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pangea
01-01-2005, 07:29 AM
Previous postings from this thread can be found in the thread "K 145".

The last posting from "K 145", is duplicated here though.
-----------------------------------------

First of all I would like to wish everyone a HAPPY NEW YEAR, although the new year celebrations have been very somber here, since estimates say that more than 150 000 people have died in Asia, of which more than 3000 were Swedes.
None the less I have been occupied trying to learn some about my project.
I'm anxiously awaiting the return of Earl K and hoping the discussion will continue soon.

-Earl K
In case you're back already, there have emerged a few questions during the holidays, which I would be grateful if you would like to address first.

You wrote:

While Operating in 43XX mode :
- This concept of some form of overlap within the 4-way crossovers' slopes ( between bass and mids ) is something I believe you can do with your Behringer. This will help provide some sonic "glue" for the split between the 2215 and the 2123 . You'll need to experiment some to find the best combination .
For example ; the 2215h lowpass could be set for around 340 hz, while the 2123H hipass might be set around for 120hz ( you will need to port/tune) the 2123 to add a bit of midbass extension. I'd mix and match slopes , like 12db for the 2215 lowpass and 6db for the 2123 hipass .
I’ve been thinking, perhaps I should try to make the boxes sealed. I’ve read that sealed boxes have a much better transient response, so I was thinking of using a large (D, 30cm*L, 15cm) cardboard duct, for the 2123’s. For the bass-bin I was thinking of making it possible to go both sealed (80L) and vented (163L), by plugging the holes in the internal bracing.

Do you think a bit of shelving EQ, on both woofers would be able to extend the frequency range somewhat, as well as making it possible to lower the output, so that they won’t be as pronounced in the 300 - 600Hz region, like you said and at the same time keep the sonic “glue” intact?
Any comments on this?

I have also read somewhere that a first order x-over on the bass and mid-bass (giving a 90 degree phase shift), should be complemented by an equally first order x-over, or a third order (90 or 270 degree phase shift) x-over on the midrange, giving a total of 180 or 360 degree, or a full turn, phase alignment, which would give a perfect summation.
In my case, using the 2441, I think a third order x-over would be better/safer with a x-over at 1000Hz. Wouldn't you agree?
Then the task of time-aligning the drivers, would be much easier for the Behringer UltraDrive, at least I think.

While you were away for the holiday’s, I’ve also been busy trying to figure out the best/ideal x-over point between the 2441 and the 2123 and all things considered I think that 1000Hz/34cm distance between driver-center, seems best in my view.

I’ve also come across a program called XDir, which is said to calculate lobing-effects, though I’m not sure how it works, or how to find the best values. Perhaps you’re familiar with the program? http://www.tolvan.com/xdir/ .

BR
Roland
This is the latest design attempt of my MTM project and there are also a few pictures of the first pieces and a few of my tools.

http://img.photobucket.com/albums/v421/pangea2012/MTMdemo2.jpg

http://img.photobucket.com/albums/v421/pangea2012/Ektopp2.jpg

http://img.photobucket.com/albums/v421/pangea2012/Ekbas2.jpg

EDIT: Here are a few of my tools, as well as one of my "co-workers", as always taking a brake!
http://img.photobucket.com/albums/v421/pangea2012/verktyg2.jpg

Earl K
01-01-2005, 08:28 AM
Hi Roland !

Just checking in, I'm leaving for Montreal shortly - so, I'll have to answer your questions after I return .

Briefly; You should take the time to discover for yourself whether or not "you" think that sealed boxes offer better transient response versus ported boxes. "Theory" which hasn't been personally experienced, is at best just that, it's only "Theory", and at worst this type of info can quickly become "dogma". So, that means building something that has ports that can be stuffed so that you can discover your own preference .

Regarding, Crossover Points and Slopes ;
I think that you are are putting the "cart before the horse" by trying to predict in advance what will work best . Since you own a very variable DSP based crossover - you can discover this later / and then tell us what worked best for your project .

Lobing Prediction Programs ;
The unrestrained use of this sort of program , coupled with any dogmatic belief in its' "theoretical predictions", will "severely challenge" your current belief that your asymmetrical MTM-hybrid is worth pursuing as a project .

ie ; "Invest in & Believe" - at your own peril

( Personally - I think "floor-bounce cancellations", as measured within your "listening-window" - warrant as much or more scruntiny )

Happy New Year ! Earl K

pangea
01-01-2005, 10:45 AM
-lfh


Quote:
Originally Posted by pangea
About "Xdir", I'm sorry I used the word "supposed". It wasn't my intention to be critical or anything of the program, it only meant that I didn't know how to use it correctly.
So perhaps I should have said, "it is said to"..., instead.
I'm sure the program is very good.



No worries, I just wanted to say that it most likely does what it's supposed to do (as opposed to some crappy freeware out there...). And yes, it should still be useful for your purposes. E.g. first look at the frequency range where the twin basses operate but the tweeter is silent (e.g. do one plot per octave) and then study what happens around the crossover frequency where all drivers contribute. Vary one parameter at a time (spacing/level diff/phase diff), and you'll get a good grasp of how the array works, and how the filter properties come into play. It should also be interesting to compare a conventional design and an MTM around the crossover frequeny.

It seems that when the distance between each driver is 34cm and at the same time, the "phase lag" is zero degrees, there will always be a significant lobe heading for the "sweet spot".

Could this be interpreted in such a way, that I most likely won't experience any negative surprises?

I'm still not sure how to read the various graphs.

-Earl K

I know I'm trying to put the cart before the horse! You're absolutely right, but I'm a cautious guy, who doesn't like to make any errors. I've always been this way, trying to find the weaknesses and potential problems in advance and subsequently trying to avoid them.:duck:

You said earlier the 2123 will perform best in a sealed box, so I figured a 7L (10L minus 3L driver displacment) "tube" box would be best, as well as easiest to make. As for the bass bin I'm planning of making it possible to go either way (80L sealed or 163L vented).

Regarding slopes, I'm counting on the Behringers being able to find the phase problems and help me to set up all the other parameters.

About "floor-bounce cancellations", I'm hoping I've managed to minimize those problems, by stuffing my listening room with lot's of stuffed furniture and carpets and last but not least having treated the room with quite a few absorbers and traps.

And there is not a chance; I'll give up this project!!!:D

BR
Roland

lfh
01-01-2005, 04:05 PM
It seems that when the distance between each driver is 34cm and at the same time, the "phase lag" is zero degrees, there will always be a significant lobe heading for the "sweet spot".

Could this be interpreted in such a way, that I most likely won't experience any negative surprises?

I'm still not sure how to read the various graphs.

Yep, a main lobe in the horizontal plane is the expected behaviour, and the pattern should be symmetrical above and below the "x-axis". No unpleasant surprises. :) The graph basically shows the variation in readings you would get when moving a mic along a half circle (at large distance from the array) in the vertical plane around the array center (and on axis in the other dimension) in an anechoic environment. The frequency response at any desired angle (e.g. 30 deg above/below horizontal plane) can be derived from a set of such polar plots calculated for a sequence of frequencies. (Disclaimer: Again, I can't run it conveniently on my Macs, so I don't know whether he does some normalization, but in principle this holds true.) Note that such a FR is due solely to the array geometry (and possibly source phase and level diffs), and the corresponding interference patterns. A more realistic simulation would (at least) take the driver directivity patterns into account (possibly modeled with the well known directivity patterns of simple propotypes such as a piston in a baffle), but the model used in the program still gives a good demonstration of the fundamental properties of a certain array.

