Corner Trap dimensions and effectiveness

M

mta250

New member
Hey everyone - i'm getting ready to buy my first pair of monitors (adam a7s), but i obviously want to treat my room to get the most out of them at the same time.

i'm going to diy the treatment myself (which i have some experience with), but i had a question about the relationship between corner trap dimensions, coverage, and effectiveness.

I plan on making corner traps out of 703 or an equivalent material, by cutting it into triangles and stacking them together to make a "superchunk" style trap. i'm not sure how deep to make these triangles though.

using a typical 2'x4'x2" panel of 703, i could cut it into 4 or 8 triangles. This would create triangles of dimensions 24"x24"x34" (which has a depth from the face to the corner of 17") - or - 17"x17"x24" (which has a depth from the face to the corner of 12"), respectively. (if this is a bit confusing the way i wrote it, i can try to post some drawings of my ideas)

Which would be more effective? Creating deeper superchunks to fill the corners, or having twice as much corner coverage (or more money to spend treating other areas of the room)?

I do want to add more (non-corner based) bass traps - probably 4" thick 703 panels - as funds permit.

Also, besides this treatment, I have two framed 2'x4'x5" panels consisting of a two 1" 703 panel sandwiching a 3" air gap, which I plan on using at the first reflection point. Also, I have four 8'x2'x1" panels of framed 703 hinged together accordian style to act as a gobo to change the reflectiveness of areas as needed. Additionally, I plan on eventually adding a krk ergo to compensate for the problems inherent in the less than ideal (read: symmetrical) situation i currently have to work with (living in an apartment, unable to create permanent installations). Any advice/criticism/etc. of my plans would be greatly appreciated.

Sorry for the lengthy post - I just wanted to be clear!
Thanks in advance for your help and time!

-Mike
 
Last edited:
mta250 said:
using a typical 2'x4'x2" panel of 703, i could cut it into 4 or 8 triangles. This would create triangles of dimensions 24"x24"x34" (which has a depth from the face to the corner of 12") - or - 17"x17"x24" (which has a depth from the face to the corner of 12"), respectively ... Which would be more effective? Creating deeper superchunks to fill the corners, or having twice as much corner coverage (or more money to spend treating other areas of the room)?
Click to expand...

More surface coverage is always better, assuming panels reasonably thick such as 4 inches. If you have the room for 34 inches wide I'd go for it. That's exactly the width of our MegaTraps. (Sorry, couldn't resist.)

--Ethan
 
great! thanks for the replies!
i realized i made a little typo in the depths - which are 17" and 12" respectively, not 12" and 12" haha.
Either way, it seems the consensus is that its all good - the more the better.

Thanks again!
 
The ones I built were 17 by 17 by 24. Work just fine. 34 was gonna take up too much real estate for my taste.

(couldn't resist either ;) )
 
More surface coverage is always better, assuming panels reasonably thick such as 4 inches.
Click to expand...
Hey Ethan, what does the thickness have to do with it? If you are cutting triangles from 2'x4' panels, and stacking them, who cares? You could use 2" thick panels...although it would take TWICE as many.:eek::p Now, if you were placeing the panels DIAGONALLY across the corner...well, thats an entirely different animal.;) Which is something I've wondered about. At least considering this...

Here is a comparison test curtesy of Studiotips(hope I don't piss Eric off:p)

is.php

is.php



http://forum.studiotips.com/viewtopic.php?f=8&t=536


What these results show to me, is the drop off from 100hz to 125hz in Sabins
and the cost it requires to gain that extra absorption in that relatively narrow band, seems to be extrodinarily expensive, at least for my pocketbook.:D Considering it takes (6) 2'x4' panels of 4" thick 703, to make 1 corner superchunk vs doing this....
is.php

is.php

is.php



Assuming 4" thick 703....
For Panel A(front) it takes (8) 2'x4' panels, and for Panel B, considering you can get (3) 16"x24" pieces from a 2'x4' panel, and it takes 4 per corner, that equals 16 pieces cut from 6 panels, with 2 pieces left over.

So, do the math. To get ALMOST the same absorption, using my method only takes (14) 2'x4' panels.......VS (24) 2'x4' panels to make 4 Superchunks..:eek: Not to mention the time it takes to cut all those triangles.

Considering it takes (24) panels to make 4 Superchunks:eek:..I don't know about your pocketbook, but mine is rolling its eyes.:D I don't know what 703 costs anymore...but I'd submit, you'd save enough to buy a new toy for the studio:laughings: That is unless you can afford that little bit of extra absorption and the new toy.;)
fitZ
 
RICK FITZPATRICK said:
what does the thickness have to do with it? If you are cutting triangles from 2'x4' panels, and stacking them, who cares?
Click to expand...

I was speaking generically. It's much better to have, say, 20 square feet of surface done with 4-inch thick panels, versus 1/4 that much surface but with the corners filled.

--Ethan
 
also, just a quick note to clear things up for anyone else that is reading this...

the thickness i was referring to is the thickness of the superchunks (or, the height of the cut triangles), not the thickness of the panels i was cutting the triangles from.
 
The above idea of stacking panels to build a corner trap can be improved in several ways. Here we consider using 4" thick absorber 24"x48" sheets.

1) Instead of cutting a 24x48 sheet into 3 24x16 panels, and using only 2 of them to make a 48x16 panel, it is simpler to cut a 24x48 sheet into a 16x48 panel and a 8x48 panel. The 8x48 panel can be added to the chunk in between the corner and the 16x48 panel.

