# Acoustic, Fabric Covered Panels............questions....



## SvK (Feb 26, 2009)

Acoustic, Fabric Covered Panels............questions....

Hi all,

I am working on my home-studio walls to kill all slap-back echo between them.....
........I want to take the route of having one wall lined with 3 BIG fabric covered panels that are circa 6ft by 3ft and circa 2 inches thick, with fabric covering them.....

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## midphase (Feb 26, 2009)

Steven,

In my old studio back in Florida we had our acoustic panels custom built at quite a huge saving over the "brand name" type.

The two big keys are....what goes in and what goes on the outside. You can use 1x2's to build the frame with, and then install good acoustically absorbent material inside them. The outside also need good quality acoustic fabric, not all fabric is created equal and we had to special order acoustic fabric (usually sold by the rolls). companies that deal with construction materials for theatres and entertainment venues should have what you need.


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## SvK (Feb 26, 2009)

jeff c mid-phase,

Thanx!

SvK


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## SvK (Feb 26, 2009)

100% bonded cotton 2 feet by 4 feet......35$ a pop......
http://www.soundproofingamerica.com/Echoless.pdf

frame it, cover it....done...right?

SvK


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## SvK (Feb 26, 2009)

completely green....made from old denim, etc.....

thoughts?

SvK


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## Nick Batzdorf (Feb 26, 2009)

A couple of things, SvK. First, as I ranted in another recent thread, there's a difference between a tracking set-up and a mixing/monitoring one. In the latter you only have to worry about bounces between the front and rear walls, and the panels you're talking about should go on the front wall.

Then you can put diffusors on the rear wall (and overhead) if necessary. And for tracking all bets are off - that's a totally different thing.

Second, the main purpose of panels like this is to get rid of excess reverb; if you only need to get rid of slapback, diffusors might be a better idea. But I think you want to put the panels on the front wall, because if you mount them the way I'm about to suggest, you'll get rid of slapback and have broadband absorption (including pretty good bass trapping).

And now what I want to suggest is that you bend the panels between the ceiling and the middle of the wall like an ASC Mix Station baffle:

http://www.asc-studio-acoustics.com/mix-station.htm

I don't agree with their idea of using three of them to create a "reflection-free zone," but the baffles work really well (they're what I'm using). The only thing you don't really see is that between each of the four panels is maybe a 1/3" thick piece of pressboard with about a 3" diameter hole in it; you don't need the side boards if you're using it in the front (ASC doesn't). What happens is that in addition to absorbing highs, this way of mounting lets them flex to catch low freqs as well.

I don't know what the material they're made out of is, but it's like really heavily compressed insulation.


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## Nick Batzdorf (Feb 26, 2009)

That stuff you linked is supposed to be really good, according to an acoustician friend of mine.


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## SvK (Feb 26, 2009)

Nick and Co.:

You guys are really helping!
Thanx ..GREAT INFO....

thanx,

SvK


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## midphase (Feb 26, 2009)

Send us pics when you're all done!


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## Hannes_F (Feb 27, 2009)

SvK,

2 inches would be a no-no for me since on the long view it will bring you into an unresolveable dilemma. 

If you go to gearslutz or any other acoustic forum you will find them full of "Emergency, I have my room stuffed with acoustical treatment and all is fine except those nasty bass booms (or notches depending on where you stand). How can I get rid of that?".

Fact is, you can't with 2 inches absorption, so at that point you will go back and start all over with thicker panels. 

Some try to have thick absorption at the front and back wall but 2 inches for ceiling and side walls. They still run into bass boom problems.

Also, don't mount your panels directly to the wall. A 4 inches panel mounted 4 inches away from the wall is nearly as effective as an 8 inches panel mounted to the wall.


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## Hannes_F (Feb 27, 2009)

While we are at it ... don't ever take the word "bass trap" too literally. It is not like you can put a device into the corners or elsewhere and the bass frequencies will run there like mice being attracted by cheese. For effective treatment of bass frequencies you need all important areas to be covered: 3D corners, 2D corners, reflection points, standing wave points.


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## madbulk (Feb 27, 2009)

midphase @ Thu Feb 26 said:


> Send us pics when you're all done!



Just don't put them on your website.


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## SvK (Feb 27, 2009)

madbulk @ Fri Feb 27 said:


> midphase @ Thu Feb 26 said:
> 
> 
> > Send us pics when you're all done!
> ...



