Superlow frequency subwoofer

soiset

I'd like to build an extremely low frequency sub-subwoofer, to cover the range from 10 to 28 Hz. I'll have availble 15 cubic feet of enclosure, and plenty o' wattage. What I lack is a driver that will respond way down there.

The "cabinet," if you will, will be a 4' x 8' platform, on top of which will sit the second tier of HT seating. The amp will be a Crown professional model, probably the Macrotech 1200, running mono-bridged.

I see that Velodyne makes subs that can reach down to the 12 Hz range, but an extensive search on "subwoofer drivers" has turned up little, and that little doesn't seem to feel the need to mention anything below 20 Hz. I'm sure that it will take an 18" driver, and the fs will be below 30 Hz.

Any ideas?

janmike

Sid would be your man for this one. I am sure he will chime in at some point.

hoosier21

want 10hz here you go get building

http://www.royaldevice.com/custom.htm

hoosier21

want 5hz got 25k?
http://www.rotarywoofer.com/

ben62670

I'm not a pro at subs, but you would have to brace the piss out of a cab that big. I am assuming that you are thinking or using part of your structure for the enclosure? Maybe 2 or 4 sensitive 15's series/parallel? Here is a pair of 8 ohm 15's that go deep without huge power needs.

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=295-130

Systems

One of these bad boys in a big sonotube might get you what you what you want http://www.hometheatershack.com/forums/soundsplinter/3810-new-premium-series-18-driver-soundsplinter-unleashes-beast.html

Also check out TC Sounds for some excellent woofers.http://www.tcsounds.com/

RuSsMaN

http://www.mccauleysound.com/component_overview.cfm?ID=126

Horn loaded will play over 121db all day long at 19hz. Also, see if you can find a Bag-End sub driver. Parts express has a 'Bully' 15" that's a monster also. Properly loaded, you'll get all the response any media you have is capable of producing.

Cheers,
Russ

Systems

RuSsMaN wrote:

Also, see if you can find a Bag-End sub driver.

Cheers,
Russ

Bag End's sound fantastic but it is their dual integrator EQ circuit that gives them the potential to go very low. With a very good long throw 12" or 15' woofer and this circuit
http://sound.westhost.com/project48.htm you can duplicate their performance.

unc2701

Yep, get a bigass long throw driver, like an Aurasound 18" via www.madisound.com, put it in a sealed box, then add a Linkowitz compensation circuit (as in GV#27's post) to control the low end roll off (this will limit your max DB's, but keep it flat), then get a BFD or Velodyne SMS-1 to control the room modes and you're done. You should be able to pull >100 db's at 10 hz, but if you bring your goal up to more like 15-20hz, you're looking at 110+ db's easy.

soiset

hoosier21 wrote:

want 10hz here you go get building

http://www.royaldevice.com/custom.htm

I should specify that I don't want to build a sub that would require a building permit, or more than a dozen drivers. But that shaping they did is interesting

soiset

hoosier21 wrote:

want 5hz got 25k?
http://www.rotarywoofer.com/

I have not found this one. $12,700 seems like a lot for a really nice fan (maybe I could find one on ebay:D ). I had thought that it would be nice to run really low freqs from an electric motor somehow, but getting the req'd response times would be the hard part. I guess they've figured that out. I could also bolt down a briggs and stratton to a piece of plywood and attach the handle end of a hammer to the crankshaft. Then I'd let my pre throttle it up and down.

More seriously, could, in theory, a tactile transducer be mounted to a rigid diaphragm, to do the low freq job? Clark models respond at 5 Hz, but the response is really ugly down there.

soiset

ben62670 wrote:

I'm not a pro at subs, but you would have to brace the piss out of a cab that big. I am assuming that you are thinking or using part of your structure for the enclosure? Maybe 2 or 4 sensitive 15's series/parallel? Here is a pair of 8 ohm 15's that go deep without huge power needs.

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=295-130

I looked at the Dayton drivers. The stated response is 19-1K Hz. Not low enough, and a lot higher than I want. As far as the cab goes, yes, the structure of the platform will be the cabinet. I figure 2 4x8 sheets of 1" MDF, with 6-8" clear between them, with 2x2 bracing in a 1' grid ought to do it.

tryrrthg

do you have an adjoining room, attic, crawlspace that you could use to run an infinite baffle?

http://home.comcast.net/~infinitelybaffled/

if not, get yourself the soundsplinter 18" driver (or two) and brace the heck out of the enclosure. if you can build a sonosub then you won't have to worry about bracing just two big **** silos in your room like below

http://www.polkaudio.com/forums/showthread.php?t=50296

soiset

GV#27 wrote:

One of these bad boys in a big sonotube might get you what you what you want http://www.hometheatershack.com/forums/soundsplinter/3810-new-premium-series-18-driver-soundsplinter-unleashes-beast.html

Also check out TC Sounds for some excellent woofers.http://www.tcsounds.com/

Assuming they aren't lying, BINGO.