This way, 12" thick, 8' high corner trap exhibiting a 24" wide front is built from only 4 sheets, using only 2 cuts.

2) Can also add an outer 32x48 layer, using 3 extra sheets, as illustrated in the attached diagrams. So a 16" thick corner trap exhibiting a 32" wide front can be made using 7 sheets and only 5 cuts
SheetCuts.jpg
Panels.jpg
StackedPanels.jpg


If thinner sheets are used, 2" for instance, either we use the same cutting layout as shown above, but cutting two sheets together, and we continue to use 4" thick stacked panels.

Another way is to use the following successive panel width, 32, 28, 24, 20, 16, 12, 8, 4. I won't discuss the cutting layout of the 24x48 sheets in details, just saying that we can cut 24 along the 48 direction into 20 & 4, 16 & 8, 12 & 12, while the larger panels are created by cutting sheets along the 24 direction.

Since the empty triangles in between walls and panels are located where air flow velocity is small, this stacked panel approach to build corner traps is likely to be almost as acoustically efficient as the superchunk technique. Also worth noting that the front of this corner trap is located further away into the room than the front of a superchunk of same front width, precisely where airflow velocity is the highest. This also improves the efficiency of the approach
 
The above idea of stacking panels to build a corner trap can be improved in several ways.
Click to expand...
:cool: Welcome to the bbs mhch. Always nice to see a different/better way to do things.

Since the empty triangles in between walls and panels are located where air flow velocity is small,
Click to expand...
Just curious. Why would the velocity be any different there than at the face of the outer panel? Does something tell the traveling wave there is a void there?:D From my understanding, that is an area where diffraction occurs. So why would the "velocity" change?
 
For the same reason, panel traps parallel to a wall are more effective when there is an air gap in between them and the wall vs. when they are installed against the wall.

The perpendicular to the wall part of the air flow velocity is null at the wall/air boundary, isn'it ? because the wall is a fixed boundary. But it is true that the tangential part may be non-null.
 
Last edited:
Some quick thoughts about the framing.

The idea is to build staircase like wood pieces as shown in the sketchup drawing below. Two such pieces are screwed to the wall forming a kind of square. probably need one such square per 48" high panel, so 2 for each corner trap.

Panels are installed one at a time, smallest first, each secured with a small wire running across the panel between the two branches.

Then the external frame plus fabrics can be attached to the visible side of the squares.

One nice thing about this approach is that such corner traps could easily be installed at ceiling/wall corners, since the building is incremental, one 24"x48" panel added at a time !!

StaircaseFraming.jpg
 
Just to mention that the triangular pieces can be smaller. No need for a 4"x4"x (4"*sqrt(2)). Just enough to hold a panel then secure it with a wire.

Can also use a 1"x2" cut at a 45 degree angle at each end (same shape as the 30 1/64" but much shorter).
 
Bass traps

Hi Everyone, I guess my post will be classified a a newbie. (◕‿-)
Thanks for the information posted here...
Rick, I realize it has been a while since this post...but do you have test results of your approach? Did you or will you post them?
Etan, I appreciate your post as well.
I am dealing with a budget studio for a friend's control room that has the following:
1017 ft3, Room Fc of 143 Hz, Ceiling 7'4". (Obviously, typical modes for those dimensions).
Dominate standing waves are ~ 89 Hz and pretty bad from 150-250 Hz.
My questions are:
1. Is it worthwhile in such a small space to lean toward tuned (Helmholtz/slat) absorbers in addition to corner traps?
2. Are the cost of tuned absorbers an effective cost-to-performance trade off?

Thanks for allowing me to join this group. I have strong expertise in designing electronics and extensive system design experience if I can assist anyone.
 
Rick, I realize it has been a while since this post...but do you have test results of your approach?
Click to expand...


:eek: You got to be kidding.:laughings: Me? Hardly. My "opinion" is classified under my disclaimer.:D In reality...I posted this as an alternative to full Superchunks via a perceived "gut feeling"...in my less than deep pockets.:D HOWEVER, there are a few members over at Studiotips that recommend this approach when your pockets are only as deep as mine.:p So there you have it.


1. Is it worthwhile in such a small space to lean toward tuned (Helmholtz/slat) absorbers in addition to corner traps?
2. Are the cost of tuned absorbers an effective cost-to-performance trade off?
Click to expand...
Note..My disclaimer is in full force...ie...I ain't no expert.
1. From my "understanding", generally, no. See note.
2. It depends on a few things. Like how deep your pockets are vs what you demand from your room response. :D Again..see note.
 
As Ethan has said broadband is the way to go. If you can not afford the space, use a heavy mass membrane type to get those pesky frequencies below 100Hz. But know this, if your walls are gypsum board, they may already offer absorption below 100Hz. Test to find out. - If your construction is solid concrete, you'll need this.

Rick, you have an excellent point that I often try to express - cost-effectiveness. This is very important for most musician owned studios as they must make every penny count.
The absorption value of a superchunk style trap compared to the double corner panel that you had drawn would be interesting to see. I would venture a guess that your trap would have an absorption coefficient very, very close to the value of the 'superchunk'. In fact is is documented that an air space behind absorbent will act with the absorbent to increase it's coefficient. (Master Handbook of Acoustics, Acoustic Absorbers & Diffusors... Andre Vare's papers & posts...)
As Broadband absorbers, they will follow the 1/4 wavelength = LF cut-off, so make them as large as you can afford the space.

Cheers,
John
 
You must log in or register to reply here.
Back
Top