This is my way of killing two birds with one stone. I have a large number of 12-inch Pioneer woofers sitting around that I want to "get rid of," and I also need a high fidelity subwoofer that is of reasonable finished size. These woofers are of high quality and go pretty low, but are not designed specifically for subwoofer use. That's another reason why I want to use multiple drivers. BTW I only listen to classical music, including pipe organ music.
I started off thinking of just building a simple sealed enclosure, using woofers in isobaric alignment to keep the size down.
Then I started to think, "How can I add more woofers?" One approach is to start putting woofers on more than one face of the sub. However, I wonder if that will tend to contribute to phase cancellation problems. Especially since I am also thinking of using more than one sub. (I lean toward a pair of subs -- one under each main speaker.)
It occured to me that I might be able to eliminate any phase-induced cancellation problems by making a design like the one shown in the drawing. (I'm not sure I would used woofers on four faces, but that's how I drew it.) Am I correct in assuming this is essentially a 4th-order bandpass design? If so, is my having the woofers firing directly into the port a problem? And how do I actually design something like this so it will work? I would be grateful for tips on free or cheap software that would help me work this out. If the design is going to be too daunting, I may just stick with a more foolproof simple sealed enclosure.
Thanks!
Christopher Witmer
Tokyo
I started off thinking of just building a simple sealed enclosure, using woofers in isobaric alignment to keep the size down.
Then I started to think, "How can I add more woofers?" One approach is to start putting woofers on more than one face of the sub. However, I wonder if that will tend to contribute to phase cancellation problems. Especially since I am also thinking of using more than one sub. (I lean toward a pair of subs -- one under each main speaker.)
It occured to me that I might be able to eliminate any phase-induced cancellation problems by making a design like the one shown in the drawing. (I'm not sure I would used woofers on four faces, but that's how I drew it.) Am I correct in assuming this is essentially a 4th-order bandpass design? If so, is my having the woofers firing directly into the port a problem? And how do I actually design something like this so it will work? I would be grateful for tips on free or cheap software that would help me work this out. If the design is going to be too daunting, I may just stick with a more foolproof simple sealed enclosure.
Thanks!
Christopher Witmer
Tokyo
Attachments
I cant see how it will work, plus I dont see why you need 4 drivers in the box - have you quadrupled the volume to account for the added drivers?
I would check out http://www.diysubwoofers.org
If you like organ music then I would suggest a 1/4 wave TL - they are not that hard to design (Ive made 3 of them). Only drawback is size.
I would check out http://www.diysubwoofers.org
If you like organ music then I would suggest a 1/4 wave TL - they are not that hard to design (Ive made 3 of them). Only drawback is size.
Some clarifications on this proposed sub design
Regarding the size shown: first, it is just a conceptual drawing, --nothing even remotely to scale. Second, I was thinking of using electronic circuitry that would help me to drive the woofers below their resonant frequency, and also get away with a smaller cabinet than usual.
Thanks,
Christopher Witmer
Tokyo
Regarding the size shown: first, it is just a conceptual drawing, --nothing even remotely to scale. Second, I was thinking of using electronic circuitry that would help me to drive the woofers below their resonant frequency, and also get away with a smaller cabinet than usual.
Thanks,
Christopher Witmer
Tokyo
Hey, here's an idea: You said you had a load of these 12" drivers...how about isobaric push-pull to cancel out those pesky nonlinearities and lower distortion? You might be able to pull off a reasonable-size sealed box system that would extend fairly low. Isobaric Push-Pull If you had eight woofers, then you could do two subwoofers each with four woofers in two isobaric pairs.
If you dont know the TS parameters, then should test them before choosing an alignment - much less running the saw.
12-inch drivers, not speced for sub use? If I absolutely had to get down low with something like that, I would go with horn-loading, but you've got to know the parameters before you start designing/building.
If you have some of those ugly-low QTS Pioneer woofers, you should use some of your "loads" as passive radiators. Pioneer also made some high QTS woofers, where a OB/dipole sub would be any easy build. If you're never going to check those parameters, I think I'd start with the dipole first.
12-inch drivers, not speced for sub use? If I absolutely had to get down low with something like that, I would go with horn-loading, but you've got to know the parameters before you start designing/building.
If you have some of those ugly-low QTS Pioneer woofers, you should use some of your "loads" as passive radiators. Pioneer also made some high QTS woofers, where a OB/dipole sub would be any easy build. If you're never going to check those parameters, I think I'd start with the dipole first.
Use as many drivers in as many placements as you wish so long as the farthest distance from the cones is somewhat less than 1/4 wavelength. For a passband up to 100 Hz you will be safe with maximum cone spacing of up to about 2.5 feet.
