Dual drivers, One or Two chambers in enclosure?

[panduro]

Maybe a simple question, but somebody gitta ask it 😂😂😂😂
If making a speaker with two midbass drivers(2225), where both drivers cover same frequency range(35-700hz) What are the advantages/disadvantages with having One room in a Big enclosure(10cf), compared to having 2 chambers of 5cf each?

Best regards

panduro

[berga12]

Theory: If there are T&S difference due to building/material tolearances, separate chambers have the benefit to isulate every speaker from the back emission of the other (a bit different, not in phase, impedance minors differences etc...)

Practically: in that range, no one will be able to recognize those difference in the final acoustid emission, so the driver differences are negligible.

2 chambers keep the enclosure strongher with the need of less bracing.

[Flodstroem]

One enclosure could have the benefit of a better lower bass extension. If you can make a simulation of the speaker:
one with an internal volume of 5 cf for one speaker
and another with an internal volume of 10 cf with two speakers
For the 10 cf enclosure, calculate T/S as:
same Bl,
4 ohm or 16 ohm, your choice
cone area is doubled
rest of the parameters is the same as for one speaker

Compare both simś and look for a lower bass extension in the 10 cf enclosure if any? :p

[more10]

A PPSL (http://www.diyaudio.com/forums/subwoofers/177905-thread-those-interested-ppsl-enclosures.html) (Push Pull Slot Loading) box will reduce distortion in bass. It is not recommended for midrange tough. I have not heard the 2225, but I believe the ribbed cone will not sound good in midrange anyways.

[audiomagnate]

One of my favorite speakers, the ADS L1530, uses the two chamber approach, so maybe there's something to it. That surprisingly small speaker did 14 Hz extremely well.

[ivica]

Maybe a simple question, but somebody gitta ask it 😂😂😂😂
If making a speaker with two midbass drivers(2225), where both drivers cover same frequency range(35-700hz) What are the advantages/disadvantages with having One room in a Big enclosure(10cf), compared to having 2 chambers of 5cf each?

Best regards

panduro
Hi panduro,
I do not think that to use such combo over 300Hz, as mid bass wolud about 3dB lass then bass region
Regards
Ivica

[panduro]

hello all and thanks a lot for sharing your knowledge,

im asking this question because I've never made a speaker with dual bass drivers before. active xover. the orientation of the bass cabinet im planning is very similar to the 4435(woofers side by side), and im thinking about making the cabinet deeper on the side than the other(making it toe in when facing straight). this would be considerably easier if the two woofers can share a share the same room en the enclosure. if it has no severe drawbacks, compared to the one chamber pr driver setup.

berga, thank you for your info, that makes it more clear to me :).

flodstroem, i tryed simulating it, but i can only do it on an online program that i found, im a mac user who hasn't found a good sim program ? my sim did not show any differens in low extension?

more, thanks for making me aware of that option also, i will read about it, maybe for a future project.

ivica, would you be kind and explain to me what the reason for that is? im using these drivers in there current cabinets(2x2225 + 1x2445) although not high end , it sounds good with a active xover .

magnate, it seems like consensus is to go with one chamber pr driver, maybe i should move slowly away from my toe in idea and just go square :)

best regards

panduro

[Flodstroem]

One enclosure could have the benefit of a better lower bass extension. If you can make a simulation of the speaker:
one with an internal volume of 5 cf for one speaker
and another with an internal volume of 10 cf with two speakers
For the 10 cf enclosure, calculate T/S as:
same Bl,
4 ohm or 16 ohm, your choice
cone area is doubled
rest of the parameters is the same as for one speaker

Compare both simś and look for a lower bass extension in the 10 cf enclosure if any? :p

I forgot the VAS, its also doubles if calc. with two speakers.
I have done an instant sim with two 2225H in a 10 cf (283 lit) in a made-up box with following internal dimensions: 120 cm x 50 cm x 47 cm and you can see the results here in this file: But there is a lot to do for the shape of the box. Also I dont know what type of box you are thinking of......... :o:
74762

[panduro]

Thank you very much flodstroem,

That is a awesome sim, so much info i dont have the knowlegde to interpret :).

would you be willing to do A sim for me If i drew the plans and send Them to you(it Will be a scanned image of a paper drawing as Im a computer idiot)? Only If Its not to much trouble!

Best regards

panduro

[Flodstroem]

Hello "panduro" in Københvn
Of course I can do a sim for you. I need the specified internal dimensions (H x W x D)
I also need the positioning of the two LF speakers including the port (ports?) and if you intend to have the HF compression driver inside I also need the position of it..