EDIT: In this particular case - using a 10" and a 15" in an MTM setup - I'd want to use the piston model (or better yet; measured magnitude and phase data) for the simulation. Such a hack is on my to-do list, but ETA is like Q2... Perhaps you could convince SG to add this (piston model), along with a few text book filters, and means to enter driver acoustical centers?

EDIT 2: Then (after reading Earls post again), what would you do with the more accurate plots? New conclusion: Point sources are just fine. Time better spent would most likely be to build test boxes and experiment! "Probieren geht ueber studieren." :)

lfh
01-01-2005, 04:53 PM
I’ve read that sealed boxes have a much better transient response [than ported], ...

Well, it depends. Sealed boxes behave like 2:nd order high pass filters whereas ported boxes behave like 4:th order ones. Thus, a sealed box has the theoretical possibility to perform better in this respect than a ported one. However, performance depends on the "filter" tuning/alignment. A closed box with a high Q-value will "ring"/"boom", and a ported box with a shallow roll off will have a "tight" character. That said, a 2:nd order HP characteristic with a Q around 0.6 (or even lower, when factoring in room gain at lower frequencies) is pretty much as good as it gets, but a ported box tuned with transient performance in mind yields very good results as well. (Not that JBL always used to do this, though: Work through the old JBL recommended tunings with a good box design program some rainy day ;) ). Often the latter is the better overall compromise, when weighing in other aspects such as the desired cutoff frequency, the acoustical output capability etc. Yet another thing to keep in mind is that the "best" box type to a large extent depends on the driver at hand. Typical JBL drivers often work best in ported enclosures (if you still want some LF, that is). Finally I agree with Earl K: Let your ears be the judge and steer clear of dogms ("must use 6 dB filters, must not use feedback, must..." yada yada). Audio design is the fine art of making compromises and many (most?) audiophiles seem to have forgotten that...

lfh
01-01-2005, 06:31 PM
You're not doing a middle-of-the-road design here... Do you have some references of similar "hybrid MTMs" (IIRC Earl runs such stuff - I must read the entire K 145 thread) and have you looked into D'Appolitos designs - noteably the crossover networks? How will you tackle the low end where the 2123s runs out of steam but the 2215s keep pumping? I think some careful thinking is needed here when designing the two boxes. (Sure, you're "cheating" with your trick EQ and all, but some master plan on how to design the disparate bass boxes for the desired combined LF response (10"+15"+EQ+room) is called for IMO.) Finally; why is the tweeter not above the mid horn?

4313B
01-01-2005, 06:53 PM
You should take the time to discover for yourself whether or not "you" think that sealed boxes offer better transient response versus ported boxes.Absolutely!

Ian Mackenzie
01-01-2005, 08:23 PM
Bullock on boxes is a great read on this subject.

He says a properly tuned low Q woofer will sound every bit as good as a seal design. He then goes on to discuss the finer points of reflex tuning, accounting for Rx, QL and actually T/L measurements.

I know myself you can alter the quality of the bass in sublte but audible degrees by optimising the woofer for a given enclosure Vb, tuning frequency Fb and Rx the total Dcr behind the speaker.

Ian

pangea
01-02-2005, 02:04 AM
WOW, lot's of response, great!:D


Yep, a main lobe in the horizontal plane is the expected behaviour, and the pattern should be symmetrical above and below the "x-axis". No unpleasant surprises. :) The graph basically shows the variation in readings you would get when moving a mic along a half circle (at large distance from the array) in the vertical plane around the array center (and on axis in the other dimension) in an anechoic environment. The frequency response at any desired angle (e.g. 30 deg above/below horizontal plane) can be derived from a set of such polar plots calculated for a sequence of frequencies. It wasn't until now, that I realized this. I thought a nice even curve looking like a half circle was the target at all times.:o



Note that such a FR is due solely to the array geometry (and possibly source phase and level diffs), and the corresponding interference patterns. A more realistic simulation would (at least) take the driver directivity patterns into account (possibly modeled with the well known directivity patterns of simple propotypes such as a piston in a baffle), but the model used in the program still gives a good demonstration of the fundamental properties of a certain array.
Isn't it possible that the Behringer UltraDrive will take care of this, or isn't it the same thing as time aligning the drivers?



EDIT: In this particular case - using a 10" and a 15" in an MTM setup - I'd want to use the piston model (or better yet; measured magnitude and phase data) for the simulation. Such a hack is on my to-do list, but ETA is like Q2... Perhaps you could convince SG to add this (piston model), along with a few text book filters, and means to enter driver acoustical centers?
I'm not sure I understand these abbreviations and also, wouldn't these additions to the program complicate it quite a bit?



EDIT 2: Then (after reading Earls post again), what would you do with the more accurate plots? New conclusion: Point sources are just fine. Time better spent would most likely be to build test boxes and experiment! "Probieren geht ueber studieren." :)
"Aber natuerlich". Though being able to predict or knowing even, makes it possible to avoid spending a lot of time and money on building boxes, when the odds are stacked heavily against any solution.:D


Well, it depends. Sealed boxes behave like 2:nd order high pass filters whereas ported boxes behave like 4:th order ones. Thus, a sealed box has the theoretical possibility to perform better in this respect than a ported one. However, performance depends on the "filter" tuning/alignment. A closed box with a high Q-value will "ring"/"boom", and a ported box with a shallow roll off will have a "tight" character. That said, a 2:nd order HP characteristic with a Q around 0.6 (or even lower, when factoring in room gain at lower frequencies) is pretty much as good as it gets, but a ported box tuned with transient performance in mind yields very good results as well.
I have already been using JBL's "SpeakerShop Enclosure Module 1.0" and stopped at a net volume of 7L sealed box (10L minus 3L driver displacement) and a Q of 0,591, giving a Fc=166,9 and F3=205,7 and no filling.:D



Often the latter is the better overall compromise, when weighing in other aspects such as the desired cutoff frequency, the acoustical output capability etc. Yet another thing to keep in mind is that the "best" box type to a large extent depends on the driver at hand. Typical JBL drivers often work best in ported enclosures (if you still want some LF, that is). I don't think I've ever seen the 2123 in a vented box and I was hoping I'll be able to EQ the 2123 to some extent, giving it a wider FR and at the same time lowering the output somewhat.


You're not doing a middle-of-the-road design here... Do you have some references of similar "hybrid MTMs" (IIRC Earl runs such stuff - I must read the entire K 145 thread) and have you looked into D'Appolitos designs - noteably the crossover networks? How will you tackle the low end where the 2123s runs out of steam but the 2215s keep pumping? I think some careful thinking is needed here when designing the two boxes. (Sure, you're "cheating" with your trick EQ and all, but some master plan on how to design the disparate bass boxes for the desired combined LF response (10"+15"+EQ+room) is called for IMO.) Finally; why is the tweeter not above the mid horn?Mainly I'm acting on a very strong hunch and then I wanted to use the things at hand! I've been reading some D'Appolito papers and I've seen a few asymmetric solutions. So when Earl K suggested that I should build just that, I knew I had to.:D
About the overlapping, I'm hoping it will help creating a sonic "glue", like Earl K is suggesting. To me it seems very reasonable, given the need to look at the combined sound level and a lot of fiddling with x-over points, slopes and EQ'ing.
Hmmmm, "master plan", I don't think it ever came to that...:o

The tweeter has been moved around a few times. at one time there wasn't enough room between the 2441 and the 2123. Then again Earl suggested a placement, which resembled the JBL 43XX design and therefore should be quite a safe position.
I take it you would like to place it above? If so, could you please elaborate on why? Hopefully it would help me understand the principle a little better.


Bullock on boxes is a great read on this subject.

