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05-27-2020, 11:30 PM
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#1
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Human being with feelings
Join Date: Sep 2009
Location: Oz - Blue Mountains NSW, formerly Geelong
Posts: 944
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Recording room treatment
I've just had a room built in the back corner of our garage. It's 4m x 3m x 2.4m. It's not quite finished and empty (paint and electricals still to come). As expected it's extremely lively. When the room is finished there will be soft furnishings, bookcases and sundry other items, as well as a carpet square on the concrete floor.
Left over from the building are a couple of acoustic batts, i.e. fibreglass sound insulation approx 80mm x 400mm x 1200mm (3" x 16 " x 46"). I could use these for a couple sound absorbing panels.
There are also 20 or so gyprock/drywall/plasterboard offcuts: several 210mm x 1200mm (8" x 48"), plus 3 or 4 larger pieces, e.g. 500mm x 1200mm, 700mm x 1200mm and one 360mm x 2080.
Questions:
1. Am I right in thinking that more sound absorbing panels might be needed?
2. Could the drywall offcuts be useful? Possibly cut into smaller shapes and fixed to the wall with various spacings from the wall, to disperse the sound somewhat? Any other possibilities?
3. Any other suggestions? The first two questions are a trial and error approach and there will probably be better ways of attacking the problem.
This room is for recording mostly vocals and acoustic guitar, not mixing or mastering.
Thanks for any help.
__________________
It's "its" except when it's "it is".
alanofoz, aka Alan of Australia
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05-28-2020, 12:23 AM
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#2
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Human being with feelings
Join Date: May 2017
Posts: 3,204
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The smaller the room, the more absorption it needs. If the walls and ceiling are all drywall, maybe start with covering 15-20% of the wall and ceiling area with broadband absorbers.
I built 12 panels 2x4 feet, 2 inches thick, for my 32x18x8 foot room for around $300, and it did wonders for the sound. Best investment I've made in the studio.
If the leftover insulation is rigid fiberglass, it could be used to make a panel.
My source for materials:
https://www.atsacoustics.com/cat--DI...ials--102.html
and joann.com for fabric covers for the panels.
A good reference site:
http://ethanwiner.com/acoustics.html
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05-28-2020, 01:03 AM
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#3
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Human being with feelings
Join Date: Jan 2009
Location: New Zealand
Posts: 2,912
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Here is something I came up with I have placed this in Reaper forum before I do not know if anybody has taken it up.
I purchased and installed real traps units and while they did a great job so far for me the room was as yours drywall and I had heaps of flutter echo.
I thought about this problem for over a year and studied my options for
absorption and diffusion.
So I had the absorption thing done, what of the diffusion?
I had seen the company stuff, all those square blocks of solid wood all blunt and so called mathematically studied and made.
I thought I could do better ( at a cost mind but still cheaper ).
I saved up and purchased some bamboo poles 4'-5' at the large end and about 3-4 metres long. I got them a bit cheaper than usual they were off a previous job.
I made a mat covering the far wall from ceiling to half way down the wall
real trap products below. Then I did one side facing wall ( angled to the ceiling about 8' out from the wall from the floor.
Where I mic my amps and have my vocal mics I made a 3ft mat on the ceiling
side to side.
I reckoned the totally vague oval-round nature of the bamboo would give me a great perfect in nature sound and really I can say this has performed so well I am so pleased.
I am sure many of you will have a Bamboo grove just around the corner from where you live that is being weed killed now and then. Go grab it while it is legal to do so. I think what I am letting you know is something that will give you great pleasure.
This took me three days just for the big wall as I assembled my bamboo with a key hole slot and screws on all ends so very little steel would be in view.
I found some Bamboo growing in a public area of my town of 130 people, most would not know the bamboo was there however it grows so slow the case for purchasing was the way to go.
Grinder
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05-28-2020, 10:01 PM
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#4
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Human being with feelings
Join Date: Sep 2009
Location: Oz - Blue Mountains NSW, formerly Geelong
Posts: 944
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Thanks Philbo & grinder,
Based on your answers I'll start with another pack of Sound Screen batts and make panels for the walls & ceilings, try that out & go from there.
grinder, I think I'll keep referring to your post regards diffusion, I suspect I'll need to address this aspect. Not sure I'd even recognise flutter echo - I'm starting to google it.
Anyone else with thoughts on the idea of using the drywall offcuts for diffusion? Looks like nobody likes it much. Just thought I'd toss it in before the builder takes it all to the tip (dump?).
Google is providing me with much reading material.