???
what do you mean 

SvK


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## JMDNYC (Feb 28, 2009)

To go only slightly off-topic, my wife just posted detailed directions on how we built out home studio on the Instructables site. Here is the link:

http://www.instructables.com/id/Build_a_music_studio_in_an_apartment_building/ (http://www.instructables.com/id/Build_a ... _building/)

If you read it, you'll see that our acoustic panels were bought from a studio that had gone out of business. It's worth checking Craigslist often. Building them yourself from the Owens-Corning materials with the acoustic fabric in the custom frames is certainly possible, but it's a lot of work and requires some substantial skills.


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## Lunatique (Feb 28, 2009)

Take a look at the acoustic treatment I designed for my studio. It's 100% DIY--I spent a year doing research, design, and construction:
http://www.ethereality.info/ethereality ... studio.htm

You really want to be asking this kind of question in forums like recording.org or johnlsayers.com or gearslutz.com because there are tons of resources and threads about this stuff there, and they were instrumental in my research (in additional to reading 3 books on the subject).

Depending on the layout of your room (which you haven't really said anything about), you could do superchunks like I did--they are awesome for basstrapping and if you keep them to the ceiling/wall corners, they don't really take up any room either. I used 4" 703 panels at 4x2 ft, spaced 6" from the walls. This is very important if you want the best broadband performance out of your panels. I used 2 layers of burlap for the fabric covers--breathes fine yet keeps the fibers secure. My ceiling cloud is on a rail so it can be moved if I move my listening position. The panels in front of the window are on legs so they can be moved as well. All the hard work I put into it paid off--the room sounds f-ing amazing--best room I've ever heard outside of expensive commercial studios. And it didn't cost me much either


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## Nick Batzdorf (Feb 28, 2009)

"Emergency, I have my room stuffed with acoustical treatment and all is fine except those nasty bass booms"

That's the reason for mounting the panels the way I suggested: the absorption is broadband and it won't simply kill the room and make it sound boomy. In that design you actually want panels that are around 1" thick so that they can flex and absorb the bass freqs.

Everyone's first instinct is to absorb as much sound in the room as possible, as if sound bouncing around is the enemy. The reverse is true; what you want to do (in my opinion, which isn't unique) is control that sound, not kill it.


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## Nick Batzdorf (Feb 28, 2009)

And I'd definitely recommend bigger guns than Lunatique's. I have three huge machine guns in my room.


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## artsoundz (Feb 28, 2009)

Owens corning 703 is great stuff. 703 can be cut on a table saw for precise shape. 


1" and 2 " framed w/2x2 cover and go. Some add 2 mil plastic to prevent sloughing off of glass fibers and the plastic is thin enough to transfer little sound waves.

Also-really important- for safety make sure to fire retard your fabric if it isnt' already so.


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## Hannes_F (Feb 28, 2009)

Everybody in this thread ....

... care to post a frequency response (+ waterfall graph if possible) of your rooms?


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## madbulk (Feb 28, 2009)

SvK @ Fri Feb 27 said:


> madbulk @ Fri Feb 27 said:
> 
> 
> > midphase @ Thu Feb 26 said:
> ...



Sorry Steven, I don't even remember what I meant. It was a throwaway reference to something I think Kays had said in another discussion that was at the time right above or beneath yours. Meant to be funny, if minimally.


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## DKeenum (Feb 28, 2009)

I purchased 4" thick panels from ATS Acoustics. I've been very happy with the way they smoothed out my room's sound.


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## Lunatique (Feb 28, 2009)

Nick Batzdorf @ Sat Feb 28 said:


> That's the reason for mounting the panels the way I suggested: the absorption is broadband and it won't simply kill the room and make it sound boomy. In that design you actually want panels that are around 1" thick so that they can flex and absorb the bass freqs.
> 
> Everyone's first instinct is to absorb as much sound in the room as possible, as if sound bouncing around is the enemy. The reverse is true; what you want to do (in my opinion, which isn't unique) is control that sound, not kill it.



What you're talking about is Helmholtz traps--resonators. Those are more complex to implement because the precise thickness and dimensions of the resonators need to be tuned exactly to the frequencies you want to absorb (Rod Gervais's book has the math equation you need for it), and that means you first need to do know exactly what's spiking in your room's mode. With simple glassfiber broadband absorbers, you don't have to be as precise, although there are reference data you can find. Below is the data data of 4" for 703 at 4”~6” distance from the wall (the numbers below the frequencies are the absorption--higher the number the better. 1 is actually great, and above 1 isn't really necessary but has no negative connotations).

4” spacing from the wall
125hz--250hz--500hz--1000hz--2000hz--4000hz--NRC
0.84----1.24----1.24----1.08-------1-------0.97----1.15

6” spacing from the wall
125hz--250hz--500hz--1000hz--2000hz--4000hz--NRC
1.19-----1.21----1.13---1.05------1.04-----1.04----1.1

Below 125hz the absorption will start to drop, but at a slope, not a sharp drop. 

