Accoustical Panel Placement Decissions - AVS Forum
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Old 08-28-2013, 09:03 AM - Thread Starter
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A while back I got my hands on 24, OC703, 2" X 2' X 4' Panels.

I have already made and placed (4) 2 on each side first reflection points. These panels are 2x4; 2" OC703 with 2" air gap. They improved the sound significantly.

I also made (2) 2x4; 2" OC703 Panels for first reflection points on the ceiling however have not mounted them yet, because I am not real confident on proper placement. Can you help here?

So that leaves me with (18) panels of OC703........

I was thinking to build Front Corner Absorbers/Traps from floor to ceiling using 6" (3panels deep); 6 from floor to ceiling on each side and straddle the corners. However that only leaves me 6 panels left. If I would to build these Front Corners with 4" would the performance be far less than 6"?

My rear corners will be difficult to place panels due to an entry door and CD/BluRay Racks.

My question is, where would be the best places for panels to use up my remaining OC703 Panels.

My room is 12.5 W x 17.5 D with 8' Ceilings.

Your recommendations are appreciated!
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Old 08-28-2013, 10:29 AM
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Ethan Winer recommends more bass traps at 4" thick rather than less bass traps a 6" thick. Panels with a paper backing and air gap also help absorb lower frequencies. I'd do 12 4" thick panels as that way you may be able to cover the entire corners of the room.
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Old 08-28-2013, 11:26 AM
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I would double up the remaining panels to make them 4" thick (so their absorption is broadband). Place a couple of them (covering a 4'x4' area) at the middle of the back wall, with a 4" airgap. Spread the rest of them (with same 4" air gap) across the front, including corners. This will minimize hearing reflections from the same direction as your front soundstage.

Sanjay
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Old 08-28-2013, 12:58 PM
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For the ceiling, sketch the room cross-section to scale, draw triangles to find the first reflection points from speakers to listening position, and mount the center of the panels there. I suspended mine using heavy plant hangers (hooks) for drywall (ceiling) mounting and chains to the frames of my panels.

Thicker panels improve bass absorption but how much improvement you'd get going from 4" to 6" vs. placing more panels around the room gets tricky... Ethan's site has several articles well worth reading to help determine the best place in your room. www.realtraps.com

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
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Old 08-28-2013, 02:33 PM - Thread Starter
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"sketch the room cross-section to scale" Not sure what is meant by this? Please give more details?

The first reflection points on the walls were easy with the Mirror Technique. How ever the ceiling???? Where do you begin to move the mirror from??
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Old 08-28-2013, 08:06 PM
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Draw a vertical slice (floor to ceiling) of the room including speakers and listening position on graph paper or using software to provide accurate dimensions.

You can use the mirror technique by having a friend stand on a chair or ladder to hold the mirror on the ceiling.

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
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Old 08-28-2013, 08:18 PM
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I believe the first reflection on the ceiling is midway between you and your speaker,measure from the front of your speaker to where you sit.
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Old 08-29-2013, 11:01 AM
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There are a couple of methods to handle this, my suggestion:

1) Mirror trick; most simple/basic way - Ethans website shows how to do
2) Software; pretty neat http://www.avsforum.com/t/822273/free-software-to-help-determine-your-first-reflection-points
look at post #215,
Quote:
Originally Posted by reaper View Post

Huh? I downloaded the .rar from that web page you just posted... no problem.

frv1.02.rar.zip 172k .zip file

gives you this:
Reflections%2520side%2520view.jpg
3) Measurements & ETC graphs; need equipment and a deep dive into acoustics
http://www.avsforum.com/t/1374014/room-measurement-treatment

I'd suggest 2) first, then physical confirm via 1)

Frankly, 3) is for those HT enthuasists who want to go the extra mile.

For my acoustic "journey", I did 2), then 1), then 3).
DId mine for the front soundstage, R/L and C.

Have fun, and don't over think it too much.....OCD kicks in sometimes then smile.gif


For corner broadband bass traps, look here:
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Old 08-29-2013, 12:45 PM
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Quote:
Originally Posted by drummermitchell View Post

I believe the first reflection on the ceiling is midway between you and your speaker,measure from the front of your speaker to where you sit.

It also depends on the height of the speakers and listening position relative to the ceiling -- if you use triangles in a drawing program (makes it easy to keep the angles the same coming and going) you can see how the apex moves a bit.

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
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Old 08-29-2013, 01:38 PM
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For corner superchunk style traps, these are easy to build, moveable, low cost.....
Quote:
Originally Posted by Eric2000 View Post

Hi guys,

I've been following a number of the acoustics threads here for a while, though I haven't been very active on the AVS forums. Mike suggested that I share some of my work on room acoustics with everyone here, so here are my corner bass traps:

I followed a similar construction technique that Mike posted for his corner bass traps, but made mine from pink fluffy R-19 instead and wrapped the fabric around the outside of the threaded rod. Here is the photo journey:

My traps are 24x24x34 inch triangles, are about 3.5 feet tall, and probably weigh less than 10lbs each. Since I need access to one of the corners for a doorway, I made them stackable and moveable. I started by cutting triangles, drilling holes for the threaded rod, and inserting T-Nuts for the sides that stack on one another:
287

Then I cut 23" squares of insulation, cut them diagonally for triangles, and clipped off the corners so they fit snugly between the threaded rods:
390


A wire mesh made from separated Cat5 wire goes between each layer to keep the insulation from sagging over time. The numbered arrows indicate the direction of winding the wire to support the insulation. A bead of solder keeps the wire from unwinding. Each layer of insulation is about 5" thick.
400

Here is the first one all stacked up. You can see the supportive wire mesh wrapped around the threaded rod on each side:
516

