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PostPosted: Mon Jun 01, 2015 5:46 am 
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Location: London, ON, CA
Hello all,

I'll open with a disclaimer: I'm not an expert in room acoustics, this project is the culmination of having read about the topic of room treatment for a number of years, and finally dedicating myself to do something to improve my listening room/home cinema.

After a lot of careful planning, I built a listening room/cinema/family room in the basement of our new house, on a budget. I finished it one year ago. It is about 21' x 15', with the screen and speakers on the long side of the room. The ceiling joists are 9' above, so once I boxed in some duct work and beams, I was able to still have a high ceiling, with LED valence lighting for effect. The room has no windows, so it's as dark as a cave in its natural glory.

Here's a picture of the room shortly after completion (equipment and decor have changed a bit since then):

Image

I designed the room so that it is not a perfect rectangle; the front corners are broken (twice), the room has several different depths (front to back) and the ceiling cascades in two or three different heights in an effort to combat standing waves and break reflections. The main walls are paralell, however.

The effort to break things up seems to have been successful, as measurements I have done have shown almost flat response in the FR, with a bump at 45Hz and 90Hz (room modes). A simple clap test revealed that flutter and ringing was an issue, especially between the front and rear walls, which are bare on the top 2/3 except for the 100" projection screen (which is acoustically reflective). This week I set out to see if I could remedy this problem.

I brought home a couple 4'x6'x1-1/2" sheets of Roxul Comfortboard IS last week, and stood them up against my right and left walls; their presence in the room was certainly doing something good, taming echo and reflections. However, the effect was greater when I put a sheet of it behind me, so I decided to start with the rear wall (I actually did a thin sound cloud on the ceiling prior to this project, more on that later). This product has a density of 8 pounds per cubic foot. The acoustical data can be found here:

http://www.roxul.com/files/RX-NA_EN/pdf ... d%20IS.pdf

Three inches was over 3x more effective at 125 Hz, so I decided to use two layers for this panel. For side reflections I would probably use a single layer.

Step 1: I cut up a 3/4 inch pine board that I had in the garage into 3" strips ... it doesn't have to be pretty, but should be straight. A 30 degree bevel on one edge helps to make the panel look more interesting. The 5th board is un-beveled and was used as support for the picture hangers.

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Step 2: Corners are glued and screwed, pilot holes drilled with a countersink bit. I used 1-3/4" flooring screws.

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Step 3: Finishing of the corners is done with a sharp utility knife.

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Step 4: Flat black spray paint was applied on areas that might show through the fabric:

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Step 5: Cutting the rockwool panels to fit.

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Step 6: Laying the panel out to be covered by fabric. I purchased the fabric from Lens Mill in London; it is dark Navy blue and breathable. Held up to a light you can see right through it, it looks like miniature chain mail up close, but is fairly opaque due to the darkness of the fabric. The dark fabric has the advantage of reducing light that reflects from my beige rear wall back on to the screen.

Image

Step 7: I tensioned and stapled both long ends, from corner to corner.

Image

Step 8: Making good looking corners is tricky. Tension and tack down the corner with a few staples, as shown, and then cut out the square of unneeded fabric (which would just add extra bulk). Be sure not to cut too deeply, as it will leave an ugly void. Detail:

Image

You want to pull a sharp, tight crease right on the corner, which will make it unobrusive:

Image

Here's a finished corner, from the back:

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Finished panel, from behind:

Image

The exposed rockwool will need to be covered, I was short of material for this project. I plan to use spray adhesive to fill this at a later date.

Rear wall, untreated:

Image

Panel hung:

Image

Image

Another panel, made from one layer of Comfortboard IS, to absorb some of the extra acoustic energy from the front, but mainly to deal with the insane amount of light that reflects from the screen, which visibly lowers contrast:

Image

Image


Last edited by L-Man on Tue Jun 02, 2015 4:16 pm, edited 18 times in total.

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PostPosted: Mon Jun 01, 2015 6:41 am 
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Location: London, ON, CA
Results:

The panel above the screen was the first install. The acoustic effect is slight, but dialogue from the center channel has improved, it's cleaner, and (for better or worse) it is easier to locate the center channel speaker.

The greatest improvement is visual. Even though the ceiling directly above and around the screen is painted a matte midnight blue, the amount of light spilling onto the white ceiling in front of it was incredible. It lit up the whole room, including a lot of spill back on to the screen.

