Hi, Started my stage build.

Here's the framing (not coupled yet). It's 139" long and 35" deep. The 2x6 are spaced roughly 12-14" apart. The interior cavities will be filled entirely with sand.

http://i469.photobucket.com/albums/rr54/91BlckGT/Home%20Theater/DSC_0152.jpg

I'm pondering adding a 2x4 cross bracing bisecting the middle, cutting that 32" span into a roughly 16" span (i'm going to stagger to make nailing / srewing easier).

The stage will be sitting directly on a dri-core floor, with green glue between the wood framing and the floor itself.

I bought standard OSB 4'x8' sheets to put on top. I had planned on two layers, but I may end up with three. I'll likely put just roofing felt between the layers.

As a point of reference I'm following this model:
http://www.bobgolds.com/Stage/DennisErskineStage.gif

However I don't plan on stuffing fiberglass around the sides, as I'm fine with the air cavity there.

Here's the finished design I'm shooting for. The stage will be primariy as an architectural feature, and for my kids to dance on. :)

http://i469.photobucket.com/albums/rr54/91BlckGT/Home%20Theater/stage_exterior_lip.png

Ideally I'd put my SVS sub on it, but I currently have a 16-46 PC plus. It shakes the whole house, even IN the theater. And that takes some doing. I'm hoping sitting it on the stage will dampen it down a bit, because I think what's happening is the sub is vibrating the concrete, which is shaking the house structure. That's the only piece that is coupled, as the walls / ceiling are room within a room construction (except for two rafters where I was forced to use whisper clips).

Anyway, my point is, will that be TOO much wood in the stage? I know we are shooting for a maximum mass here, so more sand is better, but I wasn't sure if more cross-bracing (which would lower the resonate point of the wood itself) would be good too.

Thanks in advance!

Allow me to rant a bit more about the sub. First off, these SVS subs are beasts. ANd I don't even have the ultra! Just one single 12" in a very small (240 square foot) room.

The room (which I've just about finished) is fully room w/ in room, with 5/8" DD + GG on walls ceiling, soffits. double insualted, ceiling rafters stuffed with insulation. The works. big heavy 1.75' solid MDF door too.

Anway, I was amazed at how much the room damped the SPL when I measured my pyle mains: 120dB in room, ~50dB above.

That is, until I tried the SVS. I've never ran it in a room this small, it's always had to pressurize my whole house.

oh. my. god.

I can't get the gain up past halfyway, it's quite loud. Anyway, I run it in 12hz tune, and I went upstairs to check out the affect while listening to a bass CD. And my wife is sitting there with a cross look on here face going "Yeah, I feel it".

It wasn't *loud* per say, but the entire floor was shaking, mainly on the sub 40hz tones.

Am I just screwed here? THe whole point of investing thousands of dollars in this theater is to crank the bass up! And it seems like that can't happen. Sure, the room is nice and quiet, but my whole physical house is shaking!

Is the nature of low-frequency (10-40hz) wavelenghts such that they are basically "uncontainable"? I don't think the air is escaping, but it's the massive house shake that's the problem now.

And yes, I did have all my bass traps (3 full height super-chunk 703 filled traps) rolled into the room for testing purposes. I have one more to build, but sheez.

Ted, Terry, Bryan, or Dennis will be the best resource to answer this.

My thinking here is that you really don't need the cross bracing. I think that the wood will be fine on it's own, and that the vibrating sand will dampen down the vibrations quite a bit. I don't know about how the amount of wood affects the dampening, but I do know that more mass (of sand) will surely dampen the vibrations significantly.

If you are really concerned about killing the vibrations, talk with one of the folks mentioned for help. I could see this becoming a significant issue if the vibrations through the structure are not addressed.

CJ

I think the sand for the stage will help and also if you haven't finished the window plug it might play a small part in your problem. But I understand your rant, I went back and reviewed your build thread and It appears you did everything right and to be shaking the house down is a disappointment.

I think the sand for the stage will help and also if you haven't finished the window plug it might play a small part in your problem. But I understand your rant, I went back and reviewed your build thread and It appears you did everything right and to be shaking the house down is a disappointment.

I wouldn't say it's shaking the house down, but it is noticebly distracting. I might have had it a bit louder than I would traditionally watch, but not outrageous. I doubt the SPL was over 100dB. I'll have to measure it at some point.