Also post the internal dimensions of the smaller cabinets (5 cf) you wore considering in your first post. If you do I also can do a sim so you get something
to compare. ;)

Im also a Mac-man but using Windows-XP on Oracleś virtual PC https://www.virtualbox.org/ (I can recommend it) My simulation program are Martin Kings calculating sheets :)
My calculating program is a demo version of the MathCad and this demo program is for free. Its an older version and last Windows for it was the "XP" version. The drawback is that I cant save my sim sheets so I had to print them as .pdf files for to save them. Its a little bit more complicated but best thing is, it works :D

[ivica]

hello all and thanks a lot for sharing your knowledge,

ivica, would you be kind and explain to me what the reason for that is? im using these drivers in there current cabinets(2x2225 + 1x2445) although not high end , it sounds good with a active xover .
....?panduro

Hi panduro,

Drivers mutual coupling depends to the driver relative distance...
Regards
Ivica

[panduro]

Tak hr.norge,
ill do that tomorow and check out the sim software when time permits.

hello ivica,
To make sure Im getting your point, driver coupling/boost happens If the centers of the drivers, is less distance appart then 1/4 of wavelenght. In my case that Will limit the coupling to below 200hz. Good point, ill have to correct that via my xover i guess. Or should i try to flatten out the frequency response with box size and tune it for a more gradual Roll off?

best regards
panduro

[ivica]

Tak hr.norge,
ill do that tomorow and check out the sim software when time permits.

hello ivica,
To make sure Im getting your point, driver coupling/boost happens If the centers of the drivers, is less distance appart then 1/4 of wavelenght. In my case that Will limit the coupling to below 200hz. Good point, ill have to correct that via my xover i guess. Or should i try to flatten out the frequency response with box size and tune it for a more gradual Roll off?

best regards
panduro

Hi panduro,
YES, I think -3dB, is somewhere round 1/2 wavelength center to center, so round 40cm, or lambda 0.8m,
So 345/0.8 = 345*1.25 Hz = 430Hz....so 300Hz crossover freq. Is OK.
But more ,????

Regards
Ivica

[Flodstroem]

panduro, I have done 2 simś for you. But....... Im unsure of the tuning frequency for two x 2225H. I havnt checked what is the most optimal tuning frequency for such cabinets like those you send a drawing of. If you choose other tuning frequencies, modifications of the ports would be necessary. ;)

7481374814

There is practically no differences between the two models, only different port tubes as far as I can see...............

[panduro]

hello Ivica and Flodstrøm,
thanks for your help and guidance, this newb needs it :)

ivica,
there must be something im missing, im not sure how you come up with those numbers if i look at flodstrøms sim, -3 is around 140hz and the response starts to drop very slowly from 300hz and down. so to me it looks like i have to boast a bit from 200 and downwards to get it flat and a bit more to get a bit heavier target curve.
are you factoring in some cabin gain or what am i not getting?

hello flod and thx for doing the sims, its much appreciated!

not knowing a lot about this, i dont know how to interpret what i see, other than the respons curve looks good to me. i do think ill see if i can lower the tuning a bit, to get a more gradually decanting bass respons.

best regards

panduro

[Flodstroem]

hello flod and thx for doing the sims, its much appreciated!

not knowing a lot about this, i dont know how to interpret what i see, other than the respons curve looks good to me. i do think ill see if i can lower the tuning a bit, to get a more gradually decanting bass respons.

best regards

panduro

Your welcome panduro :)

I can do a new sim for you and set the tuning frequency to for example 25 Hz so you could see whats happens
The simś so far indicate that you have to boost from where you pointed out and downwards. You also need to put in same high pas filter for to protect the woofers from infra sound/frequencies where the woofers dont have any damping at all.
The impulse response looks good (good damping) the same with group delay which is important to hold low with bass drivers. Also there is a minimum of side wall reflections inside the cabinets so I think your model is OK.

[Flodstroem]

OK here is the sim. As you could see the efficiency of 20 Hz has grown with at least 4 dB which is a lot. But you will get lower efficiency between 25-75 Hz. The response from 80 Hz and upwards to 900 Hz is unchanged.
Group delay has risen but not much.
Port length is 8" and location of the port had to be moved a bit from former sim.
Otherwise it looks like as before (when tuned to 30 Hz)

74832

[panduro]

hello flod,
again thanks mate, mighty fine curves you got ;)

ill do some reading on ports and port velocity, but to me it looks like i need bigger ports.

tomorrow im picking up the "new" 2440's(with 2441 diaphrams) and 2350 horns, so now i just need uhf tweeters and a good pile of wood :)

best regards

panduro

[ivica]

hello Ivica and Flodstrøm,
thanks for your help and guidance, this newb needs it :)

ivica,
there must be something im missing, im not sure how you come up with those numbers if i look at flodstrøms sim, -3 is around 140hz and the response starts to drop very slowly from 300hz and down. so to me it looks like i have to boast a bit from 200 and downwards to get it flat and a bit more to get a bit heavier target curve.
are you factoring in some cabin gain or what am i not getting?

hello flod and thx for doing the sims, its much appreciated!

not knowing a lot about this, i dont know how to interpret what i see, other than the respons curve looks good to me. i do think ill see if i can lower the tuning a bit, to get a more gradually decanting bass respons.

best regards

panduro

Hi

May be useful

regards
ivica

[panduro]

