[*Scotty*]

Jim, having 4 subs I would start with the basic CABS set up. Two woofers on the front wall and two woofers on the rear wall 180 degrees out and see what you get. This assumes you have the basic square to rectangular room with a complete front wall and rear wall for a solid boundary condition in those locations.




This set up may not be perfect but I would be surprised if it measured worse than what you have and it "might" sound better.
You will probably have to run the anti-phase rear subwoofers at a lower volume than the front to allow for room absorption and transmission through the walls.
Snapshot from the pdf doc  http://vbn.aau.dk/files/12831869/AC-phd.pdf
Scotty

[JohnR]

That's what Scotty explained to me earlier in the thread too. If the air between your speakers and ears contains +12 dB bass modes I would think that would be somewhat akin to an obstruction, at least partially.

Only if air is non-linear. Scotty's description, while colorful, seems to indicate that there is intermodulation distortion between different frequencies. I did some searching on (non) linearity of air and found comments to the effect that it is observable above 120, 130, or 160 dB, but didn't find anything specific with regard to amount of distortion. It does seem, however, that it is much more likely to be a factor inside the box. I'd be interested to know if anyone finds anything more specific.

[kevinh]

Nice presentation by Earl Geddes on the issues surrounding Bass reproduction
in small rooms, and multiple LF speakers.

http://www.ustream.tv/recorded/28637776/highlight/319149

This is a link to an online pp file of the presentation at his website:

http://www.gedlee.com/

[THROWBACK]

I have been reading this thoughtful thread with great interest. I have been augmenting a pair of Soundlab M-1 ESL’s with a triple stack of OB GR Research 12” servo subs per side (24dB/octave xover at 100Hz). They integrate well, but I am missing some of the “punch” factor.
Most of the “punch” in music, I believe, comes from what is called in this Forum the “modal region.”  By moving the subs behind the ESL’s and using the one-band PEQ feature of the A-370 plate amps, I have achieved a fairly smooth room curve. But I am still missing something.
It may be that modal region punch is not something I should expect from ESL’s. Perhaps I would be better off raising the crossover point to 300Hz or so and building a tower of 6” or 8” speakers to handle the region below that (suggestions welcome!).
But I am wondering: might I get better results by placing one sub atop each of the two 7’ bookcases on either side of and adjacent to my listening position? The easiest way to implement this would be to take one of my stacked subs per side and move it. I could use the same amp with longer speaker wire for the moved subs.
Or, I could get 2 more subs (Geddes??) and place them there. I would have to buy another amp and figure out how to lash everything together, but I assume that I (with the help of Forum members) could figure it out.
Ideas?

[rajacat]

Maybe, instead of stacking your subs, you should scattered them randomly around the room at different heights and distances from  the walls. This might result in less cancelling of various frequencies.

[underdawg]

I would have to disagree with random placement of subs. During my testing over the years the best depending on room of course has been in between the left and right centered. Most people place subs in corners due to space, as I have mine in the right side corner. When we do listening tests I bring the out the subs, centered between l & r speaker. just my two cents.

[rajacat]

The theory goes that in order for the random placement of subs to be effective you need to use at least three or preferably 4 or more subs. It seems to me that stacking subs is the worst possible placement and would not lead to equalization of the response throughout the room. If you have enough subs to stack, you'd be better off with scattering them to eliminate concentration of response in just a few locations.

[THROWBACK]

Thanks guys.

Maybe I'll try moving two of the cubes to the tops of the bookshelves: zero cost, minimum pain. Some pain because those little suckers are hea-vy, plus I'll have to splice on some extra speaker wire, two pairs per speaker because of the servo loop. Vissi d'Arte.

I'd sure like to hear from some of the gurus (Dr. Geddes, are you tuned in?) on this.

[kevinh]

Placing 1 sub above the center line of the rooms will do the trick.

You can also look at reversing the polarity of 1 sub.

Start placing 1 sub in the corner (presuming mono signals to subs)

2nd mid sidewall them move the third around to get smoothest response
(if you can measure FR), or until you get the best response. This approach
is for the modal region for the room.

[skatingrocker17]

I have 2 Sundown SA-12s in a box running at a little over 1500 watts RMS and an Atomic sub in a competition but running at a little over 1200 watts RMS. The Atomic, is about a 70 pound sub whereas each SA-12 is almost 30 pounds. The Atomic setup is just as loud. All of the subs are 12" in diameter. I think it comes down to more box and power vs. number of subs. I mean more subs usually equals more woofer area but in some cases one can still be louder.