It's possible the missing window plug contributed. More likely I was sloppy and errounously coupled something. I doubt it's the fiberglass, it can't transmit that much bass. Darn dri-core. I should have laid down acoustic mat and just dropped a subfloor on top of it.I guess it's not too late, but the walls are still coupled to the floor. Cest la vie.

If one small svs sub can do all that then they must be well worth the money...EVEN the 1500$$ top of the line ones. Dont know why we would build our own that end up costing that much anyways if you can buy them already done?

Of course my diy sub cost hardly anything so im not in the same boat as some of they people here that spend 1000+ and then having to set everything up too..

The stage will be sitting directly on a dri-core floor, with green glue between the wood framing and the floor itself.

I bought standard OSB 4'x8' sheets to put on top. I had planned on two layers, but I may end up with three. I'll likely put just roofing felt between the layers.



Hello 91...

I'm making the assumption you are talking about putting GG on the bottom side of the stage framing between the 2x's and the Dri-core.

Originally, people experimented with GG on their studs before the first layer of Dwall, however I think the general consensus was this had little effect becasue the surface area of the studs did not offer enough area to provide any damening effect.

Based on conversations with Ted and John at the soundproofing company I got the impression this was a waste of effort and GG.

IMHO the better approach would be to put the Tar Paper ( A couple of Layers or maybe even Acoustik Mat.)under the stage and the GG between the layers of the OSB.

Hopefully Ted or someone will correct me if I got this wrong...

Brad

I had another thought. Perhaps although you did everything right in managing the sound escaping via the HVAC, your system is still connected to the houses system. The low frequency air pressure waves could be traveling out via the duct work. You could try an experiment of totaling sealing your vents in the theater and see if it makes a difference. If that is the case than you would know what you have to work on. Obviously you can't leave them sealed.

One other note that may be worth consideration is to make the cut in the in the Dri-core around the entire perimeter of the stage (Like in DE design), particullarly if your walls are framed on top of the dricore.. I would think this would help to de-couple the stage from the walls and the rest of the flooring somewhat, and to utilize mass of the concrete to gain a "little" more dampening.

Brad

I had another thought. Perhaps although you did everything right in managing the sound escaping via the HVAC, your system is still connected to the houses system. The low frequency air pressure waves could be traveling out via the duct work. You could try an experiment of totaling sealing your vents in the theater and see if it makes a difference. If that is the case than you would know what you have to work on. Obviously you can't leave them sealed.

Boy I wish. My HVAC's are fully decoupled, both structurally and acoustically. They use dedicated room-controlled fans to push / pull the air in. They vent into the adjoining room. They are built using the "dead vent" Ted recommends. When I put my ear up to them I can't hear any thing coming through them. The room itself does a decent job of blocking sound waves, but not vibrations once you pass a certain threshold.

The door itself is by far my weakest link. I can ear dialog thorough it, and it rattles in it's hinges. I haven't yet put any weather stripping on it, so that will clearly help air / sound transmission, but have little affect on physical vibration.

If one small svs sub can do all that then they must be well worth the money...EVEN the 1500$$ top of the line ones. Dont know why we would build our own that end up costing that much anyways if you can buy them already done?

Of course my diy sub cost hardly anything so im not in the same boat as some of they people here that spend 1000+ and then having to set everything up too..

Well, I haven't heard Hsu, or eD subs, but I suspect they are just as good. SVS makes an excellent "bang for the buck" sub. You need bigger subs when you have a bigger room to pressurize, or are striving for concert-level bass (>120dB). For tiny sealed rooms I'm finding that one 12" is plenty, thus far. That's not to say I won't upgrade though.

I had wired / left my options open for 4 sealed adire 15" or 18" sitting in a giant box on the stage (in essence, the stage because the bottom of the box and ceases to be a stage). That won't happen for two reasons:
1. Me personally, I can not design or build a sub enclosure that will max the sound quality of a professionally designed box.
2. I would be wasting money by paying for more bass than I use / need / want. That's not say I wouldn't like it. I can never have too much bass "capability", but I can certainly have "too much bass". It needs to blend with the system, not overpower it and throw it down like a WWE wrestler on a 'roid binge. :D

Hello 91...

