Max distance of traps from walls before it becomes inefficient? - Gearslutz.com
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666666
#1
19th May 2013
19th May 2013
#1
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Joined: Jan 2005
Location: Long Island, NY
Posts: 2,969

Max distance of traps from walls before it becomes inefficient?

Let's say you have a bass trap made of 4" thick of OC 703.

You can affix it directly to the wall surface... or space it out from the wall by a given amount. As I understand, in general, the more you space the trap out from the wall, the better it will perform... will reach down to lower frequencies.

Of course there is a practical limit as to how far you're going to be able to space traps out from the walls due to space limitations. But for now let's assume space is not an issue.

So for a 4" thick 703 trap, is there a point of "diminishing returns" in terms of the spacing from the walls? Like, for instance, perhaps a 4" trap will perform "optimally" at 12" from the wall, but at 24" will not perform much better than at 12" ?

I'd imagine that, in general, the farther from the wall, the better... always. But remember, we're just talking about a 4" trap here... with no other insulation behind it. I'd think that as you space the 4" trap out from the wall farther and farther, there would come a point where, for things to be truly efficient, the trap should be thicker. In other words, perhaps for spacings 12" and under, a 4" trap is "ideal", and for spacings 12" - 24", a 6" or 8" trap would be ideal. etc.

I'm just messing around with some ideas for using 4" OC 703 traps possibly as partitions / dividers or closet doors etc where they might be anywhere from 18" or more from walls... and wondering how to take the most advantage. Depending on distance, maybe it pays to add another 2" layer of 703, or...?

Well, I suppose that another general rule might be, for 703 traps, thicker is always better. But again, I'd imagine, per the situation, there comes a point of inefficiency / diminishing returns, etc.

Anyway, just thought I'd throw this out to be kicked around. Didn't know if there might be a "rule" that designates optimum thickness for rigid fiberglass depending on distance from walls.
DanDan
#2
20th May 2013
20th May 2013
#2
Lives for gear

Joined: Aug 2003
Location: Cork Ireland
Posts: 9,823

Worthy questions. Q 4 Avare
The one factor you haven't mentioned is surface area. In particular surface area of the trap in comparison with the wavelengths of sound of interest. If they are not of the same order the LF wave will simply sail by the trap unhindered.
You can calculate the likely behaviour of fibre with gap. But note this presumes a full surface area. i.e. A Wall of fibre.
Porous Absorber Calculator - Results
The classic suspended ceiling is an example of a whole boundary of fibre. It is very effective broadband absorber, down to LF.
Typically 16:1 Gap to Fibre.
DD
666666
#3
20th May 2013
20th May 2013
#3
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Joined: Jan 2005
Location: Long Island, NY
Posts: 2,969

Thank you

Excellent point about the surface area

As for the surface area here... well, in the specific instances I may be dealing with at this time, the short measurement would be about 4 feet... in one instance I believe the total surface area may be a rectangle of about 4' x 8' in size.

When dealing with rectangular surface area, I am guessing that the effective trapping area will be limited by the short side... in this case 4'. Then again, the long side must be grabbing at least part of the 8 foot waves, yes? Perhaps partial trapping of the 8 foot waves?
DanDan
#4
20th May 2013
20th May 2013
#4
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Joined: Aug 2003
Location: Cork Ireland
Posts: 9,823

I am quite sure an 8 foot area would have a significant effect on wavelengths longer than 8 feet. There are probably rules of thumb, but IMO of little consequence when we usually just do as much as we can. Bigger is simply always better in terms of LF absorption. Luckily there are some free lunches. e.g. Corner placement multiplies the LF absorption by about 3 times.
Also, the edges of traps have an effect of their own. If possible I like to leave a gap of say 6 inches between 2x4 traps to avail of edge effects.

DD
#5
21st May 2013
21st May 2013
#5
Gear interested

Joined: May 2013
Posts: 22

Hey guys i have a similar question.
I have ordered giks 24r panels for side reflections.
On my left side wall the panels will stand on a wooden stand 1 meter from the wall.
On my right side they will be on a stand again but since on this side is the kitchen (living room and kitchen are one room ) the panels will be about 3 to 4 meters from the wall. Is this a problem?
21st May 2013
#6
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Joined: May 2012
Posts: 1,781

Quote:
Originally Posted by 666666
Thank you

Excellent point about the surface area

As for the surface area here... well, in the specific instances I may be dealing with at this time, the short measurement would be about 4 feet... in one instance I believe the total surface area may be a rectangle of about 4' x 8' in size.

When dealing with rectangular surface area, I am guessing that the effective trapping area will be limited by the short side... in this case 4'. Then again, the long side must be grabbing at least part of the 8 foot waves, yes? Perhaps partial trapping of the 8 foot waves?
There is also a small gain for the hypotenuse of the rectangle, 4x8 having about a 9 foot hypotenuse. 4 feet is where the trap's effectiveness drops off the fastest.
#7
22nd May 2013
22nd May 2013
#7
Gear interested

Joined: May 2013
Posts: 22

Quote:
Originally Posted by hamurabi
Hey guys i have a similar question.
I have ordered giks 24r panels for side reflections.
On my left side wall the panels will stand on a wooden stand 1 meter from the wall.
On my right side they will be on a stand again but since on this side is the kitchen (living room and kitchen are one room ) the panels will be about 3 to 4 meters from the wall. Is this a problem?
DanDan
#8
22nd May 2013
22nd May 2013
#8
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Joined: Aug 2003
Location: Cork Ireland
Posts: 9,823

Guessing

More details would help an educated guess. But it is constantly humbling to find that testing really does deliver a better result than just listening or let's face it, guessing.
You may have to move those traps different distances from your ears to achieve an acoustic balance, as opposed to a visual one.
DD