Acoustical treatment behind acoustically transparent screen

RandyR

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When I built my home theater several years ago, I went way overboard with diffusion and absorption. Probably at least 50% of the wall had custom deep well quadratic diffusers. Including behind the now ATS screen. The theater currently sounds very spacious and much larger than it is and I don't want to ruin that. I am in the process of redoing everything and want to know the best practices for treatment behind the ATS screen. It currently has a 100" x 48" difusser plus mixed in absorption. I had filled in most of the wells with absorption when I put in the ATS screen. Typical on line information is for full insulation behind the screen, but I don't want to over absorb the room. Is diffusion behind the screen bad?
 

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Travis Ballstadt

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I use all absorption on my screen wall. I would repurpose the diffusers elsewhere in your room, ceiling is always a great area for diffusion to really raise the roof.
 

VinceHoffman

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IMG_0734.JPG

I prefer a more spacious sounding acoustic too, particularly when listening to stereo LP and CD. So the front wall of our music & cinema room features a combination of diffusion and absorption, leaning more towards the former. My music optimized front stage setup is quite different than most HT optimized setups like that of the OP though. The front baffles of my LCR trio are 5' off the front wall and I use a motorized tab-tensioned AT screen.

IMG_0854.JPG


Screen Shot 2022-05-19 at 12.20.20 PM.png
At center wall is a huge 8" deep polycylindrical diffuser built from an entire 8'x4' sheet of masonite. the space behind the big poly is lightly filled with mineral wool to provide some limited bandwidth upper bass trapping.

Screen Shot 2022-05-18 at 11.52.15 PM.png

Flanking the huge poly are a pair of 6'x24"x8" stacks of modified RPG BAD (Binary Amplitude Diffuser) Arc panels. These gradually transition from 100% absorption below 1kHz to about 70% diffusion above 5kHz.

Further outboard, 11' tall floor-to-ceiling stacks of 16" diameter ASC Isothermal Tube Traps provide efficient corner bass trapping. However the Tube Traps are oriented so their reflective poly diffusor side faces into the room. As a result they only absorb frequencies below 400Hz while diffusing everything above.
 
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AudiocRaver

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My vote: for best soundstage and imaging (SS&I), which is important for cinema and extremely important for music, go all absorption behind the screen.
 

RandyR

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View attachment 65082
I prefer a more spacious sounding acoustic too, particularly when listening to stereo LP and CD. So the front wall of our music & cinema room features a combination of diffusion and absorption, leaning more towards the former. My music optimized front stage setup is quite different than most HT optimized setups like that of the OP though. The front baffles of my LCR trio are 5' off the front wall and I use a motorized tab-tensioned AT screen.

View attachment 65086

View attachment 65084 At center wall is a huge 8" deep polycylindrical diffuser built from an entire 8'x4' sheet of masonite. the space behind the big poly is lightly filled with mineral wool to provide some limited bandwidth upper bass trapping.

View attachment 65085
Flanking the huge poly are a pair of 6'x24"x8" stacks of modified RPG BAD (Binary Amplitude Diffuser) Arc panels. These gradually transition from 100% absorption below 1kHz to about 70% diffusion above 5kHz.

Further outboard, 11' tall floor-to-ceiling stacks of 16" diameter ASC Isothermal Tube Traps provide efficient corner bass trapping. However the Tube Traps are oriented so their reflective poly diffusor side faces into the room. As a result they only absorb frequencies below 400Hz while diffusing everything above.
Thanks for the response. A very cool looking setup. It appears that there is some serious music listening going on besides the cinema portion. Did you do anything special with electronics to divide the two? I ended up doing completely seperate systems in the same room.
 

RandyR

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My vote: for best soundstage and imaging (SS&I), which is important for cinema and extremely important for music, go all absorption behind the screen.
Thanks for the response. I wanted to do all absorption behind the screen but was concerned with over absorbing the room.
 

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Simple rule of thumb... 1/4th to 1/3rd of all surface areas needs wide band and bass absorption... Your one wall behind the screen is only 1/6th...
 

VinceHoffman

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Thanks for the response. A very cool looking setup. It appears that there is some serious music listening going on besides the cinema portion. Did you do anything special with electronics to divide the two? I ended up doing completely seperate systems in the same room.
Yes I did @RandyR. Two completely independent source, preamp, and bass management front ends. Only the L & R front active ATC monitors and the quad Seaton subwoofer array with a DSPeaker AM2.0 subwoofer eq are shared between the two front ends. All the silver boxes are 2 channel and black boxes are multi-channel. I use a pair of ARX RS-1 12v triggered, relay actuated XLR switch boxes to seamlessly and transparently switch between the front ends.
IMG_0851.JPG



Prior attempts at having stereo playback duties performed by the two iterations of an almost entirely Meridian high-end digital active 5.1multi-channel system seen below resulted in disappointing stereo sound.
Screen Shot 2023-10-23 at 8.40.13 AM.png

Screen Shot 2023-10-23 at 8.42.09 AM.png

Screen Shot 2023-10-23 at 8.57.18 AM.png



The current setup with its independent stereo & multi-channel front-ends along with refinements to the acoustic treatment strategy proved to be spectacularly better for stereo reproduction while also offering the best multi-channel I've experienced to date. Then adding Atmos/DTS X functionality to this latest iteration of the "big rig" truly put the cherry on top!
IMG_0844.JPG
 

AudiocRaver

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I did not mention that the controlled-dispersion character of front main pair (electrostatics or a good HF horn like the JTR or Seaton designs - I use MartinLogan electrostats) effectively helps "increase" the area of absorption, i.e. little to no absorption needed at the usual first reflection pointes, where I would also normally advise absorption.
 
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