Building an Enclosure Around a D.A.S D-401 2395 Clone

[RMC]

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]

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/vbullet...l=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/Se...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]

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]

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]

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]

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]

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]

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]

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]

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]

Hi Robert

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



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

[RMC]

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]

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]

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]

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