The superchunks (solid triangles lined in the corners of ceiling/wall, wall/wall) are great for basstrapping, so if you've got enough of those in the room, boomy bass will not be a problem. The same pair of monitors in this room (Klein + Hummel O 300D's) sounded much better than in the two previous rooms I've used them--I especially notice it on jazz recordings where the double bass used to sound very boomy, but now is very tight and articulate.

As far as controlling sound but not killing it--this is true. My room doubles as both control room and recording room, so the monitoring half is fairly dead, but the other half of the room is alive enough to have a more natural sound. 



Nick Batzdorf @ Sat Feb 28 said:


> And I'd definitely recommend bigger guns than Lunatique's. I have three huge machine guns in my room.



Hahah, only one FAMAS in the studio. The other guns are all placed in other parts of the home (bedroom, living room, foyer). The batteries are kept charged, but I use large capacity mags and I don't have the dials turned (which is required to make a large capacity mag actually feed the plastic BB's) so even if someone grabs a gun and tries to fire it, nothing will happen except dry firing of the air piston (and this is if the person knows to first disable the safety on the gun first). I used to play airsoft and loved it (for those of you who never heard of it, it's kind of like paintball) but haven't for years now. If we still lived in the States I wouldn't bother having those airsoft guns around--I'd just put real guns around the home. :mrgreen:


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## Nick Batzdorf (Feb 28, 2009)

Helmholtz resonators are different. They work on the same principle as blowing into a bottle - they're boxes with little holes in them (and hopefully some stuffing to increase the range of freqs over which they work).

What I'm talking about is curving maybe 1" panels from the ceiling (out about a foot from the wall) down to the middle of the wall. That places the panel away from the wall, creates a resonant box behind it and the wall, and lets the panel flex to absorb lows - in addition to the highs, which it'll do anyway.

Take a look at the pix in the link above. It's very clever - although once again I don't believe in their "reflection-free zone" concept at all. But as an acoustic device it works really well.


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## Lunatique (Feb 28, 2009)

Nick Batzdorf @ Sat Feb 28 said:


> Helmholtz resonators are different. They work on the same principle as blowing into a bottle - they're boxes with little holes in them (and hopefully some stuffing to increase the range of freqs over which they work).
> 
> What I'm talking about is curving maybe 1" panels from the ceiling (out about a foot from the wall) down to the middle of the wall. That places the panel away from the wall, creates a resonant box behind it and the wall, and lets the panel flex to absorb lows - in addition to the highs, which it'll do anyway.
> 
> Take a look at the pix in the link above. It's very clever - although once again I don't believe in their "reflection-free zone" concept at all. But as an acoustic device it works really well.



I see. Do they have data on which range of low frequencies that curved panel absorbs? 

I wonder how that design is in practice different from simply placing glassfiber panels in corners.


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## SvK (Feb 28, 2009)

Lunatique.....

First off.....you have wwwaaayyyy to much gear...just give me some of it, and all will be fine ......

Your DIY panels look great.....any chance of a closeup of them and your specs??

Also, why do you guys not use the realtraps wood diffusers? Or other similar ones? Is it the high pricing? 

SVK


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## SvK (Feb 28, 2009)

the reason I ask is, if yu go to realtraps.com and watch the video of the realtraps dude playing his acoustic in front of barewall, then absorber....and then his 500$ Diffusor (he plays in front of 3 of them), the difference is striking.....

Thoughts?

SVK


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## SvK (Feb 28, 2009)

I would post the link, but I'm in couch potato mode with my iPhone, which is utterly incapable of copy/paste...

Hehehe

SVK


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## Nick Batzdorf (Feb 28, 2009)

The front baffle has three inner "fins" separating the panels but not on the outsides, while the side ones has them on the outsides as well (but not the insides since they're mounted against the front wall. There's also about a 2-1/2" hole separating each of the inner "boxes"; that diameter is probably important for the tuning.

I don't have a measurement mic to sweep my room, and chances are it would look pretty bad anyway. But it sounds pretty good - good enough that I can hear what's going on.


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## Nick Batzdorf (Feb 28, 2009)

"I wonder how that design is in practice different from simply placing glassfiber panels in corners."

Well, the baffles are bigger and there are four "boxes" in each one. Plus they flex. But that doesn't mean putting fiberglass panels (we put it the other way around in the US  ) isn't also a good idea.