With the panel, the room is much darker, so the image appears brighter. And blacks in a bright scene are definitely blacker; black bars on the top and bottom (or the sides with 4:3 aspect ratio) are much darker.

The panel on the rear wall killed the flutter and ringing almost entirely in that direction. There is still a bit of "liveness" from left to right (untreated as yet) but these are far from the speakers. The rear wall was receiving the full acoustic force of the front speakers, reflecting it to the front wall, and back to the listener.

For 2-channel music, the room seems much quieter, sounds start and stop more correctly, and ambiance mixed into the music is more apparent, since it is not masked by a ringing room. Dry mixes sound much dryer. Imaging is more accurate, and vocals bloom in space. An annoying edginess in the treble is now gone, and the midband is more articulate. Bass seems a bit better too, though this isn't a bass trap.

Movies can be played louder, with less annoying "over-loudness" from room resonance. Over all, I'm happy with this, and may continue to experiment with more treatment on the side walls and in the corners. The first refection points of the left and right speakers would be my next project, perhaps followed by some small bass traps in the small corners behind the main speakers.


Last edited by L-Man on Mon Jun 15, 2015 6:09 am, edited 1 time in total.

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PostPosted: Mon Jun 01, 2015 6:55 am 
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Location: Richmond Hill, ON, CA
Would love to see the pics but for some reason only the first one loads. The rest do not - anyone else having this problem.


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PostPosted: Mon Jun 01, 2015 6:57 am 
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I see that ... in another browser. I'll work on it!


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PostPosted: Mon Jun 01, 2015 7:10 am 
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big_willy wrote:
Would love to see the pics but for some reason only the first one loads. The rest do not - anyone else having this problem.


Yes, I have the same problem viewing and 2 or 3 other users have the same problem when posting pictures from external sites. I have already advised the programmers about this and they should be working on this.

CAM Moderation Team


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PostPosted: Mon Jun 01, 2015 7:14 am 
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Location: London, ON, CA
It should be fixed now. Please let me know.


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PostPosted: Mon Jun 01, 2015 7:26 am 
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Location: Richmond Hill, ON, CA
Looks good - especially like the added touch of the bevel. If I had the tools needed to do that I would.

Burlap is another material to consider for wrapping. What's the best material to use to cover the backside?


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PostPosted: Mon Jun 01, 2015 7:39 am 
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L-Man wrote:
It should be fixed now. Please let me know.


Works fine now, thanks. What did you do to fix this problem so we know what to have others try who have the same problem in the future?

CAM Moderation Team


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PostPosted: Mon Jun 01, 2015 7:51 am 
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Using Google Drive. The links they provide won't work, so I put them through this:

https://sites.google.com/site/gdocs2direct/


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PostPosted: Mon Jun 01, 2015 7:53 am 
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Location: Courtice, ON, CA
Nice work!

BTW mods. The pictures show up in Firefox but not IE.

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A listening test comparing components is valid only when you are able to instantaneously switch between components which have been properly level matched and whose identities are unknown to you.


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PostPosted: Mon Jun 01, 2015 7:59 am 
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Pneumonic wrote:
Nice work!

BTW mods. The pictures show up in Firefox but not IE.


I'm using IE here and everything works fine Kerry.


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PostPosted: Mon Jun 01, 2015 8:44 am 
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Images not working on my Mac and Firefox … Most (not all) images show in Safari.


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PostPosted: Mon Jun 01, 2015 9:04 am 
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OBI56 wrote:
Pneumonic wrote:
Nice work!

BTW mods. The pictures show up in Firefox but not IE.


I'm using IE here and everything works fine Kerry.

Hmmmm, Marc. Must be why I rarely use IE. :P

BTW, I did a screen capture of the IE page and tried to upload the picture into this thread but was unable to do so. I am getting a "The uploaded file is empty" error message.

Perhaps, something is amiss?

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A listening test comparing components is valid only when you are able to instantaneously switch between components which have been properly level matched and whose identities are unknown to you.


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PostPosted: Mon Jun 01, 2015 9:41 am 
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Location: Toronto, ON, CA
Suggest thin pegboard for rear cover of the absorber + mount it one inch off back wall. This will increase effectiveness with marginal extra weight. Some sound will leak through, that is OK.


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PostPosted: Mon Jun 01, 2015 9:58 am 
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Location: Markham, ON, CA
Nice !

(BTW, I can see the pics in Firefox but not in Chrome. This is Win 7).

What about on the side?

Also will you be able to move the speakers out a bit?


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