__________________
It's "its" except when it's "it is".
alanofoz, aka Alan of Australia
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05-28-2020, 11:22 PM
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#5
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Human being with feelings
Join Date: Jan 2020
Posts: 1,927
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Drywall is about the worst acoustic surface there is
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05-29-2020, 12:18 AM
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#6
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Human being with feelings
Join Date: Jan 2009
Location: New Zealand
Posts: 2,912
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Flutter echo is insanely razor sharp and intrudes so much
it defeats the audio's best intentions!
Dry wall needs taming.
Grinder
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05-29-2020, 02:34 AM
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#7
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Human being with feelings
Join Date: Sep 2009
Location: Oz - Blue Mountains NSW, formerly Geelong
Posts: 944
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Quote:
Originally Posted by Philbo King
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Thanks for that, I was aware of EW's site but until now had no need for an in-depth look. I now have a better idea of what to listen for re flutter echo...
Quote:
Originally Posted by grinder
Flutter echo is insanely razor sharp and intrudes so much
it defeats the audio's best intentions!
Dry wall needs taming.
Grinder
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Quote:
Originally Posted by valy
Drywall is about the worst acoustic surface there is
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I think I'm starting to get the point! It'll get treatment!
__________________
It's "its" except when it's "it is".
alanofoz, aka Alan of Australia
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05-29-2020, 05:33 AM
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#8
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Human being with feelings
Join Date: Mar 2018
Posts: 31
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Quote:
Originally Posted by alanofoz
I've just had a room built in the back corner of our garage. It's 4m x 3m x 2.4m. It's not quite finished and empty (paint and electricals still to come). As expected it's extremely lively. When the room is finished there will be soft furnishings, bookcases and sundry other items, as well as a carpet square on the concrete floor.
Left over from the building are a couple of acoustic batts, i.e. fibreglass sound insulation approx 80mm x 400mm x 1200mm (3" x 16 " x 46"). I could use these for a couple sound absorbing panels.
There are also 20 or so gyprock/drywall/plasterboard offcuts: several 210mm x 1200mm (8" x 48"), plus 3 or 4 larger pieces, e.g. 500mm x 1200mm, 700mm x 1200mm and one 360mm x 2080.
Questions:
1. Am I right in thinking that more sound absorbing panels might be needed?
2. Could the drywall offcuts be useful? Possibly cut into smaller shapes and fixed to the wall with various spacings from the wall, to disperse the sound somewhat? Any other possibilities?
3. Any other suggestions? The first two questions are a trial and error approach and there will probably be better ways of attacking the problem.
This room is for recording mostly vocals and acoustic guitar, not mixing or mastering.
Thanks for any help.
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Superchunks in the corners. Do anything you can to combat parallel surfaces. It's a shame you didn't design the room to avoid parallel surfaces given it has been newly built. Would have saved you lots of issues and is easily done.
Tony
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05-29-2020, 06:35 AM
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#9
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Human being with feelings
Join Date: Oct 2007
Location: Lincoln, UK
Posts: 7,942
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The problem with glass-fibre and similar type broadband absorbers is that they absorb high frequencies very well and tail-off towards lower frequencies. The problem with smaller rooms is that the room modes (resonant paths) correspond with frequencies that aren’t absorbed by those “absorbers”.
So you end up with a very (HF) dry room with resonant issues in the LF. What you really want is a controlled, balanced-frequency ambience; ie some liveliness, but even across the frequency range. You’re missing mid and HF ambience so you use too much reverb, and you have peaks and troughs all over the sub and LF range, so you can’t judge bass levels. For performance and recording in this space the effect will be unbalanced roominess in your tracks.
If you’re up to learning to measure your room’s response, you could construct some home made traps with dense insulation, but you need to treat your corners and flat walls and you need thickness.
A 4” thick 2x4’ frame trap will reach further down your frequency range than a 2” thick one without significantly absorbing more HF, and a 6 or 8” will reach further still. It’s somewhat of a diminishing returns deal, so don’t expect miracles, but it is noticeable and very obvious in measurements. Unfortunately you need the thickest in the rooms that don’t have “room” for them
Treat your “mirror points” with foam or thinner traps, definitely traps on your back wall, and then your corners and other reflection points need thick traps.
Flutter is coherent mid and HF reflection between parallel smooth walls, a super fast multi-tap echo. Drywall is acoustically flat and “shiny”, so you need to break the sound up into “incoherent” ambience. Diffusers do that, they reflect sound, but “randomise” the reflections so you get room ambience back, not an acoustic copy (fast echo). Bookshelves do a reasonable job at this, especially with lots of different-sized jumbled books (and their depth and density absorbs some LF too). Don’t forget to put and out absorb at the mirror points though, even if you have to hang foam over your bookcase at that point.
