C37 as a Subwoof Enclosure

Hi, Guys -

I have waited a while to post this because I wanted to see what came out of previous forum postings. Thanks, Giskard and Mr. Widget, et. al. for your input.

I have a project where I plan to use an old, resurrected, C37 enclosure as a subwoof box. I have two choices, assuming use with a BX63, which I have:

Use the C37 with new 2235H or recone D130 with C8R2235H.
Enlarge cabinet and use a 2245H.

In the first case, the existing volume is 5.77 cu ft, so I would cut down the volume to the 4.5 cu ft size of a B380. Could even add half inch ply to the inner surfaces for more rigidity and still fall under the required 4.5 cu ft. I might use the 2235H mounted to the rear of the baffle, using the existing grill assembly, making it easier to install in the C37.

In the second case, I could expand the cabinet by rear 6 inch extensions to make it 8 cu ft, or use stuffed fiberglas for the equivalent. In this case, I think I would front mount the 2245H and devise a new grill assembly.

Questions arise:

What is the downside of rear mounting for a subwoof driver?
Would the 2" setback of the front panel (C37) be bad?
Can I stuff the 5.77 cu ft C37 to make it usable with a 2245H?

Appreciate the help.

John

"What is the downside of rear mounting for a subwoof driver?"

Nothing sonic that I know of... the BX63A has an upper limit of something like 126Hz.

"Would the 2" setback of the front panel (C37) be bad?"

I highly doubt it.

"Can I stuff the 5.77 cu ft C37 to make it usable with a 2245H?"

Probably not, that's a whole bunch of fiberglass and that much could cause problems. How about a pair of LE14H's? Will they fit on the baffle? Two of them are roughly equivalent to 1-1/2 2235H's. Plus you'd end up with double the power capacity of a single 2235H and roughly 2 to 3 dB more output. Anyway, just another thought to help confuse the issue. I can't remember how big that baffle is and I'm too lazy to look it up.

*****

Oh, BTW, that reminds me. I can get the new LE14H-3's. If you've ever suffered foam surround rot (I personally haven't but I've seen plenty of it) you might think the rubber surrounds on the LE14H-3's is cool. G.T. certainly is excited about it! :)

Since I like the 2235 in a five cu ft box and the older JBL cabinets can be a bit lively (read under braced) I would brace the hell out of it and make it a 5 cu ft box and use a 2235. For bracing adding a sheath of MDF on the inside is fine, but I would definitely add some kiln dried 2 X 4s as well. Remember not to forget the volume of ports and the woofer to be added to the 5 cu ft. You really need about 5.4 cu ft. after the bracing.

I do think Giskard's idea of twin LE14s sounds interesting too though.

Giskard,

Thanks. You just won't let me use my 50 year old speaker system (C37 + D130 reconed with 2235H) without a fight. Also, what am I going to do with my (need to be refoamed, but never used) 2245H? BTW, I have two new 2245H's from the tent sale waiting to be used in my home theater when I get, or make, 8 cu ft enclosures.

I like your idea of the two LE14H-3's. The baffle of the C37 is about 34 x 22, so it would work nicely and I still could use the enclosure without increasing the volume from 5.77 cu ft. What volume would be ideal for the pair of LE14H-3's? Bet I could line the inside of the 3/4" cabinet with half inch baltic ply for rigidity and still come out with a volume big enough.

John

Yeah, Mr Widget is right, that box will need some beefy bracing.

"I do think Giskard's idea of twin LE14s sounds interesting too though."

Just thought I'd toss a wrench in and see what happens. The mutual coupling from the closely spaced dual LE14H's is torrid. Well, you should know how closely spaced dual 2235H just walk all over a single 2235H :)

One thing about LE14H's and 2245H's, no mass rings to warn you that you are exceeding xmax, lol.

Mr. Widget,

I had planned on bracing the enclosure with 2x4's and had taken that into account on my expansion of the cabinet volume for a 2245H. Requires about 6 inches expansion of the cabinet depth, which then necessitates additional bracing where the joint lies.
Really makes the use of a 2235H more attractive (easier).

Giskard,

Sounds like two LE14H-3's would also require cabinet expansion, though not as much. If I made use of the C37 front 2" setback and brought the baffle forward, I might be able to create a volume large enough, but still there is the bracing volume. Hmmm. It wouldn't look like a C37, so why bother?

John