I'm making the assumption you are talking about putting GG on the bottom side of the stage framing between the 2x's and the Dri-core.

Originally, people experimented with GG on their studs before the first layer of Dwall, however I think the general consensus was this had little effect becasue the surface area of the studs did not offer enough area to provide any damening effect.

Based on conversations with Ted and John at the soundproofing company I got the impression this was a waste of effort and GG.

IMHO the better approach would be to put the Tar Paper ( A couple of Layers or maybe even Acoustik Mat.)under the stage and the GG between the layers of the OSB.

Hopefully Ted or someone will correct me if I got this wrong...

Brad

That is a correct assumption, but I think you're on to something with the lack of surface area. I'm not sure how much GG I have left (I bought it in two giant pails). Might not be enough to fully treat an entire stage, but I'll give it a shot there. I'm heading out over lunch to pick up the roofing felt / tar paper anyway, so I'll lay that down at the bottom.

The Green Glue will do nothing on the edge of a framing member. Not enough surface area to damp anything.

The low frequencies aren't likely travelling through the slab.

In my opinion, this is LIKELY simply a result of the frequencies being played are lower than the resonance frequency of the walls or ceiling or both.

Good to know.

I picked up #30 roofing felt. I'll put as many layers down as I can (probably about 4) below the framing.

With the GG, does it have to mate with similar materials to be effective? Meaning, can I lay down a layer of OSB, a layer of felt, THEN a layer of GG, and then more OSB?

That's probably a bad idea, but just wanted to know if anyone's tried this.

Felt will not damp nor decouple the frame. Not even a little. I would strongly recommend you just set the frame on the slab. Efforts in this area will provide no benefit.

Constrained layer damping materials function optimally when the materials are of similar stiffness. Double 1/2" drywall is OK, while 1/4" + 1" drywall isn't so hot.

You can mix plywoods and drywall with similar thicknesses since these materials have similar stiffness.

In my opinion, this is LIKELY simply a result of the frequencies being played are lower than the resonance frequency of the walls or ceiling or both.

Looking at your decoupled wall plan and pics. I have a bad feeling your walls aren't actually decoupled. The foam on them reduces the air cavity volume. You have many, many small air cavities, not one big one. The walls also appear to be pushed up snug to the concrete, limiting their ability to move and flex. This also raises the low frequency resonance point of your system.

Felt will not damp nor decouple the frame. Not even a little. I would strongly recommend you just set the frame on the slab. Efforts in this area will provide no benefit.

Ted:

If the tar paper under the stage and riser do nothing acoustically, why do we do it? I did it on my stage, but I didn't know why.

CJ

It's common to install in the layers on top of the stage to maybe help with squeaks.

I can only assume the same logic holds for those that place the paper between the frame and slab?

...

I had wired / left my options open for 4 sealed adire 15" or 18" sitting in a giant box on the stage (in essence, the stage because the bottom of the box and ceases to be a stage). That won't happen for two reasons:
1. Me personally, I can not design or build a sub enclosure that will max the sound quality of a professionally designed box.
2. I would be wasting money by paying for more bass than I use / need / want. That's not say I wouldn't like it. I can never have too much bass "capability", but I can certainly have "too much bass". It needs to blend with the system, not overpower it and throw it down like a WWE wrestler on a 'roid binge. :D

If you are getting "overpowering" bass it likely has little to do with the size and/or number of drivers, but more to do with how the sub is integrated into the room. It really takes little money and not a ton of effort to build your own sub that will easily rival a pro, store bought sub. The many difference is that pro usually can get more out of a smaller sized sub then the home builder. I spent around $1,000 to build a custom IB sub with four 18" drivers. I had to sacrifice some space, but theoretically (I haven't done the tests yet) I should be able to get a smooth response down to 10 Hz and maybe even lower. It will be an experience like no other.

It's common to install in the layers on top of the stage to maybe help with squeaks.

I can only assume the same logic holds for those that place the paper between the frame and slab?

I had read that it provides a cushion and help with the dampening of the sub's vibrational energy. I did it only because I had some handy. I didn't know why, so I followed the pack.

Ted, maybe you could do a write up about stages and risers; best building practices and the impact of sand in a riser (emperical data is always best). You could also cover what to do when you can't put sand in a stage (on a second floor for instance), and give some idea of what you would lose by this.

