My New Year's Resolution is to improve the bass on my HT. I've started building my own subs but I've also decided to try to treat my 1800 cubic foot below grade theater room. My first thought was to put a bass trap in a nasty corner. The GIK Acoustics 244's (http://www.gikacoustics.com/product_info.html) seemed ideal (and only $60) but I wanted to try the DIY route first (mainly because I had a lot of extra insulation lying around).

After doing some research I figured I would try to build a 4' x 2' frame out of 2x6's and stuff it with compressed fiberglass insulation. My goal is to get a 4x compression into 6 inches. From the pictures, you can see it kind of poofs out a bit but hopefully I'll be able to fix that.

When I'm done I'm going to show before and after plots for my room. Dealing with the fiberglass has been a pain so I'll probably get two of the 244's as well and can compare / contrast.

Oh yeah, FYI, the room plot I showed was before I hooked up my Behringer Feedback Destroyer and got Room EQ Wizard working. That took care of the peaks nicely. :)

As another FYI the costs for this break out something like this:

1 x 12' 2x6: $6.50
2 x bag o' insulation: $9.50 each
1 x roll of 4' x 10' chicken wire: $8.00
+ 3 x yards of sage burlap: $6.50 total
-----------------------------------------------------
$40.00 + staples and such

The only tools I'll need is a hammer, staplegun and scissors. Lowe's did a good job cutting the wood for me.

Get OC703 rigid fiberglass... Here are the measured absorbtion values.

Owens Corning 703 ... 48 kg/m^3 - 3 pcf
(OC 703) (Size) (125, 250, 500, 1000, 2000, 4000 Hz )
OC 703 · 1.0" · 0.11 · 0.28 · 0.68 · 0.90 · 0.93 · 0.96
OC 703 · 2.0" · 0.22 · 0.82 · 1.21 · 1.10 · 1.02 · 1.05
OC 703 · 2.0" · 0.17 · 0.86 · 1.14 · 1.07 · 1.02 · 0.98
OC 703 · 3.0" · 0.53 · 1.19 · 1.21 · 1.08 · 1.01 · 1.04
OC 703 · 4.0" · 0.84 · 1.24 · 1.24 · 1.08 · 1.00 · 0.97
OC 703 · 6.0" · 1.19 · 1.21 · 1.13 · 1.05 · 1.04 · 1.04

There isn't anywhere convenient to get OC703 here AND I had a bunch of R13 insulation lying around. So, it is an experiment, maybe it will work, maybe it won't. I also have two GIY 244 panels on order (which seem comparable to the 703 in performance and price) so if this doesn't work well for bass I can put it somewhere else for other frequencies.

BTW, I can't seem to find 6" thick pieces of the OC703 anywhere. Do you just layer three pieces of the 2" stuff instead?

BoomieMCT,

I got GIK 244 panels earlier this year - worth the money - new or used.

Have you considered cylindrical bass trap recipes? Jon Risch posted a great DIY recipe - you already have the ingredients :)

Have fun,

- Steve O.

There isn't anywhere convenient to get OC703 here AND I had a bunch of R13 insulation lying around. So, it is an experiment, maybe it will work, maybe it won't. I also have two GIY 244 panels on order (which seem comparable to the 703 in performance and price) so if this doesn't work well for bass I can put it somewhere else for other frequencies.

BTW, I can't seem to find 6" thick pieces of the OC703 anywhere. Do you just layer three pieces of the 2" stuff instead?

Well if you are doing corner traps you can just layer them from floor to ceiling, I don't see how layering 3 of the 2" would not give you the same performance as 6" thick peices (assuming they were all unfaced).

Well if you are doing corner traps you can just layer them from floor to ceiling, I don't see how layering 3 of the 2" would not give you the same performance as 6" thick peices (assuming they were all unfaced).

That's what I figured.

My room has lots of bass problems. I figured I would play with the R13 I have and see if I could make anything useful from it. I have the 244's on order. If those don't do the trick, maybe I'll try tracking down some OC703 too.

Also, if this R13 doesn't work as-is I can try removing the chicken wire and sealing the box with plywood to make a panel trap.

These guys will ship you small quantities of oc703 and mineral wool, as well as glue and fabric:

http://www.atsacoustics.com/

Look under 'raw sound absorption materials'. The prices aren't bad at all; they're a bit more than what you'd pay locally but not excessive.

