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# The Once and Future Theater - Page 13

My wife gets frustrated when I try to help when it's not really asked for, but here goes anyway.

7/16" OSB = 1.7 #/s.f. (varies by site, but we'll use this one )
5/8" DW = 2.75 #/s.f
Light 5/8" DW = 2.75 * 0.85 = 2.34 #/s.f.

So, OSB + Light DW + Light DW = 6.38 #/s.f.
DW + DW = 5.5 #/s.f.

Looks like the per unit mass of your assembly is higher than just two layers of regular 5/8" drywall. I'm sure there are reasons this comparison doesn't work, but we don't have to look at that, right?

BTW, now caulking those seems sounds like a great idea

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Thanks, J_P_A. The googles are in line with what I was thinking. Plus, one could argue that having three layers, one of different mass, allows for an impedance mismatch that would further inhibit transmission in some bands. Still Ted's point remains: more mass is always better and pushes the LF resonance point down.

And the caulking is already done! (no picture)
No doubt that OSB + 2 layers of heavy 5/8" would be better. I was just making the case that two layers of light 5/8" plus one layer of 7/16" OSB might outperform just two layers of heavy 5/8". More total weight than the standard DD+GG assembly and all

EDIT: Clarified the above a bit
Edited by J_P_A - 3/13/13 at 9:56am
Quote:
Originally Posted by HopefulFredÂ

Plus, one could argue that having three layers, one of different mass, allows for an impedance mismatch that would further inhibit transmission in some bands.

If we were not using damping material that would be true
Huh. I knew that the mismatch was the old-school approach, before CLD was readily available, but I didn't realize the principles wouldn't operate simultaneously.
The idea of mixed thicknesses was to have each panel resonate at different frequencies. Good strategy, but flawed from a practical perspective. Once you bond different panels together, they behave as one. The panels, whether loosely tacked or bonded with Liquid Nails will still have resonance. No resonance elimination happens in the old days. To drop resonance itself, we have to turn to damping compounds, whether extensional or constrained.
Here's a sidebar distraction for you. I've been toying with the idea of building a weeping angel and installing her (maybe two) behind a AT screen, then lighting the figure behind the screen - the same way people light their speakers for display to highlight the AT screen. If done correctly, especially as part of an animated sequence of lights, it could be the scariest thing ever.

Well, it's doable. It's not in my budget, but I sure hope someone does it.

http://www.thisplanetearth.co.uk/main/page64.html

If you don't know what a weeping angel is, you're not alone, but you're missing out. Dr. Who episode, "Blink" http://www.amazon.com/gp/product/B003KH46GO
I got my first bead of caulk all around the room today. It took half of my full order, so I guess my order was enough. I wasn't able to plug all the holes around the pipes, but I'm not going to sweat that either. I'll just be sure to triple build the soffits, just like the walls.

In the mean time, I'm taking a couple days vacation from building. Until my dad comes to town Saturday to start hanging drywall, my only job around here is to pester you all - in your own build threads. J_P_A? Mr. Tim? TMcG? And where has RTROSE been lately? Maybe I'll go bother him.
Edited by HopefulFred - 3/13/13 at 3:24pm
Who me? I'm making popcorn with my new popper.

Regards,

RTROSE

Oh, and the "Weeping Angel" would be enough to scare the pants off some unsuspecting guest, especially if they knew the Dr. Who back story!
Quote:
Originally Posted by RTROSEÂ

Oh, and the "Weeping Angel" would be enough to scare the pants off some unsuspecting guest, especially if they knew the Dr. Who back story!
I know, right!? I just imagine the crowd settles in, the lights dim, and just before the projector comes up, the lights behind the screen flash - for about 3/4 of a second - just long enough for everyone to think, "Holy Crap! Who is behind the screen?!"
I figured as long as one of us was making progress.. the rest of us were off the hook!