Need to feel it deeper in the gut? Think size matters? For those who seek the cleanest, lowest of lows,
where your brain won't hear it all but your bones will sure feel it.. snap up those single Hertz signals by
strappin' this bulldog into an IB and brace yourself for something fierce!

single hertz...
Now we're talking.

soiset

RuSsMaN wrote:

http://www.mccauleysound.com/component_overview.cfm?ID=126

Horn loaded will play over 121db all day long at 19hz. Also, see if you can find a Bag-End sub driver. Parts express has a 'Bully' 15" that's a monster also. Properly loaded, you'll get all the response any media you have is capable of producing.

Cheers,
Russ

Thanks, Russ. I found the Mccauley driver. It runs about $890, and has a stated response of 15 Hz. No doubt this is an awesome driver, but it's talents and price have been geared toward stadium sound. It has something like an 800 Hz upper limit, which is a lot more than I need. I think that SoundSplinter 18" might be the thing to have, and maybe I'll bump up the enclosure volume to 20 cubes. That price, $702 for a pair of them, with promised responses in the single digits, is sounding mighty sweet to me.

Now to find out if putting swoopy channels in the cabinet a la "waveguides" does anything.

soiset

GV#27 wrote:

Bag End's sound fantastic but it is their dual integrator EQ circuit that gives them the potential to go very low. With a very good long throw 12" or 15' woofer and this circuit
http://sound.westhost.com/project48.htm you can duplicate their performance.

I may be wrong, but aren't there physical limits in woofers that determine their low end limit? I mean, if a motor will simply not move when presented with a 12 Hz signal, then no amount of circuitry would overcome that. Is that not exactly true?

madmax

A subwoofer in a sealed box will respond down to 0 hz. The problem is they become less and less efficient because of the box size and the electrical efficiency. Add to that what is lost in the recording process and the rolloff of your hearing abilities and you end up with nothing. It can be pulled off with the right frequency slope, cutoff point and lots of amplifier gain.
madmax

Serendipity

janmike wrote:

Sid would be your man for this one. I am sure he will chime in at some point.

Yes, Trey seems like the expert on this stuff...

soiset

appadv wrote:

Yes, Trey seems like the expert on this stuff...

It's like waiting for Jesus or something...

soiset

madmax wrote:

A subwoofer in a sealed box will respond down to 0 hz. The problem is they become less and less efficient because of the box size and the electrical efficiency. Add to that what is lost in the recording process and the rolloff of your hearing abilities and you end up with nothing. It can be pulled off with the right frequency slope, cutoff point and lots of amplifier gain.
madmax

Are you implying that in a ported box, the response limit is higher than DC? As far as box size, I may extend the rear seating platform all the way to the sides and rear of the room, to push it to maybe 40-50 cubic feet, depending on the return in investment (this is a dedicated HT room in ACAD 3d for now, but it will happen in about 1.5 years).

soiset

It looks like this "Ascendant Audio" is quite a popular brand right now. I guess they make the Avalanche 18" driver that is referred to earlier here in a sonotube design. The Ascendant website is under construction, and it looks like the whole company is getting an overhaul.

Perhaps the market for super-low capacity drivers is heating up? Maybe in a year I'll have some really great choices. Can anyone offer a comparison between the Avalanche 18 and the SoundSplinter 18? What does the Avalanche cost?

madmax

A ported box wont give you much output below the resonance freq of the cabinent.

soiset

madmax wrote:

A ported box wont give you much output below the resonance freq of the cabinent.

Because I have so much volume available, and because of the technical difficulties of a ported box, I am pretty certain that I want to stay with a sealed enclosure. I can always build a stiff box (pretty easy job for a structural engineer with a ton of tools:D ).

Systems

soiset wrote:

I may be wrong, but aren't there physical limits in woofers that determine their low end limit? I mean, if a motor will simply not move when presented with a 12 Hz signal, then no amount of circuitry would overcome that. Is that not exactly true?

What happens in a sealed box is the driver exhibits a 12db per octave rolloff below the resonant frequency of the driver and box combo.This rolloff can be compensated for with special EQ circuits like the Linkwitz transform,EAS,or shelving filters.
This means that there is a substanial amount of electrical boost so a good hi excursion driver or drivers are needed.You can extend the bass response atleast an octave lower this way.Here is a good link to read about this. http://www.linkwitzlab.com/thor-intro.htm .Im using the EAS circuit on my 2 12"sealed subs and it works marvelous.This circuit with the right drivers and a big amp can get you into the low teens.

