H.

I think you'll have to forget your 36.5 inch wide cabinet dimension, as it may not make sense in the circumstances. Don't forget "... no single dimension should be more than three times any other."(same p.4)Also, you should try to avoid cabinet dimensions that are multiples of another dimension (e.g. 12", 24" and/or 36"). In the example below none is > three times another and none is a multiple of the others.

Not counting the volume displaced by the 15" woofer (6L. or 0.212 cu. ft. according to JBL) nor the space taken by proper cabinet internal bracing (? volume), the Winspeakerz software gives me INTERNAL cabinet dimensions of 38.833" H X 24" W X 14.833" D = 8 cu. ft. Naturally, you'll have to add some box volume here (on box dimensions) re driver and bracing space taken. This still gives an idea of what kind of EXTERIOR width and depth you can expect to mount your hardware. If you use 3/4" thick plywood, then your cabinet would be 25.5" wide (maybe a bit more re box overvolume), still less than your lens at 36"wide. But probably still feasible in my view. And I don't think it would look worst, if done properly, than a JBL 4675C Cinema Loudspeaker system for example. Regards,

Richard

robertg
08-08-2017, 07:09 AM
So what if I turned the cabinet sideways, it would be approximately 40" wide and 25.5" tall. If I add another box for the lens and tweeter that would make it 40" x 38". Kind of a waste of a cabinet for the lens and tweeter, but it would look good.

Lee in Montreal
08-08-2017, 08:39 AM
Hi Robert

To avoid lobbing, the famous Augsberger monitors were designed that way.

http://www.gearslutz.com/board/attachments/high-end/122825d1243506249-gear-face-just-laughs-augspurger_monitors.jpg

And the Fostex guys (from Winnipeg) made the integration that way. One of the product designer pictured on the right BTW.

http://www.preservationsound.com/wp-content/uploads/2013/09/Gillespie-LS4.jpg

RMC
08-08-2017, 11:30 AM
Hi Robert,

Your idea of putting the cabinet with longer side down and a second cab on top of that for horn/lens/tweeter doesn't sound bad. If that looks good to you then the better. The only concerns I might have with that kind of setup is the woofer being very close to the floor: objectional increase in bass ? Early mid-bass sound reflections on a hard floor? To minimize the effects you may have to put a base or pedestal under the woofer boxes to raise them somewhat off the floor. Try it without and if you have issues with those then add it. My impression is that you might as well build the bases at the same time as the speaker boxes... Maybe use some carpeting on floor ?

BTW to conclude on a funny note, vertically aligned boxes would not have made the front page of the National Enquirer, as scandal of the week, if your lens had 5" excess width on each side of the box...

Richard

Lee in Montreal
08-08-2017, 11:51 AM
BTW Robert, the frequency of the coupling of the woofers is calculated at half wave.
Per exemple, if your center-to-center distance between both woofers is 1.00 meter, then 344/1.00/2 = 172Hz (which is perhaps what the Fostex cab pictured above does- with a crossover frequency of 172Hz into the midrange driver). Basically you should calculate the distance between woofer in consideration of the cross-over frequency for a flatter response.

And if you run two cabs separated by a distance of 4 meters, then the coupling occures under 43Hz (344/4/2) and you get your 3db coupling boost in that range.

RMC
08-08-2017, 08:28 PM
Hi Robert,

In my post # 24 (4th paragraph) I wrote about the possibility of using 4 X 4" ports but had to re-check this since I was in a rush at the time. I did that and also re-modeled the E-145 with 8 cu. ft. box in a different software just to see if any different results. In Win ISD Beta the only difference is an F3 of about 42 hz instead of 40 hz in Winspeakerz. The rising response of + 2 db from about 200 hz and up also appears in Win ISD software compared to flat bass response, hence my previous suggestion to tune the box at 45 hz with a small bump of 1.5 db @ 50 hz to avoid perceived thin sounding bass vs prominent mid-bass sound...

As for the box port, in the same JBL document as mentioned in my post # 24, the recommended port surface for that box/driver is 38 sq. in. or 245 cm^2. In Winspeakerz, the minimum recommended port area is 35.3 sq. in. To meet JBL's recommended port area, three 4" dia. vents will do the job (no need for four as stated previously), since three 4" tubes have an area of 37.7 sq. in. (quite close to 38). Less work and money... To resonate the box at 45 hz Winspeakerz says these will need to be 1.237" (or 1 1/4") long. Regards,

Richard

ivica
08-09-2017, 12:36 AM
I was reading about the 4435 yesterday. The two chambers are divided horizontally, so my mid range would have to go above the cabinet because the divider would hit it. The 36" lens would have to be centered in the cabinet. Possible, but wasted cabinet space. Also the 2234 and 2235 are difficult to find.

Would it make sense if I built a 15 cubic foot enclosure with two chambers. I could use an 18" 224x series driver up to 80-100 hz and use my E-145 above that? This enclosure is going to be at least 38" wide, so making it a foot taller isn't a big deal.

Im running a DBX Driverack PA2 with a McIntosh MC2500 for the bottom end and two small amps for the minds and highs. I'm not sure if I want to throw another amp in there. I'm assuming I can throw a passive crossover in there and use the MC2500 for both the 15" and 18"?

Hi robertg,

using E145, while looking at its data info , it can be seen that such driver become very 'beamy' over 1kHz (about 1.8kHz is the peak), and so emphasizing that region and 3-rd THD too, so if you planning to use it (over 300Hz) , may be it would be good to spread driver dispersion characteristic in the way JBL has done on EON615 models by putting special shaped opening (grill) over EON615 bass driver.

regards
ivica

robertg
08-18-2017, 03:27 PM
I'm not going to win and design awards. I think a wooden horn would look better than the large DAS lens.

I'm doing the cabinets in rosewood, and probably paint the baffle blue.

RMC
08-18-2017, 04:54 PM
Hi Robert,

Doesn't look bad to me. We don't build boxes to win awards, but for our listening pleasure, remember that. My numerous boxes aren't sexy but they are technically correct. That's what matters in my view. Let us know how yours sound...

Richard

ivica
08-19-2017, 12:42 AM
I'm not going to win and design awards. I think a wooden horn would look better than the large DAS lens.

I'm doing the cabinets in rosewood, and probably paint the baffle blue.

Hi robertg,
it seems to me tahat You are not going to use MA15 clamps for fixing the driver.
http://audio-heritage.jp/JBL/etc/speakeroption.html
http://www.audioheritage.org/vbulletin/showthread.php?21626-Blown-2042H&p=406251&viewfull=1#post406251
http://img05.shop-pro.jp/PA01015/403/product/1704404_o1.jpg


regards
ivica

robertg
08-19-2017, 05:06 AM
Hi robertg,
it seems to me tahat You are not going to use MA15 clamps for fixing the driver.
http://audio-heritage.jp/JBL/etc/speakeroption.html
http://www.audioheritage.org/vbulletin/showthread.php?21626-Blown-2042H&p=406251&viewfull=1#post406251
http://img05.shop-pro.jp/PA01015/403/product/1704404_o1.jpg


regards
ivica
I wanted to, but the E145 looks to be over an inch thick.

ivica
08-19-2017, 05:59 AM
I wanted to, but the E145 looks to be over an inch thick.

Hi robertg,

may be wooden ring round the E145 would help in order to compensate so large distance from the baffle.

regards
ivica

robertg
08-19-2017, 06:47 AM
Hi robertg,

may be wooden ring round the E145 would help in order to compensate so large distance from the baffle.

regards
ivica
What would be the advantage of that? Less chance of the basket flexing at the mounting points?

robertg
08-22-2017, 08:28 PM
Hi Robert,

The JBL recommended enclosure volumes for a single E-145 is in the range of 3-8 Cu. Ft. or 85-227 liters net(see JBL, E-series, Instruction Manual, 02/81, P. 5). So a box of 9-10 cu. ft. is too large in JBL's view for proper performance. In order to help you "fit" on box top the compression driver/horn/lens assembly, I took the largest proposed volume (8 cu. ft.) and ran a quick computer simulation in Winspeakerz v. 2.5.2 speaker design software.

The T/S parameters used were those of JBL from the E-series brochure (Fs 35hz, Qts .25, Vas 275L./9.7 cu. ft, etc.). In such a box, tuning at 40 hz leads to an about flat response in the bass range. But this woofer has a rising response in the mid-bass like many other Musical Instrument drivers.

After testing a few, my preference would go to a 45 hz tuning (Fb) for two reasons. First, tuning lower usually puts more strain on a woofer (Increased excursion) and you therefore reach X max faster and at a lower output level. Second, the little higher tuning here creates a small bump in response of about 1.5 db at 50 hz which will about match the mid-bass sound level since that driver has a rising response of + 2 db or so from about 200 hz and up. At a flat response tuning of 40 hz, the mid-bass level will be about 2 db higher than the bass level. Giving more emphasis to a mid-bassy sounding speakers. I hate that. The small bass bump would then be usefull to "match, equalize or balance" perceived bass and mid-bass sound levels.

With an F3 (3 db down point) at 40 hz (with 45 hz tuning) this is still lower bass than MOST Sound Reinforcement cabinets sold. To achieve that tuning frequency, the software suggested two ducted ports of 6" dia. and 3.25" long. I think four ducted ports of 4" dia. and 2.55" long might do the job, but I have to check that again since I was in a rush to leave for an appointment today when looking at alternative port dimensions...

Personnaly, I would use a steep (18-24 db/oct.) high-pass filter for below 40 hz. Then, if you wish, you may beat the crap out of it... Although, at the JBL rated 300 watts input (program material), with NO high-pass filter in the lows, Winspeakers indicates you would reach Xmax (7.11mm) at about 37 hz! (111 db) and from about 45 hz and up close to 123 db. Sounds like enough to rattle the silver, as they say. BTW the cone excursion curve shows that the usual bump (here at 55-60 hz) in this curve, just above the 45 hz tuning frequency (Fb), represents about 4.75 mm of excursion at 300 watts out of 7.11 mm... I'm getting excited compared to my 2205H.

I think you'll have to forget your 36.5 inch wide cabinet dimension, as it may not make sense in the circumstances. Don't forget "... no single dimension should be more than three times any other."(same p.4)Also, you should try to avoid cabinet dimensions that are multiples of another dimension (e.g. 12", 24" and/or 36"). In the example below none is > three times another and none is a multiple of the others.

Not counting the volume displaced by the 15" woofer (6L. or 0.212 cu. ft. according to JBL) nor the space taken by proper cabinet internal bracing (? volume), the Winspeakerz software gives me INTERNAL cabinet dimensions of 38.833" H X 24" W X 14.833" D = 8 cu. ft. Naturally, you'll have to add some box volume here (on box dimensions) re driver and bracing space taken. This still gives an idea of what kind of EXTERIOR width and depth you can expect to mount your hardware. If you use 3/4" thick plywood, then your cabinet would be 25.5" wide (maybe a bit more re box overvolume), still less than your lens at 36"wide. But probably still feasible in my view. And I don't think it would look worst, if done properly, than a JBL 4675C Cinema Loudspeaker system for example. Regards,

Richard
After doing some reading there is a misprint on the E145 parameters, the VAS is supposed to be 427.7, not 275. What does this change?

RMC
08-23-2017, 10:27 AM
Hi Robert,

What is the source for this "misprint" on E-145 Vas figure ? Who says that ? I re-checked all my JBL stuff and that is their published number (275 liters). It may change things . I will re-do a speaker design run in Winspeakers software with the "revised" Vas number and come back to you soon... One thing that did not seem to change (misprint) is JBL's mention that max appropriate box volume is 8 cu. ft.

Richard

ivica
08-23-2017, 11:06 AM
After doing some reading there is a misprint on the E145 parameters, the VAS is supposed to be 427.7, not 275. What does this change?

Hi robertg,
using correct Vas for the JBL E145 and JBL 2235 the comparative response using 150 Lit ( E145 tuned 50Hz,green, 2235 tuned 29Hz, red) .
at about 150W input power

regards
ivica

robertg
08-23-2017, 11:43 AM
I'm at 227 l, or 8 cubic feet with three 4" ports that are 1 1/4" long. It looks like the E145 will make a lot of noise.

I downloaded winisd, and it looks like my ports should be longer if I entered everything correct.

robertg
08-23-2017, 02:19 PM
Hi Robert,

What is the source for this "misprint" on E-145 Vas figure ? Who says that ? I re-checked all my JBL stuff and that is their published number (275 liters). It may change things . I will re-do a speaker design run in Winspeakers software with the "revised" Vas number and come back to you soon... One thing that did not seem to change (misprint) is JBL's mention that max appropriate box volume is 8 cu. ft.

Richard

It's here.

http://www.audioheritage.org/vbulletin/showthread.php?361-The-purpose-of-JBL-E145/page2

RMC
08-23-2017, 03:56 PM
Hi Robert,

Which Win ISD did you downloaded? ISD Beta or ISD Pro Alpha? In Pro Alpha there is a sequence to follow when entering the data, otherwise that software bugs... In case you need that sequence let me know I have two of those. I did mention here or in another thread that different softwares lead to slightly different results. IF my memory is correct, ISD Pro uses QL 10 as default box loss assumption? Verify that. While others use the usual QL 7 box loss assumption. This may make a small difference in cab volume/tuning.

