Surface Coefficients in Room Simulation

Nordo

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My AV System  
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Denon AVR X1500H
Additional Amp
Sub amp - Behringer EP2500
Universal / Blu-ray / CD Player
Panasoic BD35
Front Speakers
DIY
Center Channel Speaker
DIY
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I've been dabbling with the Room Sim section of REW.
I did a search for "surface absorption coefficients" to ascertain what coeffs I should be putting in for the various surfaces.

In the Help section of REW, it states that the surface absorption is "independent of angle or frequency".
However all information I found regarding surface absorption indicates that the absorption coefficient IS frequency dependent.

Can John or anyone throw some light on this?

In my case the walls are timber framed with plasterboard (drywall) on both sides, and the ceiling is timber framed with plasterboard on the lower face.
The floor is a carpeted concrete slab.

BTW, I have recently realised that lightweight walls, like I am looking at, become almost transparent below certain frequencies.
i.e. the LF wave velocity is NOT zero at the wall face. Which questions some of the theory behind bass traps.
 

John Mulcahy

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Actual absorption coefficients are dependent on frequency and angle of incidence but the simulator uses a fixed value.
 

Nordo

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Thread Starter
Joined
Oct 7, 2019
Messages
77
My AV System  
Preamp, Processor or Receiver
Denon AVR X1500H
Additional Amp
Sub amp - Behringer EP2500
Universal / Blu-ray / CD Player
Panasoic BD35
Front Speakers
DIY
Center Channel Speaker
DIY
Surround Speakers
DIY
Surround Back Speakers
DIY
Front Height Speakers
-
Rear Height Speakers
-
Subwoofers
Four 15" infinite baffle drivers
Other Speakers or Equipment
HTPC (windows 10 with Kodi)
Video Display Device
Epson EMP-TW2000 projector
Screen
Matt white "blockout" curtain liner
Thanks John.
Is there any guide I can use to estimate what values I should be using in the Room Sim?

I'm only biding my time until we take possession of our new house that has this room I'm modelling, which will be my (very poor) media room (there's no way I can call it a Home Theatre).
 

John Mulcahy

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There are useful tables of absorption coefficients here, use the 125 Hz values. The coefficients will mainly affect the height of peaks/depth of dips, the overall distribution won't be affected so for experimenting with positioning options the coefficients aren't that important.
 

Nordo

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Thread Starter
Joined
Oct 7, 2019
Messages
77
My AV System  
Preamp, Processor or Receiver
Denon AVR X1500H
Additional Amp
Sub amp - Behringer EP2500
Universal / Blu-ray / CD Player
Panasoic BD35
Front Speakers
DIY
Center Channel Speaker
DIY
Surround Speakers
DIY
Surround Back Speakers
DIY
Front Height Speakers
-
Rear Height Speakers
-
Subwoofers
Four 15" infinite baffle drivers
Other Speakers or Equipment
HTPC (windows 10 with Kodi)
Video Display Device
Epson EMP-TW2000 projector
Screen
Matt white "blockout" curtain liner
That's great.
I had already downloaded a similar table.
But knowing to use to 125Hz coeff. was what I needed to have confirmed.

Thanks so much for your time - yet again. :T
 

VolunteerPin

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Question on this also...I looked over the table above. It has been recommended to me to use two layers of 1" linacoustic with a 3mil plastic between the layers on the front wall (behind my AT screen wall). Any thoughts on what kind of coefficient that would create that I can plug into the simulator? Thanks in advance by a new member (first post).
 

Nordo

Member
Thread Starter
Joined
Oct 7, 2019
Messages
77
My AV System  
Preamp, Processor or Receiver
Denon AVR X1500H
Additional Amp
Sub amp - Behringer EP2500
Universal / Blu-ray / CD Player
Panasoic BD35
Front Speakers
DIY
Center Channel Speaker
DIY
Surround Speakers
DIY
Surround Back Speakers
DIY
Front Height Speakers
-
Rear Height Speakers
-
Subwoofers
Four 15" infinite baffle drivers
Other Speakers or Equipment
HTPC (windows 10 with Kodi)
Video Display Device
Epson EMP-TW2000 projector
Screen
Matt white "blockout" curtain liner
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