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DIY Absorbers for the Less-Than-Handy Man - Part 2

by April 21, 2005

Continued from Part I … So the big question - How do they work? In my opinion - great. The difference in my room is dramatic. I don't have any fancy measuring devices (only my SPL from radio shack) so I can't do a before and after room measurement (though if someone would like to come over and do one for me I'd be happy to oblige). My wife is happy with how they look, I'm happy that I successfully built something, and the sound in our home theater room is much improved.

The advantages of using my design are:

  1. Cost - uses minimal lumber, hardware, and materials.
  2. WAF - the wife likes the low cost, the fact that she gets to pick out the fabric, and the unique quality it gives the room.
  3. All research points to the fact that fiberglass absorbers work better the farther the fiberglass is from the wall. Many designs require that some sort of spacer is placed between the wall and the absorber. My design leaves two extra inches within the frame which means that the fiberglass can still be two inches off the wall while the frame sits flush (a big WAF plus in my house).
  4. My design, unlike others, does not have to be attached directly to the wall, nor is it so heavy that you need stands. You can move these absorbers as much as you like, change locations, rooms, homes, whatever.
  5. Because I can't measure, I use the fiberglass for all my cuts. This means that if you need an odd shaped absorber, you just cut the fiberglass with a sharp kitchen knife (it cuts really easily) and use the piece to measure your boards. I'm sure I'm not inventing the wheel or anything but it's liberating to know that you don't have to stress over how straight you cut the fiberglass (which in my case wasn't that straight, another surprise).
  6. Ease of design - If I can do it, so can you.

The disadvantages of using my design are:

  1. PanelEdge3.jpg You very well may lose a finger (or two).
  2. Finding the fiberglass may be difficult depending on where you live.
  3. The absorbers are bulky (4" thick). This may not work for you. You can modify the design and get 1" thick fiberglass, frame it in a 1" by 1" board, and mount it flush to the wall. The reason for spacing the fiberglass away from the wall is that it increases its effectiveness, but 1" thick on the wall is still a heck of a lot better than nothing at all.
  4. While my wife thinks they look cool, your significant other may not. Even the added bonus of having them pick out the fabric may not be enough. If this is the case, buy some big, fluffy furniture (for absorption) and put up some bookshelves with many different sizes of books spread out in them (for diffusion).

I've said from the beginning that I'm no designer. This absorber will not win any awards. You will not become rich selling these absorbers (and if you do I want 10% of the gross). I wrote this simply because all the other designs I found on the net were either not to my liking or assumed that you understood basic woodworking techniques. I wanted to find something that took me through step by step because I really didn't know what I was doing. I'm hoping that there are more people out there that are in the same boat, feel as lost and intimidated by the whole process like I did, and don't know Jimmy. This is to help them get a low cost absorber that they can proudly stand by and say, "I did this." Hopefully, it won't fall off the wall as they say it.

Links

1) For a long thread about one guy's home theater project (turned his master bedroom into a home theater - don't ask me how he convinced his wife): http://www.soundandvisionmag.com/idealbb/view.asp?mode=viewtopic & topicID=33004 & num=20 & pageNo=1

2) Link to a thread discussing where to purchase rigid fiberglass board: http://homerecording.com/bbs/showthread.php?t=119730

3) Description of how to build a French Cleat (or Freedom Cleat if you're still in that mode): http://www.newwoodworker.com/frenchcleat.html

4) More good info about absorbers and diffusers: http://www.ethanwiner.com/acoustics.html

5) A fiberglass baffle design that I did not use: http://www.mindspring.com/~c_campbell_2000/eyedrum/baffle-design.html

6) Example of the batting that I used: http://www.joann.com/catalog.jhtml?CATID=82280 & PRODID=11884

7) Fabric stretching link (actually for canvas' but the principle is the same): http://www.rexart.com/stretching.html

8) Hanging absorbers like pictures: http://www.realtraps.com/install_mt.htm

9) SPI's website: http://www.spi-co.com/

10) How to hang a picture: http://www.lowes.com/lkn?action=howTo & p=Improve/fastnrwall.html

Glossary

' Feet (8' = eight feet)

" Inches (1" by 4" = one inch by 4 inches)

Absorber Something that absorbs sound

Clap test Walk into a room and clap - if it rings you need absorbers

Diffuser Something that instead of reflecting sound in one direction, it

splits it into many directions

DIY Do It Yourself

HT Home Theater

WAF Wife Acceptance Factor

Disclaimer

I'm an idiot. I don't know what I'm doing. If you have a better design, great. Post it. I could have used it. If you follow this design and something terrible happens, I'm not responsible. Don't call me. Don't send me hate mail. Don't sue me (I don't have any money, anyways). I'm not affiliated with Audioholics.com (though I'd like to be, hint, hint) so don't sue them either. If you use this design and it works out for you, great. If you want to pay me for it, better (though I don't see why you would). Consider this article to be for entertainment purposes only (though if you find this entertaining I suggest you find a hobby or go outside or practice blinking or something). If this article is not detailed enough or if you find anything unclear, please contact me. My whole point is to make sure that EVERYONE can replicate these absorbers. I've been thinking about it and I believe that there are three possible reasons why I found online information about absorber designs incomprehensible:

1) Some of the more basic techniques are so second nature to the authors that they don't even think about describing them in detail.

2) It takes a lot of time, energy, and space to write up a plan like this, skipping some of the more trivial details is an attractive way to shorten the process (especially towards the end).

3) If you are unsure about any aspect of your design, you will be tempted to gloss over that description, making it unnecessarily obtuse, in order to protect yourself from criticism. I've had to fight the urge to leave out specific details because I felt like such an idiot for not knowing them in the first place. Plus, I'm deathly afraid that someone will respond with, "Those won't work! You wasted all that money and time. You need to start over again and do …."

In my opinion, it's probably a combination of the three. Have a nice day.

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About the author:

As Associate Editor at Audioholics, Tom promises to the best of his ability to give each review the same amount of attention, consideration, and thoughtfulness as possible and keep his writings free from undue bias and preconceptions. Any indication, either internally or from another, that bias has entered into his review will be immediately investigated. Substantiation of mistakes or bias will be immediately corrected regardless of personal stake, feelings, or ego.

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