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height of absorption panels Dynamics Plugins
Old 16th December 2010
  #1
Here for the gear
 

height of absorption panels

Hi all,

I have a dedcated home theatre room and have planned the installation of superchuncks in the corners. I am now planning to install 4" broadband wall absorbers and would really appreciate any help with the following 2 questions.

1) For the side walls (once i have determined the reflection points) can the absorber panels be mounted at any height on the side walls? My preference is from seated ear level down to the floor (room aesthetics), but i have seen panels mounted centrally in height on a wall, or from seated ear position upwards. Is there an ideal position or will it not make much differene if i install them on the lower part of the wall?

2) My rear wall has 2 bi-pole wall speakers mounted about 2' above the seated ear position. The lwhole of the lower part of the rear wall has a row of cinema seats, 6" from the rear wall. Is it worth installing a broadband absorber behind the row of seats or will this not have any effect. My only other position appears to be above the seats and below the bipole spealers, is this worth it?

Thanks
Old 16th December 2010
  #2
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I attch a photo of the front speakers with cones down to the floor, in case that is relevant to the question.
Attached Thumbnails
height of absorption panels-ma-rx-8-speakers.jpg  
Old 16th December 2010
  #3
Lives for gear
 

the side wall absorbers need to be mounted at the reflection points of the mid-range and tweeter (which should be about ear level at the listening position)

the mirror trick will help you find the perfect spot - i would put the center of the absorption panel right at the center of the tweeter/ear level height.
Old 17th December 2010
  #4
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Thanks, and i can see the logic of this height being the ideal, but will it make much of a difference if the panels go down to the floor?

Any thoughts about the absorber behind the sofa?
Old 17th December 2010
  #5
SAC
Registered User
 

the application of absorption is not done based on aesthetics.
Let me rephrase. They should not be placed base upon aesthetics - although they too often are!

Absorption used for the control of specular (focused) reflections is placed based upon need. Likewise, areas that do not serve to specifically control the anomalous reflections should remain untreated!

Here is a simple and fundamental way that placement is determined.

Download Room EQWizard - a free software measurement program.

Generate the ETC response for each speaker operating by itself.
This response(s) provides detail on all of the reflections in the room at a given listening position for each source.

Without too much difficulty, you can identify the paths of the various strong reflections. And among them will be the reflections that are incident on the side walls.

By properly placing the panels you will significantly remove/reduce the gain of the reflections at those points. Properly placed panels will address all of the reflections from that region. And you verify this by repeating the test with the one speaker being driven for whose ETC you are analyzing and mitigating the reflections and verify that you have adequately treated the offending reflections. You do this for each speaker.

So, bottomline, you adjust the panels appropriately to the functional need, not simply to where you think they look 'nicest'.
And if it is applied where it does not add functional benefit, you are just putting 'artwork' on the walls.
Old 19th December 2010
  #6
Here for the gear
 

Thanks for that; i do of course apprecaite that compromises will have to be made with the aesthetics, but it would still be helpful to know whether a broadband bass absorber located behind the sofa area is worth considering or not. It may well be that it will take me several weeks to do the study work mentioned above, so early opinions on the questions would still be helpful, thanks.
Old 19th December 2010
  #7
SAC
Registered User
 

Quote:
Originally Posted by Tinytim View Post
... it would still be helpful to know whether a broadband bass absorber located behind the sofa area is worth considering or not. ...
First a 4" thick broadband absorber is not a LF bass trap.

Secondly, while we know nothing about the room itself, I think I am safe in sticking my neck out and assuming that you will have modal activity.

Seeing as how you have somewhat absorptive seating within 6 inches of he rear wall. i am not sure how much additional LF trapping you would receive by the addition of an additional 4" broadband trap located withing 2" behind the seating.

I would however suggest that if you need more LF bass traps that you look at installing additional corner trapping in the wall/ceiling interfaces for maximal benefit.

Assuming that the room is used only for surround sound movies, the risk of over damping the room is somewhat reduced, as the surround speakers are designed to introduce the ambiance that a later arriving soundfield might otherwise provide.

But again, treatment is based upon performance and demonstrated real problems verified by measurement and analysis. So, exactly what bass modes may exist, and the degree to which multiple modes may sum is impossible to predict with the information at hand. In additional to simple measurements, you might drive the room with a series of sine waves (be careful with this process - if you are not sure why, ask!) in order to empirically identify resonant frequencies and distributions. This will help you identify where optimal bass trapping should be located.

As far as generic placement, you might want to read the various stickies and tutorials located on the Realtraps and GIK websites.

But beyond that, we require much more information about the room, and test results would tell us what is really happening as opposed to what might be happening.

One thing , that I am sure of, and which I suspect you do not want to hear, is that locating room treatment according to room aesthetics rather than according to optimal placement corresponding to ACTUAL regions of incidence is a good way to waste money and materials without achieving optimal effectiveness. And that less than optimal effectiveness will not be the fault of the treatment.

But in any case, as suggested above and without more specific room and test information, I would suggest sufficient LF corner trapping (featuring a 2foot wall contact and an ~35 inch face width minimum) including additional wall/ceiling, wall/floor interfaces above and beyond the vertical corner traps (note - there are 12 corners in a room, not just 4). And the broadband traps for early reflections are necessarily places where the reflections are actually incident. But, generally speaking, ankle to knee high is not typically a critical incident region for vector paths on the way to one's ears.
Old 19th December 2010
  #8
Here for the gear
 

SAC

Many thanks for taking the time to offer further assistance.

I have downloaded and completed a room mode calculator, but the results (at this stage) do not mean too much to me as below. I also attach the file if that provides any further info.

I am already committed to installing superchunks in four corners but am on work oversaes at present so was trying to do as much research as possible before getting back in a month and working on this properly. Again, i fully accept that there will be the need for compromise on aesthetics in the room, and that is why i am researching the topic rather than just proceedng, but i do have other considerations (wife) so was just seeking views on rough placement and options. Apolgies if i used the wrong terminology in describing the panels! tutt

Arranged in ascending orderAdjacent mode spacing33.535.52.166.230.766.90.771.04.1100.429.3106.56.2132.525.9133.81.3142.08.2167.325.2177.610.3198.721.1200.72.0213.112.4234.221.1248.614.4264.916.4267.62.7284.116.5
Attached Files
File Type: xls Room Mode Calculator.xls (90.5 KB, 348 views)
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