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Discussion Starter #1 (Edited)
Let me catch you all up to speed with my build. I've been stock piling materials for several weeks now and am slowly making progress on the framing.

My first theater design was in 2009 for a new home I had designed (architect by trade), but we didn't build it. Fast forward 3 years, bought a newly constructed home in January of 2012 and put in a couple of provisions for my dedicated theater during the build. My dad builds homes for a living (and built mine), so I got the chance to add some dedicated electrical outlets and coax to the closet under the central stairs which will be my future AV/Media closet.

Pay no attention to the color scheme as I haven't decided on ANY of the colors yet.


Xray view facing the screen:


I'm moving this water pressure tank next weekend so that it's out of the theater:


Framed the entry door:


I'm using 2x4's spaced at 24" on center and will be using one layer of 5/8" drywall for the walls and soffits (more on this later). I'll be using a million and a half tubes of acoustic sealant anywhere I can. I built the wall parallel to the existing stairwell wall and held it off by 1". And also built the return wall which creates the storage space behind the back of the HT. I'll be picking away at the other two walls over the course of this week. I plan on holding the walls along the concrete foundation walls by at least 2" to allow for the water inlet pipe run back to the storage room. I'll be wrapping the new pipe in insulation so that it doesn't create noise within the wall.

The finished room dimensions will be approximately 12'-2" x 19'-8" x 7'-3" before acoustic treatments. I've fully decoupled the walls using the room within a room concept. The only attachment points to the pre-existing structure will be at the sill plate that rests on foam sill sealer and the tops of the walls which will be held utilizing RSIC-DC04's fastening thru the existing drywall into the floor trusses. The existing ceiling is 5/8" drywall with engineered floor trusses with the cavities filled with R19 fiberglass batts. Since I'm building a "fish-tank" I'm hoping I can watch movies and play my video games while my wife and son sleep two stories up. We'll find out since, once I get the first layer of drywall up in the room, I'm going to do some serious, full range, high SPL testing. If I find that my methods are not sufficient I will add another layer of 5/8" drywall with Green Glue between the staggered layers. If that still doesn't function, I'll just have to adjust the maximum volume setting on my Onkyo! :heehee:

I'm new to posting here but have been an avid reader/researcher of both this forum and AVS. So I'm familiar with the methods used for sound isolation and the like. I haven't set a budget on this build as I will pick away at it as funds allow. So far, I've got a stock pile of all the 2x4's I'll need with only the riser and stage lumber to purchase. I've got seven 3" can lights for the soffits, black Lutron dimmers, black outlets, electrical boxes, wiring, 200' of CL2 speaker wire, PVC electrical conduit which will create a raceway around the soffit for future low voltage runs, RG6 subwoofer cable, a 7.1 HDMI wall plate for the AV closet, High Speed HDMI cable for the PJ, all the R13 insulation I'll need for the walls and soffits and probably a bunch more of miscellaneous items I'm currently forgetting.

Every trip I make to Home Dustpan :rofl: from now on, I pick up at least one 50lb bag of sand since I will need 30 of them to fill my stage. I'm currently at 8. It's less burdensome to lug one or two bags down every couple of days rather than trying to do it all at once. BTW, that's over 1500 pounds of sand...

I've got some 3/4" MDF left over from subwoofer builds (I install car audio as a part time job) which I will use to make backer boxes for outlets/lights and such. I'm going to mount my PJ within a hush box which will have an exhaust fan dumping the hot air into the adjacent storage space and keeping as much of the PJ's noise out of the HT.

I'm framing the soffits in such a way that actually makes them more like roof framing. They will not touch the existing ceiling and will hang from the new wall framing at the perimeter of the HT utilizing Simpson Strong-ties. Therefore, it will be decoupled from the rest of the house. Any penetration into the HT drywall will receive a backer box of MDF and sealed with acoustic sealant. The soffit and the main ceiling cavities will be filled with fiberglass batts as well.

