Request for assistance please room treatment


I do have it treated now, but I don't think it's correct. I need to treat it properly. I've tried a multitude of different positions, absorption, diffusion, trapping, etc. and my walls are starting to look like swiss cheese. I'm at the point now where I need to strip the room, putty, sand, and paint. But when I re-install the room treatments, they have to go in the correct position the first time. This is where your assistance comes in. I've tried many different web sites and so on, but it all seems best guess. I'm hoping to lean upon your "experience".
My room is 22'long, 11'wide, and 7'4" high, and is in a finished concrete basement. I look forward to reading your suggestions.
Thank You.
128x128shawnlh
Hi, You use room treatment to solve certain issues that will not be altered by your equipment selection. Can you describe your actual issues? Are you having problems with imaging, low frequency buildup, etc? It is hard to know what to recommend without knowing what you are trying to improve. The first thing I notice is that your room is exactly twice as long as it is wide. That is going to give you some really nasty standing waves at certain lower frequencies and their harmonics. I would expect that to not sound so good. I just googled to find a reference for you and found this link:
http://artsites.ucsc.edu/ems/music/tech_background/TE-02/modes/Modes.html
The fundamental frequency of concern is going to be more effected by room geometry than surface treatments. Can you angle any of the walls? This can be done in small pieces, perhaps four feet long so that you do not lose too much floorspace.

Another typical problem in a room is the first order reflections. These are much easier to reduce, but using absorptive treatment won't do much below 100 Hz.

An easy way for you to find those is to use a mirror. Sit in your normal listening position. Have someone move the mirror around flush to the side walls and the ceiling. If you see the tweeter in the mirror, then that is an area of a first reflection. Those points will all be somewhere between the speakers and you on the side walls and ceiling. This happens on the floor as well, so just put a rug in between you and the speakers, you can use the mirror to see where the rug wants to go as well. The material that you use for the absorption matters as well.

There is a lot more to this than what I am pointing out here, but these are the items that typically cause issues in a rectangular listening room. I would need a lot more info to actually suggest more. Hope that helps.
Just ordered the XLO Test CD. Thanks Geo.
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also understand the ‘pin cusion’ problem regarding walls of a dedicated audio room. I believe my room is over damped now and intend on removing some of it. Will keep treatment at the primary reflection points and behind the listening chair however.
Mesch, I assume you are the OP. FWIW I found the XLO disc fine for fine tuning a system, but for helping to identify the existence and location of nulls and nodes you can't beat using a SPL meter (as made by Radio Shack) and a frequency test disc as made by Stereophile.
One more thing. Anyone who has Sonex anywhere in the room is advised to remove it poste hasten even in small amounts Sonex does something unfavorable to the sound, maybe it's the open cell construction, who knows, making it sound phasey and unpleasant. Try taking all Sonex out of the room and see what you think. Sonex is one of the most insidious, sonically disastrous products ever perpetrated on naive and gullible audiophiles. And it looks so cool, just like an anechoic chamber. Lol
Now you know why acoustic design engineers get paid mega bucks. All will tell you designing a concert hall is a crap shoot.