Time for an update. I feel like my theater would have been more aptly named the "Two Steps Forward and Tear It All Out And Start Over Theater." My latest bit of progress to get back to where I used to be is yet another revision to my exhaust setup. I tore out the drywall on about 1/3 of my soffit that was my exhaust in the back of the room, and replaced it with two 6" insulated flex lines. You might be asking why I didn't do that to begin with, and the answer is two-fold. First, it's a serious reduction in flow capacity. At the beginning I was trying to maintain the 5 air exchanges per hour. This won't do that, but after spending some time working in the room with it sealed up, I don't think cooling will be an issue, so I'll have to put a strict "No Farting Allowed" policy in place to compensate for the reduced air exchanges. Stale popcorn smell doesn't bother me as much
Second, There's only 6-1/2" between the ceiling and the soffit framing (the narrowest points) and 7-1/4" to the soffit drywall. A 6" insulated duct is around 10". So it's a tight fit. There's also the issue of getting the register boots crammed in there as you'll see in the picture below.
Here's some proof. This pick shows the two lines exiting the room and dumping into my deadvent. Those two lines connect to a single 8". I'll be able to adjust the vent in the equipment closet to balance flow between my 8" supply and the two 6" returns.
Here's the old setup for comparison.
This is the inside of the room. The ducts enter the room on the right side and snake around to the back of the room. You can see it's a tight fit.
Here's the two register boots. If you'll notice, they are both tilted a bit. That's because there's really not enough room between the soffit framing and the ceiling, so I had to shove them in the best I could.The good news about this is I believe it has solved the low frequency rumble I was hearing.
I can still hear it at the the deadvent where I had to take the insulation off to get the flex through the opening. All I can figure at this point is it's just the sound that the fan makes as the blades "slap" the air. In my old setup, I don't think the Linacoustic provided enough absorption to eliminate the noise. Now, it's inaudible inside the room even with the drywall missing on the bottom of the soffit. Also, when I adjust the vent in the equipment closet so that there's little to know negative pressure in the room, the two vents are nearly inaudible when standing right next to them. So I'm encouraged that I'll be able to keep the wind noise down, too.
Finally, if you look to the right of the picture above, you can just make out where I've started fixing the drywall on my ceiling after taking down the framing for my previous coffered ceiling design. I really don't like drywall, but I need to fix this before I can prewire for my ceiling lights.
Sorry for the long post just to update my thread on negative progress. Maybe in a few more weeks I'll be back to where I was before I started tearing everything out
As an interesting side note. I've spent several hours at a time in the room with two 500 W halogen lights (that's 1,000 W total for those that don't like maths
), me working pretty hard, and the door closed with nothing but the deadvent running at about half speed, and the room stays cool. So my space seems to be staying cool even with no AC running. Again, very promising! I think this has a lot to do with the size of the room. There's a lot of air in there, and a lot of pre-cooled surface area to absorb heat.