Advice on rooms with angled side walls in an attic space

Nuprin

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Jan 9, 2020
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We are moving into a new existing home that has a 17‘x13’ living room with 9ft ceilings that I could use as my 2 channel room. The other option is to finish the attic, which is about 1,200 sqft rectangular but of course the side walls are part of the roofline at a 45 degree angle.

My question is should I frame the space with straight side walls for a more “rectangular” box shape room but loose overall sqft and lower ceiling or would it be better to have a bigger space with higher ceilings that will have angled sidewalls/knee walls. Does the typical “attic shaped” room sound worse for acoustics?

With bedrooms below, would some sort of acoustic block be recommended especially for bass?
 

spiritofmusic

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Jun 13, 2013
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Nuprin, are you saying the space is triangular on cross section so you have no vertical side walls at all?

When we were converting my 18x48 loft attic space, I could have left the space triangular too giving me an overall width of 30'. But I decided on 4' high side walls, bringing width down to 18'.

I have no way of knowing what the acoustic differences would have been. But happy I chose side walls.
 

Nuprin

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Yes, the attic is basically a large single "A" shaped room that rests on top most of the 2nd floor bedrooms. I should have measured when I was last there but I'm estimating it is at least 40ft long with flat wall ends and at least 25ft wide side to side from the 45 degree to 60 degree angled walls. My guess is the very top of the "A" frame point is probably 12ft high. I would like to make it at least a 9ft high flat ceiling. There are large metal hvac ducts in the attic so hopefully the sound doesn't bleed into room or I would at least need to surround the walls with some acoustic block.

Will take proper measurements tomorrow during the inspection.
 

sbnx

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Bigger space is almost always better. Use the lower part of the wall that you cant stand under for acoustic treatment or media storage. I would put some sound damping under the floor.
 
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Nuprin

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Bigger space is almost always better. Use the lower part of the wall that you cant stand under for acoustic treatment or media storage. I would put some sound damping under the floor.

That is a great idea...I could line the sides with shelving and put books and media to help break up the weird side reflections. I'm assuming it would matter more in the front half of the room where the speakers are, the first reflection point to the seating area.
 

spiritofmusic

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Nuprin, my centre line apex closer to 9' than your 12', so a conventional flat ceiling wasn't an option for me. And I truly dreaded the effects of maintaining the 30° descending roofline in respect of acoustics. But actually it's completely worked out for me. I'd implore you to consider keeping your eaves.
 

christoph

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That is a great idea...I could line the sides with shelving and put books and media to help break up the weird side reflections. I'm assuming it would matter more in the front half of the room where the speakers are, the first reflection point to the seating area.
Some pictures would really help to understand your space
 

sbnx

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If you want to isolate the floor there are several options that range in price. It can be very costly for complete isolation. If you google it you can find lots of options. Here are a couple places to start. There is a product called mutemat sold by ikoustic in the UK. (I am sure similar products exist elsewhere). You will simply put this down on top of the existing subfloor and then float your new floor on top of this.

If you don't have a subfloor yet then Aurelex makes a rubber U shape piece that goes over/around the floor joists and the subfloor floats on these. They are call U-boat floor floaters.

There is also a company in the UK called Brighton soundproofing that has a nice webpage that explains several of the different ways to soundproof a floor. You can read through some of those options.

Soundproofing is tricky and there are a lot of very subtle ways to spend a lot of money and not get good results. Unless you are an engineer and/or really want to do a lot of reading and research I suggest reaching out to a reputable company for help on doing it right.
 
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Nuprin

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Will take some pictures today and get some proper measurements...
 
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Nuprin

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Useable space for 9ft ceilings measures to be about 24ft x 15ft. By going with lower height knee walls to say 7ft, I would get an extra 3ft in each dimension. Another potentially space issue is where the stairs would have be located based on the floor below.

C869EB60-83E4-488F-92A5-C082ABF211B6.jpeg


C869EB60-83E4-488F-92A5-C082ABF211B6.jpeg
 

Nuprin

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F06021D5-D385-4FBF-A1D2-C31DF74036FC.jpeg
Can only post one pic at a time for some reason on my phone.
 

Nuprin

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403EE3AB-F8CB-49EB-8C2F-487F67C8488A.jpeg
Only access right now, would have to create new set of stairs.
 

spiritofmusic

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Nuprin, I cannot tell you what to do, or obviously predict things. Every room is different.
All I can say is that by maintaining my 30° descending eaves, despite my year long anxiety this would likely prove to be a white elephant, I've ended up with a really positive acoustic.
And this despite the few reports I'd read that said attic/loft/roof space rooms with said eaves are universally challenging.
All I would say to you is at least gather further opinions on maintaining your eaves versus going for a conventional flat ceiling.
And FWIW, I really like the look of descending eaves. And the sound.
 

spiritofmusic

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View attachment 67388
Only access right now, would have to create new set of stairs.
Haha! I know that hatch VERY well Lol.
My 4x2 hatch is right behind my speakers, midway on front wall. Luckily I already had stairs up to my space. But the way the roof was constructed using A-trusses aka Queen trusses, meant a $50k major structural steels project to cut these away and replace w massive load bearing steels at 7' centres , and another $30k to insulate and fit out the space. At least you don't have much major steelworks to consider. And in my case, I believe the steels have contributed to my superior sonics.
 

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