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Why build a stage at all??? Why not not just build a half stage and place speakers on basement...

post #1 of 15
2/20/13 at 1:30pm
Thread Starter 
I have been working on my proscenium and stage design and keep thinking about the why? The zillion lbs of sand required to fill the stage keeps making me go hmmm.

I think I understand the reason for the stage in an AT set up. To align the screen with the eye of the viewers, frame the screen, put the speakers at proper height, etc. It also looks visually appealling. Any others?

The reason for the sand is to allow the speakers and sub to function on a non resonant solid surface. Maybe as good as placing the speakers directly on the concrete floor. So.....

Why not just put the speakers directly on the concrete floor using a slightly taller stand to get the speakers at ear level? If you want the look of the stage, you can build out the front part and elevate it to match the riser, but leave the area behind the screen without a stage and put the subs and speakers directly on the basement floor. That has got to be a lot easier, cheapers, and probably just as effective.

Thoughts???
Edited by Johnnymenudo - 2/20/13 at 1:38pm
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post #2 of 15
2/20/13 at 1:37pm
Another reason is that it acts as a visual barrier. I've seen grow ups and kids from 2 to 70 try to touch screens. If the stage is there it deters them.

It's very easy to tell a group if 7 year olds "Don't touch the screen and do NOT get on the stage"
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post #3 of 15
2/20/13 at 1:38pm
Oh, and placing speakers on a concrete floor is NOT the same as sand. Concrete rings like crazy. With sand you have to shake a WHOLE LOT of mass (hint: more than your subs are capable of) for it to transfer into the floor.
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post #4 of 15
2/20/13 at 1:38pm
Yup, you can do that, I've seen a couple builds do just that. Would give you some extra flexibility for speaker / sub placement too (like if you had very tall floorstanders).
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post #5 of 15
2/20/13 at 1:41pm
Thread Starter 
Quote:
Originally Posted by jdanforth View Post

Another reason is that it acts as a visual barrier. I've seen grow ups and kids from 2 to 70 try to touch screens. If the stage is there it deters them.

It's very easy to tell a group if 7 year olds "Don't touch the screen and do NOT get on the stage"

That is the front half of the stage. I agree totally. But the area behind the screen where the speakers go that no one ever sees? Why build a hollow box that requires great effort to fillow with sand, place roofing felt and double plywood etc. just to make it function like a concrete floor? You already have a concrete floor ready at your disposal? I think the decoupling aspect might be one, but I doubt that is a practical advantage over tons of concrete.
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post #6 of 15
2/20/13 at 1:47pm
Thread Starter 
Quote:
Originally Posted by jdanforth View Post

Oh, and placing speakers on a concrete floor is NOT the same as sand. Concrete rings like crazy. With sand you have to shake a WHOLE LOT of mass (hint: more than your subs are capable of) for it to transfer into the floor.

If that is the case, wouldn't that actually be beneficial as we want to feel the subs as well as hear them? The thing that I like least about my current theater is that the concrete floor absorbs the sub energy so much compared to when I had them in my main level. I had to use clark tactile tranducers in the risers to get the tactile sensation of the low frequency content.
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post #7 of 15
2/20/13 at 3:24pm
Quote:
Originally Posted by Johnnymenudo View Post

If that is the case, wouldn't that actually be beneficial as we want to feel the subs as well as hear them? The thing that I like least about my current theater is that the concrete floor absorbs the sub energy so much compared to when I had them in my main level. I had to use clark tactile tranducers in the risers to get the tactile sensation of the low frequency content.
Depends. If you want the sub energy to travel directly into your slab/foundation and bypass your soundproofing, then go ahead. However, if you have taken the steps to do sound containment to your HT, I believe you would want to have the sub on a sand filled stage rather than directly on the concrete. If you have the right sub for your room, you'll still feel that sub (and shouldn't need bass shakers IMO...).
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post #8 of 15
2/21/13 at 8:22pm
Quote:
Originally Posted by GWCR View Post


Depends. If you want the sub energy to travel directly into your slab/foundation and bypass your soundproofing, then go ahead. However, if you have taken the steps to do sound containment to your HT, I believe you would want to have the sub on a sand filled stage rather than directly on the concrete. If you have the right sub for your room, you'll still feel that sub (and shouldn't need bass shakers IMO...).

 

I've been questioning the same thing over the last few weeks as I've read builder after builder hauling thousands of pounds of dirt into their homes.  On the one hand, you have to believe that so many people doing the same thing must be doing so for a good reason.  But then again you have the cultists who cheerfully tell you to just drink the Kool Aid.  

 

This is the one statement that I've read so far that makes me go "hmmm....".

