hence the 4 drivers. Those boxes are long gone and thinking 3 drivers, mag to front configuration (tunnel) would be interesting e.g. [>>>]
I could use all 4 in a tunnel, which would be easier to wire up – back to 8ohm.
I started gluing up 2 - 15” square boards (1 ½”), will cut them, and glue up/laminate stacks as needed. This is a 2 sheet MDF and glue project ~ $60 bucks total.
Suggested box size for 1 driver - CONNOISSEUR BOX = 160L, PORT = 100 x 400mm, F 17Hz.
831857 12" POLYPROPYLENE WOOFER
Parameters: Free air Common Baffled
Nominal impedance Zn (ohm) 8
Minimum impedance/at freq. Zmin (ohm/Hz) 6.3/124
Maximum impedance Zo (ohm) 46.9
DC resistance Re (ohm) 5.5
Voice coil inductance Le (mH) 2.8
Capacitor in series with 8 ohm
(for impedance compensation) Cc (μF) 24
Resonance Frequency fs (Hz) 24.0 22.9
Mechanical Q factor Qms 3.72 3.90
Electrical Q factor Qes 0.49 0.52
Total Q factor Qts 0.44 0.46
F (Ratio fs/Qts) F (Hz) 50
Mechanical resistance Rms (Kg/s) 3.25
Moving mass Mms (g) 80.2 88.2
Suspension compliance Cms (mm/N) 0.55
Effective cone diameter D (cm) 25.7
Effective piston area Sd (cm²) 520.0
Equivalent volume VAS (ltrs) 210.0
Force factor Bl (N/A) 11.6
Reference voltage sensitivity
Re 2.83V 1m at 124 Hz (Measured) (dB) 89.3
Voice coil diameter d (mm) 39
Voice coil length h (mm) 26.0
Voice coil layers n 4
Flux density in gap B (T) 0.99
Total useful flux (mWb) 1.52
Height of the gap hg (mm) 8
Diameter of magnet dm (mm) 134
Height of magnet hm (mm) 22
Weight of magnet (kg) 1.28
Power handling:
Long term Max System Power (IEC) (W) 220
Max linear SPL (rms) / by power (dB/W) 110/170
ROCK BOX = 80L, PORT = 100 x 200mm, F 33Hz.
THEATER BOX = 120L, PORT = 100 x 220mm, F 25Hz.
CONNOISSEUR BOX = 160L, PORT = 100 x 400mm, F 17Hz.
I could use all 4 in a tunnel, which would be easier to wire up – back to 8ohm.
I started gluing up 2 - 15” square boards (1 ½”), will cut them, and glue up/laminate stacks as needed. This is a 2 sheet MDF and glue project ~ $60 bucks total.
Suggested box size for 1 driver - CONNOISSEUR BOX = 160L, PORT = 100 x 400mm, F 17Hz.
831857 12" POLYPROPYLENE WOOFER
Parameters: Free air Common Baffled
Nominal impedance Zn (ohm) 8
Minimum impedance/at freq. Zmin (ohm/Hz) 6.3/124
Maximum impedance Zo (ohm) 46.9
DC resistance Re (ohm) 5.5
Voice coil inductance Le (mH) 2.8
Capacitor in series with 8 ohm
(for impedance compensation) Cc (μF) 24
Resonance Frequency fs (Hz) 24.0 22.9
Mechanical Q factor Qms 3.72 3.90
Electrical Q factor Qes 0.49 0.52
Total Q factor Qts 0.44 0.46
F (Ratio fs/Qts) F (Hz) 50
Mechanical resistance Rms (Kg/s) 3.25
Moving mass Mms (g) 80.2 88.2
Suspension compliance Cms (mm/N) 0.55
Effective cone diameter D (cm) 25.7
Effective piston area Sd (cm²) 520.0
Equivalent volume VAS (ltrs) 210.0
Force factor Bl (N/A) 11.6
Reference voltage sensitivity
Re 2.83V 1m at 124 Hz (Measured) (dB) 89.3
Voice coil diameter d (mm) 39
Voice coil length h (mm) 26.0
Voice coil layers n 4
Flux density in gap B (T) 0.99
Total useful flux (mWb) 1.52
Height of the gap hg (mm) 8
Diameter of magnet dm (mm) 134
Height of magnet hm (mm) 22
Weight of magnet (kg) 1.28
Power handling:
Long term Max System Power (IEC) (W) 220
Max linear SPL (rms) / by power (dB/W) 110/170
ROCK BOX = 80L, PORT = 100 x 200mm, F 33Hz.