To get a lot of bass from a bunch of cheapo drivers I'd go with a line array from floor to ceiling. With the drivers spaced edge to edge the phase issue won't arise as they'll act as a single source. For even more oopmh have the array facing into the room corner. Aside from working well this would also take up the smallest possible amount of floor space for the number of woofers used.
To get a lot of bass from a bunch of cheapo drivers I'd go with a line array from floor to ceiling. With the drivers spaced edge to edge the phase issue won't arise as they'll act as a single source. For even more oopmh have the array facing into the room corner. Aside from working well this would also take up the smallest possible amount of floor space for the number of woofers used.
Some more details of my woofers
Thanks to all who have replied so far. Some details on my woofers:
I have a total of 16 woofers -- eight woofers of the type shown in the attached image, and eight of an earlier version of the same woofer. The version shown has a "carbon graphite" polypropylene cone, dual voice coils, and is shielded. The rated efficiency of the speaker from which it was taken is 93dB/1W1m. The earlier version differs in that it lacks dual voice coils, has a paper cone, and the rated efficiency of the speaker was higher, 95dB/1W/1m. The power handling ability of the loudspeaker systems was about 120W rms, although I don't know if the woofers themselves are capable of handling more (it may have been the tweeters that were the limiting factor in determinng the allowable power input). The xmax for these is not huge like one normally expects from a modern subwoofer driver; that's why I'm inclined to use multiple drivers. Again, space is tight. (This is Tokyo!) I would like to fit however many woofers I use into a space that does not exceed 1.5 meters wide, by 50 x 50 cm tall and deep. (I suppose I could go a bit higher or deeper, to perhaps 60cm.)
Thanks!
Christopher Witmer
Tokyo
Thanks to all who have replied so far. Some details on my woofers:
I have a total of 16 woofers -- eight woofers of the type shown in the attached image, and eight of an earlier version of the same woofer. The version shown has a "carbon graphite" polypropylene cone, dual voice coils, and is shielded. The rated efficiency of the speaker from which it was taken is 93dB/1W1m. The earlier version differs in that it lacks dual voice coils, has a paper cone, and the rated efficiency of the speaker was higher, 95dB/1W/1m. The power handling ability of the loudspeaker systems was about 120W rms, although I don't know if the woofers themselves are capable of handling more (it may have been the tweeters that were the limiting factor in determinng the allowable power input). The xmax for these is not huge like one normally expects from a modern subwoofer driver; that's why I'm inclined to use multiple drivers. Again, space is tight. (This is Tokyo!) I would like to fit however many woofers I use into a space that does not exceed 1.5 meters wide, by 50 x 50 cm tall and deep. (I suppose I could go a bit higher or deeper, to perhaps 60cm.)
Thanks!
Christopher Witmer
Tokyo
Attachments
Looking at the magnet size, they're fairly low Q drivers so you might need some EQ to get the lowest organ notes with a dipole. Otherwise you could easily fit 8 per side in a W Baffle cab as long as you can accomodate at 67cm or so height. You may even be able to fit 8 accross in WBaffles within your 1.5M limit. If it didn't get you what you to the output level you wanted, you could still use the small alignment and go with an aperiodic cab by stuffing the back chambers. You might even be able to have it be both with stuffed vents on the sides and/or top near the back and use a foam rubber seal around the back edges to form a seal with the wall. Then you'd have an aperiodic enclosure against the wall and dipole away from the wall.
That's such a good idea that I think I'll try that one myself.
That's such a good idea that I think I'll try that one myself.
Hi,
I am new here but well with my knowledge of adding subwoofers like that,there are only 2 ways of hooking up a sub with single voice coil. I would ahve thought that if you ahd 4 subwoofers inside one enclosure they would cancell each other out?? sorry if I am wrong.
Cause I know from expirience that it would if you had the subs hooked the same one way.
Thanks
I am new here but well with my knowledge of adding subwoofers like that,there are only 2 ways of hooking up a sub with single voice coil. I would ahve thought that if you ahd 4 subwoofers inside one enclosure they would cancell each other out?? sorry if I am wrong.
Cause I know from expirience that it would if you had the subs hooked the same one way.
Thanks
cdwitmer said:
I suggest you take look around the infinite baffle forum http://f20.parsimony.net/forum36475/
What you drew up is very similar to some of the manifold designs that the guys on that forum build.
Your idea of operating the drivers below their resonance is the idea behind BagEnd's ELF Infrasubs. There are circuits and descriptions for that design on ESP website:
http://sound.westhost.com/
look for ELF.
I don't think you should mix woofers in the same enclosure. It's been done before, but it's definitely not amateur hour.
Good luck.
