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DIY Absorption panels - positioning

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DIY Absorption panels - positioning

Postby Untune » Tue Oct 07, 2014 3:38 pm

Hi all, lurker making a first post here. I've been pondering this for a while and thought it might be a good idea to ask and get some opinions since searches didn't turn up much - bit of info first.

I made six absorption panels as you'd expect them to look - standard 600x1200x50mm Earthwool slabs, 10mmx60mm timber frames so there's a 10mm air gap between the back of the slab and the wall, total front area of 620x1220 (including the frames) and covered with weed barrier fabric at the back and 50/50 polycotton over the front and sides.

My room is intended for recording rather than listening but I may move a computer in there at some point down the line. The room is 4.4m long, 2m wide (around 1.98m to be more precise) and 2.4m floor to ceiling. There's a curtain covering one of the smaller (2 x 2.4) walls. I'm trying to dry things up more for sound effects/foley and voice recording. Due to furniture, the door and window I can only put panels along the longer walls.

What I'm curious about is what the ideal positioning of these panels will be given that there is no fixed 'listening' position - Should I evenly 'stagger' the panels along the opposing 4.4m walls so that there are three each side, each facing a patch of bare wall, or would I be better off having three evenly spaced pairs facing each other? This was my original intention until I started to think that it might not have the best effect. Any other options? I'm thinking of getting a few foam diffuser panels to place in the gaps and will probably be hanging a duvet behind over or behind the curtain. It will probably depend on the spot I record in - given the room dimensions would there be a particular sweet spot?

Cheers for any input!
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Re: DIY Absorption panels - positioning

Postby Hugh Robjohns » Tue Oct 07, 2014 4:42 pm

Untune wrote:Should I evenly 'stagger' the panels along the opposing 4.4m walls so that there are three each side, each facing a patch of bare wall

Yes -- that's what I'd do, at least as a first stage of the room treatment.

I'm thinking of getting a few foam diffuser panels to place in the gaps

Absorbers control the acoustics by taking energy out of the room. Diffusers keep the energy in the room, they just spread it about a bit to remove obvious direct reflections. So you need to think about what you need to do with the energy at different frequencies, and whether it is best treated with absorption or diffusion. One is more or less the reverse of the other.... if there's too much energy you need absorbers. If the energy is fine but too direct, you need diffusers. Sometimes you need both...but in the right places!

H
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Re: DIY Absorption panels - positioning

Postby Untune » Tue Oct 07, 2014 4:59 pm

Hi Hugh, thanks for that. I feel better about knowing the options before I go hammering nails into the wall :) Of course I've fitted brass hangers so that I can take them down and move them around as needed so I can always tailor things to suit.

What you say about retaining and removing energy makes a lot of sense - it's not that the room sounds particularly bad (given the modest dimensions) but I'm tempted to kill as much reflection as possible. Plenty of Studio SOS articles have pointed out the potential disadvantages of overdoing it, so I was thinking diffusers might help to keep some balance and stop things sounding too dead. I actually have four more slabs that I've not decided on a use for yet - either a couple of panels for the ceiling, or some corner bass traps. Choices! :P

Cheers
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Re: DIY Absorption panels - positioning

Postby Hugh Robjohns » Tue Oct 07, 2014 5:06 pm

In general, it seems to be best to make a small rooms as dead as possible because they tend not to sound particularly nice when they're live. And its easier to add electronic space to a dead recording than to try to remove boxy space from a live one!

However, it's easy to overdamp the mid and HF, but very hard to control the LF without a room full of bass trapping, and again the result is an unbalanced reverb character which sounds muddy.

So the aim is to try and make the reverb as balanced as possible. The reverb time (if we can call it that in a small space) will always be a little longer at LF than mid and HF, but keeping it as equal as you can in each octave band is the target to aim for.

Diffusors can be helpful to counteract the often inherent MF/HF overdamping associated with a lot of bass trapping in a room.... but in the situation you describe where you basically just have a bunch of MF/HF absorbers, they'll largely just be undoing the absorbers work! So definitely try before committing...

