I think you did an amazing job touching every base possible. In my case, since there are two large openings in the space, I just don't think it makes sense to make the walls that bullet proof when there are large openings elsewhere in the room. So, on a cost/benefit analysis basis, I have to figure out what makes sense.
just remember that a free standing wall (where the wave form hits both sides) will act like a bass trap if it's not stout. if it flexes it will absorb. or if there is something inside that is not solid, that mushy mass will absorb. if it's stiff it will then transfer or reflect and direct relative to it's stiffness and mass.
Quietrock (the company) is adamant that Quietrock sheets do not have an NRC rating and are not effective at absorbing vibrations generated from within the listening room. Quietrock is certified only as to preventing sound from being transmitted through the wall from one room to another.
So why do so many audiophiles use Quietrock at least partly for the purpose of absorbing vibrations generated from within the listening room?
(...) In my case, since there are two large openings in the space, I just don't think it makes sense to make the walls that bullet proof when there are large openings elsewhere in the room. So, on a cost/benefit analysis basis, I have to figure out what makes sense.
IMHO at this phase you need some measurements particularly as your room seems too irregular to simulate. The mass of the walls is critical in a room. Remember that sometimes less is better!
just remember that a free standing wall (where the wave form hits both sides) will act like a bass trap if it's not stout. if it flexes it will absorb. or if there is something inside that is not solid, that mushy mass will absorb. if it's stiff it will then transfer or reflect and direct relative to it's stiffness and mass.
Mike, I am afraid I do not understand what you're trying to tell me. Isn't flexing of the Quietrock desirable –– as that is how it prevents the transmission of sound. And that is why required installation is to screw it and glue it to wood framing, 24" on center, so it is able to flex (as opposed to gluing it to a hard wall).
Quietrock (the company) is adamant that Quietrock sheets do not have an NRC rating and are not effective at absorbing vibrations generated from within the listening room. Quietrock is certified only as to preventing sound from being transmitted through the wall from one room to another.
So why do so many audiophiles use Quietrock at least partly for the purpose of absorbing vibrations generated from within the listening room?
optimal strength, minimal depth. add strength to the wall to better hold the bass. and make both sides equal as room boundaries near the speakers, for the initial wave launch.
symmetry was important to me for optimal imaging and life.
I kinda think that microstrip is headed in the right direction. Solving these puzzles is quite complex from a mathematical standpoint and assumptions are dangerous. MikeL is absolutely correct that to retain bass you want to maximize mass, stiffness and strength. However depending on your room dimensions, you may want to manage standing waves by using walls that flex and absorb bass (using KNC ISO Clips and hangers) and also reflect (530 quiet rock) and absorb (Roxul) at other frequencies. This is all before even beginning with the wall treatments. There is a fine balance between reflecting and diffracting for liveliness, killing standing waves that boom and still getting tight bass. That's what computers are for IMO. Way over my head. But if its done right its magic.
I used 2 layers of 3/4" drywall with Green Glue in between, screwed to ASC damped resilient channel. The second layer of drywall was turned 90 degrees from the first. Before any of that went on though, all studs/joists were caulked with acoustical sealant and blocking screwed between every 3-4'. I used over a ton of Roxul. I had the option of Quietrock, but the folks I was working with at KNC and ASC recommended the drywall route.
A quick story taken from the F. Toole book (page 480).
A listening room had been built, and the friendly builder thought he was doing us a favor by adding an extra layer of gypsum board on the interior surface. The “favor” was discovered too late, and the room was used in that condition for a couple of years, during which it acquired a reputation for having somewhat boomy bass and upper-bass/lowermidrange coloration. The evidence was in measurements. Eventually, we had the interior of the room stripped and the originally intended single layer of gypsum board installed.
A quick story taken from the F. Toole book (page 480).
A listening room had been built, and the friendly builder thought he was doing us a favor by adding an extra layer of gypsum board on the interior surface. The “favor” was discovered too late, and the room was used in that condition for a couple of years, during which it acquired a reputation for having somewhat boomy bass and upper-bass/lowermidrange coloration. The evidence was in measurements. Eventually, we had the interior of the room stripped and the originally intended single layer of gypsum board installed.
my installation of Quietrock 545 was a result of measurements that showed stunted bass decay, and uneven bass response in a physically symmetrical room.
I used 2 layers of 3/4" drywall with Green Glue in between, screwed to ASC damped resilient channel. The second layer of drywall was turned 90 degrees from the first. Before any of that went on though, all studs/joists were caulked with acoustical sealant and blocking screwed between every 3-4'. I used over a ton of Roxul. I had the option of Quietrock, but the folks I was working with at KNC and ASC recommended the drywall route.
