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No real hard rule - it all depends on what else it may be reflecting off of either before or after that surface.

Bryan
 

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Discussion Starter · #3 ·
So,lets say if there was a flat glass surface that was 4-5 inches above seated ear height behind the listening position, would that still need to be treated?
 

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Glass in general should be addressed regardless of location. And, in that location, it's definitely going to still be reflective down to you.

Bryan
 

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Just asking "what reflective surfaces need to be treated" is a bit amorphous.

You treat reflective areas that result in specific detrimental high gain reflections. You do not simply treat something because it has the potential to reflect. That is the recipe for a dead space.

The more prudent procedure would be to employ the ETC response in REW to determine the existence of Actual anomalous detrimental reflections present in the listening position.

Once these have been identified, it is a rather simple process to determine their precise path and point of boundary incidence, and to then employ the appropriate treatment type, be it absorption of diffusion, to resolve the problem and to verify that said treatment is effective.
 

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If the speakers are at ear height, and the glass is located above ear height, specular energy is going to be incident on the glass at an upward incident angle, and the resultant reflection off the surface will be oriented in an upward direction; not downward towards the head.

You can of course dampen any surfaces you want if the goal is to simply deaden the space. Or you can address actual detrimental high gain specular reflections that are actually of issue in the listening location...the choice is of course yours.

But I would suggest that the process and results will benefit from the identification of ACTUAL issues rather than simply potential issues. Not only will the required work and associated cost be less, but as a result of the retained energy in the room, the acoustical results will be improved as well.
 

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Discussion Starter · #8 ·
If the speakers are at ear height, and the glass is located above ear height, specular energy is going to be incident on the glass at an upward incident angle, and the resultant reflection off the surface will be oriented in an upward direction; not downward towards the head.

You can of course dampen any surfaces you want if the goal is to simply deaden the space. Or you can address actual detrimental high gain specular reflections that are actually of issue in the listening location...the choice is of course yours.

But I would suggest that the process and results will benefit from the identification of ACTUAL issues rather than simply potential issues. Not only will the required work and associated cost be less, but as a result of the retained energy in the room, the acoustical results will be improved as well.
The speakers are on 46" Sound Anchor stands,angled down 8 degrees,which puts the speakers tweeters' height at about 59".My seated ear height is 49 1/2" and 6ft. from the LCR's.The glass surface is 29"L x 22"H and is about 3" inches above seated ear height and 4ft. centered, behind the listening position.

The room already has plenty of HF absorption,placing it more on the dead side of things.Would it be better to leave it untreated?
 

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The easiest way to tell is to measure using the ETC response (using a program like REW). That will identify ALL anomalous high gain reflections, from which you can accurately determine the precise path and point of boundary incidence.

Also, as you mention that it is on the 'dead' side; if you are adventurous and can easily remove the panels and generate the ETC and identify the Actual reflections and paths, and replace the absorption only where it is Actually needed, thus mitigating the detrimental reflections and preserving the remaining ambient energy. You might also consider diffusion as well depending for addressing later arriving reflections rather than absorption.
 
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