THEATER BOX = 120L, PORT = 100 x 220mm, F 25Hz.
CONNOISSEUR BOX = 160L, PORT = 100 x 400mm, F 17Hz.
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Can any of the Isobaric lovers suggest a box size/tuning frequency using 3 - 831857? I have 4 of these laying around, collecting dust and been planning on building a box.
I made a clamshell (1 pair) once, it was okay, but ended up building 2 sets; I might ~ that looks like a better plan than I had.
I remember reading about the death box, e.g. the speaker baffle board moves up and down for tuning.
$20 bucks plans wouldn’t be bad at all, however, not sure if my 12” woofers would work. The chambers would have been the right size. It would require some engineering.
Wouldn’t take long to build; a box with holes, PVC and baffle boards (sliding I guess).
I made a clamshell (1 pair) once, it was okay, but ended up building 2 sets; I might ~ that looks like a better plan than I had.
I remember reading about the death box, e.g. the speaker baffle board moves up and down for tuning.
$20 bucks plans wouldn’t be bad at all, however, not sure if my 12” woofers would work. The chambers would have been the right size. It would require some engineering.
Wouldn’t take long to build; a box with holes, PVC and baffle boards (sliding I guess).
Ive built most of decwares subs, the housewrecker is one of the best, imo.
4 x 12s would be really good.
ODougbo
I've never tried a triso-baric or quadso-baric. I tend to like the clamshelled rather than tunnel; I don't have to build a tunnel, I get the cones closer together, and I like the symmetry. I clamshelled some JBL 18's, mostly because the ideal cabinets were just unmanageably huge. Sold them a few years ago.
Yes isobarics are inefficient, yes you can achieve better results in a bigger box with non-isobaric mounting, yes it is often possible to make a better single driver with characteristics similar to an isobaric pair, yes the driver costs are doubled compared to a big-box solution.
I tend to like sealed isobarics in a low-Q system, as I get usable output well below resonance. I don't mind using EQ. I don't like the space the port tube requires. But your choice of bass-reflex is equally valid.
But for a given box size and reasonable driver budget, few things are more impressive than a little isobaric dense-pack kicking out low bass like a big box, except perhaps a bunch or a stack of isobaric dense-packs. Or perhaps a big tapped horn with more extension, more bandwidth, and FAR better efficiency. Yes, there are some new long-displacement drivers that go really low coming out of the auto sub industry, but the cost is usually outrageous.
I've now got 20 reasonably-matched 12" poly drivers I picked up for a good price (since I was about broke at the time): 10 used and 10 new; and I've done simiilar math. I'm contemplating clamshelling pairs and mounting them in sealed cheap knocked-down flat-pack enclosure kits that make wedge-shaped PA enclosures. I'll probably brush on marine epoxy, inside and out. I'd stack 2 cabinets on each side for the home stereo. Maybe use the spare cabinet in another room or for bass guitar. My particular drivers are no longer available, so the last 4 drivers are really spares, but the cabinets are cheap so I'd might as well load them up for now.
Luckily I have plentiful and well-endowed (lots of FETs) power amps.
My first problem is that the drivers I want to clamshell don't really have a gasket for mounting their faces to a baffle-board; they're meant to front-load with a gasket behind the lip.
My next problem is re-wiring enough electircal circuits to plug in all the power amps.
