Acoustical Treatment of Soffit

[RobP]

I would like to get some suggestions here, in the picture below there is a soffit face (colored in Pink) that I believe would benefit from some acoustic treatment. I would like to see what you guys think, absorbtion or diffusion, or a little of both? Or would it even make a difference?

[Chris D]

Hmmm... because it's the ceiling, not floor, I would venture a guess (and only a guess based on my amateur knowledge) that you'd want to put diffuser traps in that corner where the soffit meets the ceiling.

I'm going to sit here for a moment in awe of the drawing you made. (or stole)

[RobP]

I was thinking along the same lines, I am getting a ringing noise at certain frequencies that you can hear in that front area, plus it seems like the sound is somewhat "trapped sounding" if you sit behind the soffit, I may benefit from some diffusion on the bottom of the soffit as well, but, being that it hangs down 12" it may make the room feel really short under that area.
I just got my items the other day to complete my RTA and such, so I hope to get some time this weekend to take some measurements.

I made that little picture 8) , I was turned on to a little free program called Google Sketchup, its a really neat program. I have seen some impressive mock ups of peoples home theatre plans made with it. I put a link below if you want to try it out, maybe you could model up your new home theatre with it. :T

http://sketchup.google.com/download.html

[Chris D]

Hey, cool, I'll check it out! :T

[aud19]

That's beyond my meager expertise but good luck Robert :T

[RobP]

Thanks Jason!

[basementjack]

Hey soundgravy, did you get your RTA setup working?

Is the surface under the sofit drywall, If so I would think that's your biggest problem.

Generally you want to have a 'clear time window' of at about 1/100th of a second (10ms)

What this means is that you want ALL of your refections to arrive at your ears AT LEAST 10ms or later.

The time it takes for sound to leave your tweeter, hit that low sofit, and arrive to your ears is probably less than 5 ms, which is clouding the direct signal from the drivers to your ear.

On the other hand, sound that goes up at a 45 degree angle will likely take more than 5-10ms to reach your ears, and is also likely to make one reflection off the carpet on the floor.

So I would think your offenders are as follows:
1 ceiling (soffit)
2 side walls if your seat is far from the back wall
or
2 back wall if your seat is near

- Jack

[basementjack]

hey one more thing, you might find the program CARA to be really interesting.

It is not as cheap as sketchup (sketchup is free, CARA is $75)

but it models all sorts of acoustic properties.

I started to write a review on it, but I haven't finished it yet :-(
however there is some contact information on the review page:

http://www.acousticsoftwarereview.com/SoftwareReviews/CARA-Software-Review.htm

[RobP]

Hey Jack,

Thanks for the info! Ill look into CARA.I think Danish here has that program, maybe he can chime in and give some thoughts on it.

I actually just got my RTA up and running and did some initial measurements late last night, the response actually was not too bad at all. I hope to get a little more time to play with it this coming week. I think I will also try the Room EQ Wizzard software, I believe it allows for RT60 measurements.
The soffit is finished in drywall and I think you are right about the bottom surface being the culprit, I moved my seating position from behind the back of the soffit to right under the soffit and things improved, but I think it could be better. I do have treatments on the first reflection points, a heavy tapestry hanging in the center of the back wall, I also have bass traps in the corners in the front of the room as well as big fluffy furniture, so Im fairly good on the side walls and such.
If I do address any of this stuff right now it will be a temporary fix for I will be gutting the room hopefully within the upcoming year. There is another room behind this one, so I plan on knocking out the wall and turning the room around, so the soffit will be in the back of the room not the middle. Maybe a little easier to deal with.

[basementjack]

Wow sounds like you have a project ahead of you there!