Help with McCauley Subs

[strevo]

I have recently acquired a pair of 18" McCauleys that I would like to build a subwoofer out of. I am looking for relatively flat response from 15Hz-150Hz. I am considering a horn, but the significant other is not too fond of a giant refridgerator-size box anywhere in the house. I think if I can find a way to put the horn in the basement and out through the floor it might work. Does this sound possible? I have never designed a horn before, but have done numerous bandpass and sealed enclosures. I am not averse to spending weeks or even months designing it. I just really want some awesome bass.

I am also building a tactile transducer out of a 15" JBL motor that I have, but I can't seem to find a source for voice coils anywhere without buying a whole recone kit. Any ideas?

Thanks.
-Steve Warden

[Dennis H]

Hmmmm. A 15Hz horn would have a mouth about 18'x18'. How does your SO feel about a hole that big in the floor? Perhaps an IB would work better. Once the manifold is built, if the McCauleys don't have enough output, it's a simple matter to add drivers or swap for some with more excursion. Pay a visit to the Cult page hosted by our own ThomasW.

http://f20.parsimony.net/forum36475/index.htm

[strevo]

Unfortunately, I don't currently have the resources to expand much. I got the McCauleys at an extremely low price (under $100/pair) from someone who didn't know what they were. I will look into the IB though, but Im not quite sure how I would implement it in my room. 2 walls are outside walls, one wall is non-existent open to two other rooms, and the other wall is the stairway to the basement. That would probably be the best place if I can figure out a way to get them in around my HT system also on that wall.

[Dennis H]

Some of the projects in the gallery use a manifold in the floor covered with a heating grate. The backwave would go into the basement. Attics are good too.

[ThomasW]

I replied to Steve's post on the IB forum. If these drivers have an accordion surround, IB use isn't recommended.

I don't think JBL will sell separate VC's, the only way to get them is with a reconing kit

[strevo]

Some of the projects in the gallery use a manifold in the floor covered with a heating grate. The backwave would go into the basement. Attics are good too.

Dennis, was that 18'X 18' for a corner loaded horn? If not, theoretically I could squeeze it down to 6.5'X 6.5' with the mouth in the corner.
Also, I guess I should have said I want 15Hz "in-room" response. I have no acoustical damping in my room besides couches, so presumably the bass will be boosted right?
Where would I get a good testing rig? I have never been able to do a "real" test of any of my designs, just used my ears. Is getting a condenser mic and some computer software the best way to go, or is there a standalone testing rig out there somewhere?

Thanks.
-Steve

[strevo]

Has anyone ever considered making test boxes out of gatorboard or foamcore. Not so much for SPL, but to get an idea of frequency response? I know it would resonate like crazy, which could be fixed somewhat by using some damping material on it. I just don't have an unlimited wood budget to keep building test boxes. Especially really really really big subwoofers.

-Steve

[JonMarsh]

You might try OSB for a cheap and quick enclosure, but I wouldn't use anything less than standard PB in most cases. With the wall pressures you see on a sub with a good size driver, a weak wall enclosure will do WAY to much flexing.

What I find works well for evaluating frequency response is a combination of modeling the LF (below 100 Hz) portion of the driver response, using Unibox (free) or LspCAD, and as the driver cone and motor usually creates the most variability above 100 Hz, just a near field (1-2") dipole measurement (chirp, MLS, or sine) tells the tale quite well. This combination has always corrleated very well with the behavior of the finished product for me.

~Jon

[ThomasW]

I'll post some data here I posted on the IB forum. If you really want output to 15Hz, sell these drivers. You should be able to get more than enough to buy drivers well suited to IB use. Doing that will get you output to 15Hz.