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Discussion Starter · #1 ·
I am currently in the planning stages for a HT in my basement. The room is 17' 6" w by 20' 1" long with a concrete floor. I have talked with a local HT shop and they are recommending a subfloor and resilient channel for wall construction. I have seen Dennis Erskine and several others recommend no subfloor and 2 layers of dry wall (1/2" & 5/8"). That was the direction I was leaning in until they made it out to sound wrong. Can someone help clear my mind.:confused:
 

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The Drywall Channel makes rooms really quite, much more than two layers.


While redoing the basement I decided to use this channel on the ceiling and floor and it worked wonders. My noisey computers can't be heard upstairs anymore...


Its a simple channel that goes on the studs and you screw the drywall to these little tabs... even we could hang it.


Divert :)
 

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This is a long standing debate on this forum. The resiliant channel is really hard to get right and even when you do it can be unpredictable from a sound performance standpoint.


HT shop guys are notoriously ignorant from my experience.


JMO of course but mine is Dennis specified and it is wonderful.


Greg
 

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The crux of the debate centers around the resilient channel's risk of absorbing desirable bass within the room.


Double walls + double drywall makes for a very stiff wall, keeping bass IN and audible.


Resilient channel makes for a looser wall and while somewhat effective at keeping bass from escaping, you risk absorbing (removing) it also. You may wind up adding a second sub.


The most efficient (yet reasonably achievable) system is a double wall + floating ceiling. This provides for a far more de-coupled system without risking bass loss, and provides increased acoustic isolation.


Don't get me wrong. A system of resilient channel MAY work fine and NOT excessively absorb bass. Lots of fine theaters have resilient channel.


Ted
 

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I have cut and pasted a post of mine from another thread. This post does not directly address the resilient channel topic; however, the idea, and the potential negative impact is the same. With RC you are still creating a diaphramic absorber. Yes...RC is effective in the reduction of sound transmission through walls. Something important in sound studios (the small rooms....large sound stages have different issues). With near field monitoring in the booth and close mikes, bass response requirements are considerably different than in your playback environments.


I should note, the following quote mentions Dr. Floyd Toole. He is a gentleman whom I hold in high regard and I have followed his research over many years...even as far back as his work with Sean Olive in Canada when I was with Bell Canada (BCE) & BNR.

Quote:
Dr. Toole and I disagree on this point entirely. On the other hand, he, as do I, suggests 1/2" drywall over 5/8". That suggestion, I believe, is in a different white paper but within the same series. I also believe Floyd has been known to ask why you're spending a bunch of your watts moving walls and floors instead of your ear drums.


When you create a flexible wall you are creating a diaphramic absorber. Diaphramic absorbers are excellent tools to provide bass frequency absorption (as are other mechanisms such as Heimholtz resonators, bass traps, etc.)


That being said, when you build and design your room, you have a few things going against you. Among them is, unless you have some very expensive tools at your disposal, you will not be able to accurately predict which bass frequencies will require reinforcement and those that will require some amount of reduction. Even those modal speadsheets can quickly lead you down the path to disaster. First, they are only accurate in a perfectly rectangular, 100% reflective room; and, secondly they only point to the potential frequency of a mode but not to it's amplitude. Without knowing the amplitude, you don't know if you are predicting a big problem, a little problem, or no problem.


Now, back to flexible walls. If you built a flexible 2x4 framed wall and install your drywall vertically, you've created a diaphramic absorber that has entirely different characteristics than the exact same framing with the drywall positioned horizontally. (Oops..someone forgot to tell you that?) Equally to the point, you'll find very little correlation of the flex structure between sheets of dry wall. Much less, sheets of drywall cut differently (to go around doors, windows, outlets, light switches, sconces, etc.). Did I ask which way the crown and grain were going on the studs...and were they 7'-8" or 9'?


So, in the end, you've created a diaphramic absorber that absorbs an unknown series of frequencies to an unknown degree within a room for which you have no clue about which frequencies need to be absorbed nor what degree. It might work out for you. I'd suggest the odds are against you. This is really, really a problem if the frequency your walls are absorbing is a frequency that needs a bunch of boosting. (Double oops.)


Of greater concern, however, is if you create these flexible walls and you are wrong, your only fix is to tear out the walls and do it again. An expensive and discouraging process. On the other hand, if you have stiff walls, once the room is completed you can measure (to within 1/12 an octive or better if you wish) exactly what frequencies need correction and exactly to what degree. The columns and soffits that were created specifically for your room can now be bass traps, heimholtz resonators, etc. (You don't have such elements in your room? Oh, oh.) Now you can fix the exact problem, to exactly the right degree without tearing out your walls. I'm just not fond enough of drywall to want to do it over.
 

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Discussion Starter · #6 ·
Thanks all for your replies. This helps a lot and makes perfect sense. After lurking here for a few months I have come to trust the opinions here more so than my local guy. He does however have a HT in his showroom built the way he has suggested, but as Dennis noted in his post, I am sure they have the equipment to make it right that I don't have.
 
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