Originally Posted by Jens Eklund
Important when throwing numbers around, is to also include the assumed resolution. If 1/24 octave resolution (what we normally use when looking at FR curves); a +/- 5 dB swing through the FR (including the lowest octaves) is exceptional by any standards and a +/- 7 dB is still very good. The median notch depth found by Genelec when evaluating 164 professional control rooms was -14,2 dB, -20 dB or deeper was not uncommon … The deepest notch below about 150-200 Hz is often related to the floor bounce.
Also important to remember is that the FR curve is usually the least interesting one. The ETC and decay plots are usually the most revealing ones.
Yea, I thought about better defining what I meant after I posted, and then got sidetracked by something else. Yes, 1/24 octave is what I use, but I usually leave out the last octave (20hz-40hz) for my +/- numbers.
So, id say:
+/- 5db, 40-250hz @ 1/24th octave smoothing is very good
+/- 7 db 40-250hz @ 1/24th octave smoothing is acceptable
+/- 9 db 40-250hz @ 1/24th octave smoothing is marginal