;)


CJ

Hey CJ,

That sort of topic really falls into the realm of the theater designer. I really know little with respect to proper design.

Looking at your decoupled wall plan and pics. I have a bad feeling your walls aren't actually decoupled. The foam on them reduces the air cavity volume. You have many, many small air cavities, not one big one. The walls also appear to be pushed up snug to the concrete, limiting their ability to move and flex. This also raises the low frequency resonance point of your system.

Well... Crap. :mad:

No one's fault but my own, of course, but I went through great expense (both time and money) to end up with a compromised system.

I could have, (and did have the opportunity) to hire a professional acoustic engineer to help me design / build the room. But I couldn't afford them. Sole source of income and three kids does not provide for much disposable income.

I had to put the foam up to provide for a vapor barrier. There is still about a 0.5" air gap all around. I put spacers down before I put the walls up. The spacers themselves might actually be doing the coupling.


Anyway, can you clarify how the gap between the framing and wall affects the resonance point? Isn't the resonance point a function of mass of the structure, not it's proximity to other structures? Or are we discussing the resonance of the air trapped around the structure?

If you are getting "overpowering" bass it likely has little to do with the size and/or number of drivers, but more to do with how the sub is integrated into the room. It really takes little money and not a ton of effort to build your own sub that will easily rival a pro, store bought sub. The many difference is that pro usually can get more out of a smaller sized sub then the home builder. I spent around $1,000 to build a custom IB sub with four 18" drivers. I had to sacrifice some space, but theoretically (I haven't done the tests yet) I should be able to get a smooth response down to 10 Hz and maybe even lower. It will be an experience like no other.

The room isn't tuned. When i had my last theater set up with proper bass traps and a tuned BFD taming my room peaks, I had near flat response from 12hz to 80hz where it rolled off. near flat being no more than 3dB differences along the line. I was very pleased with linearity of it. I have no reason to suspect that this system will be different.

In fact, the bare room exhibits far fewer modal issues than my last theater. Un-trapped, I can still hear decent bass all around the room, except for dead center in the room, where there is a pronounced "null". It isn't as bad as my last theater where I had a "noise canceling affect" at the room mode points.

I had read that it provides a cushion and help with the dampening of the sub's vibrational energy. I did it only because I had some handy. I didn't know why, so I followed the pack.
CJ

heheh

I wonder how many of us did that?

Well, the felt was only $25. And it's heavy, so it's gonna have some sort of mass affect just sitting on my dri-core. Mainly it will act as a nice seal between surface irregularities on the board, should the plastic leak sand.

And oh yeah, back to the thread topic:

Should I caulk the interior cavities of the stage? I have three tubes of silen-seal still sitting around, one of which I opened up when I put the columns up.

Should I caulk the interior cavities of the stage? I have three tubes of silen-seal still sitting around, one of which I opened up when I put the columns up.

I wouldn't bother.

I could have, (and did have the opportunity) to hire a professional acoustic engineer to help me design / build the room.

Entirely possible if not likely that they would not have known what to do. I have found that most acoustical consultants understand sound conditioning (in-room) but not sound isolation. Theater designers are a different story since they deal with isolation all the time.


Anyway, can you clarify how the gap between the framing and wall affects the resonance point? Isn't the resonance point a function of mass of the structure, not it's proximity to other structures? Or are we discussing the resonance of the air trapped around the structure?


We're discussing the overall resonance point of the system which is defined by several things:

The mass of the system as you said

Decoupled? yes / no

Absorption? yes / no

The size of the air cavity as you said.

I was looking at your old pictures and wondered if that foam was tight to the foundation. If so, you would limit the decoupling, which raises the resonance point.

In a typical system, the area behind the drywall is one big open cavity with insulation. That big cavity lowers the resonance point a lot. The foam sealed to the back of the studs and the drywall sealed to the front of the studs creates many small air cavities rather than one big one.

I'm speculating but that would fit some of what you're describing.

Entirely possible if not likely that they would not have known what to do. I have found that most acoustical consultants understand sound conditioning (in-room) but not sound isolation. Theater designers are a different story since they deal with isolation all the time.




We're discussing the overall resonance point of the system which is defined by several things:

The mass of the system as you said

Decoupled? yes / no

Absorption? yes / no

The size of the air cavity as you said.

