[Russtafarian]

I’m about to put together some corner traps and would like some feedback on what I’m thinking about doing.  The primary room-boom culprit in my 16x20x8 foot room is 71Hz.  Because of the room layout, I can’t get any traps into the four corners of the room except within a foot of the ceiling.  So I’m thinking of making four 15”x48” triangle traps that will flush into each ceiling corner and extend out along short wall-ceiling junction.

I have four 4x2x2” mineral wool panels to work with.  For each trap I can slice the panel lengthwise at a width 15” and a 45 degree angle then stack the two pieces.  After some trimming I’ll have a 48” long, 4” thick panel with 45 degree sides that vary in width from 15” to 9”.  When mounted there will be 9”x7”x7” airspace between the panel and the wall-ceiling junction for the length of the panel.

My questions: 

Will four of these 48”x15”x4” ceiling corner mounted panels be enough to get any significant absorption at 71Hz? 

With the same 15"x48" footprint, would it be better to add another 2" of insulation thickness and decrease the airspace behind the panel?

Would it help to mount a thin piece of pressboard behind the insulation to act as a membrane resonator?

Is there any benefit to using aluminum foil between and/or behind the stacked pieces of insulation?

Any other thoughts or comments?

Thanks.

Russ

[bpape]

For less material you can do a 17x17x24" triangle chunk.  1 piece of 2" thickness will give you 16" of height.  The foil will do nothing between layers. If, however you put it on the face, it will restrict how much of the mid and high frequencies are absorbed.

Just understand that your 71hz issue may have nothing to do with the corners of the room.

Bryan

[MaxCast]

For less material you can do a 17x17x24" triangle chunk.  1 piece of 2" thickness will give you 16" of height.  The foil will do nothing between layers. If, however you put it on the face, it will restrict how much of the mid and high frequencies are absorbed.

Just understand that your 71hz issue may have nothing to do with the corners of the room.

Bryan

If the 71hz does not have anything to do with the corners of the room, how do you treat the 71hz?

[bpape]

Depends on what's causing it 

Seriously, if it's seating position related and has to do with the length, you can address the wall behind the listener.  If it's height related, you can address it on the ceiling over the seating position. 

If it's a diagonal mode and you can only deal with the top foot or so of the corner, you may have to physically move the seating and/or move the speakers/sub to get them in a position to deliberately create an opposing dip in response around that frequency to try to compensate that way.

Bryan

[Russtafarian]

Thanks Bryan.  The triangle chunk sounds like a good idea.  It should be easy enough to frame and mount it.