I used a few of those lightweight sheets when I was finishing up, so you're not alone. I worried about it until I put the first screw in.. then.. whatever. I figure you try to do the best but sometimes you have to work with what you've got.

Tim
Quote:
Originally Posted by Mr.TimÂ

you have to work with what you've got.
For real.
Quote:
Originally Posted by HopefulFredÂ

My only job around here is to pester you all - in your own build threads. J_P_A? Mr. Tim? TMcG? And where has RTROSE been lately? Maybe I'll go bother him.

Sorry brotha! I can't help you for now as I am on nursery detail once I get back from work travel. Besides, I've been officially Loganed so there is pretty much no point in living anymore....
Quote:
Originally Posted by TMcGÂ

Sorry brotha! I can't help you for now as I am on nursery detail once I get back from work travel. Besides, I've been officially Loganed so there is pretty much no point in living anymore....

Oh, you can go on living, just no progress will occur. Living yes, progress no.

Regards,

RTROSE
A vacation from building?!?! That's brilliant! No more hassling over lack of progress! From now on, my last post in my thread is the official start of my next building vacation
Vacation is over! My dad and my father-in-law came over today and we put in about 6 or 7 good hours in the basement learning how to use the speedloader and figuring out the layout we wanted. The results are 14 sheets (more or less) of drywall hung - the ceiling and the left wall are completely done.

A couple notes. We decided, at my dad's urging, to use the 2" screws I had planned for the second layer for the first layer instead. I think I'll return the 1 5/8" screws and get some 2 1/4" for the second layer.
We went through about 2.5 gallons of GG. Does that add up right? The ceiling is approximately 12 by 23, or around 275 sqft. The wall is 9 by 22, or close to 200 sqft. So that's 475 sqft hung today or around (guessing) 190 sqft per gallon.

My dad an I also discussed the soffit size and the vent routing. I want to get some opinions, so I'll be putting a post together about that later.

Were all of you also productive this weekend?!
Edited by HopefulFred - 3/17/13 at 4:42pm
Looks good Fred! How are you going to do the last layer? Stand-ups or horizontal?

Tim
Looks great! Way more progress than I made!

EDIT: looks like you might be going a little thin on the GG. At 1 load per 32 s.f., I think 2.5 gallons should cover 365 s.f. According to the soundproofing company website.
Edited by J_P_A - 3/17/13 at 4:37pm
Thanks guys - I'm pretty happy with the way it's fitting together. There are some gaps in the joints in the ceiling, but none bigger than 1/4". The second layers will go in differently so as to overlap. On the walls, I'll just start at the other end of the room with verticals, like I did today, but offset by one stud.

I see the math you did, J_P_A, and it makes sense. 1 28oz tube covers 32 sqft as 1 load. That's 7/8 oz per sqft. If I hung 475 sqft of drywall, I should have used 475 x .875 = 415 oz. 415oz/128ozpergallon=3.25 gallons. Well here's some good news - I actually used more than the 2.5 gallons I thought I used.

After going back to look again I can say two things: first, we used three gallons or so - maybe a little more - so we're doing pretty good with the application rate, I think. Second - I didn't explain to my fathers the importance of not wiping the nozzle of the speedloader all around the rim of the bucket.
My dad was concerned about hanging all the weight from the ceiling, because he's a worrier. He wanted me to go ahead and frame in the soffit, or at least set a ledger board and anchor it carefully to the joists before I get all the drywall in the middle and have trouble finding firm places to screw into. I see his concern, but I didn't let it change my plans. In any case, it got us talking about how big the soffit will need to be. This is where I'd like some feedback.

The purpose of the right side soffit is four-fold. First, it must encase the plumbing as well as possible to stop water draining sounds. Second, it must encase the HVAC duct that will bring cold air to the front right of the theater (a similar duct will also run to the front left). Third, it will provide a raceway for both wiring for the lights (not the lights themselves) and the speakers and other LV signals. Fourth. it will integrate with other design features that have not yet been decided - moldings, speakers, columns, etc. Keeping all those uses in mind, I'd like to make them as small as possible.

