How to diagnose the need for room treatment?

The ceiling.

Al wrote: "Particularly once you get above bass frequencies, tuning the room for flat frequency response using a test cd, microphone, etc., is not necessarily going to get you the best sound, and in fact probably won't. The microphone is not going to discriminate very well, if at all, between early arrival sound (the direct path from the speakers to the listening position) and later arriving sound (reflected off of walls, ceiling, etc). But your ears will!"

I think your comments apply better to the bass frequencies, not above bass frequencies. In the bass, the arrival/decay times are more easily measured and corrected whereas at higher frequencies room mode interactions approach randomness. Thus, at those higher frequencies, only FR adjustments are feasible.

Kal

Bob wrote: "I take exception to those statements. The REW (Room EQ Wizard available at the Home Theater Shack) is sophisticated and does time domains. It is for FREE FREE FREE FREE FREE"

Yes, yes, yes...................but REW is a measurement tool, only. It cannot implement a correction even if it defines it. One needs an additional tool to use the results.

Kal

If you are trying to assess room acoustics based on system throughput, aiming the mic forward, or at any speaker, biases the results to the performance of that speaker. Pointing it upwards makes for the least biased results. Also, averaging more than one mic position helps.

Kal

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

Paper egg trays are, fundamentally, useless.

Kal