Hi CDwitmer,
"I lean toward a pair of subs -- one under each main speaker"
IMO you are on the right track there for several reasons... but don't use those speakers just because you have them. Get some drivers designed to act as subs. In my project studio I listen to and produce mostly orchestral music and so need truly full range un-hyped response from my system. To avoid room modes interfering with equalization as much as possible, I monitor in the near field so I had to get my speakers on my countertop - including, after a lot of messing about with single centrally located sub and various crossover points, stereo subs. I now
have two 8" Peerless subs in closed boxes 10" square face, 14" deep OD, of 3/4" mdf actively crossed over to full range Jordans @ 110hz (bi-amped) sitting on top of the subs which are themselves on 4" or so stands which effectively isolates the speakers from the counter. Each combination collumn stands just over 22" tall including stands and is 14" deep. This is the first of many monitor systems I tried that I can stand to listen to! These little subs go subsonic in my cabs with ease. For example, the first time I ever really heard (and felt!) the 16 and 32 foot pedal pipes in Holst's Planets #5 (in about the 8th minute) was through these speakers. It had me scrambling for the score to see what
the hell was making that sound. They get pretty loud - granted, I listen at moderate levels, but a pair of these would do for a medium sized room. A system like this can render organ the way you want to hear it. Peerless subs $40 each at Parts Express,
http://www.partsexpress.com/pe/show...&St3=-85497067&DS_ID=3&Product_ID=16242&DID=7
Specs: * Power handling: 150 watts RMS/210 watts max * Voice coil diameter: 1-1/4" * Voice coil inductance: 1.2 mH * Nominal Impedance: 8 ohms * DC resistance: 5.0 ohms * Frequency response: 25-5,500 Hz * Fs: 25 Hz * SPL: 87 dB 2.83V/1m * Vas: 3.07 cu. ft. * Qms: 2.65 * Qes: .54 * Qts: .45 * Xmax: 5.5mm *
Cheers.
"I lean toward a pair of subs -- one under each main speaker"
IMO you are on the right track there for several reasons... but don't use those speakers just because you have them. Get some drivers designed to act as subs. In my project studio I listen to and produce mostly orchestral music and so need truly full range un-hyped response from my system. To avoid room modes interfering with equalization as much as possible, I monitor in the near field so I had to get my speakers on my countertop - including, after a lot of messing about with single centrally located sub and various crossover points, stereo subs. I now
have two 8" Peerless subs in closed boxes 10" square face, 14" deep OD, of 3/4" mdf actively crossed over to full range Jordans @ 110hz (bi-amped) sitting on top of the subs which are themselves on 4" or so stands which effectively isolates the speakers from the counter. Each combination collumn stands just over 22" tall including stands and is 14" deep. This is the first of many monitor systems I tried that I can stand to listen to! These little subs go subsonic in my cabs with ease. For example, the first time I ever really heard (and felt!) the 16 and 32 foot pedal pipes in Holst's Planets #5 (in about the 8th minute) was through these speakers. It had me scrambling for the score to see what
the hell was making that sound. They get pretty loud - granted, I listen at moderate levels, but a pair of these would do for a medium sized room. A system like this can render organ the way you want to hear it. Peerless subs $40 each at Parts Express,
http://www.partsexpress.com/pe/show...&St3=-85497067&DS_ID=3&Product_ID=16242&DID=7
Specs: * Power handling: 150 watts RMS/210 watts max * Voice coil diameter: 1-1/4" * Voice coil inductance: 1.2 mH * Nominal Impedance: 8 ohms * DC resistance: 5.0 ohms * Frequency response: 25-5,500 Hz * Fs: 25 Hz * SPL: 87 dB 2.83V/1m * Vas: 3.07 cu. ft. * Qms: 2.65 * Qes: .54 * Qts: .45 * Xmax: 5.5mm *
Cheers.
for something a little different..
8 drivers per side
4 drivers facing the listener in a vertical array on an open baffle(the single voicecoil drivers). 4 drivers immeadiatly behind them in a sealed box with an aperiodic "vent", (the dual voicecoil drivers). The single voice coil drivers and one voicecoil of the dual voice coil drivers are series/parallel wired and are either driven by your main amp or a plate amp. The second voicecoil of the dual voicecoil drivers are series/parallel wired and are conected to a subwoofer plate amp with variable crossover and eq.. The front and rear line both operate in-phase (i.e. push-push).
Physically the "box" would look similar to the Legacy Audio Whisper's bass drivers, EXCEPT it would have a box on the rear drivers (and of course you would see 4 drivers in a line). (Note: the black edge on the baffle of the Whisper isn't a black edge - its an opening where the front driver's rear radiation "exits" and where the rear driver's front radition exits.)
http://www.legacy-audio.com/2003/whisper.html
8 drivers per side
4 drivers facing the listener in a vertical array on an open baffle(the single voicecoil drivers). 4 drivers immeadiatly behind them in a sealed box with an aperiodic "vent", (the dual voicecoil drivers). The single voice coil drivers and one voicecoil of the dual voice coil drivers are series/parallel wired and are either driven by your main amp or a plate amp. The second voicecoil of the dual voicecoil drivers are series/parallel wired and are conected to a subwoofer plate amp with variable crossover and eq.. The front and rear line both operate in-phase (i.e. push-push).
