[Housteau]

This is a two part question. 

First off, I was looking at some plans for built-in corner bass traps and wanted an opinion of them.  Basically they stretch across the corner as a sealed air-tight triangular structure with the existing walls being used for two of the sides.  The side open to the room cuts across the corner 2' out from each wall going from floor to ceiling, or approximately 8' tall.  All three of the inside surfaces including the tops and bottom are lined with 2" ridged fiberglass (you could use 1" for the side facing out into the room).  The side open to the room is then sealed with a decent ply of Mylar, or plastic over the fiberglass to make the structure air tight.  To finish them off a fabric covered grill is then added to the front.  How effective would these be and are the dimensions of this trap specific to a particular room and it's dimensions?  In other words would there be an ideal dimension I could built them to suit my 15.3' x 21.7' x 10' (12' cathedral, 10' average) room?  It did not mention that.

Since I have a cathedral ceiling I do not have parallel surfaces floor to ceiling.  Still, I was thinking about building some simple diffusers that I could hang overhead.  I was thinking about something very simple such as a series of 1 x 3" boards forming a grid that would hang close to the ceiling peak, but parallel to the floor.  This way sound reflected downward from my cathedrals angle would interact with the parallel grid also striking it at an angle.  Some sound coming from below would interact with grid, while the rest would pass through and reflect back down as in the previous example.  Any thoughts.

Dave

[bpape]

The purely membrane type absorber you describe for the corner can be very effective.  However, it's going to operate over a limited range - this is just how that design works.  If you're not wanting to absorb highs as much, IMO, 4" of OC 703 or mineral wool with an FSK facing toward the room will work over a much broader range in the bass.

As for the ceiling, if I understand you correctly, I think it would be more effective to do something similar to the corners - just run some faced 703 parallel with the floor but straddling the peak. 

Bryan

[Housteau]

So, you are saying that a flat panel of 703 straddling the corner would work over a broader range of bass than the built in unit I have described?  I guess that answers my one question about if the design was room specific.  If that is the case, what determines it's range of absorption and with the dimension I have provided, what would a unit like this do in my room?  Another way to phrase this would be, what should the dimensions be to work best in my room?  I have the speakers set-up along the long wall.  The cathedral peak also run between the long walls.

With the ceiling diffuser I was thinking about just redirecting the energy and not absorbing it.

Dave

[bpape]

You MAY get some benefit from the diffusor up hight bu tnot sure how what you described will work.

As for the corner absorber, any time you deal with a membrane (sealed), you're going to get limited range - that's just how they function.  If your room has specific issues that you want to tune some for, that's great.  I'm just saying that almost all rooms can benefit from SOME broadband bass absorbtion prior to trying to tune for specific issues.

Bryan