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## Lunatique (Feb 28, 2009)

SvK @ Sat Feb 28 said:


> Lunatique.....
> 
> First off.....you have wwwaaayyyy to much gear...just give me some of it, and all will be fine ......
> 
> ...



Me? Too much gear? You've got the wrong guy--my little humble home project studio is nothing--most professional would laugh at it. Most are budget gear too, with only a few decent pieces of gear and a pair of monitors that are the only qualifying high-end gear in the entire studio. :oops: 

The idea for the exposed sides for the panels came from someone else--here are the original photos (exposed sides perform even better than closed sides for glassfiber panesl):
http://www.ethereality.info/ethereality ... panels.jpg

http://www.ethereality.info/ethereality ... /space.jpg

This is the general idea behind superchunks:
http://www.ethereality.info/ethereality ... rchunk.jpg

Essentially you cut up the panels into triangles and stack them--makes excellent basstraps.

So basically, for the superchunks, I first construct and place wooden frames in the room, then stuff them with the triangle slices, then wrap them with burlap (I used a fairly sparse weave, so I used two layers). The dark brown borders are wooden strips, and they were used mainly to keep the burlap in place, but also to double as visual design. Here's a construction photo of the superchunk being put in place:
http://www.ethereality.info/ethereality ... ress-2.jpg

Empty room without gear:
http://www.ethereality.info/ethereality ... ress-7.jpg


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## Lunatique (Feb 28, 2009)

Nick Batzdorf @ Sat Feb 28 said:


> But that doesn't mean putting fiberglass panels (we put it the other way around in the US  ) isn't also a good idea.



It's used both ways, even by Americans (which I am, BTW :wink: ). Mitch Gallagher's book uses "glassfiber," while Rod Gervais's book uses "fiberglass."


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## Waywyn (Mar 1, 2009)

Hannes_F @ Fri Feb 27 said:


> If you go to gearslutz or any other acoustic forum you will find them full of "Emergency, I have my room stuffed with acoustical treatment and all is fine except those nasty bass booms (or notches depending on where you stand). How can I get rid of that?".



I didn't read through all posts, but I recently had a chat with a sound engineer regarding those nasty bass booms. During time I encountered that I have something going on at around 114 Hz or so ... and the guy told me that it is just one thing in most cases - the ceiling above you 

I took a big cardboard and simply held it over my head while playing a tune and it was almost gone. So I would say if taking care about a room I would always consider the ceiling directly above you at first when it comes to nasty bass stuff.

Of course I am not acoustic room specialist, but I just telling out of experience and what has been told to me.

Another thing to add, if you already have shelfs and cupboards in your room you barely need something for the walls, since you already did some "kind of a room treatment"


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## Hannes_F (Mar 1, 2009)

Nick Batzdorf @ Sun Mar 01 said:


> I don't have a measurement mic to sweep my room



For the bass range up to say 1000 Hz any studio mic will do. A good and cheap measurement software is RoomEQWizard (all platforms)

http://www.hometheatershack.com/roomeq/

Please do yourself a favor everybody: *Protect your ears *before sending sweeps to your system (had to learn this the hard way). :roll: 



> But it sounds pretty good - good enough that I can hear what's going on.



Excuse me Sir ... but everybody and his momma says that his studio sounds good ... and soooo much better than before he used [insert any device here]. :mrgreen: 

Which certainly is true actually because nearly everything is better than a bare room. But "better than before" does not mean anything when comparing different methods and ideas.


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## Hannes_F (Mar 1, 2009)

BTW this is my room response:






The response is within +/- 8 dB and the RT is at 0.2 sec.
There is no smoothing applied to the data, such as 1/3 octave or the like. This is just like it is measured (slow scan).


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## Waywyn (Mar 1, 2009)

Hannes_F @ Sun Mar 01 said:


> For the bass range up to say 1000 Hz any studio mic will do. A good and cheap measurement software is RoomEQWizard (all platforms)
> 
> http://www.hometheatershack.com/roomeq/



Thanks Hannes for the link! This is exactly what I was looking for!! o-[][]-o


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## Hannes_F (Mar 1, 2009)

Alex, actually RoomEQWizard is even free. o-[][]-o 

One thing to consider if you make measurements: Only use one speaker at a time, a stereo signal will give wild results.


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## SvK (Mar 1, 2009)

Luna,

Thanx fir the close-ups of the panels ....you put alot of luv into this puppy.....

SvK


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## SvK (Mar 1, 2009)

Hannes,

Fairly even in your room....i'm jeoulous 

SvK


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## Hannes_F (Mar 2, 2009)

Nick, maybe I should not have been adressing this to you because actually I was meaning it more as a general observation. Since you have been caring about acoustics for a long time you will certainly have noticed as a general tendence that owners of more expensive treatments or studios will only post photos but not not measurements.

