# RSL C34E - Atmos Placement Help

1669 Views 1 Reply 2 Participants Last post by  Charles Collins
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I put this in my theater build thread, but i think a dedicated thread may get more attention, as there are a lot of people asking questions about ATMOS placement..

I plan to use RSL C34E speakers for atmos. I pulled from their website the vertical dispersion. looks great through 45 degrees, and still pretty darn good up to ~60 degrees...

Ceiling will be roughly 8'6". Top row listener height is ~38" from ceiling, and bottom row listeners is ~54" from ceiling. In my case, i want to optimize for both rows to have a good listening experience. Why? because in 2.4:1 widescreen mode back row should be MLP and for 16:9 mode the front row will be MLP, but i digress...

The RSL have a 15 degree angle built in, so they project out more in the direction pointed and less in the direction not pointed. So i adjusted my forumlas accordingly to calculate where the dispersion will be forward and backward as a result of the angled speaker. My calculations for good sound coverage are as follows:

60 DEGREE COVERAGE (shown in blue in picture below)
for bottom row listening height:
max distance from speaker (direction pointed): 54" * tan(75) = 16'9"
min distance from speaker (away from direction pointed): 54" * tan(45) = 4'6"

for top row listening height:
max distance from speaker (direction pointed): 38" * tan(75) = 11'9"
min distance from speaker (away from direction pointed): 38" * tan(45) = 3'2"

45 DEGREE COVERAGE (shown in green in picture below)
for bottom row listening height:
max distance from speaker (direction pointed): 54" * tan(60) = 7'8"
min distance from speaker (away from direction pointed): 54" * tan(30) = 2'7"

for top row listening height:
max distance from speaker (direction pointed): 38" * tan(60) = 5'6"
min distance from speaker (away from direction pointed): 38" * tan(30) = 1'8"

So I mapped this in two pictures...
Sound coverage if sitting with ears 38" from ceiling (back row): Looks like back row gets decent coverage from the rear speakers, but not so much from the front speakers.. This may be the best i can do...

Sound coverage if sitting with ears 54" from ceiling (front row): Looks like front row is pretty well enveloped by all 4 speakers in this arrangement.

Questions:
Am I doing this right? Did I interpret how the RSL speakers project their sound correctly?
Does anyone disagree with placement of ATMOS?
Does anyone disagree with the direction i have my ATMOS pointed to maximize coverage to all seats?

There is a lot to consider here, and I'm not even sure if I understand how the speakers work... Some validation would be great
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I can understand that you might want to watch the wider screen from further away. Especially if you have a constant image height. But as far as the sound system goes, the speakers remain in the same position. And the sound will be calibrated for one main listening position, not two different locations. You should try to make sure all seat locations get good coverage. One possibility to try to accomplish this is to define the MLP in between the two rows. If you decide to do that, Dolby suggests placing the front atmos speakers at a 45-degree angle above and forward of the MLP and the rear atmos speakers at a 45-degree angle above and to the rear of the MLP. So it appears to me that the rear atmos speakers need to be moved rearward from where you show them. They will be closer to the rear seat occupants, so the fact that those rear listeners are more off-axis will help to offset the closeness issue. The built-in directivity of the speakers should be all pointed at the MLP. All of this is what I would probably do. And what you select as the MLP is open for discussion. I would probably select front row and center.
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