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Room help: measuring and treating a vaulted ceiling room

ripmixburn

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I don't even know where to start with this vaulted ceiling room, aside from a persian carpet for in front of the sofa. I can't seem to get a focused stereo image, though the bass seems even where the subwoofer is. The room is 13.5 deep and fairly symetrical aside from the dormer window. It used to be great sounding slatted wood which was replaced with drywall for energy efficiency. I'm tempted to put in some wood tambour panel for diffusion on the ceiling. Any suggestions on where to begin without breaking the bank?
B9AEB9E5-CD42-4CE3-A45B-1D4E27D8601D_1_105_c.jpeg
 
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ripmixburn

ripmixburn

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I should add that I have several 16× 24× 2" acoustic panels you can see I designed with a carpenter friend. Poplar frame that friction fits ECO-CORE insulation. Here is a close up.

16839516-25DB-4AA6-AA75-7C9AE329C358_1_105_c.jpeg
 

alex-z

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Panels of 2" thickness have virtually zero bass absorption, which is where 95% of acoustic problems are. You also need far more surface area, 10-15% of your room.

I would start by suspending some thicker 2x4ft panels from the ceiling beams, 5.5" mineral wool or more.

Also build some free standing panels to absorb a good portion of the side wall reflections. Drywall tends to reflect more sound than plywood.
 
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ripmixburn

ripmixburn

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Panels of 2" thickness have virtually zero bass absorption, which is where 95% of acoustic problems are. You also need far more surface area, 10-15% of your room.

I would start by suspending some thicker 2x4ft panels from the ceiling beams, 5.5" mineral wool or more.

Also build some free standing panels to absorb a good portion of the side wall reflections. Drywall tends to reflect more sound than plywood.
Luckily I have many more of these panels in storage, though the ceiling is low so the usable surface is tricky. I could make some free standing panels by stacking some of the existing ones, even use 4-6 to make a box.
 

tjkadar

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Luckily I have many more of these panels in storage, though the ceiling is low so the usable surface is tricky. I could make some free standing panels by stacking some of the existing ones, even use 4-6 to make a box.
Instead of hanging anything off the ceiling beams, build a cloud on top of them. Plenty of depth for mineral wool plus an air gap. Or you can incorporate the ceiling beams as a frame for a cloud.
 

pozz

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Before doing anything take measurements.

Lack of intelligibility usually means a directivity issue (reposition speakers), FR issue (apply EQ) or high level of reverberant sound vs. direct (add absorption for a specific frequency range or reposition speakers).
 
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ripmixburn

ripmixburn

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Before doing anything take measurements.

Lack of intelligibility usually means a directivity issue (reposition speakers), FR issue (apply EQ) or high level of reverberant sound vs. direct (add absorption for a specific frequency range or reposition speakers).

I will follow Amir's guide pinned to the top of this section.

Strangely the dialog can be hard to hear without Dolby Volume on, even though the center channel is pointed right at my face. I'm hoping the space that I have it tucked into is not affecting it too much. I could treat the inside a bit.
 
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ripmixburn

ripmixburn

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Instead of hanging anything off the ceiling beams, build a cloud on top of them. Plenty of depth for mineral wool plus an air gap. Or you can incorporate the ceiling beams as a frame for a cloud.
Good idea, though the ceiling fan prevents me from going wall to wall. If I had to choose is it better for the cloud to be above the speakers, my head or against the rear wall?
 

pozz

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I will follow Amir's guide pinned to the top of this section.

Strangely the dialog can be hard to hear without Dolby Volume on, even though the center channel is pointed right at my face. I'm hoping the space that I have it tucked into is not affecting it too much. I could treat the inside a bit.
I'm not sure how those HT systems work (signal routing/processing) and I avoid using AVRs. I don't think it's placement issue necessarily. The way I would test it is to go right up to the center speaker and turn Dolby Volume on and off. And do the same for one speaker at a time playing movies/music/TV/whatever.

If it's a glaring problem, the solutions are usually simple. Diagnosis just takes a while. System config/setup is free, treatment is expensive (and even with treatment you might still have the original problem, and maybe able to hear it better :)).
 

abdo123

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if you can fill the entire space above the bars in the ceiling with (acoustic) insulation material and then cover it with acoustically transparent fabric your room would be so good that your transition frequency would be around 100Hz or less.
 

pozz

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if you can fill the entire space above the bars in the ceiling with (acoustic) insulation material and then cover it with acoustically transparent fabric your room would be so good that your transition frequency would be around 100Hz or less.
No, it would not have that effect. And this is not necessary.
 

pozz

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Why not? As far as I know Acoustic treatment brings the transition frequency down.
For treatment to have a strong effect for low frequencies up to a few hundred Hz it needs to be pressure based, not velocity based absorption. What you suggest is also ineffective because it can be accomplished with some amount of porous filler and air gaps, plus some of what is going on in the transition region is re-reradiation from coupling between the walls and structural supports. They all flex with playback, and it's not easy to control those resonances.

Creating an effective cloud also needs a mix of a diffusion and absorption. A simple way to do that would be to use a space coupler (see below) above which you have a layer of porous material. But the key is that you have to calculate how absorption much you need, so that it's kept even. Sabins per frequency. Not that you have to be too accurate, but still. Unevenness is a greater problem and easier to accidentally create than than overdeadening.

