Room Acoustics

[Labs]

....

[Dave Martin]

My DIY approach is to use either Corning 703 insulation or Mineral wool stuffed into wooden frames.

(Pardon my use of feet and inches, but I don't know what dimensional lumber is in Europe). Both 703 and rock wool come in 2 foot by 4 foot sheets, usually two inches thick. I would use 1x6 lumber to build a a square that's 2 feet by two feet, and put one sheet of 703 cut in half into that square. This mixes a total thickness of 4 inchesof insulation. After that I covered one side of the box in material, stpalede to the edges. And last I added a little piece of wood on each of the edges to hide the staples.
I used these 2'x2' squares of insulation whever I wanted absorption - on walls on ceilings, in corners. When I get to the studio later today, I'll see if I can find a picture (worth a 1000 words, of course).

[Ethan Winer]

Gustav,

> Tell us what you did, and post some pics of it, and please- Dont just link to a DIY basstrap <

You'll find a lot of info and photos in the Acoustics FAQ, second in the list on my Articles page:

www.ethanwiner.com/articles.html

> budget tips for getting your rooms measured btw ! <

There's some discussion of that in my FAQ, and a lot more in my recent series of articles for EQ and Electronic Musician magazine. Those articles are now on my company's web site. Here's a direct link to that page:

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

The short answer is you need to measure at a very high resolution either using sine waves at 1 Hz intervals, or with software like ETF from www.acoustisoft.com.

--Ethan

[NathanEldred]

Originally posted by Dave Martin
My DIY approach is to use either Corning 703 insulation or Mineral wool stuffed into wooden frames.

(Pardon my use of feet and inches, but I don't know what dimensional lumber is in Europe). Both 703 and rock wool come in 2 foot by 4 foot sheets, usually two inches thick. I would use 1x6 lumber to build a a square that's 2 feet by two feet, and put one sheet of 703 cut in half into that square. This mixes a total thickness of 4 inchesof insulation. After that I covered one side of the box in material, stpalede to the edges. And last I added a little piece of wood on each of the edges to hide the staples.
I used these 2'x2' squares of insulation whever I wanted absorption - on walls on ceilings, in corners. When I get to the studio later today, I'll see if I can find a picture (worth a 1000 words, of course).

Yep, and 705 works better for bass trapping. The thicker the better. I've heard of a few people doing 8 inches of 705. Talk to Ethan, he knows his stuff, and his ideas (and products) are solid and work very well.

[matucha]

my aproach - I'm still building the thing...

[matucha]

it is drop ceiling, partialy tilted...
- aluminium skelet
- from 12cm height with 5cm of rockwool to ~50cm and 20cm of rockwool
- will cover it with perforated gypsum board (~5% of perforation)

Should work as broadband absorbtion (helmholtz type) with "bass trap" at the most thick part.

The rest will have to be in panels... wood frames filled with rockwool, covered with cloth.

In the corners, I'd use "superchunk" style, I find here: http://forum.studiotips.com/viewtopic.php?t=535


I have some 3D models (just for an eye, not acoustical), but currently I'm working on some changes that will take some time, but will post as soon as possible

[matucha]

I'm also going to bild a Diffusors from old parquets we took of in another room ;-)

this is another picture:

[hollywood_steve]

One tip that I picked up on one of the forums (ethan's?) takes the low cost DIY thing to the extreme. Instead of building the rigid insulation into a trap, just cover it with some suitable cloth and stand it up in the corner of your room. After 6 months of hopeless searching for 703 (or equal) in the LA area, I purchased a box of 3 pieces of Auralex mineral fiber board (4ft x 2ft x 4"). I paid a local upholstery shop to wrap them in burlap and just placed them in my corners. Huge improvement, and if I ever need to build a temporary control room for a location gig, I can just toss these things in the car.

[Ethan Winer]

Gustav,

> I also think the euroslutz would like to hear what 703 an 705 is ? Maybe a picture of that stuff as well. <

It's all in the FAQ I linked above. Read it, you'll like it.

--Ethan

[kurt]

Are there any guidelines about mixer positions? My control room is 22.5 x 18 x 9 feet.
At the moment I’m sitting in the middle of the room.
Where should one place the sitting chair?

[Glenn Kuras]

Originally Posted by kurt

Are there any guidelines about mixer positions? My control room is 22.5 x 18 x 9 feet.
At the moment I’m sitting in the middle of the room.
Where should one place the sitting chair?

You do not want to be in the middle of the room.. First you want to fire the monitors down the 22.5 foot wall. Second you want to sit 38% in front of the 18 foot wall (8.55 feet)...

