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PostPosted: Sun May 01, 2016 2:32 am 
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Location: Charlottetown, PE, CA
Need help from the other acoustics guys here.

I am pretty much done in my room in terms of treating front/sidewalls and such. I am happy with the performance of the system for 2ch and home theater use overall, but the rear wall is pretty bare. I have the option of hanging artwork there to round out the room's looks, or to go ahead and treat with some sort of diffusion or abfusion hybrid. So far I am considering building a couple of diffusers reaching down to 500hz or so, and absorbing below, but they are time consuming to build. I've attached all the measurements I can think may be of interest. Maybe there is something obvious I am just not seeing. Should I just hang art and be done with it? Can I improve on these measurements with more treatment on the rear wall?

Any help or advice is appreciated. Let me know if more info is needed.

Here is the rear wall. The areas in question are on either side of the media shelf.
Image

Here is the subwoofer sweep response at the MLP. Ignore values over 120hz as no LFE content exists above it. My mains cross to the sub at 60hz. 1/12 smoothing. Red line on low extention point at 18hz.
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Here is the right channel sweep response with sub. 1/12 smoothing. Red line on 38hz width null.
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Here is the left channel sweep response with sub. 1/12 smoothing. Red line on 38hz width null.
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Here is both channels summed with averaged pink noise. No smoothing. More measurement points per octave with increasing frequency. (higher time resolution)
Image

Here are the right and left channel ETC plots.
Image

Room decay times. Corrected for room dimensions.
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PostPosted: Sun May 01, 2016 5:05 am 
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Location: Montreal, QC, CA
First thing I can see is the perfect space for corner bass trapping. As for artwork, why not think outside the box and make some decorative acoustic wall panels (1"X4" framing filled with Roxul Safe-n-Sound and covered with acoustically transparent fabric) at your first reflection points. You can have custom artwork painted on it using water colors (that do not clog the fabric or make it acoustically stiff) or maybe even use a Batik print fabric if that suits your decor better. I would avoid any canvas artwork that uses oil or acrylic paints or hardboard prints as well as anything with a glass covering.

As for diffusion, there were many 3D wall coverings (think 2 or 3 inch thick heavily textured wallpaper) that were available a few years ago that could be painted to blend into your walls. Check out you local home decoration store or even this place for ideas:

http://threedpanels.com/products.php

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PostPosted: Sun May 01, 2016 5:26 am 
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Location: Quebec, QC, CA
quadratic diffusor....you can do it yourself


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PostPosted: Sun May 01, 2016 5:30 am 
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Location: Athabasca, AB, CA
Yes,I would do those tri corners for sure.
seems that's where bass collects the most, floor wall corners,even wall corners that meet the ceiling.
I did my back wall with RT's 6" 2'x4' Mondo traps doubled up so they are one foot thick
with RT QRD diffusers in front of the traps.
Actually all my corners(floor/wall)tri corners are done.
I have a drop ceiling so I put in 4"thick RT tiles so my ceiling 12x19 is a huge bass trap with ceiling reflection panels about midway from seating area.
All reflection points panels have no membrane on the front so as to absorb mids and highs
all corner bass traps have the membrane to reflect the mids/highs.
Friends are quite amazed how clear everything sounds when watching concerts in the room.
They have been to live concerts as myself and when I put on a concert that they have been to, they prefer my room to the venue especially since everything is so clean sounding and the bottom end midbass punch is
evil.
Now they say they won't do concerts anymore that they will buy the bluray and bring it over here :lol: ,
course the 128"x50" 235.1 screen helps also as your in the best seat in the house :D.


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PostPosted: Sun May 01, 2016 8:07 am 
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Thanks guys!

Corner bass traps are already deployed behind my screen wall and probably arent an option in the rear for aesthetic reasons. I dont want them there although they would help a little. I might ge able to build something for bass trapping on top of the shelf to the ceiling. In theory this would attack the modes created by the opposing front lower wall to floor corner my subs are on. Hmmmm.

The 3D mdf panels are an attractive option I have considered. When done right they are stunning. I havent been able to find any with more than 2" of relief or so. I need to look harder maybe.

I am liking the idea of adding more diffusion to the room (front wall QRD and side polys already). I have some fractal plans to go by that should yield an attractive result. Decisions to mull over. I'll keep you posted.

