In reply to:
However, in my environment, I noticed a very significant drop-off in output as I moved off axis, one that I heard with my ears. The meter just confirmed it.
But you specifically stated this occurred when calibrating with pink noise. As i iterated to previously, this is partly an artifact of pink noise and secondly, this will occur with any horizontal centre.
Does this equate to the same 'sound' during a test tone playback or real music?
Not that i've heard and certainly not measured with an SPL. Play a song in DPLII such that the centre channel is being used and then do your SPL test from left to right. I can just about guarantee the results will not be the same as you measured with pink noise.
Keep in mind that your original measured values were 2-3dB which is at the marginal range for human perception as significantly different volume (this number seemed to increase as your later posts came along, i don't know how). If the right and left channels are working and placed for optimum performance, you should not detect any dropoffs or suckouts.
If you do not like the VP150 for this sound, then logically you should not buy towers either since they have the same 'problem' just in a different plane. Someone posted an article recently about the omnidirectinal Beolab5 speakers. You could always give them a try.
As for the design concept, everyone has different ideas for what sounds good as a speaker and not all use measurements like Axiom at the NRC. Many design speakers off the top of their heads based on principles they know, and everyone wants to have something unique. Very few companies like to copy each other, but note how recently many companies have jumped on this multi-directional driver dispersion idea like the QS8s. Sometimes the concepts take time to catch on and be accepted.
Maybe there is a company that does have the best centre channel design for off-axis response.
Who knows?
But from what i've seen so far, many centre channels are very simple. Usually one or two drivers and that's it. I find this style to have a real point source for sound such that localizing the near exact position of dialogue is distracting as it comes from above or below the viewing screen. I think this is far more a negative property compared to the VP150 shift in response by moving left or right 4 feet or more. The distance to ones listening location from the main/centre channels will greatly alter such perceived sounds.