Hi Ivica,
If possible, could you post a link or book name so i Can learn about it?

best regards

panduro

[ivica]

Hi Ivica,
If possible, could you post a link or book name so i Can learn about it?

best regards

panduro

Hi
There figures are made from the different sources, but here may be some user-able info:

1.
http://trace.tennessee.edu/cgi/viewcontent.cgi?article=3910&context=utk_gradthes
[Mutual Coupling Between Loudspeakers, Robert Edward Bodenheimer, University of Tennessee - Knoxville]

2.
http://www.zainea.com/mutualcoupling.htm

Mutual Coupling and Loudspeakers
Keith R Holland
lSVR, University of Southampton, UK
Philip R Newell Moana, Spain

3.
http://milas.spb.ru/~kmg/files/literature/Loudspeakers%20For%20music%20recording%20and%20rep roduction.pdf




regards
ivica

[Flodstroem]

Thanks ivica for the #3 link, it was a huge document but I had a sneak peek on TL (Transmission Line) speaker and I liked what was written there, because that is also my own experience. Wander why JBL never tried that type of speaker :crying:

[panduro]

Thanks Ivica,
im looking forward to Reading it all, especially the book 😀.
I did some studying on coupling etc last evening and i Will have a challenge.


just Got the last drivers for my little project.
so this is the list(pr speaker).
2404 on dolly horn
2440(with 2441 diaphrams) on 2350 horn
2225 x 2
Crossover from 2440 too 2404 Will be passive, rest Will be active thought Dbx Pa+.
so it Will Either be a 3way or 4way depending on wheather i end up running both 2225's together or just letting the second 2225 help from 200 and down.

have an awesome day

panduro

[bldozier]

Id like the idea of dual 2108s in a chamber, I think. couldn't one be removed an the, cut out capped. the 2123 is 7~ 14 ) liters. this can be one or two? the 2108 is 11.3L from what I've red not sure if this number is beginning median or end figure. anyone know. if a driver needed to be pulled for any reason at least I could be comfortable doing so.

[ivica]

Thanks Ivica,
im looking forward to Reading it all, especially the book 😀.
I did some studying on coupling etc last evening and i Will have a challenge.


just Got the last drivers for my little project.
so this is the list(pr speaker).
2404 on dolly horn
2440(with 2441 diaphrams) on 2350 horn
2225 x 2
Crossover from 2440 too 2404 Will be passive, rest Will be active thought Dbx Pa+.
so it Will Either be a 3way or 4way depending on wheather i end up running both 2225's together or just letting the second 2225 help from 200 and down.

have an awesome day

panduro
HI Panduro,
Due to passive UHF filter, and geometry, possible comb filter effects can be introduced.
Regards
Ivica

[panduro]

Hello ivica,
i value your input, but Im a newb so i benifit alot from explanations on alot of your advice, i appriciate your Continuing patience.

if necesary i Can do UHF filter active also, i Will just need 2 extra amplifier channels.

Im reading the loudspeakers book you linked to, good Reading 👍.

When you write comb.f because of geometri i assume you mean the bass drivers?
Am i corrorrect in thinking comb filter effect is mostly an off axis thing with sound cancelations?
i have Seen some older studio moniters that runs Dual 15, some on same frequency, some that runs the second woofer from 200/100 and down. Or the Everest 66000, dual 15 One running from 700hz and Down the other from 150 and Down.
how do those speakers combat the issue?

i know it would be easier to get a good result just using One 15 pr side, but i Want the awesome look and powerhandling of the dual and side by side is my only option due to hight limitations.

If i have too, ill even add a midrange driver between the basses If it minimizes the comb f. Issue.
But as this is not a normal layout so Im strugling finding info about it.

best regards
Panduro

[ivica]

Hello ivica,
i value your input, but Im a newb so i benifit alot from explanations on alot of your advice, i appriciate your Continuing patience.

if necesary i Can do UHF filter active also, i Will just need 2 extra amplifier channel
Im reading the loudspeakers book you linked to, good Reading 👍.

When you write comb.f because of geometri i assume you mean the bass drivers?
Am i corrorrect in thinking comb filter effect is mostly an off axis thing with sound cancelations?
i have Seen some older studio moniters that runs Dual 15, some on same frequency, some that runs the second woofer from 200/100 and down. Or the Everest 66000, dual 15 One running from 700hz and Down the other from 150 and Down.
how do those speakers combat the issue?

i know it would be easier to get a good result just using One 15 pr side, but i Want the awesome look and powerhandling of the dual and side by side is my only option due to hight limitations.

If i have too, ill even add a midrange driver between the basses If it minimizes the comb f. Issue.
But as this is not a normal layout so Im strugling finding info about it.

best regards
Panduro
HI
I want pay your attention to the possible path difference between VHF and UHF drivers, that would introduce time delay between sound front generated from the drivers , and that would produce comd filter
Effect on almost any direction. the real practical solution woud be proper time delay compesation between the drivers....

Regards
Ivica