[kurt]

Thanx

[zeroD]

I had a real hard time finding 703, so I found a local distributor of rigid fiberglass in Baltimore (McCormick Insulation). Get the unfaced and it will cost you about $8 for each 2'x4' piece (2" thick). I covered them myself with fabric and a hot glue gun (the stuff is pretty rigid, so you don't need a frame). I left about 2" around the edges on the back side, where I applied the glue. Then using Elmer's wood glue I attached a small piece of masonite (about 6" x 20") to the back near the top. On this I put two small squares of industrial strength Velcro. All along the walls of the room I put a thin (1") strip of the mating Velcro. This allows me to move the panels wherever I want to get the sound absorption where I need it. In a room that is about 12'x24' I have a total of 19 panels. Five are mounted side by side behind the drum kit, which has a shield in front (the space is mainly used for band rehearsal). How well does it work? At the first practice the guitarist complained that he couldn't hear the drummer well enough. Here are a series of pictures. Hope this helps.

[Scott R. Foster]

Nice!

[Alexi]

for all you european slutz that can't get 703 or 705........check this company:

www.isover.de

........they offer similar stuff.


cheers

[Alexi]

[QUOTE=zeroD]I had a real hard time finding 703, so I found a local distributor of rigid fiberglass in Baltimore (McCormick Insulation). Get the unfaced and it will cost you about $8 for each 2'x4' piece (2" thick). I covered them myself with fabric and a hot glue gun (the stuff is pretty rigid, so you don't need a frame). I left about 2" around the edges on the back side, where I applied the glue. Then using Elmer's wood glue I attached a small piece of masonite (about 6" x 20") to the back near the top. On this I put two small squares of industrial strength Velcro. All along the walls of the room I put a thin (1") strip of the mating Velcro. This allows me to move the panels wherever I want to get the sound absorption where I need it. In a room that is about 12'x24' I have a total of 19 panels. Five are mounted side by side behind the drum kit, which has a shield in front (the space is mainly used for band rehearsal). How well does it work? At the first practice the guitarist complained that he couldn't hear the drummer well enough. Here are a series of pictures. Hope this helps.Attachment 16779

am i understanding you correct.............1 absorber = 1 panel..............

[A27Hull]

Hey Labs,

I got to hear John a few days ago. If you guys are designing a room, it might be worth giving him a call.

If you want to experiment try building an acoustical membrane absorber. A flat and flexible piece of thin wood or ruber or drywall will absorb a great deal of bass freq when brought off a fixed parrallel surface (such as a wall) even so little as a few inches. Only problem is that you'd need to do calculations on how much space goes between and so forth to get things predictable. I am not an acoustician. The principle is similar to Modex RPG diffusors such as seen here: <A HREF="http://www.silentsource.com/diffusors-rpg-modex.html/">A modex example</A>

I use the 703 stuff and can vouch that DIY it is less expensive than the auralex or sonex stuff, and preforms as well or better than the foam. Plus it looks nice too.

Dave has a good idea there, also try 1/8th'' luan backing board with or without the side supports.

FWIW,

Andrew

[af_analog]

I put up an 8' x 6' cloud above the drums...12" dead space between cloud and ceiling. Cloud has 6" Rockwool. Drums have never sounded better in this room! Huge improvement...huge.

[Glenn Kuras]

Originally Posted by af_analog

I put up an 8' x 6' cloud above the drums...12" dead space between cloud and ceiling. Cloud has 6" Rockwool. Drums have never sounded better in this room! Huge improvement...huge.

wow, how did you build the cloud??? that sounds pretty heavy to me...

Glenn

[af_analog]

Originally Posted by myfipie

wow, how did you build the cloud??? that sounds pretty heavy to me...

Glenn

That's funny you ask...it is a bit heavy. I made the main frame out of 1 x 2 & 1 x 4 inch pine. Streched muslin very tight inside the frame, 2 layers of 3" roxul inside, and covered the back again with muslin. The roxul wieghs more than the frame, that's for sure, but we used the 1 x 4 pine (4" vertically for strength) as the main frame, so it's quite durable...we actually dropped it out of mid air (about 8' up) while trying to hang it the first time and it held together nicely, and no one was hurt It is in a corner so we lagged it to the two corner walls as well for support, I had to make sure it wasn't coming down since our drummer just got a brand new Gretsch kit that he's quite fond of. I ended up straddling the same corner (vertically) with 3" of roxul as well which helped even more. I use Josephson C42's for overheads and damn, I thought they sounded good before, but we have now got the polished, professional overhead sound we were looking for. Actually every mic on the kit now sounds 10 x better, I'll try to post a picture of the room & cloud next week...

CHEERZ

[zkaudio]

more pics more pics more pics!

[zeroD]

Alexi -

"am i understanding you correct.............1 absorber = 1 panel.............."

Yes, each panel is 2' x 4'. This is a standard size from the manufacturer.

