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Mijotter's Subarmine HT thread.

post #1 of 57
Thread Starter 
First of all I want to thank everyone who have helped give me tips and advice with this project. My plan for my Home Theater is to soundrpoof it but in the end have it pay homage to the Seaquest DSV submarine as I loved that show growing up. However before I start with anything I would like to give you all a plan for my room and I want blunt honesty if it's going to really make that big of a difference or not when it comes to Soundproofing(i'm getting the doubting bug)

2 outside walls: 2" xps foamular rigid board glues to the concrete wall. Stud wall 24" oc in front of that but 1" away from xps. Double 5/8" drywall with Green glue.

2 interior walls: Staggered stud formation, Double 5/8" drywall with Greenglue, batt insulation between studs, again not touching the ceiling.

Ceiling: Double 5/8" drywall with Greenglue, furring channels and sound clips, batt insulation, each layer of ceiling and wall have small cracks at their connection points to fill with acoustic sealant.

Joist cavities: 2" xps foam board properly sealed, batt insulation.

All necessary cracks and things will be acoustically sealed with acoustic sealant.

There will be 2 doors; 1 at the bottom of the stairs to enter the theater and the 2nd on the middle interior wall to enter the adjoining room of the basement(laundry room)

There are also 2 glass block windows in the theatre room with only 3/4" cavities. My thought was to seal the vent in the windows with that acoustic puddy and place 5/8" drywall in the cavity sealed with acoustic caulk. (still not sold on if that is the best to do here)

There will be 6 backer boxes for my can lights which I am currently cutting and screwing together(they will be soundproofed per soundproofing company's website)

All outlets and switches with be properly sealed with puddy.

I have 2 return vents running parallel with the ceiling joists and come down flush with them. I plan to wrap them in MLV and use the acoustic sealant in any gaps.

There are 2 vents in the theater room which blow air in the room. I plan again wrapping those in MLV and using a Flex Duct or Duct liner for them as well.


I think that's covered almost everything. I need to know if this setup will really make a difference in my home. Will I notice a big increase in sound proof when it's all said and done(from the inside of the house and the outside) And please don't be shy, let me know if i'm doing something wrong or if there's something better i could be doing with ANY of this.

Thank you for your time.

Here are some pictures:






post #2 of 57
Thread Starter 
Sorry forgot to post. The room is 216 sq. ft. I also to not have the option of double siding these walls for either space or there is simply no room on the other side of the room to do it.
post #3 of 57
Cool. I think you'll have a nice quiet room with the soundproofing. With the pics it's still hard to tell where the proposed HT will be. 216sq ft is fine but, doesn't tell us the width & depth of the room. Can you sketch up a plan view of the entire basement and where the theater room will go with some dimensions? smile.gif

p.s. I like your sled
post #4 of 57
Thread Starter 
haha thank you.

Yeah i'll work on a sketch up tonight, but the dimensions are:

2 long walls which include an outside wall and middle separating wall are 17'9 and 1/4"
2 short walls including wall built in front of the steps and an outside wall are 11'8.5"

The middle long wall will have a door since this separates the HT to the laundry.
The wall that i'm building at the steps will have a door to get in the HT from the steps.

I got my 8 tubes of 29oz Titebond Acoustic Sealant today. Had to leave work early since the store closes at 4:30 but it was worth it:) I searched and called 6 different supply places here and finally found one.

I plan to seal the joist cavities, Vents that are nailed to the ceiling joists, and the underside of the floor above since they are all thin wood pieces and not plywood. Anything else I'm missing. I turned the light on in the basement and went to the living room above it to see if there are any gaps where lights shows through and boy are there.
post #5 of 57
Thread Starter 
The thing holding me back right now is what to do with those glass block windows. What would be the best option for those as the cavity is only 3/4". Would it be best to stuff something in the window as it stands now or maybe frame around it and build a plug of sorts giving me more room in the cavity? What materials should be used in either case? Thanks guys.
post #6 of 57
Since you seem to be trying to squeeze that last bit of soundproofing out of it, you might fill the cavity with some DD+GG. You could even paint the first piece black so that it looks like a dark room from the outside, and caulk, shim, tape, construction adhesive, etc. to keep it in the hole. However, my gut feel is that the DD+GG in your room will be handling most of the soundproofing. I don't know how much benefit you'll get by filling that 3/4" cavity, but it certainly can't hurt anything.
post #7 of 57
Thread Starter 
That was my feeling as well. However i did a sound test just with the bare concrete walls and windows and the windows are a definite weak point by far. I just don't want to put this big project of a wall up only to still have the windows be aweful. Now I realize that the windows will more than likely still be a weak point, but still want to do whatever i can. I like your DD/GG idea, it would have to 1/4" and 1/2" drywall. Should i attempt to gasket it or just cut it tight and seal it with acoustic caulk? Was wondering if MLV would be helpful in the window as well...
post #8 of 57
I don't think it would necessarily have to be exactly 3/4". You'll have 2" of foam board around the window well also, correct? No reason it can't stick out past it a bit. That would give you a good edge to apply acoustic caulk when you're done. You might also use Hardibacker or cement board, but I have no idea how well those work with GG.

