Easy But Effective Acoustic Treatment On A Budget

Here's what I did to get a pretty good room response out of my spare 8'2" x 11'9" x 7'10" room.

 

Response before:

 

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Response after:

 

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I wanted the best possible value in time and money for the best acoustic treatment. In 2007, I designed treatment for a small room and for my school's auditorium and had good success with building wooden frames and using 3M Super 77 Adhesive to attach UltraTouch recycled cotton insulation, then covering the frames with cloth using a staple gun.

 

This worked very well for building some 35 broadband panels in the auditorium - I brought down the reverb time quite a bit and flattened out the bass some. But it took maybe 100-200 hours to build all those frames.

 

For my new project studio, I went a different route suggested by one of the representatives at Acoustical Surfaces, Inc., where I bought the insulation. He suggested to just use corrugated board on the back of the insulation. Although there is probably an acoustical drawback to doing that, I figure that any frequencies low enough not to be absorbed by 4-6 inches of insulation are probably low enough to go through corrugated board.

 

One summer during college, I worked at a corrugated board factory, so I'm familiar with some of the types of board. I used 2' x 4' sheets of B/C flute board: a double-wall, highly rigid board.

 

Also, since I was making these in my apartment instead of at the shop at the school where I teach, I needed a way to secure the insulation to the cardboard that was as non-toxic as possible. A glue gun worked nicely, though I went through no fewer than 18 sticks of glue making all the panels.

 

I'll detail the process in the next few posts.

Edited April 14, 2010 by Matt Mayfield

First, I got some insulation. You could probably do this with fiberglass, or anything else. If you choose a different material, you'll probably want to use a different method, since the cardboard is really only there to support the floppy cotton insulation.

Next, I prepared 2' x 4' sheets of cardboard with thick cable ties to hold the hanging wire to suspend the panels. The beauty of this approach is that there is a very large margin for error - I just picked spots that seemed like they would work well for the way the panel would hang in the corner (pics coming up).

I drilled a hole in the wall up near the ceiling, then installed a screw.

Not shown: I did a test hanging of the cardboard. When you see the picture of the completed panel, it will make sense.

 

The next steps were to use a hot glue gun to securely attach the insulation to the cardboard, wrap the panel in fabric (hot glue worked well for this purpose as well), and put hanging wire onto the cable ties.

Finally, I hung the panel from the screw. It required some trial and error to get the panel at both the right angle and the right height to just touch the ceiling.

 

Cardboard warps, of course, and I made all the panels so that the bottom would warp away from the wall when the top was installed snugly. You can see it curving outward in the first picture, before I did the next step.

 

The next step was, I put another screw into the wall, lower down, and used the wire attached to the single cable tie at the bottom of the panel to pull the panel straight. In the second photo, you can see the mounting method from behind.

There were various minor variations on this basic method that I used to attach many other panels to the walls. It seems to make the most difference acoustically when these kinds of broadband porous absorbers are straddled across corners, rather than placed flat against walls or ceilings.

 

In the end, I only made a couple dozen holes in the walls and ceiling that will be easy to repair when I move out (I'm renting the place), but the acoustic difference is dramatic. The whole process probably took no more than 30 hours.

 

For the panels hanging from the ceiling, across into the room, I hung them like shown in the diagram. The idea is, you want the most weight pulling at a 90° to the screw, so the panel won't pull the screw out from the ceiling or wall.

 

The cost for the whole project was only about $375: about $125 for the fabric, and $225 for the cardboard and insulation, and $25 for the glue gun, glue sticks, wire, cable ties, etc.

Wow. I need to do this.

 

Thank you SO much for this post.

 

EDIT: Seriously, I got my loan for my business (Foley, Sound design, Music composition) but didn't factor in taxes. After I've bought all of the stuff I definitely needed, I'm not left with the original amount I budgeted for to buy a bunch of stuff from realtraps.com. I just want to really cut down on reflections and treat the room a bit, and this thread... man, I am not handy in the least (fiancee is, figure that out), but I will definitely be getting on board (haha) with this. I own a duplex, and will be taking over the other half for recording/producing. I could set the whole place up with this!

 

Again, thanks!

 

Also, your spare room reminds me a LOT of one of our spare rooms.

Edited April 14, 2010 by biff_larken

Cardboard warps, of course, and I made all the panels so that the bottom would warp away from the wall when the top was installed snugly. You can see it curving outward in the first picture, before I did the next step.

 

As an alternative to cardboard you could use Foam Core or Gator Board. It's a little more expensive but is less likely to warp. Both of these materials come in different thicknesses.

Awesome - glad it's helpful!

What kind of fabric did you use?

What kind of fabric did you use?