He says a properly tuned low Q woofer will sound every bit as good as a seal design. He then goes on to discuss the finer points of reflex tuning, accounting for Rx, QL and actually T/L measurements.

I know myself you can alter the quality of the bass in sublte but audible degrees by optimising the woofer for a given enclosure Vb, tuning frequency Fb and Rx the total Dcr behind the speaker.

IanThanks Ian, where can I find this read? Is it to be found on this forum?

BR
Roland

lfh
01-02-2005, 04:13 AM
It wasn't until now, that I realized this. I thought a nice even curve looking like a half circle was the target at all times.:o

Isn't it possible that the Behringer UltraDrive will take care of this, or isn't it the same thing as time aligning the drivers?

(Just some further elaboration.) "No surprise" since the pattern (basic properties) really can be predicted without any SW once one gets used to think about interference. The target is not necessarily a half circle. Rather one strives to control in what directions to radiate - and where not to.

As to the FR part, I was a bit unclear: "Such" refered to off axis responses derived from the polars. You should be able to get a flat on axis response, but there will always be ripple due to the twin mids/basses when you move off axis. BTW, see the Project May blog for interesting info about that.



I'm not sure I understand these abbreviations and also, wouldn't these additions to the program complicate it quite a bit?

Sorry about the technobabble. IMO it would not be so complicated (technically rather straightforward), but amount of work depends on the programming language and libraries used (read: how much "nuts & bolts" you need to implement yourself). I'll post here once I'm done (using a language that lets me be really lazy ;)).


I have already been using JBL's "SpeakerShop Enclosure Module 1.0"
/.../
I don't think I've ever seen the 2123 in a vented box

What's this SpeakerShop thing and what happens if you select vented box?


I take it you would like to place it above? If so, could you please elaborate on why? Hopefully it would help me understand the principle a little better.

Actually you have the perfect tool to explore this - Xdir ;) The question is in what plane (horizontal or vertical) you want this pattern (thinking of the overlap region where both drivers contribute).

EDIT: However, lobing is only one aspect. Even with brickwall filters (no overlap and hence no interference) a strict line array would be the way to go according to conventional wisdom for imaging reasons. Why spread out the drivers in another dimension (unless called for by size constraints)?

lfh
01-02-2005, 04:12 PM
Now I've browsed the K 145 thread, and I think I understand the rationale behind the tweeter placement, as proposed by Earl K: It's to make the top box useable up side down as well in a "43xx" mode (i.e. mid-bass close to LF, no two drivers operating within the same nominal frequency band). I think this is a clever fallback plan, in case the MTM doesn't turn out to your liking. However, reflecting the cool (and non-flippable) aestetics of your design, you might want to go for exchangeable baffles instead (maybe this was also discussed earlier), such that you "easily" can switch between MTM and 43xx and without compromising driver placement in either case. (The two-box design would still make sense for several reasons.)

BTW:

Earl, what's the source of the "MTM theory" pic you posted?

pangea
01-03-2005, 01:02 AM
Now I've browsed the K 145 thread, and I think I understand the rationale behind the tweeter placement, as proposed by Earl K: It's to make the top box useable up side down as well in a "43xx" mode (i.e. mid-bass close to LF, no two drivers operating within the same nominal frequency band). I think this is a clever fallback plan, in case the MTM doesn't turn out to your liking. However, reflecting the cool (and non-flippable) aestetics of your design, you might want to go for exchangeable baffles instead (maybe this was also discussed earlier), such that you "easily" can switch between MTM and 43xx and without compromising driver placement in either case. (The two-box design would still make sense for several reasons.)

BTW:

Earl, what's the source of the "MTM theory" pic you posted?
Going for the interchangeable baffle option; would you wan't to have the tweeter in line and between the 2123 and the 2441, when used in MTM mode?
I'm not familiar enough with the "Xdir" program to be able to say what's best.:banghead:

The SpeakerShop is a JBL program/tool, which has two modules. One for calculating/tuning various boxes and one for passive x-overs. I've used them both to my satisfaction for years now.

After having read the "Project May" thread, it seems to make even more sense and even being more likely, the boxes will be sealed when I'm done experimenting.
But it is as you both have said several times, it remains to be seen though.:D

BR
Roland

Zilch
01-03-2005, 12:25 PM
Anybody else know anything about "The Speaker Shop?"

Or its availability?

[Google says it's in North Lima, Ohio....] :p

Donald
01-03-2005, 12:49 PM
It is also software.

http://fileshare.eshop.bg/index.php?what=search2&searchstring=JBL+speakershop

lfh
01-03-2005, 12:54 PM
Going for the interchangeable baffle option; would you wan't to have the tweeter in line and between the 2123 and the 2441, when used in MTM mode?

Yes! This is one "dogm" one should obey ;) Seriously, the reasons should be clear by now: A vertical placement (empirically) yields better imaging capabilities, and the variation in FR will be smaller when moving off axis in the horizontal plane (which normally is more important than vertically consistent FR). But don't take our word for it - you can evaluate the alternatives yourself by laying your current "outboard" 2445/075 combos on their sides.

pangea
01-03-2005, 02:36 PM
Yes! This is one "dogm" one should obey ;) Seriously, the reasons should be clear by now: A vertical placement (empirically) yields better imaging capabilities, and the variation in FR will be smaller when moving off axis in the horizontal plane (which normally is more important than vertically consistent FR). But don't take our word for it - you can evaluate the alternatives yourself by laying your current "outboard" 2445/075 combos on their sides.
Most likely I'll end up with several different baffles, although I'm really hoping the MTM version with all the drivers in a straight vertical line,will be the winner.:band:

BR
Roland

Donald
01-03-2005, 03:21 PM
This is the start screen for Speaker Shop.

lfh
01-03-2005, 03:37 PM
Thanks, Donald...erm...I mean Kevin ;)

Earl K
01-04-2005, 10:57 AM
Hi Roland


About "floor-bounce cancellations", I'm hoping I've managed to minimize those problems, by stuffing my listening room with lot's of stuffed furniture and carpets and last but not least having treated the room with quite a few absorbers and traps.

Well,,, then,, to test your room for these forms of cancellation, use your Behringer 8024 or a facsimilie ( in the RTA mode ) with a half decent test mic ( set the 8024 screen resolution to .5 db for now ) . Put some pink noise into one woofer of your current system( run it at least crossed over at 1200 hz ) and then look for and measure the nulls. Obviously, make sure any EQ dialed into your 8024 is bypassed or "zeroed" - this also means bypassing any parametric filters your Behringer may have .

(i) Setup the test mic on axis ( to the 15" woofer ) above the floor at a height that equals the center of the woofers' dust-cap ( In my case , @ 16" ). Also, setup the measuring mic (on axis ) , out in front of the woofer, at the same distance as the mics' height off-the floor ( also 16" ). Make some measurements and jot down some response notes . Now, Repeat measurements, at distances that are whole number multiples ,( ie 2 or 3 or 4 times the distance of the microphone distance from the floor )

(ii) An example : - ( both types of my test boxes have woofers that are centered @ 15" to 16" from the floor )

- So : say,,, 16" times 2 ( this multiplier is present to recognize that the sound wave travels down to the floor and backup to the mic - this is 1 full cycle of "bounce" ) divided by 12 ( this transforms, inches to feet ) = 2.66666667 ft

- Then ; 1130 ( the "speed of sound" stated in feet per second ) divided by 2.6666667? will equal the center frequency of "null" . In this case , its @ 423.75 hz. The "Q" or "width" of the null "can" become quite wide . This "Q" will be determined by a few other factors, including the fact, that 424 hz ( along with all the other frequencies ) is being reproduced all over that 13.5" wide cone ( not just the center ). Therefore, the full wave measurements down to the floor and back up the mic will vary in total distance travelled . "Effects" of these other parameters will combine to produce the actual shape ( or "Q" ) of any measured "null" .