I've never tried a triso-baric or quadso-baric. I tend to like the clamshelled rather than tunnel; I don't have to build a tunnel, I get the cones closer together, and I like the symmetry. I clamshelled some JBL 18's, mostly because the ideal cabinets were just unmanageably huge. Sold them a few years ago.
Yes isobarics are inefficient, yes you can achieve better results in a bigger box with non-isobaric mounting, yes it is often possible to make a better single driver with characteristics similar to an isobaric pair, yes the driver costs are doubled compared to a big-box solution.
I tend to like sealed isobarics in a low-Q system, as I get usable output well below resonance. I don't mind using EQ. I don't like the space the port tube requires. But your choice of bass-reflex is equally valid.
But for a given box size and reasonable driver budget, few things are more impressive than a little isobaric dense-pack kicking out low bass like a big box, except perhaps a bunch or a stack of isobaric dense-packs. Or perhaps a big tapped horn with more extension, more bandwidth, and FAR better efficiency. Yes, there are some new long-displacement drivers that go really low coming out of the auto sub industry, but the cost is usually outrageous.
I've now got 20 reasonably-matched 12" poly drivers I picked up for a good price (since I was about broke at the time): 10 used and 10 new; and I've done simiilar math. I'm contemplating clamshelling pairs and mounting them in sealed cheap knocked-down flat-pack enclosure kits that make wedge-shaped PA enclosures. I'll probably brush on marine epoxy, inside and out. I'd stack 2 cabinets on each side for the home stereo. Maybe use the spare cabinet in another room or for bass guitar. My particular drivers are no longer available, so the last 4 drivers are really spares, but the cabinets are cheap so I'd might as well load them up for now.
Luckily I have plentiful and well-endowed (lots of FETs) power amps.
My first problem is that the drivers I want to clamshell don't really have a gasket for mounting their faces to a baffle-board; they're meant to front-load with a gasket behind the lip.
My next problem is re-wiring enough electircal circuits to plug in all the power amps.
Sounds like you want flat response. I can't get Bjorno's thumbnails readable. I don't really care about flat response, just so it's smooth, since I have decent EQ available, decent power available, and all those voice coils can collectively dissipate the power associated with using a lot of EQ. Using ported enclosures you have to be careful to make sure the cones won't ever exceed xmax, so plot cone displacement against frequency for some output level if you have the handy-dandy software available. Even then, you'll probably need a high-pass filter or the cone(s) might be uncontrolled (unloaded) really low, where my sealed system is still putting out something (with EQ boost). Just one man's prejudices; can't really make any recommendations without knowing yours too.
Sounds like you already know what you want, which is the sound of a 160 L. box shrunk down to 80 liters via isobaric or a 53.3 liter trisobaric? The bigger the original box the more the cubic volume savings isobaric (or trisobaric) provides.
Diminishing returns vs. cost and efficiency as you go from isobaric to trisobaric to quadsobaric etc. I would have thought that for 4 drivers 2 cabinets with 2 drivers in each would seem like a natural choice.
You have some big class-d switching-mode amps?
Sounds like you already know what you want, which is the sound of a 160 L. box shrunk down to 80 liters via isobaric or a 53.3 liter trisobaric? The bigger the original box the more the cubic volume savings isobaric (or trisobaric) provides.
Diminishing returns vs. cost and efficiency as you go from isobaric to trisobaric to quadsobaric etc. I would have thought that for 4 drivers 2 cabinets with 2 drivers in each would seem like a natural choice.
You have some big class-d switching-mode amps?
Well, a T/S max flat alignment would be ~105.6 L net tuned to ~20 Hz, but requires a TL length vent unless stuffed to the point of might as well seal it up, so a folded, inverse TQWT is the way to do it.
GM
Yes , exactly, trisobaric: 1/3 of the 160L box, I would have to add back in the size of the tunnel, (1cf or more).
As far as flat, I tend to increase the lowest part of the curve, the bass is disappearing anyway.
Don’t have any D class amps, only large A/B, typical stereo amps, 200wpc.
