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Guidelines for treating cathedral ceilings

My listening room is 18' wide x 18.5' deep, with a cathedral ceiling symmetrically over the room.
I have done the 'standard' room treatments (absorption behind the speakers and listening seats, and absorption at the first reflection points on the side walls). Absorption is 2" thick Owens Corning 703 fiberglass.

However, I am still hearing a sharp slap echo when I clap my hands in the room. I am beginning to suspect some sort of ceiling or upper corner interaction. Is there any rule of thumb for where to first start with a treating a cathedral ceiling? I am a little bit surprised, since the ceiling is angled and does not present two parallel surfaces for sound to bounce off of.

The practical concern is some sibillance when playing certain CDs at high volumes (possibly exciting something in the room and exaggerating the treble?).

thanks in advance,
Bill

(I hope this drawing comes through OK- the A is the top of the ceiling, and the two S are the speakers).

.......................A
.................... /....\
................./.............\
............../...................\
.........../..........................\
...........|...........................|
...........|...........................|
...........|...........................|
...........|.....S...............S.....|
............ --------------------------
gnobber
gnobber OP
43 posts
 
To answer Newbee's question, I get the flutter echo pretty much everywhere in the room. I did have my wife clap at the speakers while I sat in the listening chair- pretty much the same results as anywhere else.

I have a plush carpet with 1/2" pad througout, so no hardwood floor interactions.

I haven't been able to pinpoint the source. I have some 1" styrofoam sheets (4'x4') that I can hold up in various places to do a 'clapping' experiment. So far no smoking gun, although I used this technique in another room and was able to tame it almost completely. I guess my next move is to try climbing a ladder and blocking various spots up near the peak, or maybe the high corners . . .
newbee
4,767 posts
 
I'm not sure I have a solution, but I have an experience to share which might bare some light - I worked in an office with a high pyramid ceiling. The sound all along the outside walls (the executives offices) followed the roof line and focused at the cented and beamed down in to the center of the office (the secretarial pool). Boy was that fun!. So its possible your hand clap is bouncing off the ceiling and due to the distance travelled it would be clearly heard. Try the hand clap experiment with a piece of deadening materiel held between the clapper and the ceiling. If you don't have an echo you've found your problem and can focus on what you can do to fix it....keep us posted.
theaudiotweak
2,795 posts
 
I recently have fixed a room such as the one you describe.You probably have a foam pad under your carpet. Replace the foam pad with a natural fiber pad. The panels can be made to look like large eyebrows high up on the wall behind the speakers. They can be designed to follow the angle of the roof line and can be covered with cloth to match the painted wall. You can do much the same for the rear panels as well. These panels need to be about 6ft in height and 24 to 36 inches in width, the bottom of which should be placed slightly above the television that is compounding your problem. Better than fiberglass is natural longhair carded wool. The wool is much more linear in its absorption rate than fiberglass..Wool has less suckout and will give you smoother overall response. The problem is on your walls and not your ceiling. The problem is above 4 ft and beyond. Tom
mejames
986 posts
 
its the upper corners of the room where the walls meet the ceiling causing the majority of the echo you are hearing trust me get the MICHAEL GREEN DESIGNS PZC corner controllers which are easily adjusted will totally alleviate the echo. Believe their is a review on Audio asylum
theaudiotweak
2,795 posts
 
Pzc controllers do not have enough surface area to even budge the problem. The angled ceiling is reflecting energy back into the listening room which is also a good thing. The problem lies between the front flat wall surface and the rear flat wall surface. Other than designing a multi angular cantilevered attachment to both front and rear walls the dampening panels offer the most cost effective approach..Tom
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