- Repeat the above , but with the measuring microphone at a distance above the floor, of twice the distance as compared to the first measurements taken. In my case, that equals @ 32" ( which happens to locate the measuring microphone, just about dead-center of my hi-mid horn ) .

- I'll post some pictures ( screen shots of my 8024 ) showing some real-world measurements of my 15" woofer-based, MTM setup. I'll do this sometime over the next 24 hours .

regards <. Earl K

Earl K
01-04-2005, 11:08 AM
Ifh

BTW:

Earl, what's the source of the "MTM theory" pic you posted?

Ian Mackenzie provided that picture to the first grouping of the "McRitchie Project". It's buried deep within the "closed" archives of the current "Project May" MTM effort. You'll need to ask Ian what his picture source was .

regards <> Earl K

Earl K
01-04-2005, 11:19 AM
Hi Roland


although I'm really hoping the MTM version with all the drivers in a straight vertical line,will be the winner.

- That would be a nice solution - if that "axial" postion doesn't over-stretch the "sonic glue" occuring between the woofers .

- Now, since I no longer use tweeters, this is an area beyond my "actual hands-on" experience .

- Hopefully others can add some insights and direction to you for "best tweeter position" . ( This is where replaceable baffle boards for the top box will become critical - in the "testing phase" of your project )

regards <> Earl K

pangea
01-04-2005, 01:40 PM
OK, many thanks for your insight on this!!!
I will have to read this a few times I'm sure, before I'm going to be able to grasp all this and translate it to cm/mm and I'm also sure it will take some preparation before I will be ready with my DEQ2496/DCX2496's/ECM8000.
This week/weekend I will be drowned in work, but on monday I'm due for a small operation on my left thumb and pinkie, but after that I will have plenty of time to experiment during the next 3-4 weeks.:thmbsup:

I'm also hoping to be able to pay a visit to my local lumber yard, for the missing peices, before my operation.:D

/Roland

Ian Mackenzie
01-04-2005, 02:40 PM
Frederick,

Its in several texts I have , Loudpeaker Cook Book by Vance Dickason the better test. A best buy for this project

About MTM, unless you have small diameter mid range or HF drivers DO NOT attempt, as the spacing D b/n the drivers will be greater than the wavelengh in the driver passband and there will be lobes everywhere, not as per MTM.

Otherwise better to use 3rd order or 4th order LR with standard vertical or JBL 43XX cluster otherwise.



Ian

Earl K
01-04-2005, 05:45 PM
If one has access to this section ;

- It's worth looking at this thread called MTM Theory vs "Our Approach" (http://audioheritage.csdco.com/vbulletin/showthread.php?t=1256) .

regards <. Earl K

lfh
01-04-2005, 06:16 PM
Ian, my way old copy of the cookbook doesn't have exactly that plot - seems it's time to buy a recent edition. (I agree that it's a good reference book.)

Earl, now everybody will want to get access to the restricted area. :yes: (Maybe I'll qualify after my next post, when the counter flips to a three digit figure? :) )

Earl K
01-04-2005, 06:28 PM
Hi Ifh


Earl, now everybody will want to get access to the restricted area. :yes:
(Maybe I'll qualify after my next post, when the counter flips to a three digit figure? :) )

Well actually, I'm recommending that Don impose a new ( onetime) $10.00 toll - to enter the area . :D ;)

<. EarlK

lfh
01-05-2005, 01:01 PM
Well actually, I'm recommending that Don impose a new ( onetime) $10.00 toll - to enter the area . :D ;)

Okay, okay, I could always buy some more raffle tickets :)

Or maybe speeding up development of my "Xdir-killer" would help? Here two raw previews of plots I'm adding:

pangea
01-08-2005, 10:44 AM
Now I am almost done cutting up all the peices, and the kitchen looks like a disaster area.:D

Tomorrow I'll begin putting the bins together, by mounting the braces.

The bins will be made out of three different types of panels. 26mm solid oak, 12- and 14mm plywood, as well as 12- and 19mm MDF board. Between the oak and plwood I will try to use some elastic glue, which I'm hoping will reduce resonances.
On the baffles I think I will use some leather imitation I found, which is very close in color the JBL blue.

The coming week I will also try to perform the the test/analysis procedures, described a few postings back.

BR
Roland

pangea
01-29-2005, 03:53 AM
Hi all!

Slowly but surely it's coming together in my disastrous kitchen and so far so good, i.e. no big mishaps yet. :D

BR
Roland
http://img.photobucket.com/albums/v421/pangea2012/toppbotten2.jpg

http://img.photobucket.com/albums/v421/pangea2012/Baslda3.jpg

http://img.photobucket.com/albums/v421/pangea2012/inreportbaffel1.jpg

lfh
01-29-2005, 05:26 AM
Wow, that's impressive! :applaud: (I wish I had woodworking skills like that.)

johnaec
01-29-2005, 05:34 AM
Wow! Are those sides made of oak?

John

pangea
01-29-2005, 08:46 AM
Thank you guys! :)

-lfh
Actually it isn't that difficult, as long as you double check every measurement and always go back and check with your drawing and most importantly as long as you dont rush things.
I must admit, I've spent many slepless hours in bed trying to figure out the best way to do it. Needless to say, I loved every one of them. :D

-Johnaec

Yes, the outer side panels are made out of 27mm (>1") solid oak. :D


Hmm... I wonder why the pic's got so blown up this time?

BR
Roland

Zilch
01-29-2005, 09:16 AM
Will it have a whirlpool bath, or just a shower? :p

Nice work!

Earl K
01-29-2005, 09:33 AM
Hi Roland

Glad to see that you're moving forward on your project . :applaud:


Yes, the outer side panels are made out of 27mm (>1") solid oak.

Nice ! :yes:

- Did you glue the oak strips together and then plane this assembled panel down to its' final 27mm measurement - or - did it all start out at 27 mm with just a bit of sanding applied to smoothe any prominent ridges ?

- The reason I ask , I've had thoughts that a "cheap & cheerful" approach to something very similar to what you've done - would be to make an internal box shell of 12mm that is then clad with 19mm thick "pine shelving". This pine shelving is available from either Ikea or stores like "Home-Depot" in various sizes. Like I said, "cheap & cheerful" . And of course pine is quite easy to work with and will accept colored stains quite handily .

:cheers: Earl K

( PS; I hope those front panels are removable on your top box to facilitate some different component spacings )

pangea
01-29-2005, 12:22 PM
Will it have a whirlpool bath, or just a shower? :p

Nice work!

Neither, I'm afraid, the only option would be the "Sauna". ;)

BR
Roland

pangea
01-29-2005, 12:30 PM
Hi Roland

Glad to see that you're moving forward on your project . :applaud:



Nice ! :yes:

- Did you glue the oak strips together and then plane this assembled panel down to its' final 27mm measurement - or - did it all start out at 27 mm with just a bit of sanding applied to smoothe any prominent ridges ?

- The reason I ask , I've had thoughts that a "cheap & cheerful" approach to something very similar to what you've done - would be to make an internal box shell of 12mm that is then clad with 19mm thick "pine shelving". This pine shelving is available from either Ikea or stores like "Home-Depot" in various sizes. Like I said, "cheap & cheerful" . And of course pine is quite easy to work with and will accept colored stains quite handily .

:cheers: Earl K

( PS; I hope those front panels are removable on your top box to facilitate some different component spacings )

No, the panels are ready made "kitchen benches", which already are sanded and smooth. I think IKEA would be a good place to start.