I've been tempted to sell off the A/B, maybe a D class might be the way to go.
OK, then net Vb = the trisobaric driver's Fs doubling in a sealed cab is theoretically the most mechanical/acoustical compliance balanced or ~48.64 L/20 Hz based on the posted specs. Again, due to the long vent required, an inverse TQWT layout is the way to go.
GM
GM
I took a pounding from a lot of folks last time I bought Isobaric up; I think they are interesting; sure you lose a little bit compared to 2 "full size" cabinets, but I don’t think that’s a problem, you’re gaining back some advantages at the same time.
Two 80 liter cabinets, that’s a thought, and then I would end up with two 4 ohm loads. That would solve one problem. Tunnels are pretty easy, laminate wood and cut holes. Tunnels add volume to the box however.
I’m now using 2 - 8” 46 liters isobaric(s) (so there are 4 woofers). I do think two smaller boxes are better than one huge box.
No EQ here, also, never thought about sealed isobaric boxes.
I don’t know why I didn’t think of a D class amplifier, I’m going to look into that.
Oh btw, you can make wood “washers” 1/2” x 1/2” rings to clamshell drivers together, see pic
Two 80 liter cabinets, that’s a thought, and then I would end up with two 4 ohm loads. That would solve one problem. Tunnels are pretty easy, laminate wood and cut holes. Tunnels add volume to the box however.
I’m now using 2 - 8” 46 liters isobaric(s) (so there are 4 woofers). I do think two smaller boxes are better than one huge box.
No EQ here, also, never thought about sealed isobaric boxes.
I don’t know why I didn’t think of a D class amplifier, I’m going to look into that.
Oh btw, you can make wood “washers” 1/2” x 1/2” rings to clamshell drivers together, see pic
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CycleCamper,
Maybe I’ve been trying too hard, I could build a ½ size sealed box (e.g. 40L) and only use two. To keep the size down, may just go back to clamshell. That’s like a one day project. Good Idea (-; (-;
“This premium quality polypropylene driver has a FS/QT ratio of 55. This indicates
that this driver has relatively low damping and therefor most suitable for use in
CLOSED BOX systems. A sealed enclosure of about 80L (about 2 to 3ft will
give a smooth and controlled roll-off in the lower bass and infrasonic region. This
predictable response generally reflects the gain of most rooms (if correctly
positioned) and therefor gives a close to flat frequency characteristics at the
listening position. The sealed box also adds to produce a dry firm bass sound that's
free from typical boomy responses of some ported designs and thus this woofer has
received an admirable reputation from audiophile connoisseurs. The peerless 831857 also has extra low frequency exertion, this coupled with the protection afforded by a closed box design, will give you a sub that you can continue to turn up until your foundations are in danger. It will also respond to equalization without fear of retribution. An incredible amount of wattage will be yearned for and the box construction will have to be well braced.”
Maybe I’ve been trying too hard, I could build a ½ size sealed box (e.g. 40L) and only use two. To keep the size down, may just go back to clamshell. That’s like a one day project. Good Idea (-; (-;
“This premium quality polypropylene driver has a FS/QT ratio of 55. This indicates
that this driver has relatively low damping and therefor most suitable for use in
CLOSED BOX systems. A sealed enclosure of about 80L (about 2 to 3ft will
give a smooth and controlled roll-off in the lower bass and infrasonic region. This
predictable response generally reflects the gain of most rooms (if correctly
positioned) and therefor gives a close to flat frequency characteristics at the
listening position. The sealed box also adds to produce a dry firm bass sound that's
free from typical boomy responses of some ported designs and thus this woofer has
received an admirable reputation from audiophile connoisseurs. The peerless 831857 also has extra low frequency exertion, this coupled with the protection afforded by a closed box design, will give you a sub that you can continue to turn up until your foundations are in danger. It will also respond to equalization without fear of retribution. An incredible amount of wattage will be yearned for and the box construction will have to be well braced.”
