55 gal barrel H-frame subs/acoustic diffusers?

[goryu]

Ok, pardon me if this is bat $hit crazy, but would this possibly work well?

I have large Acoustat 6600 electrostatic panel speakers that are about 32" wide and 8' tall. They are positioned about 3' out from a concrete block wall. I have wanted to add acoustic diffusion behind them. I currently have one sealed 12" sub next to each speaker, positioned on the insides. I also have wanted to add 2 more subs to use in a distributed subwoofer set up.

Here's my idea: what if I cut the bottoms and tops out of 55 gallon plastic barrels and stacked them 2 high with a baffle between to which is mounted an 18" OB Acoustic Elegance driver. Kind of an h frame ob sub but round instead of square? I would put legs on the lower barrel to raise it off the floor say 12" and would have roughly 12" of space between the top exit and the ceiling. I would then place these behind my speaker panels between the speakers and front wall. The round shape would act as a diffuser for the rear wave of the Acoustats. Two birds with one stone, so to speak. I wouldn't play these subs above 80Hz, meaning the quarter wavelength would be longer (roughly 3.5') than the front and rear barrel sections (roughly 3'). I realize it wouldn't offer an ideal diffusion spectra but I would think it would be a large improvement over the concrete block wall. I might also be able to cover it with something to improve the diffusion...

I should add that the inside diameter of these barrels is about 23". I could put a 20" sonotube inside the barrel and fill the space between them with spray foam for damping if that is thought to be an issue...

Comments? Thanks.

 

[DVDdoug]

It sounds like a fun project and I expect the electrostatic dipoles will benefit from diffusion of the back-side soundwaves.

But I think all of this is unpredictable...

Since you apparently have the barrels it should be easy to experiment with the diffusion effects.

Have you measured the room? "Diagnosis before treatment", and of course it usually helps to measure after too.

Diffusion can be unpredictable and in a "small room" (any room in a house) absorption is usually more helpful-useful than diffusion. And with dipole speakers the room has a bigger effect and things get even more unpredictable.

I'm not a fan of open baffle subs. They usually don't give the best results. In any case I always recommend getting some speaker design software to optimize and model the design, and the software will also allow you to compare (virtually) with sealed & ported options using the same driver and the same or similar speaker volume. (I've only used WinISD and it doesn't model open baffle speakers.)

I should add that the inside diameter of these barrels is about 23". I could put a 20" sonotube inside the barrel and fill the space between them with spray foam for damping if that is thought to be an issue...

Some stiffening & dampening will probably help. Stiffness probably isn't that important with an open baffle but you don't want it resonating "like a barrel" (or like a big empty box). The main speakers may also create higher-frequency resonances in the barrel/tube and if that happens you can add some "stuffing".

 

[goryu]

thank you for your comments!