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How to diagnose the need for room treatment?

I have my stereo setup in the family living room (30x14x8 ft). I have done some work around speaker placement, and treating 1st reflection points, but don't know if I need to do more. I often read room treatment being crucial. So while my system sounds good to me (I'm new at this), it might be able to sound a lot better.

How can I come up with a diagnose, short of trial and error of every posibility?

Thanks!
lewinskih01
shadorne's avatar
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shadorne
7,477 posts
 
Make sure you have a measurement microphone - an omnidirectional condenser type. For example the Behringer ECM-8000. An ordinary microphone is not suitable
ghstudio
141 posts
 
I will first use the RS microphone. I was going to try an AKG CK-32 cartridge (good omnidirectional mike). Finally, I have a rane RA-27 with a measuring microphone that I could try (requires me to build a small interface).

Most likely, I'll never get past the RS.
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almarg
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The human hearing mechanism tends to some degree to "latch on" to the leading edges of transient waveforms, and give them greater emphasis than what may follow a few milliseconds later.

Re my earlier comments on this issue, in a post in a different current thread Shadorne referenced a Wikipedia writeup on the "Haas Effect," which is what I was referring to without knowing its name:

http://en.wikipedia.org/wiki/Haas_effect

A brief excerpt from that article:

When two identical sounds (i.e., identical sound waves of the same perceived intensity) originate from two sources at different distances from the listener, the sound created at the closest location is heard (arrives) first. To the listener, this creates the impression that the sound comes from that location alone due to a phenomenon that might be described as "involuntary sensory inhibition" in that one's perception of later arrivals is suppressed.

The Haas effect occurs when arrival times of the sounds differ by up to 30–40 ms. As the arrival time (in respect to the listener) of the two audio sources increasingly differ beyond 40 ms, the sounds will begin to be heard as distinct.

Thanks, Shadorne!

Regards,
-- Al
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kr4
3,677 posts
 
Good point about the Haas effect. One should also note that there is a lower limit to time interval needed for distinguishing direct from reflected/delayed signals. If the arrival interval is on the order of 5msec +/-, the signals are not distinguished and the perceived source location is intermediate between the original source and the phantom source related to the reflection.

Kal
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almarg
9,670 posts
 
Good info, Kal, thanks!

To put all this in perspective, we should keep in mind that as a rough approximation sound propagates through air at around 1 foot per millisecond, varying somewhat with temperature, altitude, and other factors.

Regards,
-- Al
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