Your suggestion is pretty good reminder, though, that absorption doesn't need to be symmetrically placed around the room. All it does is dampen a certain amount of energy, so you can put more in one spot than another, although you still have to account for how that will bias radiation and affect envelopment and imaging. I would imagine @ripmixburn's space to have some flutter echo that could be dampened by putting something on the walls. But if you have pure absorption for the ceiling and add stuff to walls it probably won't sound great, especially if the speakers don't have the most even directivity.
Space-Coupling-Diffuser-Product.jpg
 

abdo123

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For treatment to have a strong effect for low frequencies up to a few hundred Hz it needs to be pressure based, not velocity based absorption. What you suggest is also ineffective because it can be accomplished with some amount of porous filler and air gaps, plus some of what is going on in the transition region is re-reradiation from coupling between the walls and structural supports. They all flex with playback, and it's not easy to control those resonances.

Creating an effective cloud also needs a mix of a diffusion and absorption. A simple way to do that would be to use a space coupler (see below) above which you have a layer of porous material. But the key is that you have to calculate how absorption much you need, so that it's kept even. Sabins per frequency. Not that you have to be too accurate, but still. Unevenness is a greater problem and easier to accidentally create than than overdeadening.

Your suggestion is pretty good reminder, though, that absorption doesn't need to be symmetrically placed around the room. All it does is dampen a certain amount of energy, so you can put more in one spot than another, although you still have to account for how that will bias radiation and affect envelopment and imaging. I would imagine @ripmixburn's space to have some flutter echo that could be dampened by putting something on the walls. But if you have pure absorption for the ceiling and add stuff to walls it probably won't sound great, especially if the speakers don't have the most even directivity.
Space-Coupling-Diffuser-Product.jpg

Well i kind of said 100Hz because I know up to ~100Hz or so you can still absorb sensibly.

The Owens Corning 703 Can absorb at 125Hz well with just 4 inches (i can't find experimental data right now). So from my perspective 'making a wall' out of insulation material sounded like the next best thing next to building the entire room out of insualtion material that building a home cinema out of scratch usually entails.

Acoustical_Performance_2_inch_FG__60193.1539295043.png


Link: https://www.buyinsulationproductstore.com/owens-corning-703-fiberglass-acoustic-board-2-3/

I understand your concerns with 'uniformity' of absorption surface area across all 6 surfaces of the room. but at the same time since you're taking reflections out instead of changing it like what would happen with a window or a chimney.
 

bluefuzz

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Any suggestions on where to begin without breaking the bank?

What you need is more stuff. You need tables, bric-a-brac, chairs, books, rugs, tapestries, carpets, wall hangings, pictures, sculptures, bookshelves (don't people read books any more?), objets d'art, armoires, big fluffy pets, cushions, books, small children, musical instruments, boxes of clothes you haven't unpacked since moving five years ago, credenzas, curtains, mirrors, more books.

Don't ask me how I know this ... ;-)
 

pozz

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I understand your concerns with 'uniformity' of absorption surface area across all 6 surfaces of the room. but at the same time since you're taking reflections out instead of changing it like what would happen with a window or a chimney.
My concern is more to do with too much absorption above the transition frequency rather than how evenly it's distributed across all surfaces.

Those absorption coefficients come with a bunch of qualifications. For a porous absorber to really work at 125Hz, you'd need it to cover the half wavelength in depth, which is around 1.4m. But at 125Hz radiation is omni-like, so, you know, relying on individual panels for effectiveness probably isn't great.
 

pozz

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i thought it was 1/4 ?
My mistake. Yeah, quarter. Still around 69cm for 125Hz.
So from my perspective 'making a wall' out of insulation material sounded like the next best thing next to building the entire room out of insualtion material that building a home cinema out of scratch usually entails.
I follow too closely the reasoning for these rooms are constructed or renovated right now (by both pro and DIY builders). My gut feeling is that too much emphasis is placed on treatment rather than isolation. Isolation is way harder to achieve but has a better effect. If you have a lower noise floor everything gets a little easier to plan.
 

sarumbear

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I don't even know where to start with this vaulted ceiling room, aside from a persian carpet for in front of the sofa. I can't seem to get a focused stereo image, though the bass seems even where the subwoofer is. The room is 13.5 deep and fairly symetrical aside from the dormer window. It used to be great sounding slatted wood which was replaced with drywall for energy efficiency. I'm tempted to put in some wood tambour panel for diffusion on the ceiling. Any suggestions on where to begin without breaking the bank?
View attachment 156315
I have marked over your image and attached below.

Your main issue is the reverberation caused by ceiling, the rear wall and to a smaller extend by the floor. I can’t see the right wall (while sitting on the sofa) but the left slanting wall is perfect. You don’t need to do anything to that.

1- Trapezoidal hard partitions (marked yellow) that will split the ceiling will have the most effect to the sound.

2- Diffusion (not reflection) on the rear wall (marked red) will help to tighten the sound further.

3- Finally and much more simply, a thick carpet on the floor (marked green) will help.

As a side note, it seems you have tilted the centre speaker up a bit too much. You will be better of if you left it straight. You don’t want to excite the ceiling area.
 

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abdo123

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My mistake. Yeah, quarter. Still around 69cm for 125Hz.

I follow too closely the reasoning for these rooms are constructed or renovated right now (by both pro and DIY builders). My gut feeling is that too much emphasis is placed on treatment rather than isolation. Isolation is way harder to achieve but has a better effect. If you have a lower noise floor everything gets a little easier to plan.

Feel free to share more info on what you mean by isolation and how is it achieved.
 
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