Originally Posted by jlpowell84
I'm sorry if this question has been answered. I have mostly kept up with the thread but working 7 days a week as of recent I may have missed. I will post a clip from J's recent comment that I have yet to find a satisfying answer for. Again I have been keeping up mostly with the measurement technique discussion but didn't hear a direct answer.
If you decide to view a full range measurement with L+R+Sub(s) you will most likely be disappointed above about 1khz or so (most of the time and unless you are VERY careful and have very exact speaker and mic placement between the speakers) as the wavelengths start to become so small the slightest movement of the mic will cause phase interactions, comb filtering, and a very poor and inaccurate measurement in the higher frequencies. There really isn't any reason for this. Again, the only measurement necessary for L+R+Sub(s) - combined - should be to look at the overall bass response, below 300hz, unsmoothed.
I did accidentally do this the other day. On my Mac I have to switch audio output to sound flower 64ch as per JPA's wonderful guide to only get one speaker plus LFE channels at a time. I had switch back to my Denon, which allows for both LR to play, to listen to a song for differences during tuning and forgot to change it back. I did notice some not so good looking graph up in the top end.
Why don't we do this? It seems this would be the most important since we listen with both of these speakers (plus a center usually) during a movie or multichannel music. What is the simple answer?
Here is an example of the interaction between left and right signals at the upper frequencies:
Note the significant dip in the combined (green) response curve. Clearly, the individual speaker response curves do not suggest such a severe roll-off in the high end.
BTW, as mentioned previously, all you have to do is adjust the mic position an inch or two to the left or right, re-measure, and you will see the interaction diminished significantly. I always try to place the REW mic in the same spot as the Audyssey mic (Audyssey shows identical left and right speaker distances), but the graph shows how hard exact placement can be.