A ported box uses the port to extend the bass instead of EQ and it will have the advantage of greater output.The ones I linked to in my first post are for real they are not lying.:)

soiset

Thanks for the info. My brain is pretty full, and I don't think I have the space in it to really learn circuits, so I need a black box solution for a low-freq crossover/equalizer, or, basically, a subwoofer processor. I'd like to cross at about 28 Hz, and then be able to equalize all the way down to, well, as far as I could. Ever seen such a thing?

Someone mentioned a Velodyne processor. Would that be the way to go?

soiset

unc2701 wrote:

Yep, get a bigass long throw driver, like an Aurasound 18" via www.madisound.com, put it in a sealed box, then add a Linkowitz compensation circuit (as in GV#27's post) to control the low end roll off (this will limit your max DB's, but keep it flat), then get a BFD or Velodyne SMS-1 to control the room modes and you're done. You should be able to pull >100 db's at 10 hz, but if you bring your goal up to more like 15-20hz, you're looking at 110+ db's easy.

The room will only be 19' on the long dimension, so the lowest mode I could have would be 27 Hz, which is about where I'd want to cross the super-sub, so I think the SMS-1 or BFD (what is that?) wouldn't be necessary, except for the regular subs, which would run from 28-80 Hz, inside of which I would have a few room modes.

But this "Linkwitz compensation circuit" sounds interesting.

ETA: Actually, that SMS-1 sounds wonderful. It has a low-pass xover that goes all the way to 15 Hz, and would manage all the room modes I would have from my regular subs. Now, where to find one for less that $749...
But it equalizes "only" down to 16 Hz. As I figure below that freq, the bass would just be rolling off, I would just need something to "lift" the bottom end single digits. Obviously accuracy wouldn't be a concern below 16 Hz, just output. So an SMS-1, plus some other black box to lift the real bottom end would do all the tricks. Almost there...

Oh, look: http://www.outlawaudio.com/products/sms1.html

Systems

soiset wrote:

Thanks for the info. My brain is pretty full,

Ever seen such a thing?

Sorry for the info overload and yes there is such a device that is basically an adjustable Linkwitz circuit. If you intend to use a sealed box sub then this unit by Marchand is an excellent tool for maximizing it's potential.You can buy it as an assembled unit for $399or as a kit for $349.It does not contain a crossover however.
http://www.marchandelec.com/wm8.html

soiset

GV#27 wrote:

Sorry for the info overload and yes there is such a device that is basically an adjustable Linkwitz circuit. If you intend to use a sealed box sub then this unit by Marchand is an excellent tool for maximizing it's potential.You can buy it as an assembled unit for $399or as a kit for $349.It does not contain a crossover however.
http://www.marchandelec.com/wm8.html

It appears the graph in that link shows a 24 dB boost at 0 Hz (or, I assume, 2 Hz, as that is the listed freq response min.) The text says

,"By adjusting the BASSIS, its own frequency response (curve may be made the inverse of the speakers curve, down to 15 Hz

So, it looks like it comes close to providing a flat response down to 15 Hz, and then does the best it can below that. Correct?
The specs say that it has a limit on the low end for a speaker resonance of 30 Hz. The giganto 18" models have Fs around 20 Hz. What would that mean in terms of performance of this unit on those kinds of drivers?

Systems

soiset wrote:

The specs say that it has a limit on the low end for a speaker resonance of 30 Hz. The giganto 18" models have Fs around 20 Hz. What would that mean in terms of performance of this unit on those kinds of drivers?

That fs 20 hz spec is for the driver operating in free air.When it is put into a box the resonant frequency will always be higher.How much higher will depend on the internal volume of the box.Say you put that driver into a box that resulted in a resonant frequency of 30hz then adding 12db of boost with the BASSIS will give it flat response to 15hz.Then it will roll off below 15hz at 12db per octave.Hope that helps.

soiset

GV#27 wrote:

That fs 20 hz spec is for the driver operating in free air.When it is put into a box the resonant frequency will always be higher.How much higher will depend on the internal volume of the box.Say you put that driver into a box that resulted in a resonant frequency of 30hz then adding 12db of boost with the BASSIS will give it flat response to 15hz.Then it will roll off below 15hz at 12db per octave.Hope that helps.

Yes, this is all very helpful, thanks. How does this unit work? Is it some kind of negative feedback like the old Velodyne amps? Or do you take measurements and set the dials accordingly?

Systems

Measurements would be helpful but not neccessary.You need to know the Qtc and Fc of the woofer/box combo you are using and adjust the dials accordingly.You can even experiment and see if you prefer some other settings as well but I would avoid applying any more than about 12-14db of boost.