Acoustic design for an Odd-Shaped Room - AVS Forum
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post #1 of 7 Old 08-14-2014, 06:23 PM - Thread Starter
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Lightbulb Acoustic design for an Odd-Shaped Room

I wanted to get some ideas regarding the acoustic design and treatments for my theater room and for a false wall to support my Spandex / Acoustically Transparent screen. From the attached picture, you can see the basic room layout, with the two full Marty subs (I still need to build the 2nd), Cheap Thrills for LCR duty and Volt V10s for the surrounds (4 Atmos speakers will likely go in the ceiling before I install the ceiling).

All the walls and ceiling will be Whisper Clips + OSB + DD / GG, The floor is concrete slab and will be covered by a heavy pad and carpet. I'm planning 2-4" of OC703 or equiv. against the back wall / bathroom wall. The sliding glass door adjacent to the screen can be removed and/or plugged. The sliding glass door next to the seating area will be covered by heavy drapes. The ceiling height will be roughly 7'9".

I need regular access to the area behind the screen and to the water room. Part of that area is also used for storage. So I will need either a small door that allows crawling access below the screen, or I need to fold the screen against the ceiling and enter through a narrow, full height door between the LCRs.

With just one sub installed, and no treatments or soundproofing, I get noticeable peaks and nulls in the bass response. I'm planning a 3-wide row of recliners in front and 2-3 bar stools in back for seating. My subs go down to ~15Hz and that is low enough for me.

Now for a few questions:

1. What measurements would be most helpful for correcting the room response, and how would these be performed? I'm considering the purchase of omnimic, but I am open to suggestions as to the best combo of calibrated mic and software ($300 max). Ideally, whatever I buy would allow me to measure room acoustics as well as individual speaker performance outside and in-room.

2. False Wall - What kind of acoustic treatment would you suggest for the false wall? I was considering as much as 6" or more of insulation in all of the areas between the speakers (wall to wall and floor to ceiling) as a combination baffle wall/bass trap. But I have no idea what would work best.

3. Soffits - I was considering angled face soffits that are slightly larger than my angled surround speakers, with the largest surface angled down into the room at roughly 30 degrees and a small flat underside of 6-7". I was thinking of using AT fabric and loading these with a 1-2" face of OC703 and the back side filled with loose fiberglass or denim to function as a bass trap. But again, I have no idea what to expect or how useful this would be.

4. ??? There is a lot I don't know and don't know to ask. I've read nearly all of the soundproofing sticky, but I thought I would get some advice before I tackle room acoustics.

Thanks in advance,
Mike
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post #2 of 7 Old 08-15-2014, 08:02 AM
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Ok, numerous things here.

1. I would treat the floor as well. Just treating 5 walls allows a flanking path which is the floor. You need to treat all 6.

2. If you want to verify isolation of the room, you will need a class 1 mic. The noise floor of the less expensive class 2 mics are not low enough to measure the noise floor of an isolated room.

3. Ideally, you will need more than one mic to measure the room. Ideally, you will want a multiplexer to measure and adjust. Unless you are extremely meticulous in measuring and have a lot of time and your software is capable of averaging.

4. Currently, in my opinion, the best software out there is Audio Tools by Studio Six Digital. The next would be the freebie over at HTS.

5. Acoustics is a LOT more complicated than isolating a room. So, you may want to spend a lot more time reading on how to do that. There is a tremendous amount of art to this in addition to the physics which really cannot be conveyed since every room is different. This is something you will have to spend lots of time experimenting, measuring, experimenting, measuring, etc.

6. What are planning to use as a tool for adjustment? If you measure it, how do you adjust what the measurement is telling you?

There is a lot more to be said for your room. I would suggest reading, reading and more reading. I would also expand beyond this forum. Not all answers are here.

Shawn Byrne
Erskine Group
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Design-Video & Audio Calibration Information

The original Pro Theater Layout

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post #3 of 7 Old 08-15-2014, 10:20 PM - Thread Starter
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Hi Shawn, thanks for the reply.

1. Floor treatment - I had planned thick pad, possibly 1/2" felt then heavy carpet. Is this not sufficient to decouple the floor? Do I need to add something like the Serenity Mat and additional decoupling beneath my subs?

2. Sadly, Class 1 mics are not within my budget. Class 2 will have to do. Measuring the absolute noise floor does not seem critical to me, but then again, what do I know...

3. Where should I start reading on why I need more than 1 mic to measure my room? Are 2 Class 2 mics sufficient, or are we talking larger arrays with half a dozen or more mics?

4. I checked out Studio 6, and their software suite appears to be within my budget, especially since I can spread out the purchase until I need specific modules.

5. Absolutely agree. I've read Toole's book, but there was not a lot of practical, how-to procedures in there. Can you recommend any specific resources that would be a good starting point to further my study?

6. Ummm. Bass traps for below 200Hz, ummm, OC703 panels on the walls....

Obviously there is a lot I need to learn, including what to measure and how to perform the measurements. Then, as you say, I need to learn what the measurements are telling me about the room so that I can determine which treatment method will address the measured anomalies. I truly want to learn and understand the physics related to room acoustics, on the other hand, I also recognize that I will never have the time to learn enough to ascend to the level of expertise backing your services.

If I use the Erskine Group Pro Theater Layout Service, could I include a set of room and speaker acoustic measurements using Studio 6 Audio Tools and one (or more) of their Class 2 mics, and have that data incorporated into the information used to specify acoustic treatments and locations for my room?

Thanks again,
Mike
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post #4 of 7 Old 08-16-2014, 07:18 AM
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Hi Mike,

We don't require a measurement to layout your room. Check out the link in my signature "the original pro theater layout" for more info.

Shawn Byrne
Erskine Group
CEDIA Certified Professional EST II - HAA Level III Certified -THX Certified Professional

Design-Video & Audio Calibration Information

The original Pro Theater Layout
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post #5 of 7 Old 08-16-2014, 01:21 PM - Thread Starter
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Thanks, Shawn.

I had checked out your signature links before I replied. I was unaware of the Layout service before your original reply. I was just wondering if the additional data would improve the result vs just the raw room geometry and construction details. That, and all your experience and knowledge, of course.

Mike
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post #6 of 7 Old 08-16-2014, 06:02 PM
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No, it really won't change anything. Consider this, every location you take a measurement will be different than the previous one. Since we aren't sure where seats are going to be laid out as well as speakers, the information won't provide much useful information. Only when the room is complete would it provide the information needed, and then preferably a spatial average. We have models that we use to predict once the room is laid out and the information is placed into the model.

Shawn Byrne
Erskine Group
CEDIA Certified Professional EST II - HAA Level III Certified -THX Certified Professional

Design-Video & Audio Calibration Information

The original Pro Theater Layout
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post #7 of 7 Old 08-17-2014, 10:18 PM - Thread Starter
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I've convinced myself that contracting out the acoustic design will be the route I follow, since I could literally spend months studying this topic and still not come up with the optimal solution... I'm better served by pulling some extra shifts to pay for design services then spending months studying the topic.

At what stage of construction do you recommend getting involved for a remodel of an existing room? Before demolition, during electrical rough-in, after clips/channel/drywall is installed?

I've got the green light for design services before the end of the year.

Thanks,
Mike
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