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post #1 of 3 Old 01-11-2019, 12:55 PM - Thread Starter
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Advice regarding acoustic treatments

Hello everyone!

I've recently completed my home theater and have been enjoying it a bunch so far. The last thing I'd like to do is get some proper acoustic treatments on the wall to help with the sound quality. I don't have any frame of reference (it sounds pretty good already), but I suspect if I heard them side by side the difference will be quite noticeable.

Upfront info:

Room dimensions: 12.5' x 13.5' (3 walls) + 11' open back (see plan)
Speakers: 5.2.2. With 2 x 12" subs

I have two local suppliers selling treatments, one retail outlet re-selling commercial treatments and one local manufacturer who does it part time. A big difference here is cost, a setup with retail supplier is going to probably run me about $1500 CAD, the local manufacturer will likely be a third of that. The manufacturing quality of the absorber panels seem similar, one uses acoustic fiberglass, the other I'm not 100% sure what's inside but its firm.

I'm definitely interested in the local manufacturer as their pricing is very competitive, but they only make absorbers, whereas the other supplier would be a mix of absorbers and diffusers for that price. The diffusers supplied look very similar to this: I'm not sure how effective these are vs. the multi-tiered diffusers?

So here are my questions:

1. Does a flat diffuser like that (with foam in holes) make a huge difference compared to absorbers?
2. Is there a big difference (see my room for reference) between absorbers only vs. absorbers and diffusers
3. My distance to surrounds isn't very big (4 feet or so at closest point), do diffusers add more in this situation?
4. I have furniture (a fabric couch, covered coffee table, and book shelf at the rear), this will obviously change the properties. I'd imagine the bookshelf adds diffusion, but is it at the right point? Should diffusion be close to the surrounds?

The local manufacturer recommended the following (subject to changes, coming in around $400-500 CAD total):

24"x48"x2" x 2
36"x60"x2" x 1
12"x48"x2" x 2 OR 12"x60"x2"

- 2 acoustic panels (24x48x2") on each side wall to catch the reflection points from your front speakers.
- Cloud on the ceiling, about 36"x60" just in front of the projector to absorb unwanted reflections from ceiling to floor
- 12"x24" panel on either side of the bookcase, or one longer (12"x60"x2") one across the top would dampen any reflections coming from back there.

and pricing:

24"x48"x2" $80
36"x60"x2" $150
12"x48"x2" $65
12"x60"x2" $70

The retail supplier would be a combination of 2x2 acoustic and diffuser panels, i think 20 total. I believe their pricing is something like:

12 x absorbers ~ 800
8 x diffusers ~ 500

Does anyone have some advice here, I realize it's hard to judge the acoustics from a post, but am I going to lose much without having diffusers? I don't think the absorber suggestions the manufacturer suggest will deaden too much, but this is my first build.

Finally, I have an Anthem MRX 720. It seems to have pretty decent room correction (made a pretty big difference with the current setup alone). My plan would be to run room correction again after installing the treatments.

Any advice would be hugely appreciated! Thanks.
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post #2 of 3 Old 01-12-2019, 04:41 AM
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I think the answer to some of your questions is going to be highly subjective, which is why I'm not going to get too much into those, but I'd advise you to look into bass traps in the corners behind the subs and front speakers, as they seem awfully close to the walls.

I think that what your local manufacturer is a pretty good solution, the longer panel on top of the book case would likely give you more flexibility if you want to add an extra book case in the future or move things around.
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post #3 of 3 Old 01-12-2019, 05:36 AM
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The proximity of bass traps to the sub woofers is irrelevant. Bass traps are all about taming standing waves in a room that are caused by parallel walls and floor/ceiling. The research and science is driven by mathmatical prediction and real life measurement in rectangular rooms. Odd shaped rooms present a challenge. Bass traps do best at the room boundaries (walls) and at intersections of multiple boundaries. A back corner is just as good as a front corner when placing traps. For this room I have no idea.

As for absorption/diffusion here is what I have learned. It is absolutely possible to use too much absorption at the first reflection points in a room. In the THX/HAA sound reproduction/calibration class it was demonstrated. Using a stereo recording of a live jazz band we listened to it with no, a moderate and a lot of side wall absorption. With no absorption the imaging was poor, at times it was smeared and you were basically listening to the music with not a lot of sense of positioning. With a moderate amount of absorption when you closed your eyes you could point to the location of each band member and you could tell that they were being recorded in a room (club) much bigger than the classroom. Each instrument was clear without distortion. With a lot of side wall absorption the band occupied only the space between the two speakers and as a whole the sound lacked a feeling of spaciousness. Elite calibrators bring specific musical tracks with them to each job because they know what to listen for as they are familiar with the potential of each recording.

What does that mean, at the first reflection points a combination of absorption and diffusion is going to yield the best result. Diffusion scatters the sound but doesn't remove the energy from the room maintaining a sense of speciousness. A simple trick is to use alternating strips of material on the surface of a panel to make it a combination absorption/diffuser or to build a wall that is a checkerboard of absorption and diffusion. A few pictures attached. The complex designs were from a couple of DIY projects with the treatment plan designed by Acoustic Frontiers. The project threads are Beast Unleashed and Event Horizon. The yellow panels were from the my White Oaks Project.
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Last edited by BIGmouthinDC; 01-12-2019 at 05:45 AM.
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