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Proposed acoustic treatment of attic room - overkill?
Proposed acoustic treatment of attic room - overkill?
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Old 19th March 2018, 09:16 PM   #1
Preamp is offline Preamp  Germany
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Default Proposed acoustic treatment of attic room - overkill?

While thinking about finally tidying up my attic room, I've come across acoustic room treatment again. Been thinking about that a while back already, but never managed to try it out actually. Here's my probably somewhat unusual idea (haven't seen that done before anywhere), so please tell me what you think.

As you can see on the picture below, my room has slanted walls from top to bottom. I'm planning to generate some out-of-sight storage space by adding sliding doors to both lower sides, probably up to the height of the window sill. That will leave me with ~2m high OSB walls from above the window sill up to the top.

What about batten down those walls, put some 10cm thick rigid fiberglass in between, and then cover up that whole construction with fabric? I would basically hide the whole wall behind a huge absorber, instead of hanging individual absorbers to the wall.


Judging by a number of websites and forum posts, there're lots and lots of different approaches to treating a room and every single person seems to have its one-and-only way to go, so I'm basically hoping for some opinions whether this might work or is simply a stupid idea. In the end I'll have to try it for myself anyhow, I guess...
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Old 19th March 2018, 09:23 PM   #2
Cal Weldon is offline Cal Weldon  Canada
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Proposed acoustic treatment of attic room - overkill?
Hi Lasse,
Before you go any further, how is the roof vented?
Can you give us a drawing of the structure as it stands. That will help.
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Old 19th March 2018, 09:26 PM   #3
Windforce85 is offline Windforce85  Poland
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As it is an attic I wouldn't worry much about any room modes as they will be absent in environment free from rigid, heavy, perpendicular boundaries. What is more, an insulation layer under OSB already acts as very high performance, broad-band absorber. In order not to over-damp mid and high frequency decays I would't put any absorbing material on the surfaces of this room. Slanted walls will avoid straght-to-listener reflections and it will diffuse soundfield nicely using secondary reflections from the floor. One restriction is that heavy bass damping already buried under OSB will require powerful bass response from your playback systems. If not, the bass response will be simply too lean. An active system with capable subwoofers (capable of large displecement volume at low distortion) and properly implemented equalization will work best.

Last edited by Windforce85; 19th March 2018 at 09:31 PM.
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Old 19th March 2018, 09:38 PM   #4
Preamp is offline Preamp  Germany
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Quote:
Originally Posted by Cal Weldon View Post
Hi Lasse,
Before you go any further, how is the roof vented?
Can you give us a drawing of the structure as it stands. That will help.
Hi Cal, I'm not sure if I got you right and what kind of drawing you mean, but the attic is basically sealed air-tight like the rest of the house, and a ventilation system with heat recovery is on duty.



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Originally Posted by Windforce85 View Post
One restriction is that heavy bass damping already buried under OSB will require powerful bass response from your playback systems. If not, the bass response will be simply too lean.
I've noticed that already. Listening to The Prodigy is no fun at all... But I'm fine with the lower end - for the moment, at least.
I'm not totally satisfied with overall sound quality though. I'm still moving around the speakers to find a good position, but there're huuuuge differences.
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Old 19th March 2018, 10:25 PM   #5
Cask05 is offline Cask05  United States
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I'm afraid that those slanted walls are going to be a pretty severe problem, speaking from experience. Here is a picture of one guy's room after he finally tamed the room modes and the imaging-destroying reflections:

Click the image to open in full size.

A link to the thread where the realities of such a room shape became understood: Acoustical help with Room EQ Wizard and in room response and decay time - Technical/Modifications - The Klipsch Audio Community

Last edited by Cask05; 19th March 2018 at 10:45 PM.
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Old 19th March 2018, 10:52 PM   #6
Cask05 is offline Cask05  United States
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A link to the final acoustic measurements and resultant acoustic treatments in that room: Active Bi-Amping/Tri-Amping FAQ - Page 5 - Technical/Modifications - The Klipsch Audio Community
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Old 19th March 2018, 11:31 PM   #7
Ron E is offline Ron E  United States
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Quote:
Originally Posted by Preamp View Post
Hi Cal, I'm not sure if I got you right and what kind of drawing you mean, but the attic is basically sealed air-tight like the rest of the house, and a ventilation system with heat recovery is on duty.
Cal is a roof inspector.
Ventilation is for heat/moisture buildup in different seasons that can cause mold and/or roof failure.

How to Insulate an Attic
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Old 20th March 2018, 12:57 AM   #8
PLB is offline PLB  United Kingdom
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Hi Lasse,

It's my understanding that both absorbtion and diffusion are required for good sound reproduction. I'm right in the process of doing the same as you are in my house and have adopted for a live end dead end (LEDE) approach as briefly described in this link;

What is "LEDE - Live End, Dead End - inSync"? | Sweetwater

I'm also constructing the diffusors as detailed in this link;

Depot Diffuser construction

Hope this helps.

Peter
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Old 20th March 2018, 01:07 PM   #9
Preamp is offline Preamp  Germany
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Quote:
Originally Posted by Cask05 View Post
I'm afraid that those slanted walls are going to be a pretty severe problem, (...)
That's definitively not the way I intended to go. Don't have enough $$$ to shell out on some fancy stuff like that!


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Originally Posted by Ron E View Post
Cal is a roof inspector.
Ventilation is for heat/moisture buildup in different seasons that can cause mold and/or roof failure.
I'll give it a try (lots of new words I've never used before): The OSB on the inside is acting as a vapor barrier and all the seams are sealed with lots of sticky tape. It is mounted directly to the rafters. On the outside of the rafters is a wind brace band and soft fiberboard. On top of that comes the battening and then the roof tiles. The space between the rafters is filled up with loose-fill insulation (made out of old newspapers, judging by the look of it).


Quote:
Originally Posted by PLB View Post
I'm also constructing the diffusors as detailed in this link
Hi Peter, how would you position such diffusers in a room like mine? Is it okay to hang them on the walls, as slanted as they are? Or would they only be effective at the rear wall, which is the only straight wall in the room and thus already occupied by a bookshelf and a dart board...
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Old 20th March 2018, 01:46 PM   #10
Cask05 is offline Cask05  United States
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Quote:
Originally Posted by Preamp View Post
That's definitively not the way I intended to go. Don't have enough $$$ to shell out on some fancy stuff like that!
I think that the point is not how expensive the absorption panels are, but the percentage of the walls/ceiling that needs to be covered to kill off the side wall "slap". Basically, wherever you put your listening chair, you'll need just about 100% angled wall coverage with absorption from the front wall to the listening position to get a space that will permit any sort of critical listening. You'll also need almost 100% bass trapping of ceiling and floor/wall corner boundaries and a fairly well covered rear wall.

How you choose to do that is entirely up to you.

If you did not like the message of my posts (which were based on helping a friend with essentially the same shaped room iteratively add panels to solve the problem using measurements and listening), then please ignore them and pardon my intrusion. I thought that you were looking for help in how to handle the acoustics in your room. I guess that I was mistaken...

Chris

Last edited by Cask05; 20th March 2018 at 01:52 PM.
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