Deadline Has Been Set (and Re-Set...) Theater Build - Page 8

I've always been told it has something to do with the drying process and planing. But the conspiracy theorist in me likes your answer

And perhaps it isn't 15/32" - if you check closely, then perhaps it's 12mm.

You hear anything out of Jamestown about your screen? I ordered mine back on the 10th of October and still can't get any word on whether it has shipped or not. Supposedly it was going to be completed by the end of last week (nearly two weeks after it was quoted to be done). Have emailed them but will call if it isn't sitting on my porch when I get home today.

Dang. Sorry to hear. Doesn't give me a warm fuzzy feeling about mine showing up this week. Crossing my fingers that it is there otherwise he will be getting a phone call from me too.

good job... see it was not to bad to do

How well did the 3/8" bend? I had some 1/2" left over but kept breaking it when trying to get it to curve. I tried kerfing(?) it but it would then just break along one of the kerfs. My span is shorter (47" both ways) so perhaps thats why I'm having so much trouble.

any time

now you get to fill it with sand ha ha ha ha ....

Nice work. Beach time!

Looks good! What are you planning to layer on top of the stage?
Looking at the date on the calendar it looks like you may have to rename your thread

I wouldn't think you would want to use both. I'm guessing you would want the GG to adhere to both pieces of wood. I know that early on it was recommended to use roofing felt, but more people are going the GG route now. I recently finished my stage and am really glad I went with the sand, 2 layers of 3/4" OSB with GG between layers. It is as solid as a rock and barely makes a thump when you jump on it. If you have the GG already, I would recommend going that route.

Roofing felt is cheaper. The idea is to prevent wood to wood squeaks.

And if for any reason you ever need access to the sand, roofing felt again wins.

Well, that's feelgood for sure, but isn't it overkill vs just using the proper soft feet below the speakers? If you're using spikes I can understand why you'd need to dead dampen it.

Soft feet and rubber mats under a subwoofer will reduce, but not eliminate, energy (vibratory) transfer to the structure. Once that energy is in the structure it will manifest itself in walls, cabinets, floors, etc. which end up with the same resonance frequency. Equally to the point, as the motor moves forward/backward the cabinet will move backward/forward ... that ol' equal but opposite problem. When the cabinet moves in the opposite direction of the motor, that movement can, and will, reduce the effectiveness of the sub, if not its "crisp" response to the input signal. Subs, particularily high output/low frequency capable, need to be very firmly anchored to mass at least an order of magnitude greater than that of the sub. That mass needs to be reasonably isolated from the structure of the house. When mounted to a raised stage/platform, cavity resonance within that stage/platform should be reduced or eliminated. Sand is inexpensive, highly effective in absorbing vibratory resonances, and creates the high mass platform.

Green Glue between decking layers is preferred to roofing felt. Roofing felt was one of several different items used prior to the general and commercial availability of viscoelastic damping agents for CLD applications.

Properly tuned soft feet will make it quite difficult to measure any energy transfer. Wrongly tuned soft feet will of course be less efficient

Well, Newton's Third at work here. But what you stated is somewhat off. It's not the weight of the subwoofer you have to calculate with - it's the moving mass of the cone. And the factor that the cabinet needs to oughtweigh that mass is approximately x1000, so three orders. Making sure subwoofer cabinets are heavy enough is quite possible, say for a 10" subwoofer with an Mmd at 30grams... that gives a cabinet weighing in at 30kg (~60 pounds). (Which is the weight of my 12" subwoofer cabinets, so they may be slightly on the light side)
Now, if people at attaching the speakers firmly to the stage, then that can count as part of the cabinet. Can't say I have seen anyone glue or drill speakers into the floor in any threads, though... If spikes or similar are used - then we still have a rocking system on top of the stage with a movement much more resonant than the small half-period movement on soft feet. Even just standing it flat on surface can induce a rocking movement pivoting around back/front edges of cabinet.

With properly tuned soft feet, I mean the kind you have to weigh the speakers both in front and back in case you need different stiffness due to the weight difference. I need to have my scales out and weigh front/back on my fronts - I only have the total weight presently...
Edited by Nightlord - 11/24/12 at 7:23am

You don't have to carry them all at once, y'know.

67?? i filled every bit of my stage including the front step and i think yours is a little over 12ft wide? if so mine stage is also built like yours and is almost 16ft wide and i used a total of 60 bags ...... so i would think you be some where in the 50 or so bag range ?

I ended up needing almost 70 bags for my stage which is the same design as yours. My stage is 147" wide x 57 1/2" deep. Looks like mine may be a little deeper than yours. I think your number is going to be close. You won't be able to fill each cavity perfectly because of the plastic lining but there will also be some spillage here and there. It's worth having an extra bag or two if it means not having to run back and forth to the store. I think I made three sand runs to finish mine.

I built your stage in CAD and came up with a volume of 68701.603 in^3. After subtracting an estimate for the boards within the stage, I came up with about 68 bags. So yeah, your estimate is pretty good.

Snickers, I think I remember that you used 2x10s to frame your stage? If yes then that is likely why the numbers are a little off.
Edited by aaustin - 11/29/12 at 7:59am