There is some room for movement of the drivers, but if it requires greater movements, I will have to make new top boxes all together, but that's no problem really.

BR
Roland

Earl K
01-29-2005, 12:43 PM
No, the panels are ready made "kitchen benches", which already are sanded and smooth.

Bravo ! :applaud:

I love a clever implementation of the axiom, "economy of effort" . :D

pangea
02-25-2005, 04:43 AM
Hi all!

Finally the day has come where I got to listen to these hybrid MTM speakers for the first time.

At first I forgot to adjust x-over frequencies and therefore I could see that they were connected alright, but no holographic soundstage of course.:o:

But then I tried to sum up all the info I got from all of you guys. I can't even begin to describe how grateful I am and how much I appreciate all the help I've received from you all!!!
:cheers: :thmbsup:
I began to give the 2215H a + 3dB gain and an extra slight boost below 40Hz. (fb 23,3Hz) x-over point 330Hz/18dB/oct.
The 2123H is crossed over between 98-897Hz, 0dB gain, also 18dB/oct.
The 2441J then takes over from 897Hz up to 9,06kHz, - 7dB gain, 18dB/oct.
Finally the 075 at -4dB gain, takes care of the rest, also 18dB/oct.

Then I placed the microphone 114cm in front of each speaker and let the Behringer UltraDrive do it's thing and after that I let the UltraCurve do it's thing and guess what, there were only very small adjustments made by the UltraCurve, unlike before, where the adjustments sometimes went outside the measuring range.

As you can imagine I then sat down in my listening chair, somewhat nervous and pushed the play button....

I'm not kidding, after only a few seconds I was so moved, my eyes got moist.

Maybe it's just beginner's luck that I got it right, already at the first attempt, but I know for sure, that the outcome wouldn't have been such a success without your kind help and without the Behringers.

If you think the baffles look strange, it's because the 4mm "Masonite" baffle with the artificial leather is still missing.

Also, any suggestions or ideas that might improve things, are most welcome.

http://img.photobucket.com/albums/v421/pangea2012/MTMh.jpg

BR
Roland

Earl K
02-25-2005, 05:13 AM
Congratulations Roland ! :)

I'm glad your project is working out nicely - especially with you having to construct in a kitchen. I admire your fortitude . ;)

Sometime when you can , please tell me what you hear ( and measure ) if you move the 2215h crossover point upwards to somewhere in between 600 and 900 hz . Thanks !

:cheers:

pangea
02-25-2005, 07:06 AM
Congratulations Roland ! :)

I'm glad your project is working out nicely - especially with you having to construct in a kitchen. I admire your fortitude . ;)

Sometime when you can , please tell me what you hear ( and measure ) if you move the 2215h crossover point upwards to somewhere in between 600 and 900 hz . Thanks !

:cheers:

Funny you should mention that. That was exactly what I just was thinking of trying out, to see what happens if I let the 2215H go parallel with the 2123H up to where the 2441J takes over.
I should think the UltraCurve will have to make even fever and smaller adjustments to the frequency curve.
I was also thinking earlier during the building process and I think I even wrote about it, if it would be possible to hook the 2215/2123 up in parallel, i.e. making the system a three way, instead of a four way system.

Next time though I think I will have to get me a proper workshop before starting on a new project. There's MDF dust absolutely everywhere right now. It'll take me a week at least, to clean the place up again. So, perhaps fortitude isn't the right word. In hindsight, lack of common sense and stubbornness, is what comes to mind right now.:o: :D

EDIT:
OK, I would say the soundstage became much more solid and homogenous. It also had the effect that it drew me in and it felt as if I became a part of the music. That really surprised me!
This I have never experienced before in my entire life! :applaud: :D
I like!
Wan't more!!!

If I was addicted to JBL before, WHAT THEN, AM I NOW???

EDIT2: I almost forgot. As expected, the adjustments made by the UltraCurve, became smaller in that region! :D

BR
Roland

Earl K
02-25-2005, 08:12 AM
Hi Roland,

EDIT:
OK, I would say the soundstage became much more solid and homogenous. It also had the effect that it drew me in and it felt as if I became a part of the music. That really surprised me!
- What frequency did you take the 2215 up to ? ( Try 600 or 700 hz )
- What slope ? ( Try all these; 6 / 12 / 18 db per octave )
- What filter type ? ( Try ButterWorth & Bessel ) I'm especially curious about Bessel at 600 or 700hz at 6 db per octave .


This I have never experienced before in my entire life!

- Well, that's what one should get with MTM when using a horn that has good to great imaging qualities all on its own .

I like!
Wan't more!!!

Yeh , it's pretty addictive .

Without hearing your system , it's hard to know how much "more" is available .

I have more ideas for you - I'll post in the next week ( maybe this weekend ).





I just was thinking of trying out, to see what happens if I let the 2215H go parallel with the 2123H up to where the 2441J takes over.
I should think the UltraCurve will have to make even fever and smaller adjustments to the frequency curve.

- Yes maybe intime the adjustments will be so small that you could take the UltraCurve out of the circuit and just use the "UltraDrive" for any frequency adjustments.


I was also thinking earlier during the building process and I think I even wrote about it, if it would be possible to hook the 2215/2123 up in parallel, i.e. making the system a three way, instead of a four way system.

- Don't do it. The 2123h needs some protection from lowfrequencies (LF) below 100hz ,,, so it's best to keep going 4-way so that you can filter out everything below 100hz . If you were using a different 10" with a deeper coil winding ( say 75mm deep ) - then my advice would likely be different .


:cheers:

pangea
02-25-2005, 08:52 AM
Hi Roland,

- What frequency did you take the 2215 up to ? ( Try 600 or 700 hz )
- What slope ? ( Try all these; 6 / 12 / 18 db per octave )
- What filter type ? ( Try ButterWorth & Bessel ) I'm especially curious about Bessel at 600 or 700hz at 6 db per octave .



- Well that's what one should get with MTM and a horn that has good imaging on its own .


Yeh , it's pretty addictive .

Without hearing your system , it's hard to know how much "more" is available .

I have more ideas for you - I'll post in the next week ( maybe this weekend ).






- Yes maybe intime the adjustments will be so small that you could take the UltraCurve out of the circuit and just use the "UltraDrive" for any frequency adjustments.



- Don't do it. The 2123h needs some protection from lowfrequencies (LF) ,,, so it's best to keep going 4-way so that you can filter out 100hz ( & below ) from the 2123 .


:cheers:

I let the 2215 go to 897Hz, the same as the 2123 and I'm using 18dB/oct. BW on all x-over points.

Could you elaborate on the "Bessel at 600 or 700hz at 6 db per octave" .
I'm not sure where, but I know I read somewhere that the third order characteristics would yield the best phase alignment in an MTM configuration. Something with lobing or comb filter, I think, or something like that.
I'm sure "lfh"/Fredrik knows a lot about that. BTW Fredrik, you need to come and listen to this!!!!!

I've said it a thousand times at least, that with this hobby, you'll never be finished, but right now it feels like I'm being VERY close.

But still, I'm looking forward to your other suggestions.:bouncy:

It would be nice to be able to take out the UltraCurve from the equation and perhaps also make a passive filter for each driver, but unfortunately I don't have a clue as to how to translate milliseconds in to R/C circuits. Math's has never been my strong suit.:o:

OK, I'll stay away from the 3-way thing. I only thought there would be a natural roll-off at the low end of the 2123.:duck:

BR
Roland

Earl K
02-25-2005, 09:04 AM
Hi Roland

I need to read the operators manual for your UltraDrive before I make any more suggestions . ( I thought/assumed that each filter/output could have completely different filter characteristics assigned to it - that was just an assumption/hope on my part )

I'll get back to you this weekend . I've got to dash now .