RE IVICA Post # 39

With all due respect for him, his thing doesn't make much sense in the present context because it means scrapping your present boxes and building new ones of 150L.(5.3 cu. ft.)! Plus your 2395 clones will probably not fit on that the way you wish. Finally, on the response curve he posted himself, the woofer's rising response that I mentioned previously (+2 db from about 200 hz at 1 watt) would become your worst nightmare at high sound levels: his curve shows at 50 hz about 118 db and at 250 hz or so about 125 db... With a now 7 db difference as level is increased, this thing is prone to huge mid-bassy sound which is unacceptable sound wise (poorly balanced perceived sound), unless you placed your boxe's rear at a wall/floor junction or even in the corner to get some "room gain" in the lows. BTW I NEVER scrap a good box unless it would be a lost cause, which is definitely NOT your case at all here...

I did run in Winspeakerz some new scenarios with an 8 cu. ft. box along with the revised E-145 Vas figure you mentioned of 427.7 L. or 15.1 cu. ft. (instead of JBL's 274.7 L. in T/S data table and 275 L. in E-series brochure). There is NO problem at all with your present 8 cu. ft. box volume (That's NET volume right? You did account (increase) that volume for space taken by drivers, bracing, etc. as I mentioned before?).

If you kept the tuning (Fb) at 45 hz, as suggested before the change in Vas, you will still get flat low-frequency response, F3 at 43 hz, but you'll have the E-145 rising response issue, also with the new Vas number. Box placement as mentioned above may help. Another easy way out is that you may add EQ in the 50-60 hz range for a small bump (1.5-2 db or so) to sort of balance low and mid levels perceived.

If box placement or EQ suggestions are not acceptable to you?, then you'll have to re-tune the box a little higher around 50-52 hz (not lower with longer ducted ports). The present vents MAY not be acceptable. Did you keep the circular vent cut-outs you got when you made cabinet holes for the vents? Please answer all my questions tonight or tomorrow morning so I can come back tomorrow with vent alternative vent suggestions, if need be. Gotta go now, I'll read you later. Regards,

Richard

robertg
08-23-2017, 04:43 PM
Hi Robert,

Which Win ISD did you downloaded? ISD Beta or ISD Pro Alpha? WinISD 0.7.0.950. In Pro Alpha there is a sequence to follow when entering the data, otherwise that software bugs... In case you need that sequence let me know I have two of those. I did mention here or in another thread that different softwares lead to slightly different results. IF my memory is correct, ISD Pro uses QL 10 as default box loss assumption? I don't know where to find that? Verify that. While others use the usual QL 7 box loss assumption. This may make a small difference in cab volume/tuning. I think I was getting an error message, I thought it said division by zero or something like that, then it went away.

RE IVICA Post # 39

With all due respect for him, his thing doesn't make much sense in the present context because it means scrapping your present boxes and building new ones of 150L.(5.3 cu. ft.)! Plus your 2395 clones will probably not fit on that the way you wish. Finally, on the response curve he posted himself, the woofer's rising response that I mentioned previously (+2 db from about 200 hz at 1 watt) would become your worst nightmare at high sound levels: his curve shows at 50 hz about 118 db and at 250 hz or so about 125 db... With a now 7 db difference as level is increased, this thing is prone to huge mid-bassy sound which is unacceptable sound wise (poorly balanced perceived sound), unless you placed your boxe's rear at a wall/floor junction or even in the corner to get some "room gain" in the lows. BTW I NEVER scrap a good box unless it would be a lost cause, which is definitely NOT your case at all here...

I did run in Winspeakerz some new scenarios with an 8 cu. ft. box along with the revised E-145 Vas figure you mentioned of 427.7 L. or 15.1 cu. ft. (instead of JBL's 274.7 L. in T/S data table and 275 L. in E-series brochure). There is NO problem at all with your present 8 cu. ft. box volume (That's NET volume right? You did account (increase) that volume for space taken by drivers, bracing, etc. as I mentioned before?). Yes, net volume, should be really close to 8 cubic feet.

If you kept the tuning (Fb) at 45 hz, as suggested before the change in Vas, you will still get flat low-frequency response, F3 at 43 hz, but you'll have the E-145 rising response issue, also with the new Vas number. Box placement as mentioned above may help. Another easy way out is that you may add EQ in the 50-60 hz range for a small bump (1.5-2 db or so) to sort of balance low and mid levels perceived. I have a DBX Driverack PA2 crossover, so that isn't a problem.

If box placement or EQ suggestions are not acceptable to you?, then you'll have to re-tune the box a little higher around 50-52 hz (not lower with longer ducted ports). The present vents MAY not be acceptable. Did you keep the circular vent cut-outs you got when you made cabinet holes for the vents? I probably did, but new ones are easy to make. Please answer all my questions tonight or tomorrow morning so I can come back tomorrow with vent alternative vent suggestions, if need be. Gotta go now, I'll read you later. Regards,

Richard

When I enter in 45 Hz as my tuning frequency and 226 l, it wants a vent length of 8.56 cm. The graph that comes up crosses the -2 line at 50, rises a bit then hits -2 again between 72 and 88. It then gradually rises and hits 0 at 400.

RMC
08-23-2017, 09:00 PM
Hi Robert,

The Win ISD version number you're giving me doesn't correspond to both of my versions: ISD Beta v. 0.44 dated 15 Jan. 2002 and ISD Pro Alpha v. 0.50a7 dated 11 Sept. 2004. You downloaded the latest version issued 29 Oct. 2016, which I just downloaded and haven't had time to try and test. I've been using more Winspeakerz lately since I like it and paid for it...

In the older versions I used when you opened a project in the "Box" Tab at bottom left there's an "Advanced" mention that can be clicked-on and shows for rear chamber the boxe's QL, Qa, Qp numbers used, plus these can be changed manually if you clicked on the QL number for example another box opened and you can write 7 instead of 10 or vice versa.

You mention a 45 hz tuning frequency with flat low-end response (and rising mid-bass response) isn't a problem for you because of your Driverack x-over, then it means you can add, as required, a few db in the 50-60 hz range easily. That would be an easy way out on the issue of balancing low and mid woofer levels.

You may not be required to re-tune the boxes if you are satisfied with the present boxe's sound with the lows processed by the Driverack. The idea of keeping the cut-outs made is if a re-tuning is a must then they can be reused, glued back in their place to cover vents # 1 and 3, to plug the existing vent holes, wood filler (plastic wood) on the outside, silicone on the inside remaining cutting line, then glueing/screwing a small piece of plywood (3/8"- 1/2" thick) on the inside to cover where the previous hole was and a little more, as this gives more rigidity to the repair. If a larger vent is ever required the center hole (vent # 2) can be used as a starting point in the free space between vents 1 and 3 that are plugged.

Finally, as for a vent of 8.56 cm long from the software, I haven't tried it yet so I'll have to come back on this.

Richard

ivica
08-23-2017, 10:48 PM
Hi Robert,


RE IVICA Post # 39

With all due respect for him, his thing doesn't make much sense in the present context because it means scrapping your present boxes and building new ones of 150L.(5.3 cu. ft.)! Plus your 2395 clones will probably not fit on that the way you wish. Finally, on the response curve he posted himself, the woofer's rising response that I mentioned previously (+2 db from about 200 hz at 1 watt) would become your worst nightmare at high sound levels: his curve shows at 50 hz about 118 db and at 250 hz or so about 125 db... With a now 7 db difference as level is increased, this thing is prone to huge mid-bassy sound which is unacceptable sound wise (poorly balanced perceived sound), unless you placed your boxe's rear at a wall/floor junction or even in the corner to get some "room gain" in the lows. BTW I NEVER scrap a good box unless it would be a lost cause, which is definitely NOT your case at all here...

Richard

When I enter in 45 Hz as my tuning frequency and 226 l, it wants a vent length of 8.56 cm. The graph that comes up crosses the -2 line at 50, rises a bit then hits -2 again between 72 and 88. It then gradually rises and hits 0 at 400.

Hi,

the difference in the F/R response would not change much changing from 150 lit to 225 lit, but adding about 2 ohm resistor 'in-line' with the driver would reduce mid-bass rising in the response...

regards
ivica

RMC
08-24-2017, 11:20 AM
Hi Robert,

Thinking about all this one more time, at this point it may be best to keep the 8 cu. ft. box since that volume IS correct and keeping the 45 hz tuning frequency also makes sense in the context of two possible driver Vas numbers (275 L. from JBL or 427.7 L./15.1 cu. ft. calculated by 4313B in a 2003 post about the purpose of the E-145). If JBL's number is right, you get a small bump in the lows to sort of "match" with driver rising mid response, therefore "balancing" the sound. If 4313B's number is right, you get flat bass response which you say is not a problem with your Driverack to adjust or equalize to again sort of "match" levels with the E-145 rising mid-bass response. Keeping things as is for now, you can get "the best of both worlds" as they say, or face either applicable scenario. Not a bad thing at all, and a great outcome in this dilemma.

As for the proper vent length issue in the new version of Win ISD, I'll install the software and check that, plus I'll also review my vent numbers in Winspeakers...
Will be back in the near future.

Richard

robertg
08-24-2017, 03:52 PM
Hi Robert,
In the older versions I used when you opened a project in the "Box" Tab at bottom left there's an "Advanced" mention that can be clicked-on and shows for rear chamber the boxe's QL, Qa, Qp numbers used, plus these can be changed manually if you clicked on the QL number for example another box opened and you can write 7 instead of 10 or vice versa.
Richard

If I change the QL to 7 from 10, it flattens the hump at 50 Hz. The Qa and Qp are 100. When I change the box tuning frequency to 55Hz, it gives me a vent length of 3.26 cm, close to 1 1/4". There is still a bit of a hump at around 65 Hz and then it drops down around around 100 Hz.

RMC
08-25-2017, 10:19 AM
Hi Robert,

No time now, I'll be back tonight to answer your issues in your last post # 47 plus some news on vent length...
After many attemps, the new Win ISD just won't install on my laptop computer... Free software with free bugs! That's why I paid $40.US to get Winspeakerz. See you tonight.

Richard

RMC
08-25-2017, 08:46 PM
Hi Robert,

Using QL 7 as a starting point, like in most software, is more reasonable than QL 10. Losses do exist.

It's normal that at QL 7 instead of QL 10 the previous bass bump went away with same box volume/tuning . In a way, box air leaks mean air wasted that is not used to produce bass. Had you tried QL 3 or 5 you would have seen a dip in LF response! You've figured by now that low QL means lossy and high QL means air tight. But also that more lossy boxes mean weaker bass response... In addition to that, large boxes tend to be more lossy than small ones, hence Leach's suggestion to use lower QL (e.g. 5) for large cabinet design. You will have to go the extra mile to try to achieve QL 7 in a larger box. See further below. BTW don't change the Qa (absorption) and Qp (port losses) in the software unless you know what you are doing.

It's also normal that when you tuned the box to 55 hz in the software, instead of 45 hz, the small bump moved higher at 65 hz since you are then tuned higher. There remains the question of how long the vent need to be (see further below). Before settling on a 55 hz tuning frequency (Fb) I would definitely try to measure the Fb with the vents you have now with an Audio Test CD as I use (or an iPhone app or other that some also use) for frequency generation/counting to see what is the actual Fb you get now. With reasonable sound level, while frequencies go by in your sound system (e.g. from 60 hz to 40 hz) you barely touch the woofer cone near the surround to feel the woofer vibrations. At the point of least or no vibration you have the tuning frequency and take note of it. Any Fb in the range of 45-50 hz is ok for that box. This implies "finalizing" the boxes acoustically with the drivers in their place (no need to connect horn and tweeter), except the vents may be subject to re-work. For temporary caulking around the vent/cab junctions inside the cabinets I use Canadian Tire's Climashield, Crack Shield, product # 64-2545-0. Sticks on but removeable. Easy on, easy off, in case vents would need to be changed.

if you're not meticulous about air leaks you'll get more than you need and the bass will suffer. To compensate for box air leaks the remedy is usually an increase in box volume (Vb), not practical here because your boxes are built. You can model that in Win iSD by changing QL number. If you end-up with QL 3 or 5 (lossy box), instead of a QL 7 flat reponse for example, you will get a low-frequency dip for same volume/tuning, and to get flat response again you would need to increase box volume... You're better off working meticulously with the caulking tube/gun!

All inside joints, input terminals, around vents, etc. need to be really air tight. Plus, good quality gaskets (foam or rubber with some thickness to fill front panel minor defects where drivers sit when under pressure from screwed-in drivers) must be used to seal driver/cab, not the cheap cardboard/paper ones.

Input terminal leaks are often the bugger. The perimeter needs to be siliconed from inside the box once installed. Moreover, some input terminals even have some holes on their back side for whatever reason (seen from inside the box) and these holes somehow often connect or lead to binding posts, push terminals or 1/4" plugs on the outside face. ANY POSSIBLE way for air leaks here MUST be plugged with silicone. Seen some plastic terminals with a bit of loose around the back side's metal terminal: again silicone that minuscule space where the loose is. After all this is done, then you can hope for a large box with QL 7. As Bullock said, air must have absolutely no way to exit but through the vent... Amen !

