Ok Mark,
My intention for building this cab is personal application as a bass rig.
My original criteria was to have as much output in the 30Hz and bellow range as possible in a conventional direct radiating cabinet roughly around 10cu'.
I play a 5 string bass. Fundamental of Low B is 30Hz I drop tune 1 whole step to Low a 27.5Hz. Almost no commercially available Bass Guitar cab has much significant output bellow 40Hz let alone bellow 50Hz even worse once power bandwidth is taken into consideration.
After much cabinet and driver modeling I came up with a 12cu' cab that utilizes 4 12" Lab 12 Drivers (TS params specified by Tom Danley for the LAB subwoofer project so I feel it is somewhat appropriate that I post about it here).
What I came up with was a pair of 6cu' cabs using two 12" drivers each (think of them as one cab its just easier to move that way). I am able ot achieve 124dB at 30Hz 1 meter with very low harmonic distortion. More than enough headroom to play at reasonable stage volumes at those levels. I also have the added bonus of significant usable low distortion extension down to and below 20Hz.
I don't think that they are the best option for Large PA sub. I think We would all do a lot better with one or more of Tom Danleys Towers if extension down to 20Hz is desired. Although if that level of undistorted extension to 20Hz was required my BS-212 would do better than 90% of anything considered a PA sub. But It would take a lot of them and a lot of amplifiers to get proportional SPL.
I do think that they would lend themselves well to studio, and home theater applications. I think I actually exceed the Genelec 4X12 sub as far as distortion, extension and SPL.
I have never experienced anything else like them. Playing my 5 string bass guitar in front of the thing makes me feel like I've lost my land legs. Playing a 20Hz sinewave through them makes me feel ill, and modulates my voice.
I am not trying to sell the thing to anybody, and I plan on making the cad drawings available to anyone that is interested I just haven't cleaned them up and labeled them enough to be very useful to anyone.
Sweeps:
http://srforums.prosoundweb.com/index.php/m/82403/8490/?SQ=a b1ac9f6e1e07f049ef86293c162ec0c
This as I said is a project of personal interest and my first speaker cabinet. There is nothing extraordinary about it. It was born out of my discontent with BS subwoofer/speaker specs and wanting to have something with superior performance and much less cost.
Rory,
Can they be used in pro audio. Sure why not, are they practical, that really depends on the situation now doesn't it. I think this design is borderline in where it is applicable and doesn't need to be pigeonholed.
Antone-