The major challenge to the size is clearly the point where the HVAC duct needs to pass this junction in the pipes.

I'm sure it's hard to make out, but the bottom of the lowest drain pipe is about 10" below the ceiling at this point. Of course, that dimension will change by 5/8" when the second layer of drywall goes up. The pipes protrude out into the room about 14 inches, and that dimension will change by 1 1/4". So with an obstruction 9.5" tall and 13" wide, where would you run the duct? The duct is insulated 6" flex, which looks to me to be about 8" OD uncompressed. Keep in mind the overall dimensions of the room - 9 feet high, minus 14 inches for riser, and only 12 feet wide. The soffit will already be 81" (6' 9") above the riser, so I'd prefer not to loose that much height. But with the room only 12' wide, 1.5 feet wide soffits take up 25% of the ceiling.

Maybe I need to draw it up. But I need to float an idea first. 6" flex could be adapted down to a smaller rigid duct for a foot or two as it passes the plumbing, couldn't it? what size would you use - maybe 9x3?, or would you not consider it?
Quote:
Originally Posted by HopefulFredÂ

Maybe I need to draw it up. But I need to float an idea first. 6" flex could be adapted down to a smaller rigid duct for a foot or two as it passes the plumbing, couldn't it? what size would you use - maybe 9x3?, or would you not consider it?

Can be done. Need to know how many CFM you're going to be pushing through there to size it. If you have a metal shop that can form it for you, then the sky is the limit. If you need something off the shelf, you are looking at round-to-oval or round-to-wallstack.

Wall stack is 3.25x10 or x12. I think oval is about the same.

Tim
Quote:
Originally Posted by Mr.TimÂ

Can be done. Need to know how many CFM you're going to be pushing through there to size it.

Wall stack is 3.25x10 or x12. I think oval is about the same.

Tim
10" wall stack sounds like a good contender, as long as the offsets are right. Thanks for the tip Tim. I'll go do some research. Does anyone think this is a bad idea, and I should just suck it up and let the soffit eat up the ceiling?

Oh and about those CFM... I'm not sure I want to get back into that math - but I'm sure I will eventually.
I can't take credit for the GG maths. It was right off the website. 5 gallon pail covers 365 s.f. at 2 loads per 32 s.f.

As far as your duct goes, how much space do you have between the wall and the pipe? A rigid duct sounds reasonable to me. I'd put plenty of fluffy insulation up there around it if I could.
http://www.globalindustrial.com/p/hvac/ventilation/Duct-Pipes-Plenums/speedi-products-wall-stack-straight-boot-12-x-3-1-4-x-6
The only thing that's not clear from this picture, which is use at the link above, as well as at the homedepot website, is if the round section is centered on the wall section, or if they share an edge. (Does that make sense?) Making the duct thinner doesn't do me any good if it doesn't lay flat against the inside of the soffit.

There's no room between the wall and the pipes. You can't even really get a 28oz caulk gun up in there - at least not to where it will get caulk into the corner.
Are you thinking of running over the top of that intersection? Is this in a corner or somewhere that you could integrate it into a column?
No, it'll have to go on the side of all the pipes - away from the wall. The pipes here are all of these:

And you can see in relation to the rest of the room here:

But now look more like this:
I think I follow you now. Is this near the midpoint of the room? I'm still liking your and Tim's idea. The duct will be isolated from the room some, and there is still some length to help dissipate the sound.

The first or second post in my thread has a field sizing chart for ductwork that you can use to make sure you get close to the same flow between a round and rectangular duct without the math.
Yes, it's very near the midpoint of the room. I'll go use your cheat sheet later. Now it's time for bed. Maybe I'll read a little of my new book.
http://www.amazon.com/Master-Handbook-Acoustics-Alton-Everest/dp/0071603328
^^^^^^A little light reading for the evening right before bed time. Sounds nice.

Regards,

RTROSE
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