Your room will have four axial nodes (Parallel face standing waves) below 100Hz, so you will need treatment to judge bass frequency balance -try playing sine waves at 43, 57, 71, and 86Hz and move your head around in the room to see the differences in level between the waves’ nodes and antinodes (quietest and loudest positions at those frequencies).
You’re not going to get an ideal acoustic environment in a room that small, but if you can put up with a bunch of thick traps and some bookcases, you might get it to “useable”
Shout back if you need any help...
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05-29-2020, 01:01 PM
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#10
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Human being with feelings
Join Date: Jan 2009
Location: New Zealand
Posts: 2,912
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I initially used Bob Golds Measures I worked on these
Recording instruments room
Room Length 4320mm Room Height 2700mm Width 3400mm all internal measures.
The nodes at this size were pretty good.
Until I added to the Real Traps with my idea of using bamboo for diffusion
I was still in trouble.
When I installed the Bamboo I got the Munsen curve on my software eq's without resorting to change with the eq!
a very big smile on my dial you can be sure and I am still smiling today.
Grinder
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05-29-2020, 01:19 PM
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#11
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Human being with feelings
Join Date: Jan 2013
Location: San Jose, CA
Posts: 117
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Quote:
Originally Posted by valy
Drywall is about the worst acoustic surface there is
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I saw mentioned (wish I could remember where) that a plywood surface is better than drywall.
I haven't dug into this yet, and I freely admit I know nothing about treating a room, so I was wondering if anyone had thoughts on it.
Some questions I have are:
* Does the thickness of the panel matter?
* Should it be spaced away from the drywall behind it?
* What about surface finish - sanded or rough? Painted or stained?
Anyone have a link where more info is available?
Thanks.
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05-29-2020, 04:05 PM
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#12
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Human being with feelings
Join Date: Sep 2009
Location: Oz - Blue Mountains NSW, formerly Geelong
Posts: 944
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planetnine, thanks for that very comprehensive reply. I'll end up doing pretty much what you're suggesting. Sites such as https://amcoustics.com/tools/amroc?l...&h=240&r60=0.6 confirm the frequencies you mention and suggest the area of sound absorption needed. Once I've furnished the room and added absorption panels I'll start looking more closely at diffusers. grinder's bamboo poles look interesting. I'll actually have a pretty large number of books & magazines of random sizes so some diffusion will happen anyway.
At my level of talent there's little point in going to extreme lengths here! My vocals won't go below 160Hz with my imagination turned up to the max. If I tune in DADGAD or drop D the lowest frequency is 73Hz.
Until now I've been using a 4m square room (drywall, sofa & bookshelves, zero treatment) without disastrous results. If, after working on absorption & diffusion, the new room improves on that I'll be pretty happy. Should also be much more soundproof.
Thanks to all who have helped here.
__________________
It's "its" except when it's "it is".
alanofoz, aka Alan of Australia
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05-29-2020, 10:11 PM
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#13
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Human being with feelings
Join Date: Apr 2010
Location: Seattle
Posts: 5,637
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Quote:
Originally Posted by valy
Drywall is about the worst acoustic surface there is
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I'd vote cinderblock, but yeah. Drywall sucks.
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05-29-2020, 10:52 PM
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#14
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Human being with feelings
Join Date: May 2017
Posts: 3,204
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Quote:
Originally Posted by jp65535
I saw mentioned (wish I could remember where) that a plywood surface is better than drywall.
I haven't dug into this yet, and I freely admit I know nothing about treating a room, so I was wondering if anyone had thoughts on it.
Some questions I have are:
* Does the thickness of the panel matter?
* Should it be spaced away from the drywall behind it?
* What about surface finish - sanded or rough? Painted or stained?
Anyone have a link where more info is available?
Thanks.
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Bass absorption is improved both by spacing the panels off the walls and by using thicker absorbers. Rigid fiberglass is a velocity absorber. At the wall surface the velocity is zero. As it moves away from the wall, the velocity of air vibration increases. The velocity of all frequencies peak at 1/4 wavelength away from the wall. Here are some example 1/4 wavelengths:
Freq. - 1/4 wavelength (inches)
-------------------
1100 - 3
550. - 6
225. - 12
112.5 - 24
The sizes quickly become huge as the frequency gets into the bass... But you can get noticable (and measurable) improvement at a fraction of the 1/4 wave distance, even at 1/10 wavelength. And spacing the panel off the wall moves it toward that zone where it'll do some good at lower freqs. Most of the troublesome freqs are below 600 Hz.
Surface finish:
I covered mine with muslin cloth because it lookwd good, was cheap, and was needed to prevent possible fiberglass dust getting into the air. Some folks who want to maintain a more lively room ambience for highs put spaced wood slats over some of the panels. I didn't find it necessary for my room.
Last edited by Philbo King; 05-29-2020 at 11:11 PM.
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