bass trap placement

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dobro

dobro

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1 I keep reading that corners are the best place for bass traps, but I see pictures of rectangular traps placed along walls and ceilings. Why's that?

2 As for the bass traps that go into the corners, should they be flat against the wall, or angled at 45 degrees? It seems to me that angled would be better, but the reason I'm asking is cuz I don't know.

3 Okay, if the place where a two walls and ceiling meet (or two walls and a floor) is the place where bass buildup is worst, what about tetrahedron traps just for those eight places in the room? Dumb idea? Difficult to build?
 
Dobro,
Yeah the corners are where the bass really builds up. Crank up some music, walk around the room then stand in the corner. You'll definitely feel it there. As far as how to treat the corner, some (like myself) placed the trap across the corner because it's cheaper :D You also get more distance, therefore lower bass response, between the trap and surface behind the trap. Oh yeah, I used 2" Knauf rigid insulation here. I couldn't find Owens Corning 703 locally. The reason you see the traps butting against each other in a corner (rather than placed across the corner) is because the more square footage of wall you cover, the more effect you'll have.

To me, the traps mounted at different places on the walls are for diffusion. I had a serious problem with ringing between two parallel walls in my live room. Sounded like a "byoooonnngggg" when I clapped two pieces of wood together. By placing the traps (oops diffusors) on just one wall with two feet between each one I totally eliminated the ringing. I made the diffusors with 2' x 4' x 1/8" board (like shop peg board) with 1" foil backed Knauf rigid insulation glued to the board. Still haven't covered it but I have some beige burlap I'll be using. The effect was immediate. The only reason I used the foil backed is because it's all that's available locally. It's also a good surface for glueing.

I've seen pics of traps butting together at the wall/ceiling point. Remember that's a corner too, it's just kinda sideways.

You'll be surprised the difference it'll make just doing your four corners and a few pieces placed on one wall of two opposing parallel walls. You don't have to treat both parallel walls unless you're really trying to kill the room. I didn't want the room dead, just more balanced.

DD
 
Dobro,

> I see pictures of rectangular traps placed along walls and ceilings. Why's that? <

Yes, corners are the best place to put bass traps. But when all the corners are filled and you still have problems, more traps can be placed on the walls. Another reason you may see bass traps flat on the walls is because the people who put them there didn't know any better. I am serious. For some reason, acoustics eludes a lot of people who are otherwise knowledgeable about audio. But knowing where to install bass traps is far simpler than knowing how to align a 2-inch 24 track!

> As for the bass traps that go into the corners, should they be flat against the wall, or angled at 45 degrees? <

It depends on the type of bass trap. Wood panel traps work best when mounted near a room boundary (flat on the walls). Porous absorbers like fiberglass and foam work best with some air space behind them, such as when straddling a corner.

> what about tetrahedron traps <

Sure, but a special design like that is not really needed. A 2x4 foot panel mounted across the tri-corner does a fine job.

--Ethan
 
Don, Ethan - thanks a lot - you answered the questions that came up after three hours of online reading about bass traps.

Time for more reading now. Then build!
 
Ethan,

Do your minitraps qualify as a wood panel trap, or a porous absorber, or something entirely different?

What is the best way to install a minitrap, flat to the wall, or across the corner?

Just curious.:)
 
Dethska,

> Do your minitraps qualify as a wood panel trap, or a porous absorber, or something entirely different? <

They're sort of a hybrid between a membrane bass trap and a rigid fiberglass panel absorber. They do use rigid fiberglasss to absorb mid and high frequencies, but there's also a membrane inside that enhances low frequency absorption substantially.

> What is the best way to install a minitrap, flat to the wall, or across the corner? <

Depends on what you're trying to accomplish. For bass trapping, MiniTraps are always best mounted across corners. For general ambience and echo reduction they can be placed flat on a wall. In practice, once you put an appropriate number of MiniTraps in the corners as shown on the Placing MiniTraps page of our site, that solves all the mid/high problems too. But if there are large areas of bare wall, then a few more may be needed on the walls too.

--Ethan
 
Ethan,

I've been meaning to ask you for about a week now... can you make (well, its more like would you make :D) mini traps for a shorter than 48" dimension?

I have a short wall with a slanted ceiling, and the height is 38 or 39 inches or thereabouts.

I could in theory make them but...

Let me know at your convienence.
 
Frederic,

> can you make ... mini traps for a shorter than 48" dimension? <

We could make other sizes but it's just not practical. In fact, if we made smaller versions we'd have to charge even more than for the 2x4 size because it would be more work. 2x4 MiniTraps can fit into lots of places you might not think they'd fit. You can always prop then at an angle or, better, put them in the ceiling corners.

--Ethan
 
Hmmmm...

So they would be fairly effective angled?

I asked because I had the impression they had to have the edges (or most of them) resting on the walls, at an angle, so there is volume behind them. If they lean off, then the volume of air behind them obviously is more shared with the rest of the room.

Obviously, I don't understand how these types of traps work. I shall research and get a clue :)

The wall is 38 or so inches high, so I guess I'd touch the top of the trap to the upper corner, and angle out on the bottom? Or the reverse?

Hmmmm

Thanks for the info Ethan, always appreciated.
 
Frederic,

> I had the impression they had to have the edges (or most of them) resting on the walls, at an angle, so there is volume behind them. <

I guess I'd need to see a photo to know exactly how your room is laid out, and what you mean by 38 inches high. But in general, the three rules for bass traps are:

1. Get enough of them.
2. Put them all in corners.
3. Spread them evenly around the room as best as you can.

--Ethan
 
I live in Singapore. I've been phoning around and asking people if they sell 'rigid styrofoam' and they all draw blank. What's the usual thing rigid styrofoam is used for in the US? Is it used for heating insulation or something? If so, that would explain why it's hard to find here LOL.
 
How about rigid fiberglass Dobro. Styrofoam is for beer drinking cups ;)



SoMm
 
At my age, anything I can get "rigid" makes it a GOOD day... :=)
 
ROFL. Isn't all stryrofoam rigid? ;)

For some reason today I was wondering about the effectiveness of a triangle corner trap. I'll have to do some calculations but I wonder if you get more volume behind the absorber with less intrusion into the studio by taking a large triangle and mounting it in the corner. Has anyone done any calculations on that?
 
I'm just getting into this area, and I know nothing, but that's usually the case with me, right? :D

I seem to remember one of Ethan Winer's articles on corner absorbers saying one of the things that made them effective was the fact that the space behind them varied, so they were effective over a broader frequency range. Makes sense to me. But that would also mean that the larger the triangle (ie the wider the piece of fibreglass) the better, right? Two feet wide: good. Three feet wide: better, and so on...

Anyway, what do you mean by 'a large triangle'? You mean a triangular box - the whole thing made of plywood?
 
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