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The original was posted on /r/hometheater by /u/hungry on 2024-01-06 21:08:22+00:00.
This is a common question here, so I'm trying to put together some FAQs. If you have anything to add, or any corrections please leave a comment below. Specs are based on Dolby recommended.
Basics:
More than anything, ATMOS is based on MLP and ceiling height. Not your L/R placement. The recommended placement is 45° up, and out, from MLP.
45° up, and out, from MLP (± is the recommended range)
But angles are hard and we don't have an easy way to measure them in real life. So what can we do? One of the most common mistakes I see here are people find out what 45° is and making a square from that measurement, when it should be a circle. For example 36" MLP height, 8' ceiling would make 45° = 5'. So what people will do is go forward and out 5' but that gives you an angle of 35.3°.
Measuring 5' Forward and 5' out from MLP will give you an angle of 35.3
If you can't use software to draw it out, an easy way to get really close is to look up the 55° numbers and use those. You can make a square from the 55° numbers to achieve a very close 45° ATMOS location. So using the same numbers as before if you look up 55° from a 36" MLP and 8' ceiling you get 3' 6". Go forward and out that amount will get you almost to the perfect location*. Just verify by measuring from where the MLP would be on the ceiling (center point) to the speaker location and you should have the 45° number (5' in this example).
\ 3' 6" right angle triangle would give a hypotenuse of 4' 11 7/16" so it is not exact, but the difference is negligible. A 15' ceiling would still be less than a 1 1/2" difference.)
55° square will give you almost exact 45° circle ATMOS location
Advanced:
45° is based on 0° Ear Level. The ideal angle for ATMOS is 45°+ (half the angle of 0° to your speaker ear level).
The following is recommended specs for front to back spacing if you can not achieve 0° Ear Level
- FRONT: L/R/C ≤ 20°
- Back: Rears ≤ 25°
And sides if not 0° Ear Level
- Sides: Surrounds ≤ 20°
For example: If your Surrounds are 10° higher than ear level to fit over your couch, the optimal horizontal angle would be 45° + 5° = 50° from Ear Level. I'd recommend using software to figure out numbers at this point, but for home theater, more than likely if you just use the basic guidelines you'll be where you need to be anyway!
Enjoy your ATMOS!
Disclaimer: This is what I have learned over the last 4 months from researching here and other forums, watching videos and trying to sift through the information. If it doesn't sound right let me know, I'm learning too!