Bruce, what, exactly, were you trying to achieve? Were you trying to create a sound absorbing recording studio? Were you trying to prevent sound in the studio from escaping to other areas of the house?
Were you trying to design your walls to absorb standing bass waves (like most rooms seem to attempt) or were you trying to maximize wall rigidity to reflect bass waves and "hold the bass" (like Mike sought to achieve)?
Mike, what does it mean that your walls "hold the bass"? (I thought our rooms are supposed to "trap" and absorb standing bass waves?
And just to make this Quietrock 530 analysis more complicated, while the Quietrock company insists that 530 does not have absorptive properties (there is no NRC rating), people who have worked with Quietrock are certain that it does have absorptive properties, and many audiophile use it partly for its vibration dampening properties (as well as its sound-blocking properties).
A quick story taken from the F. Toole book (page 480).
A listening room had been built, and the friendly builder thought he was doing us a favor by adding an extra layer of gypsum board on the interior surface. The “favor” was discovered too late, and the room was used in that condition for a couple of years, during which it acquired a reputation for having somewhat boomy bass and upper-bass/lowermidrange coloration. The evidence was in measurements. Eventually, we had the interior of the room stripped and the originally intended single layer of gypsum board installed.
What was Toole's explanation as to why two layers of drywall caused these acoustic problems, whereas one layer would not have caused the same problems?
In that situation was the builder of the room trying to create flexible walls to absorb bass frequencies?
What was Toole's explanation as to why two layers of drywall caused these acoustic problems, whereas one layer would not have caused the same problems?
In that situation was the builder of the room trying to create flexible walls to absorb bass frequencies?
With minimal treatments and without any suspension of the drywall, one layer will flex much more to absorb high pressures at the walls which are strongest at the modal peaks. By making the walls more rigid, there is less loss and more reflection of energy. Depending on the room dimensions, speaker, subwoofer, and listener location, that can make for some very strong peaks to control. Having dimensions which better distribute modal peaks the difference would be less severe. Ultimately there's a balance of not wanting the wall cavity to sound like a big hollow box or drum, but still absorb some of the resonant bass energy.
The bigger the room dimensions, the lower in frequency the modes get dense enough to even out. Bigger rooms push the modal issues to the lowest frequencies and generally are easier to get smooth, good sounding bass from, while needing a little more average power to deliver the same playback levels. Drywall and other construction is also more lossy at the lowest frequencies, so the walls can do a better job of minimizing the work left to do by way of placement and acoustic devices.
So to summarize, basically every room has modes, the bigger the room the lower in FREQ the modes are, the stiffer the walls then the more reflected sound there is which are exacerbated at the room modes.
So stiffer walls are not necessarily the best for all applications, neither are lossy walls.
I think if anyone is hoping to accurately control room modes by vibrating sheetrock { of any type} wall panels they are dreaming ! - I have never seen anyone trying to calculate such an effect and I suspect it is not possible - better to have density and rigidity, keep all the bass in the room and then deal with it via traps, speaker placement , listening position etc.
At least you start from a (partially) known position
So to summarize, basically every room has modes, the bigger the room the lower in FREQ the modes are, the stiffer the walls then the more reflected sound there is which are exacerbated at the room modes.
So stiffer walls are not necessarily the best for all applications, neither are lossy walls.
It's usually a balancing act that's why so many theoretically designed perfect measuring rooms fail. It's one thing to start from scratch with ideal dimensions a different ballgame trying to force an existing room into submission without breaking it; overdamping as the trend is.
Bruce, what, exactly, were you trying to achieve? Were you trying to create a sound absorbing recording studio? Were you trying to prevent sound in the studio from escaping to other areas of the house?
Were you trying to design your walls to absorb standing bass waves (like most rooms seem to attempt) or were you trying to maximize wall rigidity to reflect bass waves and "hold the bass" (like Mike sought to achieve)?
Mike, what does it mean that your walls "hold the bass"? (I thought our rooms are supposed to "trap" and absorb standing bass waves?
These are 2 rooms a mastering room and archival room, and I tried to emulate as close as possible, a high-end listening room. Since it is below grade, I wanted the walls to flex a little, since behind them, is cement. Yes, I wanted to keep the sound within the rooms as not to disturb the rest of the house, but it wasn't my first priority. Since I live on a mountain, there isn't much noise outside to keep out. The are "rooms with rooms" and are completely decoupled from the outer structure.