Though the new Win ISD doesn't want to install itself on my laptop, In addition to Winspeakerz and older Win ISD, I still have other credible resources from the "good old days" of speaker building to determine vent diameter (Dv) and length (Lv). JBL Pro published a long time ago a porting chart, developed by R.H. Small, to help in tuning vented boxes. This is NOT the same as what JBL provided in the past with their "Speaker Enclosure Construction kits" for home or Pro builders. There is no reference whatsoever on this document to any JBL drivers or boxes. Just a lot of Vb, Fb, Va (vent area), Dv and Lv dimensions. Mc Cauley speakers also issued a similar one named "Alignment Graph". A smaller version of that chart or graph is also reproduced in John Eargle's (JBL) books: Handbook of Sound System Design, 1989, P. 109; and in his Loudspeaker Handbook, 1997, P. 68.

Since this chart/graph relates to a single vent and you have three of them (3 X 4"= 37.7 sq. in.) I took numbers for a tiny bit less than a 7" vent (38.48 sq. in., which in itself is already pretty close at ± 3/4 of a sq. in.) to get an idea regarding required vent length. For your given Vb (8 cu. ft.) and Fb (45 hz) with above-mentioned vent size, I get a vent length of 1" to 1 1/4", the latter number being what you already have in your boxes and also what Winspeakerz had given me. As I indicated above, in your shoes I would test your boxe's present tuning frequency before touching those vents. Regards,

Richard

robertg
08-26-2017, 05:11 AM
I'm pretty sure it's going to be air tight, I used a lot of glue, and there is a screw every 4 inches. Hopefully I will have everything together in a couple of weeks so I can test.

ivica
08-26-2017, 06:37 AM
Hi, the difference in the F/R response would not change much changing from 150 lit to 225 lit, but adding about 2 ohm resistor 'in-line' with the driver would reduce mid-bass rising in the response... regards ivica Hi E145 & 225 Lit Fr=45Hz with 2 Ohms regards ivica

RMC
08-26-2017, 11:09 AM
Hi Robert,

Sorry, but being pretty sure the box is air tight because you used a lot of glue isn't enough to be REALLY air tight. You DO have to silicone everywhere I mentioned otherwise you WILL have more losses than expected. And the bass will suffer...

When I built my first (of a pretty long series of boxes) in 1981 I had used LOTS of glue and screws as you did, only to find out later-on that I DID have a number of air leaks which affected bass from those low-frequency enclosures... Had to re-do all the interior air tightening to fix the problem, and doing it afterwards IS a pain in the neck. Since you are still at the construction phase its easier. Re-doing it after is too late and harder...

NOTE TO IVICA:

Out of curiosity which speaker design software do you use to show us these response curves?

I have a problem with using a resistor in series with a woofer, over and above a crossover...

Also, with a 300 W program material power capacity driver which 2 ohm resistor will easily handle that much power?

The resistor reduced the mids of 2-3 db but also seems to affect a little the bass from < 70 hz which one could have expected since a resistor in series with a woofer doesn't impact only woofer mids but the whole woofer...

To me it seems more natural to try to improve the response with some box tuning tweaking VS a resistor. Regards,

Richard

RMC
08-26-2017, 08:43 PM
Hi Robert,

To satisfy my curiosity, I checked using D. B. Keele's formulas for vented-box design the ones (Imperial and Metric), he developed for vent length calculations, to see if any discrepancies with Small's chart/graph I mentioned yesterday (1"- 1 1/4") and what I gave you earlier from Winspeakerz (1.23").

BTW since I needed an exact diameter figure to plug into Keele's equation for vent length, I first had to determine the exact vent diameter your 3 X 4" vents would represent as a single vent. The answer is a Dv of 6.9282" which, as I mentioned yesterday, is pretty darn close to a tiny bit less than a 7" vent that I used in Small's chart/graph.

With that plugged into Keele's equation for Imperial measures along with other numbers (Vb 8 cu. ft., FB 45 hz, etc.) the vent length (Lv) determined is 1.2". On the Metric equation's side, the Lv is 2.91 cm (= 1.1447"). So all the vent length numbers I gave you (from three different sources) are pretty damn close to each other... That's another good reason to test your actual Fb before touching those vents! Since air leaks affect woofer performance ("perceived" box volume or air volume to "work" with), if you get weird Fb readings, box losses may be something to investigate, as well as the T/S of your bass drivers (e.g. original? reconed with aftermarket kits? etc.). Regards,

Richard

ivica
08-27-2017, 01:50 AM
[QUOTE=RMC;408059....
NOTE TO IVICA:

Out of curiosity which speaker design software do you use to show us these response curves?

I have a problem with using a resistor in series with a woofer, over and above a crossover...

Also, with a 300 W program material power capacity driver which 2 ohm resistor will easily handle that much power?

The resistor reduced the mids of 2-3 db but also seems to affect a little the bass from < 70 hz which one could have expected since a resistor in series with a woofer doesn't impact only woofer mids but the whole woofer...

To me it seems more natural to try to improve the response with some box tuning tweaking VS a resistor. Regards,

Richard[/QUOTE]


Hi Richard,

I have used BassBox Pro sw,
Applying serial resistor with the bass driver has been applicable by JBL in the way that they enlarge the resistance of the L in their networks.
The result is lowering mid-bass, and some small amount of ultra low bass section.
Anyhow, I do not think E145 to be the best JBL driver for reaching ultra-low bass section, but may of the forum members love it for jazz reproduction, due to producing 'punch bass'/
Personally I would prefer 2245 (18") then 2231A (15", if possible to get), then 2235.
I have not heard 2216Nd (15", but 3inch vc, but would produce almost the same LF response as 2235), neither 2269ND (18").
It seems that with 2216Nd, and box (225Lit) tuned to 35Hz, F3 would 33Hz, almost flat response.

4367:
http://reconingspeakers.com/product/jbl-2216nd-1-woofer-for-4367-320-0045-002/#prettyPhoto
M2:
http://reconingspeakers.com/product/jbl-2216nd-woofer-for-jbl-m2-5041785/


regards
ivica

RMC
08-27-2017, 10:53 AM
Hi Ivica,

Thanks for your reply. Now I understand. It's not just putting a 2 ohm resistor in series with the woofer as your post # 51 implied... But rather "... has been applicable by JBL in the way that they enlarge the resistance of the L in their networks." That makes more sense, they do it in the crossover network, not just a 2 ohm series resistor alone.

As for the E-145 driver, well the thread name is "Building an enclosure around D-401/2395 clone" and Robert had a pair of E-145 sitting around (which CAN deliver some good bass). Why not make use of all that stuff (plus tweeters) since it CAN go all together in a box and make something worthwhile? The 8 cu. ft. box (largest recommended by JBL for E-145) is for the reason that Robert insisted on having the 2395 clone fit Inside the box perimeter as he didn't want the lens to extend 5 or 6" outside either side of the box...

As for the other woofers you mention they are irrelevant in the present context since Robert is not trying to build the best bass box possible but rather make good use of what drivers he already has... Plus the 2216Nd (links you referred to) in Canada would cost OVER $700.CAD each with just the currency exchange rate! I'm trying to help him make his thing fly (and I think it can do decently) instead of purchasing a new airplane! Gotta learn to work and find a way with what the "client" has, wants and can afford my friend. I always try to. Regards,

Richard

robertg
08-28-2017, 06:09 AM
I do have a pair of 2226J drivers coming, but from what I have read everyone likes the E145 better.

Hopefully my DBX Driverack can straighten everything out without adding a resistor. I'm also thinking of making a single subwoofer if I need it. I doubt if I will, but I'll probably still make one anyway.

The cabinets are pretty well done, I'm just not sure if I like the shade of blue that I picked. They will be together when I finish restoring the lenses. That's a lot of work trying to straighten them.

Ian Mackenzie
08-28-2017, 05:57 PM
Hi Robert

Have you seen this link?

http://www.audioheritage.org/vbulletin/showthread.php?10655-E145-8-150-4H

Also Don's comments on the Everest

http://www.audioheritage.org/html/profiles/jbl/everest.htm

These links may provide some practical guidance on the application of the E145 for home Audio

Good luck

robertg
08-29-2017, 04:45 AM
Hi Robert

Have you seen this link?

http://www.audioheritage.org/vbulletin/showthread.php?10655-E145-8-150-4H

Also Don's comments on the Everest

http://www.audioheritage.org/html/profiles/jbl/everest.htm

These links may provide some practical guidance on the application of the E145 for home Audio

Good luck

It looks like I have the same low and high as the Everest, and the same cabinet volume. Those E145 graphs look like it doesn't reach its peak volume until 100Hz or so? I don't have very fussy ears, so I'm sure I will like the sound.

RMC
08-29-2017, 10:32 AM
Hi Robert,

"I do have a pair of 2226J drivers coming, but from what I have read everyone likes the E145 better."
I don't own either drivers so I can't say for sure, but the E-145 is considered by many as one of the best drivers JBL made. Its a "darling" among the lineup.

On the other hand, It's not sure the 2226J (16 ohms version) would be a good fit for your present boxes, though JBL gives a recommended box size of 3-10 cu. ft. for 2226. It would have to be modeled in speaker design software to confirm a good fit or not, and a possible box re-tuning... The T/S parameters are different for E-145/2226 (Fs, Qts, Vas, etc.): 35/40hz; .25/.31; 275 (or 427.7?)/175 L, just to illustrate a few of them.

Are you planning the 2226 for subwoofer use??

I'm not a fan of a simple resistor in series with the woofer. Maybe in a pinch, as a last effort, if you are desperate... But then you would have to find a "large" power capacity resistor, if you can find one, and still use reasonable power input. Plus this would also affect driver impedance seen by amp.

My small bump tuning idea is also a way to "minimize" perceived different low/mid levels from E-145. Adjustable Parametric EQ on the "agressive or offensive" mid-bass level is another interesting alternative...

Richard

robertg
08-29-2017, 11:21 AM
I wasn't planning on using the 2226 drivers for subs, could I? I was think of getting a 2242 or 2245. My preamp has a single sub output, 80Hz to 10Hz. I would run a UREI 6260 amp.

RMC
08-29-2017, 08:33 PM
Hi Robert,

I doubt 2226 could make a worthwhile sub. The only way to know for sure is to try it in speaker design software. But in any case you would be a lot more in sub territory with 2242 or 2245... I'm not familiar with that UREI preamp so I can't comment on that. 80 hz could be a valid x-over frequency for your sub.

Richard

Ian Mackenzie
08-29-2017, 11:04 PM
Perhaps another tit bit of advice

Before getting too carried away with a flat response attempt to consider the real impact of room gain and baffle step.

Ignoring these issues can leave a crater in your midbass response while an attempt to win a flat response on paper can lead to bass bloom with inherent room gain.

For example a 24 inch front baffle width will have a baffle step shelf in the response around 190 Hz with 3-6 Db shelving of the bass response depending on the location of the woofer on the baffle.

Jbl typically use a larger than calculated series inductor on the woofer low pass filter to off set this effect with a low pass filter.

Room gain is un predictable but normally courts below 150 Hz and I'd dependant on the woofer location on the baffle and distance from room boundary ie the wall floor junction.

Proximity to the floor adds 6 Db room gain, proximity to floor and wall adds 12 Db room gain and proximity to a room corner/ floor adds up to 18 Db of room gain.

Most bass reflex box simulator assume the baffle is suspended in free space.

One way of evaluating your box response with the above effects is to try and measure your box outside on the drive way using a test set from the likes of Parts Express at 2 metres with the box on the surface of your drive well clear of any structures

Expect to see some dips and peaks.

Then start to move the box closer to a rear wall

You will notice the bass response change

By locating the box at a distance to the rear wall equivalent to your listening room you will have some idea on the impact of room gain

Every box is different as is every box turning

Subtle adjustment of the port tuning frequency can help smooth the bass response

FYI Jbl did this with their statement systems andvis the difference between an arm chair diy project and a commercial hi end loudspeaker

Room modes in small rooms also impact on the bass responses

But the point here is don't look at your box response simulation in isolation

Some experimenting will yield a much better sound in your room

if you intend to use a Db drive rack much of this can be compensated with parametric equalisation.

ivica
08-30-2017, 11:56 AM
Perhaps another tit bit of advice

....For example a 24 inch front baffle width will have a baffle step shelf in the response around 190 Hz with 3-6 Db shelving of the bass response depending on the location of the woofer on the baffle.


.......

Hi Iam,

Interesting explanation. I have never seen such behaviours on any JBL data, nor any forum presentations.
Can You show us such results.

regards
ivica

Ian Mackenzie
08-30-2017, 02:24 PM
Hi Invica,


It's nothing new

Room gain is talked about more often

Baffle diffraction is acoustic theory

Do a google

It's a case of being able to measure it under the right conditions

I use LMS which is very accurate at low frequencies

MLS is not so good at lower frequencies

The challenge is working out a measurement procedure.

That is why you first need to remove all other influences like small room modes

Jbl build it into the crossover

Look at the voltage drives (see below the woofer voltage drive starts just above 100Hz)

You probably won't see it done this way anymore as they fired the one guy smart enough to get it right.

Depending on the system the voltage drives start to attenuate at frequencies far below the crossover point

In a multi way system it's easier to deal with.

The impact of room gain also needs to be weighed up

If you have access to proper modelling software is quite obvious that what happens on a real baffle in a real room is quite different from a T/L calculated response.