H
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Re: DIY Absorption panels - positioning

Postby M57 » Mon Oct 13, 2014 12:43 am

Hugh Robjohns wrote: However, it's easy to overdamp the mid and HF, but very hard to control the LF without a room full of bass trapping, and again the result is an unbalanced reverb character which sounds muddy.

So the aim is to try and make the reverb as balanced as possible. The reverb time (if we can call it that in a small space) will always be a little longer at LF than mid and HF, but keeping it as equal as you can in each octave band is the target to aim for.

Diffusors can be helpful to counteract the often inherent MF/HF overdamping associated with a lot of bass trapping in a room.... but in the situation you describe where you basically just have a bunch of MF/HF absorbers, they'll largely just be undoing the absorbers work! So definitely try before committing...

H

So for us amateur home studio types (and I don't want to put words in your mouth), are you suggesting that in small spaces, should we should pretty much plan on needing bass traps, but play with combinations of absorbers and diffusion where MFs and HFs are concerned?
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Re: DIY Absorption panels - positioning

Postby Hugh Robjohns » Mon Oct 13, 2014 1:39 am

Pretty much, yes.
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Re: DIY Absorption panels - positioning

Postby M57 » Mon Oct 13, 2014 1:47 am

Let's just say that I'm not a DIY kind of guy. Panels I make risk not qualifying as rectangular, let alone quadrilateral. Might a product like this be appropriate on the Absorption end of things?

http://www.audimuteacousticpanels.com/acoustic-panels [/list]
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Re: DIY Absorption panels - positioning

Postby sheggs » Mon Oct 13, 2014 9:22 am

M57 wrote:Let's just say that I'm not a DIY kind of guy. Panels I make risk not qualifying as rectangular, let alone quadrilateral. Might a product like this be appropriate on the Absorption end of things?

http://www.audimuteacousticpanels.com/acoustic-panels [/list]

All acoustic companies should have their test results clearly on their site. Hopefully this will be in the form of a PDF with all the results and the conditions the panels were tested under
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Re: DIY Absorption panels - positioning

Postby M57 » Mon Oct 13, 2014 1:58 pm

sheggs wrote:

All acoustic companies should have their test results clearly on their site. Hopefully this will be in the form of a PDF with all the results and the conditions the panels were tested under

Thanks Sheggs,

The problem is that I'm not qualified to evaluate test results. I'm a musician, not a engineer, and my expectations are not to be able to create an optimal pro sounding space, though I wouldn't complain if I somehow stumbled into making one. I'm looking for easy to install reasonable and affordable products that would work for sound absorption (e.g., panels on the ceilings and walls to reduce MF and HF, and for bass traps.
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Re: DIY Absorption panels - positioning

Postby sheggs » Tue Oct 14, 2014 3:43 pm

Post any links on here and I (and I am sure others) will tell you what they mean
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Re: DIY Absorption panels - positioning

Postby M57 » Tue Oct 14, 2014 5:56 pm

Here's a link to a pretty detailed analysis..

http://www.audimuteacousticpanels.com/media/AudiMuteAcoustic...

The product:
http://www.audimuteacousticpanels.com/acoustic-panel

I'm also wondering if I re-covered them with a different material ..for instance if my wife quilted something - (with no stuffing or backing etc.) if that would dramatically change the acoustic properties? I'm assuming the material used to cover these things only affects the very highest frequencies??

Also I'm wondering why there are no absorption coefficients for frequencies higher than 5000 hz.

Thanks for any help with this.
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Re: DIY Absorption panels - positioning

Postby arik livnat » Tue Sep 29, 2020 8:44 pm

Here are some tests I performed with panels I built. Between each unit of rock wool there is plywood. Feel free to see the process

https://youtu.be/POgVZ1k7LNg

https://youtu.be/GiM3KI-tkmM
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