I'm going to build an 8' x 8' riser and push it to the back and one side of the HT. This will allow my in-swing door to fully open 90 degrees and will allow for the most seating. My seating plans are to get a reclining sofa for the front row and I'm still battling my decision for the back row. I've found some real theater seats locally on craigslist, but I'm sure they aren't all that comfortable. But at only $150 for two rows of 4, I may just buy them and see if I can squeeze both rows on my riser 8'x8'... Since the theater will be used by only me 60% of the time and by me, my wife and one son 25% more, with only the remaining 15% being for family gatherings and parties, the sofa will be the money seat while the back row(s) are "filler" seating. I may have just talked myself into buying those seats while typing this! :heehee:

Actual shot of one of the seats I might buy:


If you haven't noticed already, I tend to ramble on and type too much but it's mostly due to me keeping a running list of things I need to do or decide on or even things I need help with.

And before I get bombarded with "what are you doing for HVAC" questions, let me give you a bit more information. I live in Maine. My basement is 8 to 10 degrees cooler (even more so in the winter) than the rest of the house and currently has no heat source besides the earth below and surrounding it. I've got 2" of rigid insulation under the slab and 8" thick concrete walls around the perimeter. We, here in Maine, don't have central forced air, ducted HVAC systems because we don't usually have the need for cooling. When and if we do, we use window AC units to cool our homes. The adjacent room to my theater will be a game room / bar area which has two windows that can easily take a window AC unit if the need arises. As for heat, the adjacent room will get one of the infrared Edenpure fake fireplace heaters and that's it, no heat in the theater other than warm bodies and lighting (my equipment will all be within the AV/Media Closet). If I find that the air is too stale in the HT, I will simply open the door and run a small room fan to circulate the air. When it's just me in the theater most of the time I can't imagine it getting uncomfortable over the course of under 3 hours and if it does I'll figure out a way to manage it then. For now, there is absolutely zero plans for any venting or cooling for my HT. My initial plan was to use two dead vent systems, (one for supply and one for exhaust) and although it would be a royal PITA, I've designed the framing to allow for me to add them in if I need them, only needing to cut away the drywall. Go ahead, you can say it now... "We told ya so". Yeah, yeah.

:hsd:

List of currently owned equipment:
Denon X1100W
Xbox One
Wii
Klipsch Reference RF-62 II (LCR)
Klipsch S-10 (Surrounds)
Dayton B652's (Front heights, for now)
TubaHT (I might build another one later)
Behringer NU1000DSP Sub Amp
Epson 8500UB (traded it for the Panny I won, hopefully no hard feelings from HTS)
DIY 46x108 (117.5" diag.) 2.35:1 AT Screen
 

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If you want to be able to use the Soffits for can lights without penetrating the shell, hvac runs, etc. - they should be build AFTER you do the drywall.

Bryan
 

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Better to not break the shell at all and avoid having to build backer boxes.
 

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That's my point. If you do the room and drywall THEN frame the soffit, putting cans in the soffit does not pierce the shell.

Bryan
 

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That's my point. If you do the room and drywall THEN frame the soffit, putting cans in the soffit does not pierce the shell.

Bryan
How do you get the wires in without piercing the shell?
 

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Well, sure, you'll have that one small hole for the Romex. But, that can be caulked and is a LOT better than 6-10 6" diameter holes, figuring out how to do backer boxes, having to poke holes in the boxes anyway for Romex, etc.
 

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Discussion Starter #9
Well, actually my soffits are integral to my wall and ceiling framing, therefore the drywall of the soffits is part of my rooms shell. I'll post up a detail of my soffits to give you guys a better idea of what I'm doing. My ceiling framing utilizes 2x4's that span across the ceiling. My framing plan will illustrate this better once I post it up. Framing my soffits and ceiling of my HT this way will 100% decouple all of the rooms framing from the existing house walls/drywalled ceiling. I won't be using clips/channel to hang my HT ceiling drywall because it will be attached to the 2x4's that span across the 8' distance between my soffits. I tried to explain that the best I could but the detail drawings will depict it best.
 

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That's fine, you're just trading isolation physically for cutting a bunch of holes in the shell and having to build/decouple backer boxes.
 