 

I used some cheap cotton-based fabric from a local fabric store. I felt a bit out of place there, but the two dozen middle-aged women who made up the staff and customers were quite friendly and helpful.

 

Anything will work that is breathable - if you can blow through it and feel your breath on the other side, it'll be pretty much sonically transparent. (This tip from somewhere on the StudioTips or EQ Magazine acoustics forums; can't quite remember source.)

Matt - Great post!

 

Question though: What software did you use for analyzing the room and how did you do it?

man good results!!! good idea

Matt - Great post!

 

Question though: What software did you use for analyzing the room and how did you do it?

 

Room EQ Wizard.

 

J.

Great post! I'm also interested to hear what software you used.

Great post! I'm also interested to hear what software you used.

 

Room EQ Wizard.

Are there any advantages to song that stuff over the usual semi rigid fibre board? I managed to find a local source here that sold similar spec fibre board for cheap, au$250 allowed me to build eight 2'x4'x4" bass traps which I thought was quite cheap. Density was 48kg/m3 (same as oc703) and is very effective in my setup.

Yeah, building traps is fun. I made bunch two years ago or so..

Are there any advantages to song that stuff over the usual semi rigid fibre board? I managed to find a local source here that sold similar spec fibre board for cheap, au$250 allowed me to build eight 2'x4'x4" bass traps which I thought was quite cheap. Density was 48kg/m3 (same as oc703) and is very effective in my setup.

 

I don't think there are any particular advantages of the UltraTouch insulation over OC 703, or Rockwool. Those two are definitely the more common materials in pro studios, and they probably have a bit better performance. I used this material because it was very inexpensive, somewhat more forgiving of handling & breathing than fiberglass, and there was a warehouse that sold it fairly close to where I live.

Yeah, building traps is fun. I made bunch two years ago or so..

 

Those look really fantastic. Nice sharp corners, very professional. My room sounds good, but looks like a little kid's couch cushion fort...

 

I don't think there are any particular advantages of the UltraTouch insulation over OC 703, or Rockwool. .

 

I wonder are there any disadvantages?

Yeah, building traps is fun. I made bunch two years ago or so..

 

Those look really fantastic. Nice sharp corners, very professional. My room sounds good, but looks like a little kid's couch cushion fort...

 

Thanks. That was a project which i learned a lot, so next time i'm building traps they're even going to be better! .

 

I don't think there are any particular advantages of the UltraTouch insulation over OC 703, or Rockwool. .

 

I wonder are there any disadvantages?

Only that the material doesn't have enough mass to frictionally absorb very low frequencies. If you look at Matt's plots again, notice that the treatment was effective above about 70Hz, and less effective below. You need a heavier material if you want to solve very low frequency problems.

Great thread.

 

Has anyone got experience sweeping their room with EQ wizard and other similar apps? My 'flattest' condenser is a Neumann KM140, which are known for their treble lift. As most of my issues will be well below the 9kz bump, am I okay to use it as the mic in room testing?

 

Nuemann KM140: http://www.neumann.com/zoom.php?zoomimg=./assets/diagrams/km100_diagrams.htm&zoomlabel=Diagram&w=878&h=278

Has anyone got experience sweeping their room with EQ wizard and other similar apps? My 'flattest' condenser is a Neumann KM140, which are known for their treble lift.

The KM140 is a cardioid mic. You should NEVER use a cardioid mic for any kind of acoustic measurement. Your results will be all over the place. If you're on a budget and you don't need to measure things like very low frequencies of room modes, or your monitors bottom end, then an EV 635A will get the job done. If you want to measure low frequencies, then you'll need to spend a few more clams.

Has anyone got experience sweeping their room with EQ wizard and other similar apps? My 'flattest' condenser is a Neumann KM140, which are known for their treble lift.

The KM140 is a cardioid mic. You should NEVER use a cardioid mic for any kind of acoustic measurement. Your results will be all over the place. If you're on a budget and you don't need to measure things like very low frequencies of room modes, or your monitors bottom end, then an EV 635A will get the job done. If you want to measure low frequencies, then you'll need to spend a few more clams.

 

Thanks Fader8. I"ve never done it, so that's good to know. People have recommended the Behringer mic as being ok. Yes, I said the B word Do you know it? Maybe I'll just borrow or hire the right tool for the job. What mic type is good?

Yup the ECM8000 is great for measurement but again will have a slight lift in the response. You can however load calibration files into REW to counter this.

 

You'll probably only be sweeping from 30 - 3000hz anyway.

You'll probably only be sweeping from 30 - 3000hz anyway.

But I'll guarantee you that at 30 Hz, all that thing can measure is it's own noise! That uses a capsule similar to what's in a Macbook. As a cheaper alternative to the 635A, it might be a winner, but don't have "low" expectations.