That being said the people at ASC and their products are cool and I have used a portion of their Quick Sound Field idea for setting up my own room.


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## SvK (Mar 4, 2009)

PLEASE go here and watch the last minute of this video.......

http://www.realtraps.com/video_diffusors.htm

He'll play an acoustic up against a bare-wall (yuk), against absorbtion (really yuk) and against a wooden diffusor (wow!!!)

thoughts??

SvK


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## Nick Batzdorf (Mar 4, 2009)

Ethan is right about *most* of the things he's adamant about. 

This is one of them. But note that he's not saying the best way to record a guitar is to stick it next to a diffusor, he's illustrating the difference between a bookcase and a real diffusor.


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## Waywyn (Mar 4, 2009)

SvK @ Wed Mar 04 said:


> PLEASE go here and watch the last minute of this video.......
> 
> http://www.realtraps.com/video_diffusors.htm
> 
> ...



All I say is wow too 
When you hear his diffusors against the other surfaces, it almost sounds as if the guitar was really EQ'ed kinda wrong. I want those


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## SvK (Mar 4, 2009)

Waywyn

EXACTLY.......the WORST is the Absorbtion......I'm going to be REAL careful to not overuse absorbtion in my room........yuk

to my ears the BookCase comes in 2nd.

SvK


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## Hannes_F (Mar 5, 2009)

SvK @ Wed Mar 04 said:


> PLEASE go here and watch the last minute of this video.......
> 
> http://www.realtraps.com/video_diffusors.htm
> 
> ...



The point is that for a control room you want your reverb time (RT) decay to be in the range of 0.2 to 0.3 seconds all up the spectrum. This is why I am against thin absorption. If you start using thin absorption you need so much area covered before you get any effect in mid and low range that you suck out the treble. This is why the second complaint you regularly see in the acoustics forums is "I have my room full of treatment and now it is sounding dead".

I am not necessarily meaning the special way of thin absorption that Nick introduced (bent panels over a cavity, this may be different). What I mean are thin (anything thinner than 4" or 10 cm) materials used as gobos or panels (did I say I use between 10 and 50 cm?). No matter whether thin panels are made from mineral fiber or foam, you are going to run in problems.

BTW: There are thin compound systems available with multi layers, membranes, hole patterns etc. that have good bass absorption but they are expensive. We are speaking about systems we can build ourselves.

Now with thicker absorption you are going to have better bass control but still the treble will always be absorbed more than the bass. And this is not what we want. So a better concept is to reflect the higher frequencies by a plastic layer in front of the absorbtion and rather control them by geometry than to absorb them.

That all being said:

I was WOWed too by this video. Nevertheless I am having second thoughts, as impressive as it is. A diffusor like this is behaving like an EQ in nearfield depending on where exactly you place the mic and you certainly can find a spot in front of it that has presence enhancement so the instrument sounds as if it is right in your face. But for creating a neutral listening environment with diffusion you need certain room dimensions.

Re-reading my post maybe I should have reduced it to the first sentence: For a control room you want your RT decay to be in the range of 0.2 to 0.3 seconds all up the spectrum. That would be a good start.


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## Nick Batzdorf (Mar 5, 2009)

Remember, it's important to figure out a design based on the individual room. Saying "I like the sound of the real diffusors in Ethan Winer's video better than absorption so I'm going to buy some" is like saying "I liked the Phillips head screwdriver better than the saw so I'm going to buy it."

That video is demonstrating why real diffusors work better than arbitrary ones: they do a good job of dispersing the guitar's waves all over so they don't cause cancellations in a mic next to them. It is *not* demonstrating how to record an instrument, nor is it saying that diffusors solve every problem in a room, and it's especially not saying that flat walls are your enemy wherever they are!

So I'm going to repeat the basic "small control room in living space on the cheap" (aka Moulton Room) concept: get rid of excess reverb with broadband absorption at the front, and then if necessary use diffusion overhead and at the rear.

Unfortunately it's not always possible to create an ideal control room in a room you have to work in, especially if you don't want to make the room depressing by closing off windows, etc. If you're starting from scratch, you put the windows at the sides, etc. etc. etc. But like politics, acoustics is the art of the possible rather than the ideal.


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## SvK (Mar 5, 2009)

NIck....that's my plan .....absorbers in the front and a wall of three of those diffusors in the back......

All other obsorbtion will be in the form of bass traps and @45degree angles on corners of the room.....

What I will NOT do is line my walls with flat panel absorbtion....

SvK


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