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Discussion Starter #11 (Edited)
Actually I won't have to decouple the backer boxes since they will be screwed into my wall and soffit framing and won't make contact with the existing ceiling. My basement already had a 5/8" drywall ceiling that my new ceiling, walls and soffits won't be physically touching... Basically my room could stand on its own if you took it out of my basement. I will have a dozen isolation clips to support the top of the perimeter walls and of course the bottom plates rest on the slab but that's it for attachment to the existing house. I got two more bags of sand today, four sheets of drywall and the rest of the conduit I needed. This week I'll finish framing the walls and then next weekend my dad will be over to help me move the water tank, finally. Once that's done I can start on the soffit framing and roughing in the electrical.
 

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The drywall from the existing ceiling should be removed before doing yours to avoid creating a triple leaf which can actually make bass transmission worse rather than better. The only layers of mass you want are the floor above and the ceiling of your room.

Bryan
 

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Discussion Starter #14 (Edited)
I can't. It has to be a fire rated ceiling so I must maintain its integrity.

Should I add a layer of drywall with green glue to the existing ceiling and then do my room ceiling as I've designed? Essentially adding mass to the "middle leaf"...

Oooor, should I leave the existing ceiling then apply channel on clips to hold my HT ceiling and build the soffits as most do (after the shell is drywalled)? This still creates a triple leave though... Except the channel will bridge the gaps between the existing drywall attachment points to the floor trusses...

What are my options to optimize isolation and maintain the existing ceiling?
 

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You can't make YOUR ceiling the fire rated one?
 

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Discussion Starter #16
It won't be rated if I'm using the room within a room construction method (whereby no physical attachment to the existing ceiling)... Fire rating my HT would require some rather interesting details to maintain the integrity of the fire rated assembly, which would in effect reduce my isolation efforts more so than to not remove the existing drywall. Would the existing ceiling still be considered a middle leaf if the framing, ceiling and walls of my HT (the first leaf) are not physically touching it? I mean I know the vibrations excite my HT drywall/framing but won't my completely isolated construction methods reduce the likelihood of exciting the existing drywall ceiling to the point where it doesn't become a "drum"? Wouldn't adding mass to the existing ceiling and keep my existing design approach therefore achieve the vibrations contained within the shell and if those LFE's make their way to the existing ceiling it has too much mass to be effectively a middle leaf?

 

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You can add mass to the middle leaf. Not going to be any better isolation overall though it will lower the resonant frequency of the structure so less can try to get through easier.
 

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Discussion Starter #18
What other options do I have if I'm to keep the existing ceiling in place? Just do channels/clips for my HT ceiling attached to thru the existing ceiling and build my soffits within the shell?
 

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Clips and channel still form a 2nd air cavity. The ONLY way to do it and only have 2 layers of mass and 1 air cavity is to add to what you already have with more layers. Or (not sure why fire standard is SO strict here) you can pull down the drywall, do clips and channel on the ceiling, then put it back up with multiple layers. Not completely decoupled but better. Will this work?
 

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Discussion Starter #20
My local AHJ has been forcing homes built using open web floor trusses that are constructed out of 2x lumber to maintain a 1 hour fire rating between the floors that the trusses are supporting. The explanation given was that the wood truss will burn faster than traditional floor joists using thicker 2x's (instead of making webbed trusses out of 2x4's or x6's with air space) and therefore a fire rated floor/ceiling assembly is required.

Out of my options, which one would you go with?

Option 1:
Build as I've designed and hope that the LFE's don't create a "drum" out of the existing ceiling. Maybe add another layer to the inside shell of my HT to add mass before anything enters the first air cavity...

Option 2:
Rip down the existing drywall and add channel/clips and put back DD + GG in it's place. This option would mean I would need to either do the entire basement ceiling or figure out how to detail the wall edges to maintain the fire rating. I'm a PM at an architecture firm, so I could figure out the detailing, just not sure I want to do this though.

Option 3:
Add another layer of 5/8" with GG in between (stagger the panel joints) and that will then be my new HT ceiling. I would frame the soffits after the shell has been fully drywalled. I would put backer rod and sealant along the seam of the wall and ceiling drywall since the top plate of my new walls would be held ~1/2" below the new ceiling drywall.
 
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