You can predict with diffraction modelling

An analogy is tidal movement

There are waves on the surface from room interference.

But the baffle, and the baffle location in the room have an overriding influence over the level and balance the sea (sound level in the bass, mid bass and mid range)

It's the underlying influence of the voicing of bass and mid bass region

Narrow tower loudspeakers use dual woofer in many cases for this reason (or slice of 3-6 db sensitivity)

ivica
08-30-2017, 11:39 PM
Hi Invica,


It's nothing new

Room gain is talked about more often

Baffle diffraction is acoustic theory

Do a google

It's a case of being able to measure it under the right conditions

I use LMS which is very accurate at low frequencies

MLS is not so good at lower frequencies

The challenge is working out a measurement procedure.

That is why you first need to remove all other influences like small room modes

Jbl build it into the crossover

Look at the voltage drives (see below the woofer voltage drive starts just above 100Hz)

You probably won't see it done this way anymore as they fired the one guy smart enough to get it right.

Depending on the system the voltage drives start to attenuate at frequencies far below the crossover point

In a multi way system it's easier to deal with.

The impact of room gain also needs to be weighed up

If you have access to proper modelling software is quite obvious that what happens on a real baffle in a real room is quite different from a T/L calculated response.

You can predict with diffraction modelling

An analogy is tidal movement

There are waves on the surface from room interference.

But the baffle, and the baffle location in the room have an overriding influence over the level and balance the sea (sound level in the bass, mid bass and mid range)

It's the underlying influence of the voicing of bass and mid bass region

Narrow tower loudspeakers use dual woofer in many cases for this reason (or slice of 3-6 db sensitivity)

Hi Ian,

not to argue with You and known theory, but such baffle step can be very difficult to see on almost any JBL data presentation.
Just to remember that all 43xx speakers are "book shelf" speakers, so it is expected to 'radiate in to 2pi space', so baffle is expected to be very
large. Just to remember that most of the JBL data for 22xx (15") drivers are shown under 2pi 'surroundings' using about 250Lit close box.
Here on the Forum it can be seen a photo of "on the roof measurements' procedure.
Due to the drivers size its directivity changes so the amount of sound energy is emitted in the smaller angular space, and due to the cone flection, less moving mass is loaded to the BL force, and some large peak can be seen on the most drivers responses (over 1kHz). If we are talking about driver internal inductive part of internal impedance, I think it become 'active' almost over 0.5kHz ( 1mH in 0.5kHz is about 3.2 Ohms) not on 100~200 Hz.

Here I do not want to elaborate the influence of the other surfaces , room standing waves, reverberations, etc...just I want to see mentioned baffle-step in the mentioned 'book shelf surrounding', on some real measurements data or graph. I am totally aware that real in the room response of the speaker would very, very different then the "pure 2pi case".

regards
ivica

RMC
08-31-2017, 08:03 PM
Hi Ian, (And Robert)

I couldn't pass on this one (your post # 62). With all due respect, I don't know where you are getting some of that info, but mine is identified below.

"Before getting too carried away with a flat response attempt to consider the real impact of room gain and baffle step." Agreed. If a sub was placed in the middle of a room (away from boundaries) and on a pedestal, base or stand, its unlikely one would get the 6 db room gain from boundary (since not real half-space).

"Room gain is un predictable but normally courts below 150 Hz and I'd dependant on the woofer location on the baffle and distance from room boundary ie the wall floor junction." More or less agreed because room gain is somewhat predictable. Electro-Voice states, in the System Positioning section, that "... the audible location of a subwoofer operating at a sufficiently low crossover frequency (below about 150 hz) will not be particularly evident." (Data sheet, PI218L, Low-Frequency Sound reinforcement System, 1994, P.3) I understand from this that 150 hz, you also mentioned, is the point where bass frequencies start to get omnidirectional, and therefore more difficult to locate, plus can benefit from room boundary placement gain instead of "wrapping around" the box as "diffraction loss"...

"Proximity to the floor adds 6 Db room gain, proximity to floor and wall adds 12 Db room gain and proximity to a room corner/ floor adds up to 18 Db of room gain." Two of these numbers appear to be wrong. First, floor OR wall placement does provide half-space (2 Pi) environment that leads to 6 db room gain, but one has to mention compared to full-space (4 Pi, or free space) environment. Again, from the same E-V data sheet mentioned above, in the same System Positioning section on P.3: "Floor location provides the acoustic half-space environment associated with the 6.1% system efficiency noted in the Specifications sections." Moreover adds: "Location at a floor-wall junction (acoustic quarter space) doubles efficiency (a 3-db increase in acoustic power level)..." That is compared to floor location only. Then further adds: "Corner placement (acoustic eighth space) doubles efficiency again..." Which I understand means another 3 db increase compared to floor-wall location. So, if I count correctly, it would be 6 db gain from full-space to half-space, then 3 db gain from half-space to quarter space, and finally another 3 db gain from quarter space to eighth space, for a total of 12 db of possible room gain from speaker placement. Not exactly the same numbers as yours.

"Most bass reflex box simulator assume the baffle is suspended in free space." I think this statement is questionable. John Eargle (JBL) writes "The data calculated from the thiele/Small parameters refers only to the LF performance of the system ... Further, the analysis assumes that the loudspeakers will be locating adjacent to a single reflective boundary, such as the ground, or a wall." (Handbook of Sound System Design, ELAR, 1989, P. 106). And in the Low-Frequency Systems and Enclosures chapter, section Thiele-Small parameters, of his "Loudspeaker Handbook", Chapman & Hall, 1997, P. 58, John Eargle makes it even more clear, if it wasn't enough: "Modeling of the system's response functions assumes that the enclosure is mounted in a large wall (a so called 2 Pi, or half-space, boundary condition)." My understanding is that any software using T/S model should therefore assume 2 Pi boundary condition of use, not free space.

"One way of evaluating your box response with the above effects is to try and measure your box outside on the drive way using a test set from the likes of Parts Express at 2 metres with the box on the surface of your drive well clear of any structures" "Then start to move the box closer to a rear wall. You will notice the bass response change. By locating the box at a distance to the rear wall equivalent to your listening room you will have some idea on the impact of room gain" Bass wise, to me this is half-space front wave radiation, as inside a room, however with no reflections from walls and/or ceiling since there are none in that setup... Moving closer to a rear wall as you say, leads to quarter space radiation, as inside a room, however again with no wall and ceiling reflections in your setup. You can also get "some idea on the impact of room gain" by doing the same inside, but with reflections...

"But the point here is don't look at your box response simulation in isolation. Some experimenting will yield a much better sound in your room." Mostly agreed. Speaker placement experimentation MAY lead to better sounding, not automatically much better, since there are always constraints in a room.

"if you intend to use a Db drive rack much of this can be compensated with parametric equalisation." In my post # 59 I did suggest parametric EQ relief but on the driver's mid-bass rising response: "Adjustable Parametric EQ on the "agressive or offensive" mid-bass level is another interesting alternative..." Whereas your suggestion seems to be for the low end. Regards,

Richard

ivica
09-01-2017, 02:29 AM
Hi Ian, (And Robert)

I couldn't pass on this one (your post # 62). With all due respect, I don't know where you are getting some of that info, but mine is identified below.

"Before getting too carried away with a flat response attempt to consider the real impact of room gain and baffle step." Agreed. If a sub was placed in the middle of a room (away from boundaries) and on a pedestal, base or stand, its unlikely one would get the 6 db room gain from boundary (since not real half-space).

"Room gain is un predictable but normally courts below 150 Hz and I'd dependant on the woofer location on the baffle and distance from room boundary ie the wall floor junction." More or less agreed because room gain is somewhat predictable. Electro-Voice states, in the System Positioning section, that "... the audible location of a subwoofer operating at a sufficiently low crossover frequency (below about 150 hz) will not be particularly evident." (Data sheet, PI218L, Low-Frequency Sound reinforcement System, 1994, P.3) I understand from this that 150 hz, you also mentioned, is the point where bass frequencies start to get omnidirectional, and therefore more difficult to locate, plus can benefit from room boundary placement gain instead of "wrapping around" the box as "diffraction loss"...

"Proximity to the floor adds 6 Db room gain, proximity to floor and wall adds 12 Db room gain and proximity to a room corner/ floor adds up to 18 Db of room gain." Two of these numbers appear to be wrong. First, floor OR wall placement does provide half-space (2 Pi) environment that leads to 6 db room gain, but one has to mention compared to full-space (4 Pi, or free space) environment. Again, from the same E-V data sheet mentioned above, in the same System Positioning section on P.3: "Floor location provides the acoustic half-space environment associated with the 6.1% system efficiency noted in the Specifications sections." Moreover adds: "Location at a floor-wall junction (acoustic quarter space) doubles efficiency (a 3-db increase in acoustic power level)..." That is compared to floor location only. Then further adds: "Corner placement (acoustic eighth space) doubles efficiency again..." Which I understand means another 3 db increase compared to floor-wall location. So, if I count correctly, it would be 6 db gain from full-space to half-space, then 3 db gain from half-space to quarter space, and finally another 3 db gain from quarter space to eighth space, for a total of 12 db of possible room gain from speaker placement. Not exactly the same numbers as yours.

"Most bass reflex box simulator assume the baffle is suspended in free space." I think this statement is questionable. John Eargle (JBL) writes "The data calculated from the thiele/Small parameters refers only to the LF performance of the system ... Further, the analysis assumes that the loudspeakers will be locating adjacent to a single reflective boundary, such as the ground, or a wall." (Handbook of Sound System Design, ELAR, 1989, P. 106). And in the Low-Frequency Systems and Enclosures chapter, section Thiele-Small parameters, of his "Loudspeaker Handbook", Chapman & Hall, 1997, P. 58, John Eargle makes it even more clear, if it wasn't enough: "Modeling of the system's response functions assumes that the enclosure is mounted in a large wall (a so called 2 Pi, or half-space, boundary condition)." My understanding is that any software using T/S model should therefore assume 2 Pi boundary condition of use, not free space.

"One way of evaluating your box response with the above effects is to try and measure your box outside on the drive way using a test set from the likes of Parts Express at 2 metres with the box on the surface of your drive well clear of any structures" "Then start to move the box closer to a rear wall. You will notice the bass response change. By locating the box at a distance to the rear wall equivalent to your listening room you will have some idea on the impact of room gain" Bass wise, to me this is half-space front wave radiation, as inside a room, however with no reflections from walls and/or ceiling since there are none in that setup... Moving closer to a rear wall as you say, leads to quarter space radiation, as inside a room, however again with no wall and ceiling reflections in your setup. You can also get "some idea on the impact of room gain" by doing the same inside, but with reflections...

"But the point here is don't look at your box response simulation in isolation. Some experimenting will yield a much better sound in your room." Mostly agreed. Speaker placement experimentation MAY lead to better sounding, not automatically much better, since there are always constraints in a room.

"if you intend to use a Db drive rack much of this can be compensated with parametric equalisation." In my post # 59 I did suggest parametric EQ relief but on the driver's mid-bass rising response: "Adjustable Parametric EQ on the "agressive or offensive" mid-bass level is another interesting alternative..." Whereas your suggestion seems to be for the low end. Regards,

Richard


Hi Richard,

Generally speaking if we have TWO sources of sound (working together) very near each other, and producing the sound in the same frequency region, but independent each other (example each producing noise) we can expect the +3dB rise in the sound level, but if they are reproducing the same sound source (correlated sound) then the rise would be +6dB. Such behavior can be seen in the:

http://www.zainea.com/mutualcoupling.htm
http://www.audioheritage.org/vbulletin/showthread.php?39103-Dual-drivers-One-or-Two-chambers-in-enclosure&p=399606&viewfull=1#post399606

so if the distance between the sources is LESS then 0.5 Lambda (Lambda=345/f), or better to say LESS then 0.25*Lambda we can expect the rise in the response of MORE THEN +3dB, but not more then +6dB.

We can assume flat surface near the sound source as ideal reflecting surface (as a sound mirror), and that the sound source is not-directional (Omnidirectional) and IF THE DISTANCE BETWEEN THE SOURCE AND THE SURFACE IS LESS THEN 0.25*Lambda (or better 0.15*Lambda) then we can expect almost +6dB in rise in the sound level, because in such citcumstances such sound source and the surface behave as TWO correlated sound source that are near (twice the distance the sound source from the surface) each other.
If another surface is prezent perpendicular to the previous one, then (again imagine as another mirror) the sustem would behave as 4 (four) corelated sources working together, so another +6dB in the sound level can be expected, so totally +12dB, but again the surfaces are assumed to be less then about 0.15*Lambda from the sound source. If the distances from the surfaces are larger then mentioned, total rise would 'only' +6dB.