[Joel DuBay]

Originally Posted by af_analog

That's funny you ask...it is a bit heavy. I made the main frame out of 1 x 2 & 1 x 4 inch pine. Streched muslin very tight inside the frame, 2 layers of 3" roxul inside, and covered the back again with muslin. The roxul wieghs more than the frame, that's for sure, but we used the 1 x 4 pine (4" vertically for strength) as the main frame, so it's quite durable...we actually dropped it out of mid air (about 8' up) while trying to hang it the first time and it held together nicely, and no one was hurt It is in a corner so we lagged it to the two corner walls as well for support, I had to make sure it wasn't coming down since our drummer just got a brand new Gretsch kit that he's quite fond of. I ended up straddling the same corner (vertically) with 3" of roxul as well which helped even more. I use Josephson C42's for overheads and damn, I thought they sounded good before, but we have now got the polished, professional overhead sound we were looking for. Actually every mic on the kit now sounds 10 x better, I'll try to post a picture of the room & cloud next week...

CHEERZ

Cool! If it is anything like the one David French built over at www.forum.studiotips.com, I'l bet it is saaahweeet!


Very cool!

[aapee]

Originally Posted by Alexi

for all you european slutz that can't get 703 or 705........check this company:

www.isover.de

........they offer similar stuff.


cheers

These are good -> http://www.isover.fi/en/Product%20pa...roductID=18298

Actually, Isover is Finnish company

AaPee

[orange]

for UK slutz you can use rockwool RW3

www.studiospares.co.uk product code: 401982
or
http://www.essexinsulation.co.uk/pro.../pages_17.html
or
www.travisperkins.co.uk (can't find it on their site but they do have it)

si

[Matti]

My version: Found some acoustc material going to waste.
They are from a restaurants ceiling cowering the air conditioning.
The stands are old bookshelves "stairs" from my attick.
Took the covering off from the elements and stacked them
with electricians ground copper wire leaving space for the stands.
The thickness of the elements is 6 inches.
Will cover them with the canvas seen in the pic. ( 20€ total)
Made 4 of these.
The cheap way as it happened...
Cheers Matti

[Scott R. Foster]

Here's a link to DF's ceiling panel:

http://www.recording.org/ftopict-26889.html

Originally Posted by zeroD

I had a real hard time finding 703, so I found a local distributor of rigid fiberglass in Baltimore (McCormick Insulation). Get the unfaced and it will cost you about $8 for each 2'x4' piece (2" thick). I covered them myself with fabric and a hot glue gun (the stuff is pretty rigid, so you don't need a frame). I left about 2" around the edges on the back side, where I applied the glue. Then using Elmer's wood glue I attached a small piece of masonite (about 6" x 20") to the back near the top. On this I put two small squares of industrial strength Velcro. All along the walls of the room I put a thin (1") strip of the mating Velcro. This allows me to move the panels wherever I want to get the sound absorption where I need it. In a room that is about 12'x24' I have a total of 19 panels. Five are mounted side by side behind the drum kit, which has a shield in front (the space is mainly used for band rehearsal). How well does it work? At the first practice the guitarist complained that he couldn't hear the drummer well enough. Here are a series of pictures. Hope this helps.Attachment 16779

Attachment 16780

Attachment 16781

Attachment 16782

Attachment 16783

Man I tried Velcro with 703 and My panels kept falling. Maybe it's the masonite that I was missing. So does the Elmer's hold the masonite to the trap pretty well? Do yours never fall?

And guys why does 705 make a better bass trap? Doesnt 4"703 spec better than 705?

[Scott R. Foster]

Originally Posted by no ssl yet

Doesnt 4"703 spec better than 705?

Yep - it sure does...

http://www.bobgolds.com/AbsorptionCoefficients.htm

Makes you wonder.

[Ethan Winer]

No SSL,

> guys why does 705 make a better bass trap? Doesnt 4"703 spec better than 705? <

In my experience 705 is better than 703 for bass traps mounted across a corner. The improvement is similar whether comparing the FRK or unfaced types. There are several reasons standard lab data can hide this:

Standard lab data is given in octave bands that go no lower than 125 Hz. But it's well known that a 4-inch thick panel mounted across a corner has its peak absorption below 125 Hz. So clearly octave data down to only 125 Hz is inadequate to see what's really happening at lower bass frequencies.

The stiffness and mass of a 3- or 4-inch panel can act somewhat as a membrane all by itself. Most (though not all) lab tests are done with the material laying flat on the floor. But when a panel is on the floor any potential membrane behavior is damped.

Standard lab tests are always done with the material in the center of the room. But absorption changes with placement, and the very same material will absorb differently when mounted straddling a corner. The tests I've done to compare 705, 703, and 701 were all done with the panels in corners. In those tests there was a clear trend of increasing bass absorption with increasing density. That said:

1) As the material is made thicker the disparity is reduced. By the time you get to 12 inches thick or more even fluffy fiberglass does a good job compared to 705 and 703.

2) At some point the density can be too much and absorption will be reduced. I've never tested rigid fiberglass denser than 6 pcf, but I hope to some day.

--Ethan