I was looking at your old pictures and wondered if that foam was tight to the foundation. If so, you would limit the decoupling, which raises the resonance point.

In a typical system, the area behind the drywall is one big open cavity with insulation. That big cavity lowers the resonance point a lot. The foam sealed to the back of the studs and the drywall sealed to the front of the studs creates many small air cavities rather than one big one.

I'm speculating but that would fit some of what you're describing.

Ahh. I get what your're saying. But doesn't everyoen who builds a theater in a basement have to do that? The fiberglass inside the walls can't be directly exposed to the air behind the drywall, because that air is moist from water vapor penetration through the cement. All basements have high water vapor content, it's their nature.

I read on many waterproofing sites that this is pretty much a "must" to do, to seal that fiberglass up, if you want to prevent that "musty" basement smell after a few years.

I guess it never clicked that I'd have to make design tradeoff: Smell vs. noise.

Anyway, I'm hoping that a good majority of that bass wasn't being transmitted through the floor. It's not a deal breaker or anything for me if people above me can hear it.

Most people have a moisture barrier on the face of the studs before drywalling. This maintains a great big air cavity. Also, because of that free air space back there, there is some convection to keep moist air moving.

Since the foundation is below grade, the walls don't get too cold, therefore less reason for the foam.

If a finished basement uses both insulation and vapor barrier, the moisture from the walls stops at the vapor barrier. If the barrier is on the warm side (between stud and drywall) moisture does not condense and stays as a vapor. If the vapor barrier were moved to the cool side, the vapor would condense into liquid.

I am not near as far as you but I worked with my inspector and I glued 1.5 inch EPS foamboard to the foundation blocks. Sealed all the seams with caulk and tape. Then built the wall 1" from the foam board, inspector said not to seal the framing (wall) to the foamboard.

There was 2 ways to do it..

1. vapor barrier against block then foamboard, unfaced insulation in wall
2. foamboard on block, then vapor barrier, unfaced insulation in wall

There is a war on vapor barrier but that was the code here. Nonetheless, the inspector stated if I wanted to isolate my framing from the block, to keep in an 1" away from foamboard. I only had to put 1/2" drywall for fireblock on the top of my new wall plate over to the sill (which I am not thrilled about because it seem to go against the isolation part)

I am hoping that since air can move freely behind entire my wall because the cavities are not sealed that each cavity is not a drum.

Well, I got the stage built. Laid down two layers of felt for the heck of it. Keeps it from scooting around at least. ;)

I'm a little unclear on the technique for putting donw the plastic. Do I just cut it and put it on the bottom? Do i cover all four inner sides? Do you fold it flat? Do I drape it as one big sheet over the whole length and just smoosh it down into the cavities?

I know. Mr. questions. ;)

I'm a little unclear on the technique for putting down the plastic. Do I just cut it and put it on the bottom? Do i cover all four inner sides? Do you fold it flat? Do I drape it as one big sheet over the whole length and just smoosh it down into the cavities?

I know. Mr. questions. ;)

I used 55 gallon trash bags to line mine. My cavities were each about 33" long, 14" wide and 12" deep. I cut the bottom off and one side to make one big flat piece. I then laid it inside the cavity, and draped the sides over the wood sides. I poured sand in until they were full, then gathered the plastic in the top of the sand. I didn't seal the cavities up...I just installed OSB over them. There are photos on my build thread.

CJ

I believe I sealed up mine with caulk. Everywhere. This was 8 years ago, but I seem to recall using sealant.

Not sure that was efficient, but you want to get as much air out as possible

I guess it never clicked that I'd have to make design tradeoff: Smell vs. noise

Using an expanding foam product for insulating value is great ... high R values per inch plus a good sealer. What many foam installers will neglect to mention is your greatest value is achieve in the first 1.5 to 2" of foam. So, if you want to have your cake and eat it too, install 1.5 to 2" of foam, install framing, install fiberglass in framing, install clips/channel, then drywall.

Local codes will vary wrt where the vapor barrier needs to be installed...so check. As well, if you're in a high humidity environment ALWAYS install a central dehumidifier (it will save a fortune on cooling costs) and reduce the chance you'll have a mold remediation adventure in the future.

