AVS Club Gold
Join Date: Jul 1999
Location: Near an airport
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Mark, I start with "A".
Center channel not withstanding, the sound stage can collapse when the speakers are too far apart. The depth and width of the sound stage is very much affected by the design of the specific speaker and the acoustic treatments used (as well as the geometry of the seating in relation to the speakers). Sucking out the side wall reflections can kill a sound stage.
A point to remember is (in residential sized rooms) as the speakers move further apart, they get closer to the side walls. The impact of wall proximity can be very significant and a contributor to sound stage failings.
If the speakers are on stands behind the screen you have the advantage of pushing, pulling and twisting the speakers after construction. If you're using a true baffle wall, you've got to start with full polar radiation plots of the speakers ... this is a real engineering problem because those speakers ain't moving once installed.
Lobing may or may not be a problem depending on the speakers being used. Elevating the speakers above the ears, above the ears and aiming downward, may or may not place one or more rows (seats) in a problem area. (An advantage with raising the speakers and aiming downward into the seating area is it will reduce the SPL delta between rows.) Elevating speakers above ear level (whose ears, which rows) will not inherently exacerbate lobing issues ... it is speaker dependent. On the other hand, lobing effects are generally not realized by casual listeners who are seated ... moving around the room can make lobing artifacts very apparent. Excellent speaker designs are making lobing less and less an issue ... in many cases, much less an issue than the difference in the high frequencies between the first, second, third, etc. rows of seats ... particularly in small residential rooms ... not a problem in two channel since two channel is so focused on one and only one seat.
The two channel boys have it easy. They can get by with horrid speaker designs (from ma lobing perspective) due to two inherent factors in 2-channel "audiophilia" rooms: (1) the sound has to be good in one, and only one spot approximately the size of a 10" cube which is a bunch easier to do than good sound in 16 seats; and, (2) 2-channel is so full of it's own inherent distortions from reality ... (well, I won't go there again).
Masking panels - The impact of the masking panels when closed to 1.78:1 will vary from non-audible to a higher roll off in the high frequency range. The non-impact could be a result of really good masking panels or the fact the roll off is in a frequency range we adults tend to have lower sensitivity. The audibility issue would largely stem from a timbre mismatch between the center and L/R speakers. This, however, can be easily compensated for by an EQ device which allow for multiple profiles to be saved and recalled.