:cheers:

pangea
02-25-2005, 10:00 AM
Hi Roland

I need to read the operators manual for your UltraDrive before I make any more suggestions . ( I thought/assumed that each filter/output could have completely different filter characteristics assigned to it - that was just an assumption/hope on my part )

I'll get back to you this weekend . I've got to dash now .

:cheers:

You are absolutely right! Each and every output can be assigned, just about anything you like. Normally the x-over points are linked, but it's possible to even set them "free" and then you can overlap the frequencies anyway you want.

When you want me to use the 1st. order Bessel at 600-700Hz, do you mean that I should do that only at the overlapping points between the 2123 and the 2215 and keep the rest at 3rd. order BW?

BR
Roland

Earl K
02-25-2005, 10:24 AM
Yes, I am leaving shortly but ,,,


When you want me to use the 1st. order Bessel at 600-700Hz, do you mean that I should do that only at the overlapping points between the 2123 and the 2215 and keep the rest at 3rd. order BW?

(a) I'm suggesting that you play around with just the one crossover point ( try 450 hz even ) and slopes of ( 6 to 18 db ) the "low-pass filter" from the UltraDrive output driving just the 2215. ( leave everything else at 18db Butterworth for the 2123s, 2441, 2405 ).

(b) Also try lowering your horns' overall crossover point to 800hz or 750hz, from the @ 900 hz you are now using . Do this adjustment for both the 2441 / 2123 sections. Then again, try different points of ( say 375 hz up to 750 on just the 2215 lowpass output - again with the 3 different slopes and two filter types ) .

This should occupy you for a while ( unless some of them just sound plain bad and measure awful )

:cheers:

pangea
02-25-2005, 01:19 PM
Yes, I am leaving shortly but ,,,



(a) I'm suggesting that you play around with just the one crossover point ( try 450 hz even ) and slopes of ( 6 to 18 db ) the "low-pass filter" from the UltraDrive output driving just the 2215. ( leave everything else at 18db Butterworth for the 2123s, 2441, 2405 ).

(b) Also try lowering your horns' overall crossover point to 800hz or 750hz, from the @ 900 hz you are now using . Do this adjustment for both the 2441 / 2123 sections. Then again, try different points of ( say 375 hz up to 750 on just the 2215 lowpass output - again with the 3 different slopes and two filter types ) .

This should occupy you for a while ( unless some of them just sound plain bad and measure awful )

:cheers:

I began by lowering the horn and the woofers x-over point from 897 to 805Hz, but that made it worse. The soundstage almost collapsed, so I went back to 897Hz.

As I was about to change characteristics on the 2215 to 1st. order BW (there is no 6dB Bessel on the UltraDrive), I ran in to some problems with one of the UltraDrives, which suddenly "lost" the fourth output, it somehow got assigned to input B.
Don't know :wtf: happened there. I Had to reconfigure the whole thing, which kept me busy for qute a while.:biting:

I'll give it a new try tomorrow.

BR
Roland

Steve Gonzales
02-25-2005, 02:24 PM
Really nice job!!. Dreamy looking blue baffles and driver compliment. I hope you get to keep the vertical arrangement. SWEET!!!!

Earl K
02-26-2005, 06:43 AM
Hi Roland


I began by lowering the horn and the woofers x-over point from 897 to 805Hz, but that made it worse. The soundstage almost collapsed, so I went back to 897Hz.

- I think it's wonderful that the system already images so well that the effects produced by the lowering of the crossover point, were immediately evident / ie " the collapsing soundstage" .


BW (there is no 6dB Bessel on the UltraDrive),

- Well,,, there shouldn't be. I should have mentioned that before or chosen my words more carefully . It takes more than one pole ( producing a 6 db slope ) to create a "signature" transform ( ie Bessel, Butterworth, LR ). It's the relative spacing of the poles to each other ( quantity of, 2, 3, 4, & up, all working within the desired crossover area ), as well as the filter poles interaction with each other , that creates the characteristic crossover curve near F3. Group-delay characteristics ( and transient response characteristic ) are also dictated by how the different poles interact with each other. Taken together ( along with some other factors ) these characteristic describe the filters' name along with its unique transform function .
- So a single pole is a lonely fellow - left to interact with no other pole - therefore there is no creation of a unique "transform" ( like Bessel, Butterworth, LR ) . :blah:




As I was about to change characteristics on the 2215 to 1st. order I ran in to some problems with one of the UltraDrives, which suddenly "lost" the fourth output, it somehow got assigned to input B.

Static maybe ?

- Anyways, I'm going to put my future suggestions in another posting.

- Don't feel compelled to try them out right away / just file them for later if you prefer / the main thing is to enjoy your new speakers and get used to what they do right now.



:cheers:

BTW : I'm really curious, just how did you manage to create those angled/bevelled decorative cuts, that are on the front edges ( like you put in the drawing ) ?

pangea
02-27-2005, 11:03 AM
Hi Roland



- I think it's wonderful that the system already images so well that the effects produced by the lowering of the crossover point, were immediately evident / ie " the collapsing soundstage" .



- Well,,, there shouldn't be. I should have mentioned that before or chosen my words more carefully . It takes more than one pole ( producing a 6 db slope ) to create a "signature" transform ( ie Bessel, Butterworth, LR ). It's the relative spacing of the poles to each other ( quantity of, 2, 3, 4, & up, all working within the desired crossover area ), as well as the filter poles interaction with each other , that creates the characteristic crossover curve near F3. Group-delay characteristics ( and transient response characteristic ) are also dictated by how the different poles interact with each other. Taken together ( along with some other factors ) these characteristic describe the filters' name along with its unique transform function .
- So a single pole is a lonely fellow - left to interact with no other pole - therefore there is no creation of a unique "transform" ( like Bessel, Butterworth, LR ) . :blah:





Static maybe ?

- Anyways, I'm going to put my future suggestions in another posting.

- Don't feel compelled to try them out right away / just file them for later if you prefer / the main thing is to enjoy your new speakers and get used to what they do right now.



:cheers:

BTW : I'm really curious, just how did you manage to create those angled/bevelled decorative cuts, that are on the front edges ( like you put in the drawing ) ?

These were the tools I used to chip away and grind the corners.

http://img.photobucket.com/albums/v421/pangea2012/Verktyg3.jpg

A pair of steady hands are required though, if you dont have big machines at hand.:)

I have come down with the flue, so the pace is somewhat slow at the moment. But as soon as I feel better again, I'll give it a new try to experiment with the slopes and x-over points, on the 2215.

EDIT: BTW, so far it sounds extremely good" The soundstage is rock steady and it's very easy to locate the singers and instruments!!!:D :rockon2: :rockon1::band:

BR
Roland

Earl K
02-27-2005, 11:28 AM
Thanks ! ( for the show of tools )

- Sorry to hear that you've gotten the flu . :(

- I'll be around when you can chat more,


:cheers:

pangea
02-28-2005, 04:43 AM
Hi Earl!
I've followed your advice, while recuperating from the flu I've tried to listen to them as is.

Thus far it's already been an overwhelming experience. The soundstage is firmly placed in the middle and the stereo perspective is excellent, so what else is there to ask for?

Well, if I'm allowed to be EXTREMELY demanding, I would like the less protruding instruments to be somewhat easier to locate and pinpoint as well. But then again, that maybe isn't even possible, on the records I've been listening to.