If you need to take the thing out, then a gasket to provide a friction fit. If not, I'd look for a construction adhesive that is supposed to work with concrete and DW just to make sure it doesn't go anywhere. Then you can put a bead of acoustic caulk around the edge.
post #9 of 57
Thread Starter 
Well I was planning to just the wall the window up after i've done whatever i can in the small cavity. foam board and studs over the window.
post #10 of 57
post #11 of 57
Seems like it would be easier to cut a section of the foam out around the window than it would be to try to make your window plug match perfectly with the edge of the wall. The foam board will have little sound absorption value compared to the extra 2" of fiberglass you could put there. But again, I'm not sure either way is significantly better than the other.

EDIT: Tom's got the right idea!
post #12 of 57
Thread Starter 
Awesome picture Tom thank you. And i was just worried about any condensation that might arise on the glass block during the summer which is why i was initially considering just placing the foam board over it but perhaps it wouldn't matter. Wonder if i could use that green moisture proof drywall instead and GG that stuff. I'm starting to like the idea of framing the foam board around the window. Will give me a lot more room to work with...
post #13 of 57
Thread Starter 
I was also thinking of lining the vent in the picture of the window above with:
http://www.soundproofingcompany.com/soundproofing-products/soundproofing-accessories/putty-pads/
post #14 of 57
Yes, I was thinking about moisture and that's why I didn't specify the material. If it were me I would shy away from drywall but, maybe the green that's used in bathrooms might be ok. What is the purpose of you using the extruded styrofoam on the walls? Is it just for insulating? Because it won't do anything for sound proofing.
post #15 of 57
Thread Starter 
Yes it is strictly for insulation vapor/moisture barrier purposes. That comes first and done right otherwise I'll have mold in my theater room. And there's no leaks or anything around the windows so it'd just be for condensation i'll have to look up the properties of the green moisture drywall and see if it will make sense. Thankfully the room has been bare like this ever since July so i got a good look at any moisture problems, and a couple times all summer some condensation was built on the windows but not much. I'm also installing a nice dehumidifier down there as well so...
post #16 of 57
HardieBacker might be an option.



EDIT: Spelling corrected wink.gif
Edited by J_P_A - 11/28/12 at 12:06pm
post #17 of 57
I was going to wait until you had a plan view of the basement but, I was wondering what the vent was in the picture. Is it a supply or a return? And is that one of the walls of the theater room? If so that's a problem. Probably need to do some sort of soffit muffler.
post #18 of 57
Thread Starter 
It's a return yes. And yes I have been slowly trying to figure out how best to tackle that monster. There will be a staggered stud placement in front of the that already studded wall. I won't have room for a soffit protruding in the room though. I was thinking MLV and a duct liner?
post #19 of 57
Thread Starter 
Also to back off of post #13, does this sound like a good idea to seal that vent in the window? And anyone from Soundproofingcompany know if their putty product has a moisture rating or mold resistant?
post #20 of 57
Why do you need to seal the vent in the window? Leave it closed and put a plug over the window and call it a day.

That return is going to be an issue. Think about it all the mass from the DD and then your cutting a huge hole in the wall. MLV and duct liner aren't going to stop much of any sound from coming in or going out. Duct liner is used normally to stop some of the higher frequency noise from the other end of the run. Won't do anything for low frequency. What is on that other side of the existing wall? Maybe in that area you could build a self contained dead vent but, you still have the supply(s) to contain as well. Two doors in the room is also an issue but can be overcome with mass and proper seals around the doors.
Is the staggered stud wall going to be finished on both sides? If not I would just build another 2x4 wall in front of the existing leaving a 1" gap. You'll also pick up a couple of inches.
post #21 of 57
Thread Starter 
Yeah I haven't really fully tackled how to properly soundproof my return and supply vents. The dead vent system will take up so much space in my already small theater room. Is there a way to condense said build? The other side of that existing wall where that return is, is nothing, i have all the room back there. Do you have any suggestions for the supply vents or any of your fantastic pictures hehe. Oh and the 2 supplies and 1 return are very close to the furnace it self, I'd say the supplies are about 4 feet and the return about 6-7 feet.
post #22 of 57
A dead vent would generally be located outside the room. At the risk of oversimplifying, you just build a big DD+GG box stuffed full of insulation that you route your flex through as it exits your theater. This absorbs the sound from the duct and prevents it from escaping or entering your theater. Here's an example from one of Ted's SIMs. Hopefully he won't mind me posting it here.



