The 25 minute, $25 acoustic panel (or $42.00 bass trap)

How to use REW, What is a Bass Trap, a diffuser, the speed of sound, etc.

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JamesCzar
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Edge effect?

Post by JamesCzar »

These look really great, studio_drums. I'm currently looking at all the DIY plans for absorbers here and trying to decided on my design. I think I like these the best because of the ease of the build, as well as the fact that they leave the edges of the insulation exposed. I also looked at the ones that bangbang240 did, and they look great as well.

It seems the only draw back would be a slightly less "pro" look of the other framed units because of their square edges (even under the fabric). But then with this method you wouldn't have to worry about drilling holes in the frame.

Maybe this isn't as sturdy a frame, but if you're not planning on moving them, who cares? Perhaps one or two cross braces in the back might strengthen them.

Can anyone comment on the advantage or disadvantage of the edges being exposed like this, versus the regular edge frame everyone else seems to be using in this build? If braced properly, isn't this a better design? It sure looks a lot easier (and perhaps faster) to build.
James Czar
Creative Director - Rosetta Stone Studios - Media Production Services
Bass Player, Soundtrack Editor, Logic Studio Tech
-=Currently building my basement studio/practice room.=-
Ro
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Post by Ro »

Yes, it leaves more wool exposed which means more absorption.
There's some heavy disputes about that.... Eric and Ethan sure did have some nice threads about that ;)

I'd say: more wool=more absorption. The edges won't reflect (since there's no frame)

It's less stable, but who cares. Once placed on the wall, we don't move'm again. right?!

Less pro? dunno. do we care?

I say +1 for this design :)
JamesCzar
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My thoughts exactly.

Post by JamesCzar »

I agree with you completely, Ro.

More exposed edge should (theoretically) mean more absorption. From Rod's book:
Home Recording Studio: Build It Like the Pros, pg.171 wrote:"Note also that the 6" of 703 product using a Type "A" mounting exhibits absorption coefficients greater than 1.00 at all reported frequencies - a perfect example of edge effect in play.
For this reason, understand that installing this material inside of a wood frame (which will make the cleanest looking finished product) will result in slightly lower sound attenuation than you might expect based simply on the numbers available. This decrease is due to the fact that the frame will take the edges of the panel out of the equation."
I can understand why most manufacturers go with a frame on the outside edge, as it does look more "finished" when covered with fabric, or has more style when painted or stained. Plus, not knowing how roughly their customers are going to handle the product, or how many times they'll move it, I'd say they probably build for durability - you never want a client to think your product is "flimsy."

But in the case of DIYers, I'd say that this design is definitely one of the best, as it's easier (and faster) to build and gives the insulation more exposure. The only change I'd make, as I said, would be to add some extra support in the back with some cross members.

Now, I probably wouldn't use this design for gobos, or anything that's going to be moved often. In that case, I'd most likely go back to the wooden outer frame prevalent in most other designs. But with a little bit of carpentry savvy, I think someone might be able to adapt this design to be more stable, and thus be able to mount it easily on a gobo stand. My concern is that when people grab it to move it, they'd constantly be crushing the front edge, and over time it'd look lumpy or frumpy. Thus I'd probably do the wood outer frame anyway.
James Czar
Creative Director - Rosetta Stone Studios - Media Production Services
Bass Player, Soundtrack Editor, Logic Studio Tech
-=Currently building my basement studio/practice room.=-
JamesCzar
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Building my own...

Post by JamesCzar »

I wasn't going to be building my absorbers for a while, as I'm still working on my design for my studio. However, I'm on the board of a theatre company, and we were set building today... We discovered incredibly bad modal issues, mainly extreme flutter echo, right about the middle of the stage, probably caused by the ratio of the length of the two back walls of the set (which come together at a 90 degree angle). They're almost exactly the same length, which looks to be about the same height from the risers to the ceiling. So it's basically two walls short of a cube. NOTE: I got involved in the set build at a very, very late stage and the walls were already in place.

