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designmule
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Joined: Jan 27 2011 - 10:00am
Now What?

I recently purchased a copy of TruRTA, bought a calibrated Microphone and spent some time this weekend measuring pink noise. It was fun and all...educational, but after running the tests I'm sort of like "now what?"

My room has a very strong peak at 100hz and a strong depression at 500hz. After entering my room dimensions in the Real Traps application, I believe the 100hz peak to be related to the width of my room. The 500hz depression...I have no idea. Reflections from my vinyl couch maybe?

I'm open to moving things around but I guess that I want to avoid moving everything in the room around willy nilly with no real plan. So do any of you have any suggestions as to a course of action?

Any suggestions would be appreciated.
Matt

Kal Rubinson
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I am sure that Ethan has

I am sure that Ethan has something on this: The 100Hz peak, if it is due to a room dimension is best treated with bass traps in corners shared by that dimension. Another consideration is moving the speakers a bit orthogonal to that dimension as they may be in a node themselves.

Is the 500Hz depression found in a number of places? Consider it might be due to SBIR and, again, some speaker movement towards or away from the wall could help.

Kal

Glenn Kuras
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I agree the 500 hz could be

I agree the 500 hz could be coming from any of number of places. I would try moving the listening spot then the speakers to see if it changes. For the other peak bass trapping in as many corners as possible will help. Also placing absorption left and right of the listening spot may also help further correct it.

Glenn Kuras
GIK Acoustics

designmule
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Thanks for the tips

Thanks for the tips guys! This weekend I'll have some time to play around. I originally posted without my graph in front of me. I swear that I remember seeing a depression at 500Hz but now that I look at the graph produced by TruRTA, I see that I was mistaken. Nothing seems too bad there. 100Hz is a good 4db up over both 90 & 110Hz. The narrow peak makes me think that maybe the it is caused by something in the room vibrating.

My frequency response falls off a good bit from 9Khz to 11Khz (6db) and stays there the rest of the way up the spectrum. This is fairly surprising to me as I have a fairly reflective room.

Ok, so a bit about my system. A pair of Focal Chorus 716s in a room with hardwood floors, vinyl blinds, no acoustical popcorn on the ceiling and a vinyl couch. I do have a pair of Real Trap panels on the sidewalls at the first reflection point and a couple of the Michael Green mini corner traps (the ones that look like diapers) in the upper corners behind the speakers. I have a shag rug on the floor in front of the speakers. Behind the left loudspeaker I have a repouposed metal school locker (a likely source of vibration).

When I setup my measuring mic (a beringer ECM 8000) I place it at my listening position pointed straight forward. I am using the 0 degree calibration curve. I also have 45 and 90 degree curves as well. Looking at a plot of the correction curves, it looks like the curve include the most positive correction at 0 degrees so I would suspect that using the 45 or 90 I would see a greater depression in the high frequencies.

I'll play around a little more this weekend and post my results. I appreciate your interest in helping me get the most from my system.

Matt

designmule
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I guess that I never really

I guess that I never really reported back on my findings. Sorry about that.

I tried moving me speakers around and found that doing so really had very little impact on my 100Hz bump. So I really began to suspect my metal locker was causing me a problem. I first decided to measure each speaker individually and the left one (which sits just a few inches from the locker) produced a much stronger bump at 100Hz (the speakers sit in the room symmetrically by the way). I then whacked on the locker with an open hand and watched the RTA. Sure enough there was a very strong peak at 100Hz with some stuff higher up the spectrum probably associated the the "slap" sound. So it's the locker.

I ended up lining the interior of the locker with this stuff called "Peel and Seal" its similar to Dynamat but much less expensive. I also stuffed pillows in the bottom of the locker.

Now my system sounds so much better. The bass is much, much tighter and seems more explosive (notes kind of come and go effortlessly and naturally). I haven't remeasured the system, I haven't felt the need to.

I've been a very happy camper ever since.
Matt

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