Class-D:
I had a pair of crown CE-4000 amps. Kick-butt and available used for reasonable prices. Down-scale I had a pair of Peavey DECA 1200. Kick-butt and nobody else wants them.
But now I've gone back to all-FET class A/B and can mix/match identical amp channels for anything in this tri-amped system.
I had a pair of crown CE-4000 amps. Kick-butt and available used for reasonable prices. Down-scale I had a pair of Peavey DECA 1200. Kick-butt and nobody else wants them.
But now I've gone back to all-FET class A/B and can mix/match identical amp channels for anything in this tri-amped system.
2 Clam-shelled, no port sealed does maximize the isobaric advantages. 40 liter = 1.4 cu ft. What's the system Q with that volume? A lower Q of a bigger box will give you more gradual roll-off below resonance. At really low frequencies the ported system makes nothing, 0, and the sealed makes a little. Or you can say that a billion times nothing is nothing, so the low-Q sealed box is not flat but has more than a billion times more output at 5 hz if you want to make stats lie with a seed of truth.
The box is 1.8cf, estimating .25cf of bracing, I could add some more blocking to reduced volume, if necessary. The Q, I wouldn’t know how to calculate that: builder /woodworker :-/
Looks nice! Ever hear of Klenk's tub and tile epoxy, and Klenk's epoxy thinner? Just and idea...
I like the braces, really good job. A bit like a matrix-braced box. But with the mutiple thinner braces of a traditional matrix bracing the braces can resonate sympathetically and couple that to the outside like a sounding board, so traditional matrix braces need to be sprayed with undercoating or bedliner and then stuffed completely.
Good job putting holes in the braces too, especially with the driver a bit off-center! You're making me wish I could just buy 10 of those boxes.
A normal person would mount a class-D plate amp right on each box. I prefer more independent components.
Boxes are really nice, my compliments. Of course, grilles would be a problem over the clamshell.
I like the braces, really good job. A bit like a matrix-braced box. But with the mutiple thinner braces of a traditional matrix bracing the braces can resonate sympathetically and couple that to the outside like a sounding board, so traditional matrix braces need to be sprayed with undercoating or bedliner and then stuffed completely.
Good job putting holes in the braces too, especially with the driver a bit off-center! You're making me wish I could just buy 10 of those boxes.
A normal person would mount a class-D plate amp right on each box. I prefer more independent components.
Boxes are really nice, my compliments. Of course, grilles would be a problem over the clamshell.
The first time I used the braces with holes method, it looks cool. I did see a drawback, they do make additional parallel surfaces (more places for reverberation). I do have a full can of rubber spray – will do.
One thought I had instead of braces: simply glue/screw large scrap wood pieces to the inside of the box, super easy, would thicken the walls, also would pass the knuckle test.
OR simply wrap it with a second layer, for a 1 ½” thick box.
I usually use 1” thick MDF, the 3/4 “is not very expensive, and there’s a lumber yard 5 minutes from here that sells it; can’t beat if for test boxes.
I don’t know....never been a fan of plate amps, I’m sure the more expensive ones are nice. I was thinking about a Rotel 200wpc D Class-amp.
You only want 10?
One thought I had instead of braces: simply glue/screw large scrap wood pieces to the inside of the box, super easy, would thicken the walls, also would pass the knuckle test.
OR simply wrap it with a second layer, for a 1 ½” thick box.
I usually use 1” thick MDF, the 3/4 “is not very expensive, and there’s a lumber yard 5 minutes from here that sells it; can’t beat if for test boxes.
I don’t know....never been a fan of plate amps, I’m sure the more expensive ones are nice. I was thinking about a Rotel 200wpc D Class-amp.
You only want 10?
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I only have 20 drivers.
But I do know where you can get an exceptional deal on a lot of 15's, they were originally for a cerwin-vega clone. Shipping is a problem though (north of San Francisco).
But I do know where you can get an exceptional deal on a lot of 15's, they were originally for a cerwin-vega clone. Shipping is a problem though (north of San Francisco).
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