Physically the "box" would look similar to the Legacy Audio Whisper's bass drivers, EXCEPT it would have a box on the rear drivers (and of course you would see 4 drivers in a line). (Note: the black edge on the baffle of the Whisper isn't a black edge - its an opening where the front driver's rear radiation "exits" and where the rear driver's front radition exits.)
http://www.legacy-audio.com/2003/whisper.html
I believe the Whisper is an in-phase design. though with a little delay and out-of-phase it could be configured as a 2nd order gradient (i.e. a hypercardoid/superdirectional.) hmmmm, that reminds me.. me thinks I erred on my post on the dipole vs. horn thread - the minimal rear-wave on the hypercardoid is in-phase (not out of phase), though the principal I was getting at was correct (that the null pressure zone was reducing room mode influances).
The design will reduce non-linearity and cone-flexing to an extent. Additionally there should be some reduction in off-axis spl.. whether this is more or less than a dipole, I don't know. (I'm suspecting that it will be less.. with less roll-off than the traditional 6db reduction per octave, but it is purely a guess.) Don't you have a bunch of woofers for dipole use? If so, you could run a quick test to see what the real-world effect is.
The design I suggested is obviously quite a bit different.. the effectivness of both a reduction in non-linearity and side axis nullification will be freq. dependent. The directivity should act more like a dipole as freq. increases and more like a monopole as freq. decreases. In otherwords combine something similar to a dipole midbass driver to a monopole subwoofer with a 1st order filter, while reaping the benefits for both drivers of reduced non-linearity.
The design will reduce non-linearity and cone-flexing to an extent. Additionally there should be some reduction in off-axis spl.. whether this is more or less than a dipole, I don't know. (I'm suspecting that it will be less.. with less roll-off than the traditional 6db reduction per octave, but it is purely a guess.) Don't you have a bunch of woofers for dipole use? If so, you could run a quick test to see what the real-world effect is.
The design I suggested is obviously quite a bit different.. the effectivness of both a reduction in non-linearity and side axis nullification will be freq. dependent. The directivity should act more like a dipole as freq. increases and more like a monopole as freq. decreases. In otherwords combine something similar to a dipole midbass driver to a monopole subwoofer with a 1st order filter, while reaping the benefits for both drivers of reduced non-linearity.
With so many woofers there are many options that sound promising for high fidelity use.
* push pull mounting this is one thing I'd definately suggest no matter what alignment
* infinite baffle - one of the best options as it has a good balance of output and fidelity, probably better than anything except dipole but with more output and it takes up no space in your room
* dipole - with this many woofers you can get good ouput with a dipole and the best in room response
* TL - very good transient response and very good for classical music. Size will probably be a problem though.
I'd suggest two approaches that I think will suit best:
1. infinite baffle with all drivers mounted push pull - eq to boost low end response and to deal with room modes
2. hybrid dipole/monopole - for this you need to do some room measurements and find out where the lowest room mode is. Use monopole below the lowest room mode. The monopole might be sealed boxes or infinite baffle but won't need any eq if used below the modal range of the room. Then in the modal range use dipoles - either W frame or U frame (the latter has 6db more output but isn't as effective with room modes). You might cross from dipole to monopole at say 40 Hz, use some eq on the dipole to get down that low. This approach is used by Thorsten Loesch and I think it's one of the best for accuracy in a small to medium room. You would have to experiment with how many woofers you would need for the dipole and monopole. Although sealed for the monopole would work well, the IB will have a transient response matching the dipole which I think would be better.
* push pull mounting this is one thing I'd definately suggest no matter what alignment
* infinite baffle - one of the best options as it has a good balance of output and fidelity, probably better than anything except dipole but with more output and it takes up no space in your room
* dipole - with this many woofers you can get good ouput with a dipole and the best in room response
* TL - very good transient response and very good for classical music. Size will probably be a problem though.
I'd suggest two approaches that I think will suit best:
1. infinite baffle with all drivers mounted push pull - eq to boost low end response and to deal with room modes
2. hybrid dipole/monopole - for this you need to do some room measurements and find out where the lowest room mode is. Use monopole below the lowest room mode. The monopole might be sealed boxes or infinite baffle but won't need any eq if used below the modal range of the room. Then in the modal range use dipoles - either W frame or U frame (the latter has 6db more output but isn't as effective with room modes). You might cross from dipole to monopole at say 40 Hz, use some eq on the dipole to get down that low. This approach is used by Thorsten Loesch and I think it's one of the best for accuracy in a small to medium room. You would have to experiment with how many woofers you would need for the dipole and monopole. Although sealed for the monopole would work well, the IB will have a transient response matching the dipole which I think would be better.
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