Asumming another perpendicular surface to the previously mentoned two, would give another +6dB rise in the sound level, as in such case it would behaves as 8 (eight) corelated sound sources, so totaly +18dB in the sound level, but again sound source has to be about less then 0.15*Lambda from any of the surfaces. As an example for f=170Hz (or less) Lambda=2m (or more), so the distance has to be less then 30cm from the surface(s). If the distances are larger then total gain would be reduced from +18dB to about +9dB (fot some specific frequency even less).
The whole scene would become more complicated if the directivity of the sound source is assumed. Not to mention that when the sound frequency rises, the infuence of the surface 'reflectivity' would become factor of influence, but for relayvely low frequency, and usual surface characteristics in our home, previously mentioned model can be assumed.
I would say that if we put the speaker relatively away (say about 1m) from the wall or the flore (ceiling) in the almost bookshelf arrangement then I would expect to get almost predicted LF response, and if we want to enhace LF section (but to be aware of the irregularities) then we can move the speaker near the flore arrangement. A lot of experiments has to be done to find out the best possible compromose.
In the previously mentioned, other in-the-room effects (multiple reflections, standing waves, reverberations,...etc) are not considered.

regards
ivica

RMC
09-02-2017, 11:28 AM
Hi Robert,

Re your post where you mentioned hoping not to have to use a series resistor with the woofer, and my post where I said I was not a fan of using a series resistor on a woofer. While looking for something else in my audio library (searching for A and finding B as often happens...) , here's what I found in Bullock On Boxes, 1991, P. 7, in the Design Box, examples # 2 and three, where additional resistance with woofer is covered.

(Talking about a cut-off frequency reduction with increased box size), here's what Bullock says in example # 2: "... which can be reduced even more by adding a resistor in series with the driver. This will increase Qts and reduce F3. In my opinion, added resistance tends to degrade other aspects of performance, so do not use it unless you must. Your own ears are best judge of the results, however." In example # 3 he uses a driver with a Qts of 0.28, adds resistance to it, and concludes "Thus, a resistor of 2/3 ohms in series with the driver will raise Qts to 0.32." A 14% increase.

The point here is that driver Qts is an important number (like Fs and Vas) in determining an enclosure's characteristics. Tampering with Qts (as a side-effect of wanting to reduce mid-bass rising response with a resistor) also means different box design parameter... The parametric EQ or small bass bump ideas have more appeal to me.

One more time, searching for A and finding A and B this time!, I came across Electro-Voice's equation for vent length tuning (Lv) on the 1993 spec sheet of 15" driver EVX-150A (P.4). I gave it a try with YOUR box numbers plugged-in to see. The vent length result is 1.09347" (or 1.1") which is still in the range of 1 to 1 1/4" mentioned before...

Richard

ivica
09-02-2017, 11:54 AM
Hi Robert,

Re your post where you mentioned hoping not to have to use a series resistor with the woofer, and my post where I said I was not a fan of using a series resistor on a woofer. While looking for something else in my audio library (searching for A and finding B as often happens...) , here's what I found in Bullock On Boxes, 1991, P. 7, in the Design Box, examples # 2 and three, where additional resistance with woofer is covered.

(Talking about a cut-off frequency reduction with increased box size), here's what Bullock says in example # 2: "... which can be reduced even more by adding a resistor in series with the driver. This will increase Qts and reduce F3. In my opinion, added resistance tends to degrade other aspects of performance, so do not use it unless you must. Your own ears are best judge of the results, however." In example # 3 he uses a driver with a Qts of 0.28, adds resistance to it, and concludes "Thus, a resistor of 2/3 ohms in series with the driver will raise Qts to 0.32." A 14% increase.

The point here is that driver Qts is an important number (like Fs and Vas) in determining an enclosure's characteristics. Tampering with Qts (as a side-effect of wanting to reduce mid-bass rising response with a resistor) also means different box design parameter... The parametric EQ or small bass bump ideas have more appeal to me.

One more time, searching for A and finding A and B this time!, I came across Electro-Voice's equation for vent length tuning (Lv) on the 1993 spec sheet of 15" driver EVX-150A (P.4). I gave it a try with YOUR box numbers plugged-in to see. The vent length result is 1.09347" (or 1.1") which is still in the range of 1 to 1 1/4" mentioned before...

Richard

i
Hi Richard,

the problem of using electronically assisted EQ has one problem, if driver as E145 is used.
For the Vb=225 Lit, Fb=45Hz, and if You use hi-pass (12dB/oct) EQ where Q=1.5 at 35Hz, almost flat response can be get ( F3=40.5Hz, without EQ, F3=51Hz), but maximal cone displacement would limit max input power to about 60W instead of about 150W without EQ.

regards
ivica

RMC
09-02-2017, 06:21 PM
Hi Ivica,

The parametric EQ suggested has NOTHING to do with the bass range. That suggestion was to correct, improve or reduce mid-bass rising response of E-145 instead of a series resistor. Please read my last posts again...

Richard

Ian Mackenzie
09-02-2017, 09:01 PM
Hi Invica,

I understand your reference to Jbl test data.

We are all able to express an opinion and that is good.

But my view is the kind of Jbl designs here with a 15 inch woofer the term book shelf is "name sake ".

They are floor standing loudspeakers.

Most of the blue baffle designs talked about here are not book shelf or more appropriately sofit mounted in a forum members home.(1)

Perhaps more pertinent is the fact that JBLs blue baffle monitors are sold out of Hifi retail shops to consumers. They are not building those into walls st home.

(1) Baffle diffraction and its complex nature are at work as is boundary reinforcement.

In some cases the impact of room boundary reinforcement offsets the baffle step.

If you google baffle step out loudspeaker baffle diffraction there are some good references and spreadsheets to model the impact.

It's a fact in contemporary loudspeaker design that baffle step compensation is a consideration as is room boundary reinforcement.(room gain)

My comments concerning room gain encompass room boundary influences as the source can be a point anywhere in space meaning the room.

This is a more difficult challenge in a two way design as you are trying to get one driver "the woofer" to behave a particular way. A 3 or 4 way system can purposely use a driver to overcome a particular issue.

Jbl use a standardised measurement approach but they have varied the design of the vented systems over the years to "incorporate" the impact in a variety of listening rooms and enclosure locations.

It not necessarily a good idea to take a manufacturers test results on face value.

Unless your wife is comfortable with you digging up the back yard you are not going to be doing equivalent measurements.

On bass reflex tuning no body doubts GT's approach to banana curve tuning of the statement systems.

The next point is that in a pure diy design you are not using a Jbl engineered design that was empirically evaluated with several prototypes.

Therefore what might appear good on paper can have a less than predictable results in reality. This was the point of my earlier posts.

It really depends on how far you want to go with your own diy project.

Any diy project is just that and it's a case of looking at what's in scope and within your means.

I always find it useful to look at Jbl did with certain drivers in their system designs.

As l said most of their home systems are empirical design iterations before these go into production

ivica
09-02-2017, 11:34 PM
.......I understand your reference to Jbl test data.

...
(1) Baffle diffraction and its complex nature are at work as is boundary reinforcement.
In some cases the impact of room boundary reinforcement offsets the baffle step.
If you google baffle step out loudspeaker baffle diffraction there are some good references and spreadsheets to model the impact.
It's a fact in contemporary loudspeaker design that baffle step compensation is a consideration as is room boundary reinforcement.(room gain)
My comments concerning room gain encompass room boundary influences as the source can be a point anywhere in space meaning the room.
......
It not necessarily a good idea to take a manufacturers test results on face value.
Unless your wife is comfortable with you digging up the back yard you are not going to be doing equivalent measurements.
On bass reflex tuning no body doubts GT's approach to banana curve tuning of the statement systems.
....
As l said most of their home systems are empirical design iterations before these go into production


Hi Ian,

Many thanks for the comments.
Just to remember that our speakers are not usually in opens-pace hanged on the tree, but near the one large surface.
I think that attached "Driver Stp Response" would give the best explanation.

regards
ivica

Ian Mackenzie
09-03-2017, 06:00 AM
Hi Richard and Invica,

Thank you both for the stimulating discussion.

Half space, box simulations , ground plane measurements can be a bit of challenge to make sense of at the best of times

I wrote the earlier post on the iphone at the airport gate lounge waiting for a flight.

I hope it made sense.

This is a simple link but l like it

http://www.mh-audio.nl/Groundplane.asp

In terms of references l use hard copy manuals for LEAP software, Bullock on Boxes and the Loudspeaker Cookbook.

But Enclosure Shop can actually simulate a lot of this stuff but it take a long time to render.

Unfortunately the scientist who wrote it died recently.

I have an older version of Sound Easy but it a complicated package to use.

I will post links to some interestingly online baffle diffraction simulator when l recover from the return flight.

As you point out the JBL measurements are on a roof top (half space)

Some also splice a ground plane measurement below 100 hertz.

The rooftop (in the ground) approach gives a cleaner graph which some affectionately call magazine curves!

Of late have been getting my hands dirty with some ground plane measurements outside.

I will check out the E145 in Bass box with the amended Vas.

Bassbox allows importing of room gain data and overlay on the box simulation.

http://www.tolvan.com/edge/help.htm

http://audio.claub.net/software/jbabgy/BDBS.html

Robh3606
09-03-2017, 09:37 AM
Just to add some thoughts and information. I have been using an E-145 sub-woofer combination for years now and have been pleased with response. I originally started with Le-14 subs and changed over to B380 2235's under. I see some concern about baffle step but I would not worry all that much as between the choice of the crossover point, placement/boundary reinforcement and potential mutual coupling between drivers through the crossover it gets a bit complicated. If you are running active you can stagger the levels on the drivers as well to give an added measure of response tailoring not to mention slopes, delay and EQ in the digital domain. I am posting the simulations I used in Bass Box to build my boxes just for information.

Rob:)

ivica
09-03-2017, 09:54 AM
Just to add some thoughts and information. I have been using an E-145 sub-woofer combination for years now and have been pleased with response. I originally started with Le-14 subs and changed over to B380 2235's under. I see some concern about baffle step but I would not worry all that much as between the choice of the crossover point, placement/boundary reinforcement and potential mutual coupling between drivers through the crossover it gets a bit complicated. If you are running active you can stagger the levels on the drivers as well to give an added measure of response tailoring not to mention slopes, delay and EQ in the digital domain. I am posting the simulations I used in Bass Box to build my boxes just for information.

Rob:)

Hi Rob,
It seems to me thay on 2235 (B380) model, a kind of 'Active HP EQ Filter' is applied, while on E145 is without such 'help'

regards
ivica

Robh3606
09-03-2017, 11:54 AM
Hello Ivica

The 2235's have a BX-63A to extend their response the E-145's are more or less mid-bass drivers so no LF assist. They are crossed at about 80hz or so. The boxes would just naturally roll off. They actually don't sound bad but are missing the first octave defiantly a 40Hz system with no subs in those 5 cubic ft boxes.

Rob:)

RMC
09-03-2017, 03:58 PM
Hi Ivica, Ian, Rob (and Robert)

In Yamaha's Sound Reinforcement Handbook, 2nd Ed., 1989, P. 229 they show the Effect of Boundary Conditions (how spl increases due to boundary effect) and the effect indicated is even further, than what I wrote in post # 66, from Ivica's/Ian's 6, 12 and 18 db increases: from free field to half-space + 3 db, from half-space to quarter-space another + 3 db and from quarter-space to eighth-space another + 3 db, for a total of 9 db (half of your totals!) from Yamaha. On the first boundary (full to half-space), Yamaha's number (+ 3 db) is not in accordance with John Eargle's 4 Pi to 2 Pi 6 db step mentioned in his Loudspeaker Handbook P. 104, but for the other boundaries at + 3 db each that is in agreement with the Electro-Voice's data sheet I quoted from in my post # 66 (BTW their data sheets are usually quite informative on system positioning (speaker placement) , mutual coupling, vent tuning, etc. even more so than JBL's).

By simple logic, which is not science and could be wrong, the 6/3/3 db room gain per boundary seems to make sense considering the first boundary is from sphere (full space) divided into half-sphere (half-space) for 6 db gain because it results from division of a larger surface (full to half). Then the smaller + 3 db for other boundary added would be because it's from dividing a smaller quantity (half of half-space = quarter-space) ?

I did also think of the mutual coupling analogy (like Ivica) when writing my post # 66 but it didn't seem to make sense in my mind, so I tossed it...

RE Ivica's post # 67 mentioning Mutual coupling as a model ( analogy?) for LF room gain, which also refers to one of your previous post dated 12-04-2016 in a Dual drivers Thread. In that latter post you reproduced, among others, "Figure 7-6 Details of mutual coupling", directly from JBL's Sound System Design Reference Manual (SSDRM), page 7-8 with no mention of source ("bad boy") to support your position here.

However, since I'm in that JBL document right now, I might as well mention that your theory (or the one you report about is obscure or esoteric on the origin of the second 3 db increase re mutual coupling) and is NOT suppported in JBL's SSDRM you "borrowed" from: "In addition to the double power handling capability afforded by the two units (possible + 3 db), the dotted curve shows a 3 db increase in transmission coefficient at low frequencies. This is due basically to the tendency for the two drivers to behave has a single unit with a larger cone diameter, and hence higher efficiency."(P. 7-8). Authors of SSDRM: George Augspurger and John Eargle...

Same explanation as I've always seen before, and I've quoted extensively before from John Eargle and E-V. Nothing new here, and more important nothing obscure or esoteric on the origin of each of the two 3db increases: one for doubled power handling (if used) and one for doubled efficiency. Enough said i guess, I'll stick to my stated sources/references regarding mutual coupling, as I'm quite comfortable with them and still willing to believe in Eargle's, JBL's and E-V's words on that issue for the time being, as in my post # 66.

