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david yost 23rd December 2011 09:45 PM

Another Acoustat question (or two)
Hello, All

As I mentioned in an earlier thread, I am in the process of remodeling what I hope will become my new listening room. It is 17' x 22' with a slightly less than 8' ceiling. The floor is poured concrete and 3 of the walls are sheet-rock over wood studs. The remaining wall is cement block and it is one of the short walls.

My plan is to use the Cogent SPI processor which is basically a 4 channel version of James Bongiorno's Trinaural processor. It uses 4 identical speakers evenly spaced in a 90 degree frontal arc. My plan is to construct 4 1+1 clones from a donor pair of Model 4s I have and to use them with a set of Model 6 interfaces along with a pair of IB 31" Fostex 800 series woofers crossed somewhere in the 50-80 Hz region.

Here is where I need some advice: based on the instructions given in the SPI manual, the speakers should be set-up facing the more "live" of the long walls and 3' from the front wall with the listening position 3' off of the back wall, giving about 11' from ears to the Acoustats. in your experience, is this enough distance from the walls? I'm thinking not.

An alternate layout would be for the Acoustat array to fire down the long dimension of the room. This would give me only a foot or two clearance between outer edges of the outer pair of speakers and the side walls (if I try to preserve the 11' listening distance) but give me the opportunity to put plenty of room behind the speakers and also behind the listening seat. I could also tighten up the arc and decrease the listening distance if more sidewall spacing is needed. Also, I don't know if the 90 degree arc recommended by Cogent is sacrosanct or if it could be narrowed somewhat as long as equal distance is maintained to all speakers, thus allowing me to lengthen the listening distance a bit.

I know experimentation is the best bet here, but since I am planning to hang my 1+1s from the ceiling, I would like to move them as little as possible. What would you do?

bear 23rd December 2011 10:22 PM

So +/- 45 deg? A speaker at 45deg on either side then two symmetrical either side of the center axis??

3' behind the Acoustat is prime territory, improves bass in that range... closer, not so good. Remember, unlike most other speakers they have nil radiation off either side edge... classic figure 8 for the most part.


david yost 23rd December 2011 10:56 PM

Yeah, Bear. 4 speakers spaced 30 degrees apart. So, you think 3' isn't too close?

DaveG 24th December 2011 01:04 AM

My room is 15.5 x 17.5, with the speakers on the long wall, maybe 34-36 inches out dependinig on where they are measured, and about 32 inches from the side walls. The wall behind the speakers has drapes hanging 30 inches out from the wall hiding shelves, so it tends to dampen and break things up a little. I also have the couch moved out from the rear wall 20 inches. Seems to work fine. A bit closer to the speakers than I would like, but it's what I have for now.

I've tried wider, narrower, closer to the back wall, had the couch right up against the rear wall, and it slowly migrates back to the same position. Never rotated it all 90 degrees yet.
Model 3's and Model 4's in the same location produce better? more accurate? bass, but I prefer the more open, better imaging of the 1+1's

It took quite awhile to find the exact location for the speakers.
I would want to retain the ability to make slight position adjustments in any setup.

david yost 24th December 2011 01:12 AM

Unfortunately, I'm about 2" shy of being able to use standard frame 1+1s in this room, and why I had cooked-up the "hung-from-the-ceiling" idea. Maybe I can rig a 3 point floor stander that will allow easy re-positioning.

Any suggestions?

bear 25th December 2011 02:45 AM

If you own the place you can cut a hole ( a neat WAF approved hole) in the ceilings. Or even drop a square foot of floor strategically...

But fresh frames are a good idea since the stock frames leave a bit to be desired, you might "buy" the 2" that way.

The 3' distance should be nice...

The more solid the speaker mounting is are, as in rock solid the better they will sound. Even a little rocking will (for unclear reasons) effect the sound.

Be sure to use polypropylene caps in the interfaces and scrap the electrolytics if you have not yet done so...


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