The singers and the lead instruments however, I can easily pinpoint down to an inch or two!:applaud:


BR
Roland

pangea
03-15-2005, 01:47 PM
Hi Earl!

Do you, or anyone else for that matter, have any rcommendations on "difficult" and revealing recordings, wich might be used to (3-D) fine-tune the speakers?

What else is there to be done to improve the sound?:bouncy:

BTW, yesterday I ordered some artificial leather, wich comes as lose as it possibly could, to the JBL blue and guess what the color is called?
It's called 2402, like my dear 075's.:applaud:

BR
Roland

Robh3606
03-15-2005, 02:31 PM
You could try Peter Gabriel Up or Amused to Death by Roger Walters. Both have some wild effects with Amused taking the cake. Uses Q Source??? I use them to verify phase after the standard phase test on my set-up disk. If one driver is screwed up the effects go all to hell. Also use it to set-up toe in, seated distance and height. When it's right you have things all over the room. To your sides, well past the speakers and what sound like behind you it's really remarkable where some of the images are placed, and how repeatable it is. By repeatable I mean it works with my mains XPL's and 4344's. It's easilly tranferable from system to system so it's a good tool. Once you know where everything goes it's a cinch to hear problems.


Rob:)

Zilch
03-15-2005, 02:41 PM
"Up" is crazy. Got 20 Hz on one track. Startling when the walls and ceiling make creaking noises. :D

And from the "Amused" liner notes:


If the dog barking at the beginning of the record doesn't sound like he's in the yard next door, then your speakers are out of phase.

"Why do I have to keep reading
These technical manuals?"

Earl K
03-15-2005, 04:14 PM
Hi Roland,

Some Questions First;

- How wide/narrow is the overall viewing angle into the sound stage ?

- How far apart are the speakers ( to center of horn ) ?

- How many degrees of "toe-in" ( angle-in ) are you using ?

:)

pangea
03-16-2005, 09:45 AM
Hi Roland,

Some Questions First;

- How wide/narrow is the overall viewing angle into the sound stage ?

- How far apart are the speakers ( to center of horn ) ?

- How many degrees of "toe-in" ( angle-in ) are you using ?

:)

Two persons seated next to each other, can just about hear the music coming from somewhere in the middle, but it won't be possible anymore to pinpoint the instruments or the singers voice, as the soundstage becomes fuzzy and inaccurate.
A stable and accurate soundstage is only wide enough for one person seated in the middle.

The distance between the speakers is 225cm (horn-center to horn-center) and the distance between speaker baffle and listener is about 300cm.

The toe-in is around 20 degrees. Both speakers pointing straight towards a single listener.

BR
Roland

Earl K
03-16-2005, 10:04 AM
Roland

I'll post a "shopping list" of thoughts on this later this evening .

- In the meantime, I do find that keeping a foam surface around the complete horn area makes a bit of difference to the "sharpness" of the image . I haven't studied all the types; but I use open-cell "road-case" foam. Eventually I'll try out more closed cell stuff such as neoprene. Even those cheap foam "camping mats" could offer the necessary resistive surface. I realize you have "fake leather" coming for that same area - I'd listen to it ( and other alternatives" ) before applying it .

<. :)

pangea
03-16-2005, 11:43 AM
Roland

I'll post a "shopping list" of thoughts on this later this evening .

- In the meantime, I do find that keeping a foam surface around the complete horn area makes a bit of difference to the "sharpness" of the image . I haven't studied all the types; but I use open-cell "road-case" foam. Eventually I'll try out more closed cell stuff such as neoprene. Even those cheap foam "camping mats" could offer the necessary resistive surface. I realize you have "fake leather" coming for that same area - I'd listen to it ( and other alternatives" ) before applying it .

<. :)

THNX for the tip, I'll try it out first, before applying any fake-leather permanently with glue. But then again, perhaps I could apply the fake-leather anyhow, since the 4mm "Masonite" I have mounted with the "rough" side out, needs to be covered with something anyway and perhaps it would be possible to place some neoprene/mouse-mat ore something like that, only around the horn-mouths afterwards, don't you think?
I already have two soft mouse-mats from earlier tests.:applaud:

It would really be a shame not to use the fake-leather, since the color is soooooo JBL'ishly beautiful.:D

I think I will have to read your "shopping-list" tomorrow, I feel I need to turn in early tonight.
Once again, many thanks Earl!!!:cheers:

BR
Roland

Earl K
03-16-2005, 12:24 PM
Hi Roland


,,,,, needs to be covered with something anyway and perhaps it would be possible to place some neoprene/mouse-mat ore something like that, only around the horn-mouths afterwards, don't you think?

- Really, the whole baffle will need some treatment of sorts. Maybe the fake leather on it's own will suffice. I don't really know. Surface treatments are something that are quite new to me - so I don't have a lot of experience with all the different types. I just know that I hear a "sharpening" of the imaging when I place foam around my speakers / including all the areas around the horn mouth. I mention neoprene because JBL has used it in the past in the XPL series. The Altec Model 19 had open-cell foam all around the horn face / the full width/height of the top box.

- I also think this type of thing falls into the "final-tweaking" category ( though "final" is such wishfull thinking ). :D



I already have two soft mouse-mats from earlier tests.

- My advice would be to start with the case foam ( the "worst looking" fix ) and work towards ( best looking ) since IME the best looking usually translates into "least effective" .


:)

Mr. Widget
03-16-2005, 12:51 PM
Many of THOSE silly audiophile speaker companies including Wilson have used foam or thick felt for this very purpose. I have too. It seems significantly less useful in the horn designs I have tried it on. On a speaker like the XPLs it seams to make the most difference.

It certainly is worth trying out. Sonus Faber uses real/synthetic leather... I don't think it really does much for diffraction, I think it is mostly for aesthetics.

Widget

Earl K
03-17-2005, 07:09 AM
Hi Roland,

Rather than one shopping list , I think I'll do an item by item installation of observations/suggestions .
You can either respond or just skip an item this way. It's also better for reference.


My setup; I'm going to make all the necessary measurements & commit them to CAD sometime in the next few days. In the meantime here are a few thoughts .

(i) My speakers are 1650 mm apart ( center of horn to the same ). This 65" spacing is about as wide as I can go in my place. It does works quite well .

(ii) Both speakers are focussed at a window. That point is @ 4300 mm away from each horn. Under that focal point is a table & lamp / no chair . In other words, if this is the sweet spot, then nobody gets to sit there.

(iii) My usual listening chair is to one side of this focal point. There is a duplicate chair on the other side ( of the center table /lamp ).
Both chairs hear ( or see the horns ) at an angle that has yet to be accurately measured ( this is where the CAD comes in ). It looks to be 10° to 15° off-axis
These 2 chairs also have a center to center postion of about 1650mm ( or center of a head to a head ).

(iv) There is a couch along the long wall facing across the room ( TV viewing ). This couch is also @ 15° off axis ( wait for an accurate measurement ) to the closest speaker . This couch , because of placement is "outside" of the imaginary rectangle created by the speakers & 2 chairs. At the far end of this couch is another location of great imaging ( making the couch a great place to stretch out & listen - ears are effectievly turned towards the speakers ) .

- A drawing will follow .

:)

Earl K
03-17-2005, 07:30 AM
Hi

I don't use tweeters since I can't seem to integrate them without having them altering the imaging. But you have different gear . If anyone can integrate them you should be able to. I'm always just trying pretty adhoc approaches when tweeters are involved .

(i) I'd start with engaging your 2496(s)' most extreme slopes on the transition between the horn and the tweeters. I'd even try choosing 2 slightly different points ( & creating a small response hole ) but also minimizing any overlap ( comb-filtering ) in response .