To Ivica, again in your post # 72 your Pdf file titled "Driver step response" is partial only info, also taken from someone else with no mention of the source (MH-Audio.nl, Gound-plane Measurement) nor explanation...

To Ian, gone through my Bullock and Dickason (5th ed.) copies again and found no trace of LF room gain numbers (6/12/18 db) you mentioned in your post # 62. Not much on this from these two in the Hi-Fi side, so from the Sound Reinforcement side I quoted E-V's info in my post # 66, and John Eargle's plus Yamaha's such numbers in the present post.

To Rob, re post 74, the words of wisdom, from the sage man, as usual. Thanks for that enlighting statement. I can only hope/wish to reach that status some day, even though Audio has been my thing for 40+ years...

Regards,

Richard

Robh3606
09-03-2017, 06:33 PM
To Rob, re post 74, the words of wisdom, from the sage man, as usual. Thanks for that enlighting statement. I can only hope/wish to reach that status some day, even though Audio has been my thing for 40+ years...

Hello Richard

Hey I am no sage we are both into this for about the same amount of time. Not for nothing but with all the Hocus Pocus in this hobby there is no substitute for a willingness to read and educate yourself and then just use some common sense which you seem to be doing. I have no doubt that whatever you decide will workout just fine. Please keep us posted on how things go.

Rob:)

RMC
09-03-2017, 08:57 PM
Hi Rob,

Thanks for your good words. Your "bottom line" type conclusion in post # 74 and remedy for it could not have been said better by me: "I see some concern about baffle step but I would not worry all that much as between the choice of the crossover point, placement/boundary reinforcement and potential mutual coupling between drivers through the crossover it gets a bit complicated. If you are running active you can stagger the levels on the drivers as well to give an added measure of response tailoring not to mention slopes, delay and EQ in the digital domain"

As for the "Hocus Pocus in this hobby", well I kind of find it difficult to swallow (i.e. annoying) when members don't take the time to verify their info before posting it on a public forum, seen by many who may think all is true here, or don't show respect for author's rights and work by copying publications right and left with no mention of sources. To acknowledge the expert who wrote the stuff is elementary courtesy it seems. And may improve the quality of info shared vs hearsay. I try to. Regards,

Richard

ivica
09-03-2017, 10:27 PM
Hi Ivica, Ian, Rob (and Robert)

.............
I did also think of the mutual coupling analogy (like Ivica) when writing my post # 66 but it didn't seem to make sense in my mind, so I tossed it...

RE Ivica's post # 67 mentioning Mutual coupling as a model ( analogy?) for LF room gain, which also refers to one of your previous post dated 12-04-2016 in a Dual drivers Thread. In that latter post you reproduced, among others, "Figure 7-6 Details of mutual coupling", directly from JBL's Sound System Design Reference Manual (SSDRM), page 7-8 with no mention of source ("bad boy") to support your position here.

However, since I'm in that JBL document right now, I might as well mention that your theory (or the one you report about is obscure or esoteric on the origin of the second 3 db increase re mutual coupling) and is NOT suppported in JBL's SSDRM you "borrowed" from: "In addition to the double power handling capability afforded by the two units (possible + 3 db), the dotted curve shows a 3 db increase in transmission coefficient at low frequencies. This is due basically to the tendency for the two drivers to behave has a single unit with a larger cone diameter, and hence higher efficiency."(P. 7-8). Authors of SSDRM: George Augspurger and John Eargle...

.....
To Ivica, again in your post # 72 your Pdf file titled "Driver step response" is partial only info, also taken from someone else with no mention of the source (MH-Audio.nl, Gound-plane Measurement) nor explanation...

Regards,
Richard


Hi Richard,

Many thanks for Your suggestion about my posts here on the Forum. I have usually put the sources of some of the explanations when I thought that are not so well known, but I have to say that You are right that the other authors have to be referenced.

But if You read MY explanation with some care, You will note:

"..Generally speaking if we have TWO sources of sound (working together) very near each other, and producing the sound in the same frequency region, but independent each other (example each producing noise) we can expect the +3dB rise in the sound level, but if they are reproducing the same sound source (correlated sound) then the rise would be +6dB. Such behavior can be seen in the:

http://www.zainea.com/mutualcoupling.htm
http://www.audioheritage.org/vbullet...l=1#post399606 (http://www.audioheritage.org/vbulletin/showthread.php?39103-Dual-drivers-One-or-Two-chambers-in-enclosure&p=399606&viewfull=1#post399606)

so if the distance between the sources is LESS then 0.5 Lambda (Lambda=345/f), or better to say LESS then 0.25*Lambda we can expect the rise in the response of MORE THEN +3dB, but not more then +6dB.

We can assume flat surface near the sound source as ideal reflecting surface (as a sound mirror), and that the sound source is not-directional (Omnidirectional) and IF THE DISTANCE BETWEEN THE SOURCE AND THE SURFACE IS LESS THEN 0.25*Lambda (or better 0.15*Lambda) then we can expect almost +6dB in rise in the sound level, because in such circumstances such sound source and the surface behave as TWO correlated sound source that are near (twice the distance the sound source from the surface) each other.
..."

So the frequency where F/R the rise +6dB depends of the distance of the source from the large surface.

If talking about te EFFICIENCY when dealing with the operations of the two drivers, do not forget that their combined impedance is reduced to the half of the single driver impednace, so they take twice larger current from the amp then a single driver operating on the same amp voltage output so only +3dB can be get, as shown on the JBL data documet You have mentioned in Your #77 post here.

Regards
ivica

Ian Mackenzie
09-04-2017, 07:14 AM
Okay

To get to this l read Dons comments in the Library regards the final Everest design and l looked at 4313 post about the low Q drivers and the Vas error.

I then thought about Everest schematic and increased the Qts from 0.25 to 0.28 allowing for dcr of the chokes which seemed reasonable.

Plug that in to Bassbox and 3 minutes later you have an indicator of the tuning for a single E145

I would imagine +-2 Hz tuning would give you something quite acceptable either with a passive network or active.

I then added the Martin Colloms room gain curve that for anyone who can follow this so far knows it requires no explanation.


These are educated assumptions based on a working design

The box details below are with the above assumptions (Everest design)

When trying to figure out how JBL make a JBL woofer work I always look at what they did before screwing around with a diy design from scatch. There nothing in it really

8 cu ft
Normal fill
Fb 35.3Hz
F3 2pi 66.5 Hz
F3 in room 32 Hz with Colloms curve per the illustrated curve QTS=0.280



Raw driver box details (QTS 0.25, no room gain)

8 cu ft
Normal fill
Fb 34.6 Hz
F3 2pi 91 Hz per the illustrated curve (no Colloms rom gain, QTS=0.250)
-6 Db 2pi 38 Hz

The 2 ports are 4 inch 2.36 inches long

One E145

The tuning is really about the room and getting the best Xmax out of those woofers
You could do what Rob did in a smaller box with a sub but I sense you want to have a go at using the E145 like JBL did with a large horn

An 8 cu ft box is scalable for your horn

2 E145 per channel seems excessive unless you are going to use it in a large room.


Of course using the Drive rack makes most of this moot. Just eq out the response below 150Hz

Jbl did opt for the B460 sub for the Everest

In the Everest network Greg incorporated a network in the woofer to compensate for corner placement (see the manual)


A very useful link below if you wish to understand what a 2pi loudspeaker load is all about.

As I mentioned earlier if you look closely not all JBL system tech sheets are 2 pi response measurements. Some are also ground plane and some are a cut and paste of both as hand written notes advise probably by GT.

https://trueaudio.com/st_spcs1.htm

If you understand that then it is obvious that designing a bass reflex box to a maximally flat butterworth QB3 bass response in a 2 pi load on a similator will result in an overly excessive bass response that has the potential to hump up below 100 hertz depending on where you put the enclosure.

RMC
09-04-2017, 04:30 PM
Hi Ivica,

RE Ivica Post # 80

"But if You read MY explanation with some care, You will note:"


"..Generally speaking if we have TWO sources of sound (working together) very near each other, and producing the sound in the same frequency region, but independent each other (example each producing noise) we can expect the +3dB rise in the sound level, but if they are reproducing the same sound source (correlated sound) then the rise would be +6dB. Such behavior can be seen in the: " (...)


"If talking about te EFFICIENCY when dealing with the operations of the two drivers, do not forget that their combined impedance is reduced to the half of the single driver impednace, so they take twice larger current from the amp then a single driver operating on the same amp voltage output so only +3dB can be get, as shown on the JBL data documet You have mentioned in Your #77 post here."

I did read many times YOUR explanation and it still doesn't look more convincing to me, hence my "obscure or esoteric" qualification for that theory in a previous post. Without going into small details, first there's a contradiction between "working together" and "but independant of each other". Second, "producing noise" or "reproducing the same sound source (correlated sound)" doesn't really make a difference to me, sound is sound, and NONE of the experts I consulted (Dickason, Eargle, JBL, E-V) make that difference in real life... Maybe they do at the University of Southampton, UK in the article you referred to. But that would be at a quite different level of sophistication than others ... Hence my "esoteric" qualification.

As for the "efficiency" aspect you describe for drivers in parallel, Eargle explains that with more details (but with same results) than the quote I made in post # 77, regarding mutual coupling, from JBL's Sound System Design Reference Manual, 1999.

"It is common in many applications to mount two or more LF drivers adjacent to each other on the same baffle, normally driving them electrically in parallel. At the same time, the drivers are acting acoustically in parallel. (...) Note that the response of the dual driver system is 3 db greater than the single unit, both with the same electrical power input. This increase is caused by the fact that the two closely coupled drivers behave essentially like a single "new" driver with twice the cone area, ... The doubling of cone area will result in a doubling of efficiency, ... The term "mutual coupling" is often used to describe this effect. It is further obvious that the dual driver system can handle twice the electrical input power than the single unit. Therefore, there is a net 6 db greater output capability with the dual unit as opposed to the single unit." John Eargle, Loudspeaker Handbook, Chapman & Hall, 1997, P. 79-80, in the Parallel Operation sub-section of the Transducers in Acoustical Series and in Parallel section. 3 db re coupling, and 3 db re power handling, if used.

As everyone can see, no magic, no obscure science, no BS, no "esoteric" theory, just simple principles well explained by one of the Masters in the field, long associated with JBL, which has/had one of the most advanced speaker lab on the planet and some of the most talented Speaker Engineers on the planet he had full access to every day the sun shined... AMEN, as they say.

As for impedance and voltage, Dickason mentions "The advantage of multiple driver combinations is more obvious at higher power levels. [doesn't that sound/look like or refer to the higher power handling issue?] (...) The voltage input to get this SPL is 12.68 V for a single driver and 6.35 V for the two-and four-driver combinations." The voltage is the same for four as for two drivers because as he says: "... but putting two parallel sets of woofers in series decreases gain by - 3 db, for a net change of zero when compared to the output of the two-woofer box." In other words, he used parallel/series connections in the four-woofer box instead of four parallel. (Vance Dickason, The Loudspeaker Design Cookbook, 5th Ed., 1995, P. 30-1, in the Multiple Woofer Formats section, Standard Configuration). This is from the closed-box LF Systems chapter because in the Vented box chapter, Dual Woofer Formats section, he says to refer to the former: "Everything discussed in the closed-box section applies when you are using a vented enclosure."(p.61).

Since I'm a fair player, and because it MAY (?) help your cause/theory, Eargle does mention about mutual coupling, in his other book I have, "The above equation assumes that the LF units are located as closely together as possible, and this is an important requirement in getting the most out of mutual coupling." (John Eargle, Handbook of Sound System Design, ELAR, 1989, P. 115). The nominal spacing between drivers is considered in the equation he mentions. But at NO time in his books, same for Dickason, JBL and E-V, do they go to the sophistication level mentioned by you.

Again, enough said on this matter for me and I'm paraphrasing myself from post # 77: Nothing new here, and more important nothing obscure or esoteric on the origin of each of the two 3db increases: one for doubled power handling (if used) and one for doubled efficiency. I'll stick to my stated sources/references regarding mutual coupling, as I'm quite comfortable with them and still willing to believe in Eargle's, Dickason's, JBL's and E-V's words on that issue for the time being. Regards,

Richard

ivica
09-05-2017, 12:38 AM
Hi Ivica,

RE Ivica Post # 80

"But if You read MY explanation with some care, You will note:"


"..Generally speaking if we have TWO sources of sound (working together) very near each other, and producing the sound in the same frequency region, but independent each other (example each producing noise) we can expect the +3dB rise in the sound level, but if they are reproducing the same sound source (correlated sound) then the rise would be +6dB. Such behavior can be seen in the: " (...)

.......

I did read many times YOUR explanation and it still doesn't look more convincing to me, hence my "obscure or esoteric" qualification for that theory in a previous post. Without going into small details, first there's a contradiction between "working together" and "but independant of each other".
Second, "producing noise" or "reproducing the same sound source (correlated sound)" doesn't really make a difference to me, sound is sound, and NONE of the experts I consulted (Dickason, Eargle, JBL, E-V) make that difference in real life... Maybe they do at the University of Southampton, UK in the article you referred to. But that would be at a quite different level of sophistication than others ... Hence my "esoteric" qualification.