And then with the Kraft paper glued to the front with spray adhesive:
529

Then, turn the trap upside down to affix the cloth wrapping - a two-pack of curtains from the giant W for $15. Each pack is enough for two traps.
400

The cloth is stapled to the underside of the top plate to prevent sagging over time:
291

When the fabric is fully secured to the top panel, turn the trap right side up again and pull the fabric around to the back. Trim off the excess and then just pull it tight and use a desk stapler to hold the fabric together in the back:
550

The staples produce a few ripples in the sides, but you won't see those once you put it in the corner. The front looks nice and clean:
528

Here is a closer shot of two of them stacked together:
600

And finally, the entire back half of the theater. With a few bean bag chairs up front, we can comfortably seat 10-12 people. The colors are a little off from a combination of CFL and flash lighting:
326

Below are the before and after REW plots. The purple trace is the original measurement with no traps and no EQ. The yellow trace is the difference made by the bass traps alone. The traps took 5dB off of the room-induced peak at 45Hz without sacrificing anything else in the audible range:
329

This is the original waterfall plot made by REW - no traps, no other corrections - just a mess with room modes at 45Hz and 90Hz:
443

And here is the waterfall plot after ONLY the traps are put in place. I was surprised by how much of a difference the traps made in the decay:
447

After several days of tweaking the parametric equalizer with the traps in place and a first order high-pass filter in place, here is my "final" room response curve - flat from 7Hz to 100Hz, plus/minus 3dB :'( The peak at 105Hz won't ever really happen because the preamp crosses the LFE channel at 60Hz.
449

And the "final" waterfall plot - nice and smooth. If I adjust the waterfall graphing limits in REW, the entire response curve is down by 20dB within the first 100-120ms with the exception of a 2-3dB narrow bump at about 23Hz. I am really pleased with this result:
443

It sounds great! The EQ and high-pass filter reduce (but don't eliminate) the incidence of amp clipping, but still provide enough punch to cause visitors to literally jump up from the couch :P

All of my other projects are on my web page, which I think is linked in my signature.

Eric
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Old 08-29-2013, 02:28 PM
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Quote:
Originally Posted by DonH50 View Post

It [reflection point] also depends on the height of the speakers and listening position relative to the ceiling

Yes, though if your ears are at the same height as the tweeters, which they should be, halfway between you and the speaker is always the correct center point regardless of the actual height.

--Ethan

RealTraps - The acoustic treatment experts
Ethan's Audio Expert book

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Old 08-30-2013, 05:18 AM
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Quote:
Originally Posted by mtbdudex View Post

There are a couple of methods to handle this, my suggestion:

1) Mirror trick; most simple/basic way - Ethans website shows how to do
2) Software; pretty neat http://www.avsforum.com/t/822273/free-software-to-help-determine-your-first-reflection-points
look at post #215,
gives you this:
Reflections%2520side%2520view.jpg
3) Measurements & ETC graphs; need equipment and a deep dive into acoustics
http://www.avsforum.com/t/1374014/room-measurement-treatment

I'd suggest 2) first, then physical confirm via 1)

Frankly, 3) is for those HT enthuasists who want to go the extra mile.

For my acoustic "journey", I did 2), then 1), then 3).
DId mine for the front soundstage, R/L and C.

Have fun, and don't over think it too much.....OCD kicks in sometimes then smile.gif



For corner broadband bass traps, look here:


Can't get the software to install getting 32.dll error
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Old 08-30-2013, 02:08 PM
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Quote:
Originally Posted by Jacks5000 View Post

Quote:
Originally Posted by mtbdudex View Post

There are a couple of methods to handle this, my suggestion:

1) Mirror trick; most simple/basic way - Ethans website shows how to do
2) Software; pretty neat http://www.avsforum.com/t/822273/free-software-to-help-determine-your-first-reflection-points
look at post #215,
gives you this:
Reflections%2520side%2520view.jpg
3) Measurements & ETC graphs; need equipment and a deep dive into acoustics
http://www.avsforum.com/t/1374014/room-measurement-treatment

I'd suggest 2) first, then physical confirm via 1)

Frankly, 3) is for those HT enthuasists who want to go the extra mile.

For my acoustic "journey", I did 2), then 1), then 3).
DId mine for the front soundstage, R/L and C.

Have fun, and don't over think it too much.....OCD kicks in sometimes then smile.gif



For corner broadband bass traps, look here:


Can't get the software to install getting 32.dll error

see post #245, I had same issue and solved it!

Quote:
Originally Posted by mtbdudex View Post

Quote:
Originally Posted by 1 Infinite Loop View Post

Too bad this doesn't work any more.


Tried to run the DirectX patch, no luck.


Should have been written for the Mac. That way it would actually work.

Quote:
Originally Posted by MitchSchaft View Post

I got it to work by right clicking on first102.exe, going to the compatability tab and choosing windows2000. Now it loads up fine for some reason. Wish the author didnt fall off the map
.


I'm running XP sp3.

I'm trying to get the 1.02c version to run on my computer, I kept getting this error "missing D3DX9_32.DLL", so afte reading here
http://pcsupport.about.com/od/fixtheproblem/ht/restoredx9dll.htm
downloading the below now.

http://www.microsoft.com/en-us/download/details.aspx?id=10990
Quote:
The December 2006 SDK includes D3DX9_32.DLL. This DLL includes the Direct3D 10 HLSL compiler enabled for Direct3D 9 targets (shader models 2.0 and later). The new compiler has no support for 1.x pixel shader targets. This new compiler is the default for Direct3D 9. As a result, all developers are encouraged to author their shaders in HLSL and use shader models 2.0 and higher. The legacy compiler is available using the /LD switch.
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