Sound isolation for ductwork inside a room is usually handled with something like a soffit muffler.

The Soundproofing Company's website has some good designs for these things (here's an example). I'd highly recommend you give them a call as they have tons of information not posted on their website that they will send you as well. Awesome folks to deal with!
post #23 of 57
Thread Starter 
Fantastic, the exhause vent on the outside room is that attatched directly to the furnace or to the duct leading to the furnace?
post #24 of 57
Thread Starter 
Here are some pictures of my vents/problems haha:





So what needs to be taken out with these supplies and return? All the metal getting replaced. Also The DD+GG on the outside wall, not the outside of the box, for the duct box is that JUST for the box? I won't be able to take that all the way down the length of the wall as there is a chimney and steel beams in the way if that is the case. Also where do the batts go since there is only a 1" gap. Sorry for all the questions just trying to get this figured out thanks.

I just took these picture of the ducts from the other side of the room:




Edited by mijotter - 11/29/12 at 11:21am
post #25 of 57
That's a perfect space for dead vents because you don't put them in the room unless your doing a soffit style.

This pic just uses two fans to exchange the air with another part of the basement but, you could also come up with something that would work for your supply and return that goes to the furnace as well. You'd have to change your existing sheet metal duct work with new but, that's pretty easy.

post #26 of 57
Thread Starter 
The other side of the basement will not be as much of a controlled environment as the theater room, will that matter. So the return and supply ducts do not connect to the furnace and just use independent fans correct? Sorry i'm trying to picture this plus i'm really tired. I think i'd be fine with the return just exiting to the other room but i think i'd want the supply ducts coming from the furnace to more efficiently cool and heat the theater room.

Also on a slightly similar subject. I'm just about ready to start gluing the xps insulation the to concrete walls so i'm getting pretty excited. But if you go all the way back to my original post, third picture down is a return from the living room upstairs that goes the length of the ceiling and takes up 2 ceiling joist spaces and is also nailed to the bottoms of the ceiling joists. The vibration and echo is awful. I'm worried if i screw the furring channels over top of that the noise and vibration will carry. Is there a way to deaden or SP these buggers? I was thinking lining them with MLV a Peacemaker sheet and applying acoustical sealant to any parts that aren't flush with the ceiling joist. Ugh it's just one thing after another isn't it lol.
post #27 of 57
Thread Starter 
Anyone? advice on SPing my return air plenums in the ceiling please. Also would it be ok to seal them flush to the joists so there's no leaks with caulk?
post #28 of 57
Having a hard time figuring out what's going on in that picture. Did they cover two joist bays with sheet metal to form your return?

If that's the case, I dint know that there is much you can do. You don't have enough space to add any absorption. I think the best option might be to replace the ducts with insulated flex, and maybe build some joists mufflers. The issue will be getting large enough ducts. You can look at the first post in my build thread for a chart showing flow rates of different size rectangular and round ducts. you'll need to match the flow rates.

BTW, could you post a layout. It would make it easier to understand your space.
post #29 of 57
"BTW, could you post a layout. It would make it easier to understand your space."


I asked him to do that a while back. Still waiting. He's not getting input from others by not having a plan view of the entire space. He has said that the room next to that theater has nothing going on in it and that the supply & return for the basement go straight back to the furnace. I would take those out and redo the way he needs them to be (sound proofed). He needs to talk to Ted or John from The Soundproofing Co. provided he is going to use them for his soundproofing needs and ask them on what the best approach would be to build dead vents for the supply and return before it goes back to the furnace. Once again he needs a floor plan for the anyone to make sense of the space. As far as that weird return, there may not be area for absorption but he will still have the decoupled DD & GG underneath that area which will help out a lot. Hope this will give him a kick in the rear to get him going on the FLOOR PLAN! smile.gif
post #30 of 57
+1 biggrin.gif

It's certainly been my experience that the more you put into your thread, the more you get back out.
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