...............
As everyone can see, no magic, no obscure science, no BS, no "esoteric" theory, just simple principles well explained by one of the Masters in the field, long associated with JBL, which has/had one of the most advanced speaker lab on the planet and some of the most talented Speaker Engineers on the planet he had full access to every day the sun shined... AMEN, as they say.

.......Regards, Richard

Hi Richard,

It would be very difficult to understand each other (because MY English is very bad, as not my native language), but if You are not aware the differences between correlated and uncorrelated sources, the rest of the explanations can not be logical. May be some of the AH forum member can help.

Receive My Best Regards
Ivica

RMC
09-05-2017, 10:48 AM
Hi Ivica,

It seems I'm not the only one in that situation since Dickason, Eargle, JBL, E-V don't mention that issue re mutual coupling. Or they felt that it was not of importance or not worth mentioning in their writings... If this had been critical I guess they would have covered it. Regards,

Richard

ivica
09-05-2017, 01:53 PM
Hi Ivica,

It seems I'm not the only one in that situation since Dickason, Eargle, JBL, E-V don't mention that issue re mutual coupling. Or they felt that it was not of importance or not worth mentioning in their writings... If this had been critical I guess they would have covered it. Regards,

Richard

Hi Richard,
You are right. I believe that they did not want to deal with small frequency region.
If center of the driver is about 1m away from the surface then real influence (+6dB) would be for the frequencies LESS then 52Hz, and for the higher frequencies (say over 60Hz) almost +3dB can be assumed.

regards
ivica

Ian Mackenzie
09-08-2017, 05:04 AM
Okay you experts

Here is a trick question

When you double the cone area with two identical woofers for the same output spl what is the difference in the cone excursion of the drivers? (assuming close proximity)

Is it the same, half or quarter?

Now don't go and look up a reference and quote it like you read it out of a book

Think about it and type in the answer

robertg
09-10-2017, 07:14 PM
So I installed the woofers today and played a bit. I found a sine wave sweep that I could adjust so I played it through the speakers from 30Hz to 55 Hz. At a low volume level the woofers would stop vibrating from 47Hz to 50Hz. When I blocked one vent it would drop approximately 9 Hz and the woofer vibration would stop for a period of 2Hz instead of three. I laid the speakers on their backs and put a popcorn kernel on the cone so I could tell when they stopped vibrating.

Does this mean the enclosure is tuned to 47Hz, 50Hz or somewhere in between?

I ordered six speaker port tubes with flanged ends, they are four inches long and they should slide right in to my 4" plumbing pipe ports. From what I have read they should be slightly longer than the 1.25" that I have right now to lower the frequency. My target was 45Hz.

This is what I ordered.

RMC
09-11-2017, 12:17 AM
Hi Robert,

Good news, you are in fact tuned in the 47-50hz range. Pretty close. This need not be precise to 1 hz close. You can still try though. Also use a finger very lightly touching the cone near the surround to get the feeling for yourself, though the popcorn is clever. To get a bit lower to 45 hz you'll need little longer vents, not much. But better to have little too much which can be cut than not enough... Trial and error tuning, but real life measurements, not theory ! Once your tests are done you'll have only one vent thick right? Regards,

Richard

RMC
09-12-2017, 09:07 PM
Hi Ian,

Re your sept 8 post # 86 with a tricky question about excursion when doubling cone area. I see nobody replied to you 4 days later... For myself I didn't reply since I had already seen part of the answer, and may be told I cheated.

However, If you look at my post # 82 dated sept 4 (4 days before yours) you can see I quoted from Dickason's Cookbook, 5th ed., p. 30-1. On those same Dickason pages I read 4-5 days before your question, a partial or incomplete answer to your question appears. So no real contest. Read below for more.

However again, I'm NOT satisfied with his explanation of driver coupling effect on sensitivity, doesn't seem to make sense, looks like a contradiction or typo made its way in his text. This is why in my sept 4 # 82 post I quoted John Eargle instead for the coupling effect on sensitivity issue, and Dickason on the voltage/impedance issue.

That speaker experts seem to disagree on science (!) is surprising, but does exist. Look at Bullock's book on p. 62 bottom right column where he says + 6 db for two woofers in parallel, and on p. 66 left column from the middle and on where he repeats that, as opposed to Eargle's clear explanation of + 3db for coupling and another possible + 3 db for power handling I quoted in post # 82 (Handbook of Sound System Design, p. 114, and Loudspeaker Handbook, p. 79). Then have a look at Dickason's, 5th ed., p.30 for a confusing or confused explanation of 3 vs 6 db in 1, 2, and 4 woofer formats ...

I tend to give more credibility to Eargle since his manuscript was reviewed before publication by W. J. J. Hoge, another well-known Speaker Engineer (CTS, JBL, etc.), who would normally have picked-up a gross error... JBL's own Sound System Design Reference Manual says the same as Eargle (Authors: Augspurger and Eargle).

Same power input to identical single and double-woofer (in parallel and closely mounted) boxes, gives a 3 db sensitivity advantage to the double-woofer box and cone excursion would be half that of a single woofer box. Dickason stops here, the rest is mine.

This makes sense because a larger cone area can move more air or "take a bigger "bite" at it" and need not go as far (excursion) to reproduce the same sound. If I remember correctly the good old days, the E-V 30" woofer and the Hartley 21" woofer didn't have nor needed a lot of Xmax considering their huge cone area that moved lots of air more efficiently.

But since you mention specifically "for the same output spl" then that would imply a half reduction in input power to the double-woofer box (to get - 3 db) for spl to be equal to that of single woofer box. Logically, lower input also means less excursion and distortion, therefore the answer would be "quarter", if its already half the cone travel at + 3 db as mentioned by Dickason for double-woofer compared to single. Regards,

Richard

Ian Mackenzie
09-12-2017, 11:31 PM
1/4 excursion is correct

You are correct distortion is lower at 1/4 the excursion.

The trade off is double the enclosure size.

ivica
09-13-2017, 01:33 AM
Hi Ian,

Re your sept 8 post # 86 with a tricky question about excursion when doubling cone area. I see nobody replied to you 4 days later... For myself I didn't reply since I had already seen part of the answer, and may be told I cheated.

However, If you look at my post # 82 dated sept 4 (4 days before yours) you can see I quoted from Dickason's Cookbook, 5th ed., p. 30-1. On those same Dickason pages I read 4-5 days before your question, a partial or incomplete answer to your question appears. So no real contest. Read below for more.

However again, I'm NOT satisfied with his explanation of driver coupling effect on sensitivity, doesn't seem to make sense, looks like a contradiction or typo made its way in his text. This is why in my sept 4 # 82 post I quoted John Eargle instead for the coupling effect on sensitivity issue, and Dickason on the voltage/impedance issue.

That speaker experts seem to disagree on science (!) is surprising, but does exist. Look at Bullock's book on p. 62 bottom right column where he says + 6 db for two woofers in parallel, and on p. 66 left column from the middle and on where he repeats that, as opposed to Eargle's clear explanation of + 3db for coupling and another possible + 3 db for power handling I quoted in post # 82 (Handbook of Sound System Design, p. 114, and Loudspeaker Handbook, p. 79). Then have a look at Dickason's, 5th ed., p.30 for a confusing explanation of 3 vs 6 db in 1, 2, and 4 woofer formats ...

I tend to give more credibility to Eargle since his manuscript was reviewed before publication by W. J. J. Hoge, another well-known Speaker Engineer, who would normally have picked-up a gross error... JBL's own Sound System Design Reference Manual says the same as Eargle (Authors: Augspurger and Eargle).

Same power input to identical single and double-woofer (in parallel and closely mounted) boxes, gives a 3 db sensitivity advantage to the double-woofer box and cone excursion would be half that of a single woofer box. Dickason stops here, the rest is mine.

This makes sense because a larger cone area can move more air or "take a bigger "bite" at it" and need not go as far (excursion) to reproduce the same sound. If I remember correctly the good old days, the E-V 30" woofer and the Hartley 21" woofer didn't have nor needed a lot of Xmax considering their huge cone area that moved lots of air more efficiently.

But since you mention specifically "for the same output spl" then that would imply a half reduction in input power to the double-woofer box (to get - 3 db) for spl to be equal to that of single woofer box. Logically, lower input also means less excursion and distortion, therefore the answer would be "quarter", if its already half the cone travel at + 3 db as mentioned by Dickason for double-woofer compared to single. Regards,

Richard


Hi RMC,

Please read
http://trace.tennessee.edu/cgi/viewcontent.cgi?article=3910&context=utk_gradthes

I think there are a lot of answers. especially section : "Mutual coupling.."
"....2.3 Mutual Coupling
The concept of mutual coupling between loudspeakers is familiar to anyone who has mounted two loudspeakers close together. The power output of the two loudspeakers is approximately four times (+6dB) that of a single loudspeaker. Also, if you double the area of the diaphragm of
a loudspeaker drive-unit, given the same diaphragm velocity, the power output will again increase by +6dB. Reference to equation (2) shows that introducing a second loudspeaker close to a first will approximately double the pressure on each of the diaphragms, thereby doubling the power output of both loudspeakers.
What is perhaps less obvious however, is how introducing a distant second loudspeaker can double the power output of a loudspeaker. For the 3m separation and 0.15m radius of the pair of loudspeakers in the above examples, the magnitude of the pressure on loudspeaker A due to the operation of loudspeaker B is approximately one twentieth of the pressure on A due to its own velocity. How can an increase in pressure of 5% cause a doubling of power output? The answer lies in the phase of the two pressures. At low frequencies, the pressure on the surface of A due to its own velocity is almost in phase quadrature with the velocity - the radiation impedance is almost totally reactive - whereas that from B arrives almost in-phase with the velocity due to the propagation distance involved. Equation (2) tells us that it is only the in-phase part of the pressure that is responsible for power output. As the distance d is decreased, the magnitude of the pressure due to the second source increases but its phase approaches that of the pressure due to the velocity of the first source - the power increase remaining at +6dB but extending higher in frequency - until the "two close loudspeakers" situation exists. As can be seen from equation (3), the frequency up to which the mutual coupling occurs is determined by the distance between the two sources; as the propagation distance approaches half a wavelength the phase of the pressure from the second source is no longer in phase with the velocity. The distance over which mutual coupling occurs is known as the extent of the hydrodynamic near field of the loudspeakers.
...."

or read here:
https://books.google.com/books?id=TscrBgAAQBAJ&pg=PA21&dq=loudspeaker+and+headphones+handbook+mutual+coup ling&hl=en&sa=X&ved=0ahUKEwjlm4S74bbNAhXGcz4KHeMvDc4Q6AEIJzAA#v=on epage&q=loudspeaker%20and%20headphones%20handbook%20mutu al%20coupling&f=false


regards
Ivica

RMC
09-13-2017, 10:39 AM
Hi Ian,

To me, It's not only a question of being correct (which someone can get with a lucky guess), but more important is being able to explain why it is so, as I did.

Re your statement "The trade off is double the enclosure size." The enclosure size is not really a "trade-off" in my view since for that larger size you get double woofers and more output (these two are not give away to get something else, but rather additions).

After writing my post # 89 I thought about another way of saying the same thing as I did differently:
Halving of power to double-woofer box, to match 3 db lower spl from single woofer box, results in another halving of the previously halved excursion for coupled double-woofer box. Since the half of a half is one quarter, therefore the answer is one quarter of the excursion, at same spl, compared to single woofer box... Regards,

Richard

P.S. Ivica you keep bringing back the SAME text on and on that I already commented on... this is getting to look like a fixation on your part.

Ian Mackenzie
09-13-2017, 11:40 AM
This is no a PA website.

If the member has a Barn or Shed like l have seen in Missouri l get it.

If he drives Monster trucks l get it

Ian Mackenzie
09-13-2017, 12:18 PM
Hi lnvica,

That is a good paper. I enjoyed reading it.

Newell and Holland also did a study on horns.

Newell still designs studios and monitors in Europe

He also has a book(s) published on the subject.

I think JBLs stated sensitivity on the 4355 confirms the situation on the woofer.

http://www.audioheritage.org/vbulletin/showthread.php?10614-4355

As a practical matter (2) 2235H last longer than a single 2235H from a reliability perspective.

Ian Mackenzie
09-13-2017, 06:16 PM
My only feedback here is try and avoid quote responses too often.

It makes it a very long winded read

Try and paragraph your thoughts, not big blocks as it difficult to read.

And there is nothing wrong with intellectual curiosity as long as it relevant to the origin of the thread

If this creates a robust discussion the mark a Mod to move those posts into a new thread.

ivica
09-14-2017, 03:33 AM
P.S. Ivica you keep bringing back the SAME text on and on that I already commented on... this is getting to look like a fixation on your part.

Hi Richard,

If carefully read the pages 17 ... 22 in the suggested link,

https://books.google.rs/books?id=TscrBgAAQBAJ&pg=PA21&dq=loudspeaker+and+headphones+handbook+mutual+coup ling&hl=en&sa=X&redir_esc=y#v=onepage&q=loudspeaker%20and%20headphones%20handbook%20mutu al%20coupling&f=false

from the: "Loudspeaker and Headphone Handbook", edited by John Borwick
I believe that everything would be clear, why at low frequencies (relative to the sound sources distances) conclusions are different then at the higher frequencies.