I'm new to the whole bass trap acoustic treatments thing, but wouldn't most insulation be too thin (not dense enough) to actually curve any of the deep bass response? I believe it was on the home theater diy show they had some small sonotube filled with sand put into corners that helped them out with some nasty bass. Is there a preference or does one just straight out work better?

I ordered my OC703 from: http://sensiblesoundsolutions.com

That is Bpape's site, who posts a lot in the audio setup and a few other forums. He is very much an expert. I believe that he has joined GIK too. His prices are reasonable.

Well, this design worked but not for the frequencies I needed (I'd say greater then 150 Hz or so). So I've ordred two of the GIK 244 panels. I'm also going to order some OC703 and make a panel trap as outlined in the Master Handbook for Acoustics (http://www.amazon.com/Master-Handbook-Acoustics-Alton-Everest/dp/0071360972/sr=8-1/qid=1167741068/ref=sr_1_1/103-7163618-4792634?ie=UTF8&s=books) (which I didn't have when I started this). I may also make a helmholtz radiator for my nasty 63 Hz dip if those other things don't work well enough.

Many thanks to those who posted good places to get the OC703. I think buying those panels will be easier and work better then any DIY thing I can think up.

Hey Boomie,
You can take the 703 and cut it to triangles and stack them in the corners floor to ceiling. It may not work as well as our Tri Trap does, but if you look at the lab numbers of the Tri Trap it kicks some BUTT at 63 HZ. Since you did buy from us please feel free to email me your room layout and things and I can have Bryan help you out.

Good Luck!!
Glenn

By the way, what does one use to cut the OC703?

OC703 rocks. It'll do WONDERS. Here are pics of mine:

http://www2.breakbeatmilitia.com:8090/gallery/listpics.asp?dir=Bass+Traps

I'm new to the whole bass trap acoustic treatments thing, but wouldn't most insulation be too thin (not dense enough) to actually curve any of the deep bass response? I believe it was on the home theater diy show they had some small sonotube filled with sand put into corners that helped them out with some nasty bass. Is there a preference or does one just straight out work better?

Sand would not do anything to absorb sound. Insulation works much better.

By the way, what does one use to cut the OC703?

A bread knife works WONDERS! Something with a long blade and far spaced teeth will work too.

http://images.amazon.com/images/P/B00091SD72.01.MZZZZZZZ.jpg

My two GIK 422 panels came in. After spending some quality time with them and my homebuilt R13 panel I got rid of all dips and peaks below 100 Hz. My homemade panel actually turned out to be more useful then I previously thought after I built a stand for it so I could space it away from the wall. I think with a few more simpler (and cheaper!) solutions I can get my basement theater to something I can be happy with.

I have noticed that solving problems with panels (or by opening doors to the room) also has the negative effect of lowering room gain. I guess there is no such thing as a free lunch. ;)

Could you show us the before/after graphs?

Nice work btw :)

Could you show us the before/after graphs?

Nice work btw :)

Thanks! I will post the before and after pics once I figure out how to get my plots off of my fiancee's laptop. The long and the short of it is that I used to have a deep and wide dip at 63 Hz and a medium wide and deep dip at 95 Hz. The 63 Hz dip is all but removed and the 95 Hz dip is much more narrow now. Resetting the BFD after adding treatments helped a lot too.

I figured I'd post a quick sketch of what my room looks like. Speakers and the screen are green, furniture is light blue, architectural features are dark blue and the panels are red.

Good job. No matter how you get there, getting your room to behave a bit better is one of the most cost effective improvements you'll make.

Bryan

Thanks! I will post the before and after pics once I figure out how to get my plots off of my fiancee's laptop. The long and the short of it is that I used to have a deep and wide dip at 63 Hz and a medium wide and deep dip at 95 Hz. The 63 Hz dip is all but removed and the 95 Hz dip is much more narrow now. Resetting the BFD after adding treatments helped a lot too.

I figured I'd post a quick sketch of what my room looks like. Speakers and the screen are green, furniture is light blue, architectural features are dark blue and the panels are red.

Maybe I'm a few months late, ...and this has nothing to do with your acoustic treatment, but do you have th ability to hang your rear left speaker from the ceiling or put it on a stand so that it will be closer to the couch like the right rear speaker?