Using an expanding foam product for insulating value is great ... high R values per inch plus a good sealer. What many foam installers will neglect to mention is your greatest value is achieve in the first 1.5 to 2" of foam. So, if you want to have your cake and eat it too, install 1.5 to 2" of foam, install framing, install fiberglass in framing, install clips/channel, then drywall.

Local codes will vary wrt where the vapor barrier needs to be installed...so check. As well, if you're in a high humidity environment ALWAYS install a central dehumidifier (it will save a fortune on cooling costs) and reduce the chance you'll have a mold remediation adventure in the future.

If I had to do it all over again, I would definitly install the insullation against the wall, then air gap, then frame / fiberglass. In fact, I have to still build the adjacent room, and I'll probably go ahead and apply these techniques it as well, although I won't be doing DD this time, I'll probably just do single layer with whisper clips and hat-track. Those whisper clips and hat channel presented a very nice target for installing the drywall, and I didn't have to worry about 16" OC spacing for butting the ends of the drywall.

How "full" does the stage need to be with sand. Is this full enough? There's no more than 1/8" gap between the sand and the joints.

http://i469.photobucket.com/albums/rr54/91BlckGT/Home%20Theater/DSC_0153.jpg

I can probably fill a tiny bit more. The dimensions worked out to two bags of sand per hole. Which means 20 bags of sand, or 1000 lbs of sand.

I filled mine up to the top, then folded the bags over. I just got done finishing up the stage top. Pictures to follow.

CJ

Is there a "stage build bible" thread out there?

This one is quite useful, especially with DE's diagram but a dedicated, general stage-build thread would be handy fopr me right now.

(Same with a riser one, for that matter).

Searching sometimes reveals the best ones....sometimes not.

Is there a "stage build bible" thread out there?

This one is quite useful, especially with DE's diagram but a dedicated, general stage-build thread would be handy fopr me right now.

(Same with a riser one, for that matter).

Searching sometimes reveals the best ones....sometimes not.

Not tha tI've found. Maybe in addition to the sticky "show me" thread, we can compile a sticky "construction details for ... x" thread. Of course then, we'd never be posting anything, would be? :)

So I loaded up all the sand on the cart. Took it to the register. Took it to the van. PUt it in the van. TOok it home (the bumper was practically dragging!)

Unloaded it one bag at a time, and drug it inside, down stairs, and into the basement.

Whew.

It's beer time.

http://i469.photobucket.com/albums/rr54/91BlckGT/Home%20Theater/DSC_0154.jpg

So I loaded up all the sand on the cart. Took it to the register. Took it to the van. PUt it in the van. TOok it home (the bumper was practically dragging!)
Unloaded it one bag at a time, and drug it inside, down stairs, and into the basement.
Whew.
It's beer time.


Haw many extras are you going to have? :D

My friend Mike had 9 bags left over that he had to take back to the store: http://www.avsforum.com/avs-vb/showthread.php?p=8959157#post8959157

I had one bag extra (though I could have gone to get another 8 bags to fill the remaining 5 steps). I don't think that not filling those 5 steps will make any difference.

CJ

Not tha tI've found. Maybe in addition to the sticky "show me" thread, we can compile a sticky "construction details for ... x" thread. Of course then, we'd never be posting anything, would be? :)

It's pretty straight forward to build a stage. Dennis wrote an article on stages some time back ( http://archive2.avsforum.com/avs-vb/showthread.php?p=8162230&&#post8162230 ).

Here's an article on stage building written by Dennis E. http://www.avsforum.com/avs-vb/showpost.php?p=14176394&postcount=14

I think that there is also a riser build thread. Check the SEARCH function...you may have to go back to the archives too.

CJ

Well, I finished the sand fill. Took some more measurements. Still boomy, but not quite as much so. I'm not sure what my levels were during the last test. It was about 105 dB in room. Baby was nursing right above, so I had to take it easy.

Needless to say, and normal, nominal listening levels everyone in the house will just sleep right through whatever I'm watching, so it's still all good.

Ted is spot on with the "resonance" theory. When I smack the walls, I hear the resonating point with the dull thud and a whoomp. I need to try smacking the partition wall, which, in theory, should not suffer the drum problem, as it does not have the vapor barrier.

Hopefully my BFD can tame this peak down a bit around the resonant frequency. That might also be a good frequency to build a hemholtz resonator tuned to. :)