I'm going to build some of my broadband absorbers and try to tame some of these issues, starting by using four of them as a cloud (most of the flutter echo is coming off of the ceiling). Hopefully, since the issues are only in the lower vocal octaves and there's only going to be speaking (no music), I think this may work. I may need a few more, maybe six (don't have room for many more).

When I start my build, I'll start a new thread to document the process.
James Czar
Creative Director - Rosetta Stone Studios - Media Production Services
Bass Player, Soundtrack Editor, Logic Studio Tech
-=Currently building my basement studio/practice room.=-
studio_drums
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Man, this thread is popular!

Post by studio_drums »

For the record: THESE ARE VERY STURDY WHEN COMPLETED due to stapling both sides of the frame AND stapling the fabric to the frame.

Yes, I went for maximum absorption with the unfinished edges.
Last edited by studio_drums on Sat Jan 31, 2009 3:05 am, edited 1 time in total.
templejazz82
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Re: The 25 minute, $25 acoustic panel (or $42.00 bass trap)

Post by templejazz82 »

does the fact that the frame is on the back of the absorber, along the edge of the insulation, hurt any of the absorbtion quality? Would this method be less effective then putting the frame around the side and leaving the front and back open? I am just getting ready to build some 4" and 2" panels and want to make sure I do it right. SD, how have yours worked? My room is "boomy"
studio_drums
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Re: The 25 minute, $25 acoustic panel (or $42.00 bass trap)

Post by studio_drums »

If there's no space between the absorber and the wall, then the 'frame on the back' design will absorb more. Frame on the side is more aesthetically pleasing, but a little more time-consuming. It's a trade-off.

They work great for me, no boominess- but keep in mind I have 'superchunks' in my corners, which I also recommend.
Last edited by studio_drums on Wed Mar 25, 2009 8:47 am, edited 1 time in total.
templejazz82
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Re: The 25 minute, $25 acoustic panel (or $42.00 bass trap)

Post by templejazz82 »

Studio Drums- How do you mount these panels on a wall? I find my method of picture wire is making the trap top heavy, so the bottom is flush with the wall, but the top is about an inch or two off the wall.
studio_drums
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Re: The 25 minute, $25 acoustic panel (or $42.00 bass trap)

Post by studio_drums »

I used eye hooks screwed into the inside of the wood frame. That will keep it flush.
xSpace
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Re: The 25 minute, $25 acoustic panel (or $42.00 bass trap)

Post by xSpace »

An alternative might be using a French cleat:

http://www.askthebuilder.com/French_Cleat_Video.shtml

We hang overhead cabinetry using this method. Straight lines and secure support. Works for me!


Brien
studio_drums
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Re: The 25 minute, $25 acoustic panel (or $42.00 bass trap)

Post by studio_drums »

I also hung a couple on screws only- without hooks and wire. How's that for simplicity...
DrFord
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Re: The 25 minute, $25 acoustic panel (or $42.00 bass trap)

Post by DrFord »

Excellent Post Studio Drums, and thanks for the drawing of the eyelets inside the frame. I will be building quite a few of these in the near future, as well as the bass trap version.

Well done for novice builders like myself... very thankful for this post!!!

D
nixx
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Re: The 25 minute, $25 acoustic panel (or $42.00 bass trap)

Post by nixx »

This is my very first post on JS forum and it goes as "thank you" to studio_drums for this very simple and plain, yet effective and beautiful design!
benirose
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Re: The 25 minute, $25 acoustic panel (or $42.00 bass trap)

Post by benirose »

Sorry if this seems like a silly question, but you said to use 4 inch 703 for a bass trap, but the cheap site I'm looking at (atsacoustics) only sells 2 inch sheets and I was wondering if you could build the 4 inch bass traps by layering two sheets of 2 inch, or does that not translate the acoustic properties properly. Or do you have a site where I can get some cheap 4 inch 703? Thanks!
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Re: The 25 minute, $25 acoustic panel (or $42.00 bass trap)

Post by jbassino »

one 4inches and two 2 inches is the same
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