DIY Acoustic Treatment Master Thread - Page 4

scott, the idea is that if you claim 100 +/-1 that is very different from claiming 100 +/-50. the variance (i.e. the +/-) is in many cases more informative than the mean/point estimate. aren't they teaching stats in secondary school anymore?

Posted already but here it is again...The link has all info you need.

Ah, gotcha.


Oh, yeah...about that....*ahem* I ditched a lot...must have missed that.

scott, i didn't mean my rant about the decline in quality of secondary education to be aimed at you. sorry if that is how it came off.

here is another interesting read:

http://downloads.bbc.co.uk/rd/pubs/reports/1992-11.pdf

An airspace behind the panel makes for better absorbtion. I think a 1" panel with a 3" airspace probably works better than a 3" thick panel that's against the wall. ( I'm guessing, but data is available I think.) A lot depends on what frequency range you are most concered about.

It's cool, brosky. I was just playin' anyway.

kbgl,

Thats just it, Iam not sure what frequency I should be worried about, or what material to choose and thickness as well as placement.

Penngray offered a wonderful resource but I dont know how to interpret those numbers and charts.

Thats why I posted pictures of my setup to see if I could get some recommendations based on the layout.

I will do my best to explain....



Here are the numbers for OC703 2"

Think of those numbers as percentages of absorbtion. OC703 2" will absorb 17% of the 125Hz frequency, 86% of the 250Hz frequency and so on. In the end all sound waves > 250Hz are being 100% absorb so you get no reflection from them.


Essentially you can use 2" oc703 or Rockwool 60 on the first reflection points (side wall and ceiling). Treatments on the front wall behind the speakers is a high priority too if you can do it.


btw, the master thread for all of this is found here.

http://www.avsforum.com/avs-vb/showthread.php?t=255432

All the experts are there too and they are extremely helpful.

Yes, this is used for the much lower frequencies.

+1 for the theory behind post #99.

As this is billed as the DIY Acoustic Treatment Master Thread, I assume that this is the correct place to post this...even though the thread is inactive???

I have read a lot of the posts on the AT Master thread and since I am not an engineer or really an audiophile, much of what is "discussed" there goes over my head. I think I have picked up the basics and would like some feedback on my plan.

I have an oddly shaped room and hope to improve the basic acoustics by placing some panels in the places usually suggested for calming first reflections and by building some corner base traps.

I am trying to come up with a simple construction plan using OC703 spray glued to some 1/4" plywood with significant cutouts to allow the sound to penetrate through to the void between the back of the OC703 and the wall. All of the edges, front and rear would have drywall corner bead on them to allow for an attractive and impact resistant corner to the acoustically transparent fabric covering for the front and all the sides.

I am not much of an artist, but here is a sketch of what I am thinking of doing:


So, the OC703 would have minimal plywood between it and the space behind it. The sides behind the absorbent material would be as open as possible yet covered with the cloth covering and the edges would be protected by the corner bead. In order to maximize the benefit of the absorber the sides would not be covered by a reflective wooden frame.

Am I headed the correct direction? From what I have read and the examples I have seen, I think so. BUT...I have been known to be pretty thick sometime.

Thanks for your patience.

Looks like a good plan to me, except I'm just wondering why the 1/4" ply on the back? Is this to attach the standoffs to the panel?

RyguyOK,

Yes, the idea of the 1/4" plywood is just to give me something substantial to attach the standoffs to and to hook some sort of attachment method to.

Haha, I forgot I even made that thread!

Hi there...I'm building/treating a Basement area for a home recording studio and noticed you are in Richmond,Va. I,m looking for someone local to help or consult me on this. Please e-mail me at soulshaker8@yahoo.com. Thanks for your time and expertise,

Jason

http://www.amazon.com/s/ref=nb_sb_ss_i_0_13?url=search-alias%3Dstripbooks&field-keywords=alton+everest&sprefix=alton+everest%2Cstripbooks%2C216

Seems to me that the first two books listed under Alton Everest would be of great interest.

If nothing else, it'll tell you why Nick put that perforated plywood in his panels.

HAve fun,
Frank
Edited by fbov - 7/23/12 at 12:19pm

why not use fabric on the back and maybe some door stops for stand offs? the 1/4 ply is going to reflect sound no matter how many holes you drill in it. not to mention its a lot more work.

Update: To follow up on the posts I made a while back with my plans for DIY acoustic paneIs, figured that I would explain where I am at this point.

>>>>>>>>>>>>>>>>>>
I finally found the time to try to put together one absorber panel and found out some interesting points with regard to the physical construction that surprised me.

The OC703 is heavier than I expected and the 1/4 plywood was more flexible than I counted on. As a result, when trying to move the 2' wide 8' long assembly, it flexed all over the place and made it difficult for the spray adhesive I used to attach the OC703 to the plywood to maintain its grip.

This is a photo of the plywood (with 3 large areas cut out) with the ripped down 2-bys attached to the back.


I ended up ripping down some additional 2-by-4s to about 1 1/2" to place between the horizontal pieces to give the unit some structural rigidity and yet leave the sides partly open.

I attached plastic drywall corner bead to all the edges so there would be a clean edge all the way around for the fabric covering.

The photo below is taken while the unit was still on the work table (face down).


I have placed the unit in the theater, but have not had the time to evaluate its impact on the sound in the room. Our room has a curved back wall with a short radius, so I know the room needs serious treatment, but I don't have the knowledge to approach it very scientifically.

I have actually come to the conclusion that some of the professionals are scared away by the shape of our room, as I have e-mailed and called a few who have never gotten back to me...(and I was not asking for free services)!

With regard to the post suggesting using fabric on the back and perhaps door stops as stand offs, if I understand the suggestion correctly, I think that the weight of the OC703 would make that unfeasible. Please correct me if I am wrong - I am all for easier-cheaper-lighter!!

If you were planning to attach the 703 at the edges, your plan was doomed. It's not sructural at all! Thankfully, it works fine with support, so keep at it.

I saw the "1/4" plywood with many holes" looking more like pegboard, not a window. Pegboard is the way you actually support OC703 without affecting it's sound absorbing properties. The link, below, is a BBC report on development of a broadband absorber with good low frequency performance. Figure 16 shows the affect of 20% perforated board as a front panel over no front panel. Figure 18 shows construction details, including two options for retainng the absorbant (they are using rockwool).
http://downloads.bbc.co.uk/rd/pubs/reports/1992-11.pdf

Have fun,
Frank