 

IF the subs are on a concrete floor AND inside an otherwise sound isolated room with all the usual techniques you read about here (stagger studs, double wall, isolation clips, double drywall, green glue, clips and channels, acoustical caulk, plugging electrical boxes, tighter seals around doors, etc.) are the subs really vibrating the concrete slab itself (and by extension then vibrating the concrete walls, which would then give you your flanking path for sound transmission around your sound isolation perimeter)?  Or is the usual modality for sound transmission the vibration of the drywall and studs of the walls being transmitted through to other framing members and then the floor of the room above -- in which case your sound isolation techniques should be effective at blocking?

 

Is there any benefit to the sand packed stage if one is using in-wall LCR's (i.e. full range, no subs)?

 

If mounting subs behind the screen wall, would there be any practical difference between putting them on a full (behind the screen) stage filled with sand vs. just a sand-filled platform the area of the subwoofer itself?

 

I assume that the touted benefits of the sand-filled stage is somewhat dependent upon a certain amount of mass, but at what point do you hit the point of diminishing returns?  Is a 24" high stage filled with sand going to be more effective than a 6" high stage sharing the same footprint as the taller stage?

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post #9 of 15
2/22/13 at 3:56am
If you're not going to put your sub on the stage there is little point in filling it with sand. The stage shouldn't be coupled to anything, so you won't get any benefit unless there is something resting on it. That is unless you consider owning the world's biggest paper weight as a benefit biggrin.gif

I don't think Dennis considers himself a cult leader, but here is his explanation.

Tim
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post #10 of 15
2/22/13 at 4:54am
It is a well documented fact that carrying in a ton+ sand for your stage is a required task to earn the highest level of status and recognition as a SENIOR AVS home theater builder, It gives you the right to mock Tom Logan and laugh at any newbie who wants to use an 84 inch screen and thinks Roxul insulation is soundproofing. Think of it as a rite of passage to make you worthy of your man-cave. I make all my clients carry their own sand while I cut the bags open and pour. A picture or eyewitness account by another SENIOR member is required.
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post #11 of 15
2/22/13 at 5:47am
Quote:
It gives you the right to mock Tom Logan

Let's be fair here. It only gives you the right MO me as I carried in HALF of my sand.

You're just jealous because I was smart enough to hire some "guest workers" to carry in the rest of it in the snow storm that started as soon as we arrived at my house. They also carried in the 190 Dricore panels to replace the f-damaged first round (which, BTW I carried all 200) and the 5/8s plywood for the stage. And, oh yeah, they also pushed the HD rental truck out of the hole the tires dug in the yard.
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post #12 of 15
2/22/13 at 7:13am
I forwent a stage and all the normal things associated with it. I wasn’t about to haul out sand and all the rest if my basement floods again.

As for sub and sand they make isolation mats, I would think that would be sufficient. Mine will be sitting on 4 isolation dampers, then on a MDF platform with rubber wheels on carpet and pad. No idea if that is going to be good or not but we’ll see soon enough. If that doesn’t work I’ll add an isolation mat between the isolation pucks and the MDF.
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post #13 of 15
2/22/13 at 7:23am
Quote:
Originally Posted by Johnnymenudo View Post

That is the front half of the stage. I agree totally. But the area behind the screen where the speakers go that no one ever sees? Why build a hollow box that requires great effort to fillow with sand, place roofing felt and double plywood etc. just to make it function like a concrete floor? You already have a concrete floor ready at your disposal? I think the decoupling aspect might be one, but I doubt that is a practical advantage over tons of concrete.
it does not have to be just

if you get creative you can see what is behind it and it can turn into a great conversation piece

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post #14 of 15
2/22/13 at 11:16am
Quote:
Mine will be sitting on 4 isolation dampers, then on a MDF platform with rubber wheels on carpet and pad. No idea if that is going to be good or not but we’ll see soon enough
yeah; but, all of that will allow your sub-cabinet to move. Not good. A sub should be anchored to something with considerably more mass than the subwoofer itself.
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post #15 of 15
2/22/13 at 1:47pm
Quote:
Originally Posted by Dennis Erskine View Post

yeah; but, all of that will allow your sub-cabinet to move. Not good. A sub should be anchored to something with considerably more mass than the subwoofer itself.

I'll have Auralex isolation pads between the sides of the platform and the rack enclosure so the platform the sub is on won't be able to move around.
70AE9451-DC94-498E-9F8C-B8074B2C6897-128-0000000315442C0A_zpse520db88.jpg

For reference the sub will be on the black platform on the bottom. I was worried about the sub moving around so I'll make sure it's wedged in tight..
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