# Acoustic Treatment for a soffit...



## byancey (Jun 29, 2014)

I'm in the process of adding acoustic treatments to my 20'x15' home theater. At this point I've added a false wall 2' from the original wall, installed a super chunk bass trap in the front right corner and added a 6" layer of mineral wool over the entire front wall.

I'm in the process of adding 1" OC-703 with a 1" air gap over about 75% of the side walls, and I also have enough OC-703 to treat the first reflection point on the ceiling for both rows of seating as well as the bottom of a soffit that runs the full length of the room along the right wall.

That soffit seems to be the source of a pretty severe reverberating echo in the room. I've read that it's always good to treat the bottom of any soffit in a theater room, and if I hold an acoustic panel to the bottom of the soffit, I do indeed notice an improvement in the clap echo. However, I was playing with placement of one of the panels and noticed that spanning the upper corner along the edge of the soffit actually seems to be more effective than just placing the OC-703 on the bottom of the soffit. If I don't treat the bottom of the soffit, I have enough material to actually do a double layer (2" thick) spanning that upper corner. I wonder if that won't address the echo problem while potentially providing some additional bass trapping at the same time.

Here's my best attempt to represent what I'm talking about with ASCII art:


```
---------------
        | /  <-- span this corner here
-------
|  ^^   
|     or treat the bottom side here.
```
Any reason not to simply span the upper corner of the soffit rather than treating the bottom of the soffit?

Thanks!

--
Bryce


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## bpape (Sep 14, 2006)

No problem at all to do that. Straddling will always go lower than being flat on a surface. That said, don't expect miracles with 2" thickness in terms of how low it will go.

I would watch doing that much of the wall surface with something that thin (1"). That's way way too much upper mid and high absorption.


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## byancey (Jun 29, 2014)

bpape said:


> No problem at all to do that. Straddling will always go lower than being flat on a surface. That said, don't expect miracles with 2" thickness in terms of how low it will go.


WAF is limiting how many "visible" bass traps I can install, hence the front false wall with as much thickness as I could manage behind it and still be able to navigate the space.  Treating the soffit is mostly to address the reverb problems at the mid-to-high frequencies, but I figure if I can get even limited additional trapping in the lower frequencies, it's a bonus. Amazingly, when I held one of my panels across the span, the wife was OK with it, and actually seemed to prefer that approach to dangling something from the ceiling.



> I would watch doing that much of the wall surface with something that thin (1"). That's way way too much upper mid and high absorption.


I should clarify that I'm not actually treating 75% of the sides walls, rather, I'm treating roughly 75% of the length of the wall from a few inches off the ground to just above ear level...and now that I do the math, it's actually 12' out of 20' I'm treating, which is 60%, or roughly 30% total coverage on those walls. Based on what I've read here and over in AVSForums, I'm assuming I'm not overdoing the mid to high treatments. Please let me know if that's still too much.

How important is treating the ceilings? I've read that you should treat just the first reflection points, which is my current plan, but I've also read that the ceiling should be completely untreated. Isolated panels hanging from the ceiling is another area where my wife is concerned with aesthetics, so if it's not going to make a large difference, I could potentially use the additional OC-703 on the sofit treatments, either to add additional thickness to the spanned corners, or treat the bottom as well as the corner...or leave the bottom untreated and possibly continue the corner spanning treatments from the soffit onto and along the back wall. I think the wife would probably be OK with that as well. Thoughts? 

Thanks!


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## bpape (Sep 14, 2006)

On the ceiling you would address the reflection points like you would normally in a 2 channel room. No need to do the whole thing.


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