All of my effort here is not only to convince You, but mostly to give some information to the other AH Forum members, who are puzzled by some not technically precise information that can be get from lot of (even respectable) authors 'here-and-there' (some of them mentioned in Your posts).
Just for Your reminder:
1.even JBL said that they have to 're-tune' their card for the JBL4343 applied in the bi-amp mode (to be -6dB at the crossover frequency)
so please read
http://www.audioheritage.org/vbulletin/showthread.php?774-4355-3155-clones&p=6248&viewfull=1#post6248

2.remember why LR-networks (has -6dB for the lower crossover frequency solution...)

regards
ivica

Ian Mackenzie
09-14-2017, 06:53 AM
Ivicta has a valid point

Ian Mackenzie
09-14-2017, 07:14 AM
Anyway l have excavated a hole for in the ground loudspeaker measurements.

It's the way Jbl does it

So if you have a big box come and see me!

It needed an excavator lifted over the house by a large crane.

Spared no expense.

RMC
09-14-2017, 10:59 AM
Hi Ivica,

Trying to convince me I already replied to that. Giving info to other members is great that's what I do. But stating "... who are puzzled by some not technically precise information that can be get from lot of (even respectable) authors 'here-and-there' (some of them mentioned in Your posts)." is grossly exagerated.

I've seen here nobody puzzled but you. Authors "here and there"? Jbl, Yamaha, E-V, Augspurger, Bullock, Dickason, Eargle, I don't see them as "here and there" and find that insulting to them and me... If you don't believe in JBL then why are you here in this site? Plus I did outline specific contradictions among experts... So I do think my info is more varied, balanced and complete than yours (i.e. gives a better picture).

Richard

ivica
09-14-2017, 11:43 AM
Hi Ivica,

Trying to convince me I already replied to that. Giving info to other members is great that's what I do. But stating "... who are puzzled by some not technically precise information that can be get from lot of (even respectable) authors 'here-and-there' (some of them mentioned in Your posts)." is grossly exagerated.

I've seen here nobody puzzled but you. Authors "here and there"? Jbl, Yamaha, Augspurger, Bullock, Dickason, Eargle, I don't see them as "here and there" and find that insulting to them and me... If you don't believe in JBL then why are you here in this site? Plus I did outline specific contradictions among experts... So I do think my info is more balanced than yours.

Richard

Hi Richard,

Not to argue with You, I can understand from your statements that term "speaker mutual coupling" MEANS NOTHING, so I only wonder who on Earth "introduce" such term that from Your point of view is irrelevant.
As shown in my previous post, even JBL have accepted the evident present of the mentioned "speaker mutual coupling" phenomena,

http://www.audioheritage.org/vbulletin/showthread.php?774-4355-3155-clones&p=6248&viewfull=1#post6248

so here we are not in the church to talk about anybody personal belief or thrust, here I am talking about real physical law that exist in the sound propagation, but understanding such phenomena can not be explained with easy logic analogy.

Respecting the great scientist You have mentioned, I have said "...not technically precise information..." , so neglecting special cases where the sound sources are very near each other (relative to the wave length of the frequencies of the reproduced sound).

regards
ivica

Ian Mackenzie
09-14-2017, 02:37 PM
I have no interest in the different point of view here but l would suggest the point of the Holland article is that it gives a more complete understanding by discussing not just a single case of "mutual coupling" but the wider and equally important and less known relationship when using two drivers at increased distances.

I don't think Invica can be accused of jaw slapping here as he has bought new and fresh information that is not obvious but important in practice.

But l do think it's important as a poster to demonstrate with some examples even with a graphic how a quoted reference applies and what it means in A) your "own words" and B) so anyone other than yourselves can relate more than a reference to their own situation.

In terms of clarity it might be easier to use a footnote (1) and place a link or full detail of your reference st the bottom of the post under References

We do have an annex is the reference section where anyone can go read an article btw.

Otherwise just quote the link and let someone read it for themselves.

RMC
09-16-2017, 11:04 AM
Hi Ian,

Thanks for your summary of the Holland article: "...discussing not just a single case of "mutual coupling" but the wider and equally important and less known relationship when using two drivers at increased distances."

What would then be the interest of "using two drivers at increased distances" as you say and at the same time wanting the mutual coupling effect? Specially in view of Eargle's statement that I quoted in post # 82:

"The above equation assumes that the LF units are located as closely together as possible, and this is an important requirement in getting the most out of mutual coupling." (John Eargle, Handbook of Sound System Design, ELAR, 1989, P. 115). The nominal spacing between drivers is considered in the equation he mentions. But at NO time in his books, same for Dickason, JBL and E-V, do they go to the sophistication level mentioned by you."

Seems to me either you want the effect or not. Could someone show a desire for a "mid-way" or "middle of the road" coupling effect? For sensitivity matching issues maybe? Or for lobing related issues of closely spaced drivers?

Richard

RMC
09-17-2017, 07:51 PM
Hi Ian and Ivica,

RE MUTUAL COUPLING ADDITIONAL ISSUE RAISED BY IVICA AND CORRELATED/UNCORRELATED SOUND

Looking for something else in Dickason's Cookbook, Crossover Networks chapter, I came across something quite interesting in relation to the above-mentioned subject matter. No wonder I didn't see it in the "multiple woofer format" (mutual coupling) section of his book, since he covers it with X-over issues.

The theory outlined in the Holland article seems to have its objectors, not the least of which appears to be Dickason himself in pretty strong terms that one rarely sees in tech books, in the section dealing with Crossover Network and Power Response. Quoting his whole explanation would be much too long (short quotes with reference are preferred by some, reader can look for himself), so here are the "juicy" parts of his disagreement:

After talking about conventional wisdom re how power response is derived differently on and off axis, correlated phase for the former and "as if phase were uncorrelated" for the latter, he mentions "Although there is some disagreement as to what importance, if any, should be given to the power response difference...". (...)

"Although it is not popular to go against the mainstream of thought in any field, this view of power response is simply not correct. The reality is much simpler." (...) "Calculating a crossover's power response as though the signals are uncorrelated is unjustified, in my view." (...).

"But when two drivers are mounted on the same baffle, radiating from very nearly the same plane and being fed by the same program material, there is no other way to process the two signals as being anything but phase correlated. They are phase correlated on-axis and they are phase correlated in the power domain. No difference exists between the power response of any crossover network and the on-axis response." (...). (Vance Dickason, The Loudspeaker Design Cookbook, 5 th ed., 1995, P. 96-100).

I understand from Dickason that only some distance between the drivers could justify otherwise. Why would someone do that if it "defeats the purpose"? What would be the interest in doing so in the context of wanting mutual coupling, subject to what mentioned in my post # 102?

I think the above explains the reason why many (JBL, E-V, Eargle, etc.) don't seem to bother with the precision level outlined by the theory (i.e. too much sophistication for little or nothing in practice, if coupling done correctly). Regards,

Richard

Ian Mackenzie
09-17-2017, 09:31 PM
I think the key issue is context - A stereo pair or second loudspeaker 3 metre distance

Secondly, I don't think its appropriate to be arbitrating or questioning on what you think two scientists are saying or not saying on this site.

If you have a concern or need clarity on what you "think" just email them first.

They will get back to you and you can then report on the "truth" a supposed to diatribe debate.

In the past I alway got prompt replies from the these guys be it Douglas Self, Philip Newell, Nelson Pass, Seigfried Linkwitz, Charles Hanson.

quote for pdf Mutual coupling Dr Holland:

"What is perhaps less obvious however, is how introducing a distant second loudspeaker can double the power output of a loudspeaker. For the 3m separation and 0.15m radius of the pair of loudspeakers in the above examples, the magnitude of the pressure on loudspeaker A due to the operation of loudspeaker B is approximately one twentieth of the pressure on A due to its own velocity. How can an increase in pressure of 5% cause a doubling of power output? The answer lies in the phase of the two pressures. At low frequencies, the pressure on the surface of A due to its own velocity is almost in phase quadrature with the velocity - the radiation impedance is almost totally reactive - whereas that from B arrives almost in-phase with the velocity due to the propagation distance involved"

RMC
09-18-2017, 11:17 AM
Hi Ian,

"A stereo pair or second loudspeaker 3 metre distance" Is quite a different story and has nothing to do with what is commonly known and used for "mutual coupling" in sound reinforcement for example. That's the only issue raised by me. Other ways of getting "mutual coupling" may exist (e.g. Holland, and described by himself as "perhaps less obvious") however they are far from being widespread, and even talked about in many loudspeaker books...

Nobody has asked anyone to arbitrate or question what I think scientists say or don't say... That's purely in your mind. Dickason's quote in post # 103 only shows there are other ways of thinking, has Holland's does, but the latter remains unusual and rarely talked about in "mutual coupling" circles...

Richard

ivica
09-18-2017, 10:54 PM
Hi Ian,

"A stereo pair or second loudspeaker 3 metre distance" Is quite a different story and has nothing to do with what is commonly known and used for "mutual coupling" in sound reinforcement for example. That's the only issue raised by me. Other ways of getting "mutual coupling" may exist (e.g. Holland, and described by himself as "perhaps less obvious") however they are far from being widespread, and even talked about in many loudspeaker books...

....

Hi RMC,

As I have shown on the figure
http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=74835&stc=1&d=1480884646
re-scaling the frequency axis relative to the distance (here mentioned to 3m, e.g. by reducing the frequency 6 times) it can be seen that such effect called "mutual coupling" would occur for the frequencies LESS then about 50Hz, as in stereo sound reproduction LF speakers are producing almost the same sound program (especially "under 300Hz"). So that is real physics law of the sound. But such effect is "masked by" the sound reflections from the nearby large surfaces where "local" mutual coupling would produce +6dB up to +18dB, but a lot of my words have been 'said' about that in the previous posts here.

regards
ivica

robertg
05-04-2018, 06:31 AM
I couldn’t stand the way these things looked so I modified them. The bottom end is going to have double 2226J drivers, mids 2123H, then probably a 2395 with a 2446, and a 2405 on top.

The crossover points will be around 300 hz, 1200 hz, and 8000 hz. I think I’m going to experiment with trying them out as a 3 way by crossing the 2123 to a 075 ar 2500 hz.

I also might try to use a passive crossover between two of the drivers so I only have to use three amplifiers. It’s also a lot easier to find a 3-way active crossover.

Ian Mackenzie
05-04-2018, 12:38 PM
Wow

What comes to mind is one of those big Westlake monitors

robertg
05-04-2018, 04:54 PM
Wow

What comes to mind is one of those big Westlake monitors
I was looking at pictures of Westlakes when I designed them. They need a couple of big wood horns, but they are way too expensive.

Lee in Montreal
05-04-2018, 05:17 PM
I was looking at pictures of Westlakes when I designed them. They need a couple of big wood horns, but they are way too expensive.

You can sell your 2395 slants for $2k to a European or Nippon buyer and use the money for some wood horns ;-)

Just sayin' :D

robertg
05-04-2018, 05:51 PM
You can sell your 2395 slants for $2k to a European or Nippon buyer and use the money for some wood horns ;-)

Just sayin' :D
I think the market dried up for 2395's. I just sold a pair for $900.00 CDN, and I see another pair on Canuck for that. There was another pair with drivers in Quebec, the seller was asking $1,100.00 CDN. I have a pair of DAS D-401 that I probably try selling, but they are worth less than the JBL's.

Where's a good place to advertise to sell to the European or Asian market? eBay?

Ian Mackenzie
05-04-2018, 05:56 PM
Great minds think alike.

Those wood horns sure are expensive

There is a guy in Hungry that does really nice walnut finishes

http://athosaudio.wixsite.com/athosaudio/gallery

If you wanted to play out a few different horns here are fibreglass horns of good quality like the seos

http://horns-diy.pl/en/horns/seos/seos-24/

Ian Mackenzie
05-04-2018, 06:22 PM
http://jamminjersey.com/detail/006121/jbl-2397-wood-smith-horns

Not timber but they work nicely

It’s about the look and those big slant plate horn on post 13 have a nice industrial

I myself scored the very last pair of AH700 conical horns in black
http://3.bp.blogspot.com/_NVQujPOPx2c/Shl3rvz510I/AAAAAAAAG_8/F6pT7m5SvxQ/s1600-h/3.jpg

https://oswaldsmillaudio.com/monarch

Lee in Montreal
05-04-2018, 06:43 PM
I think the market dried up for 2395's. I just sold a pair for $900.00 CDN, and I see another pair on Canuck for that. There was another pair with drivers in Quebec, the seller was asking $1,100.00 CDN. I have a pair of DAS D-401 that I probably try selling, but they are worth less than the JBL's.

Where's a good place to advertise to sell to the European or Asian market? eBay?

Paid my set $100 something and they included a pair of 2441 w/ bad diaphragms. I restored everything. Kept them for a year and sold the slants and horn for $1000+ I think. I kept the 2441 and fitted some Radian diaphragms.

My suggestion is to advertise your slants here.

Lee

robertg
07-04-2018, 08:08 PM
Finally finished for now. I am using a DBX driverack and a DBX 234 in series, the 234 splits the 2226 and 2123 at about 300hz. One day I am going to build a passive crossover so I only have to use three amps and one active crossover.

They seem to sound good, they create a lot of wind anyway.

Ian Mackenzie
07-04-2018, 08:12 PM
Awesome 😎