Thanks for the article. I have a few questions.
How much is that RBH 661 speaker? I see a figure cited at the top of the AH review, but I assume that is for a package of 5 speakers.
That is interesting that a -10db dip at 450hz might possibly be deemed inaudible due to the narrow bandwidth, if only for real world program.
Can it be assumed that the further offaxis one is to a horiz MTM, the worse it will sound? The reason I ask is because one fellow told me that my own PSB Image C60, based upon the xover point of 2.5khz and driver spacing, I would essentially be 180 degrees out of phase at 20 degrees off axis listening.
To clarify the question above, It couldn't possibly sound better at 27 degrees than 20 degrees for my speaker, could it? (I suppose not).
Unfortunately, the extreme edges of my seating are pretty much at 20 degrees on the dot. Fortunately, I rarely sit there, probably only once for every twenty viewings.
Do you believe that with a popular speaker, such as my Image, or say a Paradigm Studio, or Ascend 340, etc, that the results would be pretty similar?
How dramatic, if at all, could one predict the differences could be with offaxis listening based upon xover point and driver spacing?
Thank you very much. I have now decided to italicize the questions above for everyone's convenience.
Ok, I tracked down the post where someone told me about my PSB design. This was April of last year.
josten,
I looked at the specs of the PSB image C40 and C60. A horizontal MTM speaker's lobing errors depend on 1) CTC spacing of two woofers and 2) crossover frequency. The C40 uses smaller woofers and as a result shorter CTC spacing. It also uses a lower xover freq, 2.2 kHz, than the C60's 2.5 kHz.
But even C40 has unacceptable horizontal lobing patterns in your situation. According to my calculation, 20 degree off axis is the exact position where one woofer is about 180 degrees out of phase with the other woofer, resulting a deep null at 2.2 kHz, at which two woofers' SPL sum is supposed to be only 6 dB down from the system SPL.
A well designed MTM speaker that can be used horizontally as CC should use 1.5 k to 1.8 kHz xover frequency and/or much closer woofers.
-jAy
Thanks again for any input!