(ii) I forget your HF xover points. I wouldn't personally take a tweeter lower than 9 or 10K and would try higher a bit higher just for the heck of it. This may mean creating a HF lift circuit for your horn/driver combo to passively flatten its resposne. A simple "inline" resistor/capacitor combo are all that is required.

- ( Values ?? 16ohms & 1.5uf to 3 uf for the cap / resistor & cap are paralleled to each other & then placed in series with the compression driver ).

- Any DC blocking cap that may already exist on the compression driver line is now in series with the new cap.

- This DC blocking cap "changes" the effective capacitance of the cap that is acting as the HF lift/bypass.

- The net capacitance is always lower than the smaller of the two caps ( at the HF lift circuit position / the DC blocking cap still "sees" the resistor & driver impedances below the crossover point of the "lift" cap ).

- If you don't like the math - ( & who does ) - just buy a quantity of caps, ( .5 uf, 1.0 uf. & 1.5uf are all good values to own ). Observe your UltraCurve EQ ( in RTA mode ) as you add different values ontop of a base cap value of 1.5uf. Add as many as required to create the flattest response above 5K .

(iii) Try adding extra delay to the tweeter. Add in a factor of .125 to .25 ( extra delay ) on top of the existing delay ( which the unit chose - as perfect alignment ). This physco-acoustic trick has no garantee of working. But there are horn advocates out there who will tell you that the higher frequencies are best listened to with a dab of extra delay ( when coming from a compression driver / horn combo ) .

(iv) If you could put your tweeters to the inside of the horn on the baffle ( I know you can't ) then you would need to add extra delay to move the acoustic center of the tweeter to be "in behind the 2441". From my listening position , there is a convergence point ( when looking at the directly opposing speaker ) that may be helpfull in the imaging department. This was the original reason that I thought that a tweeter position to the inside ( & maybe up 45° ) could be useful.



- Again, this tweeter thing is all speculation , since I haven't done it.
And, I also don't see me purchasing the required equipment - any time soon .



:)

Earl K
03-17-2005, 11:55 AM
Hi Roland,

- It's possible that you are expecting just too much from a 45° ( 6 db down point ) pattern mid-horn.

- I've always wished for a 60° - though I get by with a 45° in my tight setup.

- You may actually require a 60° for your arrangement . ( I need to see a drawing of your setup. )

- I don't know of any off-the-shelf 60° round horn ( 2" ) entry, so it's a bit of a moot point. And none of the round tractrix stuff that are around publish specs. - so they're not a help . :D

:cheers:

Earl K
03-17-2005, 12:15 PM
Hi

Believe or not, I consider this part quite important to my imaging,,, because -
if the upper mids are at all too rambunctious then the lower (horn) mids suffer . This gives an overly bright presentation that isn't really directly related to EQ. It's a form of dynamic EQ that's at work here. My ears can't relax enough to listen for imaging cues if they are bothered by the dynamics .

IME, the easiest remedy in this area is to use a "MPP in Oil , AC motor run capacitor". MPP = Metallized PolyPropylene. The current cap that has the most "industry buzz" behind it for this category is the ASC type. ( model X386S, in fact ) . Now I haven't heard these since I use a comparable Mallory product ( this Mallory cap line of motor-runs is now owned by CDE ). These things definately rearrange the "dynamic curve" of the typical compression driver by "calming" the upper 2 octaves ( say 2.5K to 10K ) while seemingly releasing dynamics in the lower frequencies.

These frequency-dependant, dynamic rearrangements, will alter the sonic presentation / and / can lead to better imaging . ( It can be a cheap tweak to try out ) . Look here for a review on the ASC caps , as well as many others . (http://home.zonnet.nl/geenius/Cap.html)

BTW: Solens' used in this same DC blocking "role" offer a somewhat "pinched at the waist" sound - that I'm avoiding with the Mallorys. "Waist = lowermidrange warmth"

:cheers:

pangea
03-18-2005, 12:43 PM
Hi Earl!

Wow, many thanks for all the info and your comments!!!!:bouncy:

It'll take me a while comprehend and digest the content, so in the meanwhile I begin by posting the picture you asked me to, hoping it covers what you were talking about.http://img.photobucket.com/albums/v421/pangea2012/Plans.jpg


I have also moved the speakers around a bit and also reduced the distance between the speakers somewhat and also reduced the toe-in angle to 10 degrees. After that I changed the slopes to 48dB/oct. B/W on the 075 and the 2441J. I also added the 48dB slopes on the 2123/2215, but only where they meet the 2441. The rest I left at 18dB/oct. B/W. I'm not sure though if this is OK, or if I should change all the slopes, or if I still should go for the 6dB HP slope even on the 2123, as you mentioned earlier.
Then I also added a small "hole" between the 2441 and the 075, like you suggested. (9,02k and 9,26)

All these things together has made a significant difference in the soundstage, so now the sweet-spot is wide enough for at least two people!:applaud: :applaud:

I'll go on with your other suggestions bit by bit! :D Is this fun or what? :yes:

BR
Roland

pangea
05-06-2005, 07:45 AM
I've been a bit lazy lately! It has been so much fun listening to my hybrids that I haven't come around to finish the cabs.:o:

But now I have placed the fake leather on to the baffles and I was surprised over the difference it made.

In comparison, the over all sound has become less harsh, cleaner and smoother somehow. It's difficult to describe in a foreign language.
But what surprised me most was that I feel the biggest improvement was in the bass region.

The bass is more tight and easier to focus.

Don't get me wrong, the sound was GREAT before, but now it's even better still. Nothing dramatic, but still noticeably better.

BR
Roland

pangea
09-19-2005, 07:25 AM
Hi everyone!
I have made a few alterations on my MTM hybrids, that I would like to share, if anyone is still interested.

I've been experimenting off and on the past six months. Some things have worked, some have not.

A few months ago, I replaced the 2215's, with a very nice pair of 2235's I found at a decent price, so I simply had to buy them.
I'm not sure tho if it made any big difference, perhaps the 2235's go slightly deeper.

The 2215 went back to my old speakers, which are now making my daughter quite happy. Yes she likes them very much!

I have also been experimenting a bit on the x-overs (two Behringer Ultradrive DCX2496)

Going with the MTM concept and having the 2235's and the 2123's blend from about 80Hz to 1000Hz, it has become obvious the 2nd order slopes won't work as well as a 1st or 3rd order slope, due to phase problems as the Ultradrive wants to invert the phase on the 2235's only and I still wasn't quite happy with the soundstage there.
While it is possible to manually alter the phasing on the Ultradrive, it felt as if it would be better to go for 3rd or 1st order slopes instead.
Thanks "scottyj" for your input there!

The 3rd order Butterworth was a big improvement, but still the soundstage was a little bit fuzzy and I wanted more.
So I went for the 1st order Butterworth and at the same time I wanted to get rid of a small dip I had at 80Hz, so, I was thinking perhaps I could let the 2123 go as deep as to where it naturally rolled of, without any HP filtering and at the same time I thought I'd try an old 075 trick, which meant that I let the 2441 go as high as it can and at the same time x-over the 075 at 20.000Hz LP with a 1st order slope.

The entire x-over looks much more simplistic now and let me tell you it sounds absolutely beautiful all the way.
The soundstage is firm as a rock, as well as 3-D holographic and the speakers somehow disappear completely. It's so easy now, to pinpoint the instruments, that my mind and eyes are focusing entirely on where the musicians "are".
It's magical, that's what it is! :D

BR
Roland

pos
10-19-2007, 12:19 PM
Hi Pangea,

Nice setup !
What is the size of your 2123 box? Is it ported?