Thanks. :)

These arranged as fractals on a large skyline layout would be awesome. Thanks OBI.

http://threedpanels.com/product-detail.php?id=1


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PostPosted: Sun May 01, 2016 8:41 am 
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Serenity_now wrote:
Thanks guys!

Corner bass traps are already deployed behind my screen wall and probably arent an option in the rear for aesthetic reasons. I dont want them there although they would help a little. I might ge able to build something for bass trapping on top of the shelf to the ceiling. In theory this would attack the modes created by the opposing front lower wall to floor corner my subs are on. Hmmmm.

The 3D mdf panels are an attractive option I have considered. When done right they are stunning. I havent been able to find any with more than 2" of relief or so. I need to look harder maybe.

I am liking the idea of adding more diffusion to the room (front wall QRD and side polys already). I have some fractal plans to go by that should yield an attractive result. Decisions to mull over. I'll keep you posted.

Thanks. :)

These arranged as fractals on a large skyline layout would be awesome. Thanks OBI.

http://threedpanels.com/product-detail.php?id=1


I attended a home show here earlier this year and there were at least 7 or 8 different vendors for this kind of stuff, each with a different variety of styles/models. None of them were MDF, but more like thick cardboard which is also pretty lightweight (think sort of much thicker egg carton material). They were doing a demo install at 1 place putting them up with nothing but strips of double sided carpet tape. The first ones I saw 5 or 6 years ago had certain models that were easily 4 inches thick (in fact I may have posted something on them back then).


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PostPosted: Sun May 01, 2016 11:44 am 
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........Auralex SFS-184 SonoFlat System.......... look into that....


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PostPosted: Sun May 01, 2016 4:01 pm 
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libor wrote:
........Auralex SFS-184 SonoFlat System.......... look into that....


Not a bad idea, but the remainder of my room is already comprehensively treated. Just the rear wall now. 8)


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PostPosted: Sun May 01, 2016 4:37 pm 
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Location: Oshawa, ON, CA
3" absorption panels behind the speakers, and then artistic diffusers on the wall at ear height.


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PostPosted: Mon May 02, 2016 1:47 am 
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davidam wrote:
3" absorption panels behind the speakers, and then artistic diffusers on the wall at ear height.


Like the idea of artistic diffusers. Since these are rear surround channels I might hold off on SBIR traps, but a great idea I never considered for back here. The rear channels will see more use once I go to an immersive playback system. Right now 5.1 is still the lions share of titles I play unfortunately.

It is looking more and more like I will build a lean fractal design from Arqen. Something different that will show nicely with the lighting above. I like the simplicity of the design and am curious to try it out.


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PostPosted: Sat May 14, 2016 12:05 pm 
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This has turned into a DIY double up. I'm building a hot wire foam cutter, then one of the fractal diffusers by Tim Perry out of foamular insulation. Will update with pics once done. :)


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PostPosted: Sun May 29, 2016 3:11 pm 
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All done. Thx for your input guys.

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PostPosted: Sun May 29, 2016 3:53 pm 
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Looks really nice! I've been mulling over the same project.

Which Foamular product did you use? The width of each well looks quite narrow from the pic.

Most importantly, what have you noticed about the effect on the sound?

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PostPosted: Sun May 29, 2016 4:32 pm 
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I used 1/2" foamular and went with the A1-LF design.

I had to spray them as the fractal wells are indeed quite narrow.

I am very happy with the result. They dried up the rear of the room a little and reduced direct reflections back to the mlp noticably. I wouldn't have known problem reflections were there, except now they're altered (for the better.) The result is a room that now sounds like nothing.... Its hard to describe, but I feel like I am sharing the same acoustic space as the recording. I can now hear every waver in a voice, breath and strain. Each hit on the ride cymbal, each strum sounds different from the one preceding. Clarity and imaging has improved again. Everything is tighter. I'm sure my decay times must have dropped, yet everything sounds open and live. Very cool. There are no speakers now. Just an open soundfield. Its a cool feeling. 8)


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PostPosted: Sun May 29, 2016 5:06 pm 
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I hate to be asking too much, but can you get a closer photo of the diffuser? I'm interested in how you cut each fractal to depth into the foam...

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