Air Cavity??

[AWS]

Hi Steve, Of course that it helps… I really appreciate your helpful tips…

I´m a little confuse about the “sheet rock”… do you have a picture or some info about the characteristics of this material? Maybe here in Argentina have another name…

My basic idea is to separate Control Room for Recording Room… so I don´t want to build only one wall for connect the two rooms.

The tip of the well-compacted (rodded) concrete has been taken!!!

Wow… 62 STC is a lot! But you´re talking about only one wall… right?

Where can I get Acoustic-rated, non-hardening caulk over the internet?

The door idea is really great, we (my brother & I) have think about it, talking about cost and performance, and we get the same conclusion… Sound-lock for our studio… about the separation between doors… 15 cm is ok? More, less?

I really don´t know what resilent channel are? I have a little clue… but I don´t have the picture in my head… so… is ok if I install RC in two walls that joint together…(north wall & east wall)?

I really get your point… but I´m between the sword and the wall… or I get good STC (a lot of mass) or I get good bass trapping... I can say that the sizes of the room maybe help me with this problem of low frequency control (room modals)… of course the room aren´t big enough to control them… but I think that we can deal with this… what do you think about it?

Well Steve… I don´t have enough words to express my appreciation for your professional help!!!
REALLY THANKS!

At your service!

Fernando Musarra
AWS

[knightfly]

Some other names I'm aware of for sheet rock - Gyp-rock, Gypsum Wallboard, (in some areas) Plasterboard - it is a compressed white (gypsum) powder, covered and contained by heavy paper on both sides, in the US the standard sizes are 4' x 8' and 4' x 12', in thicknesses from 3/8" up to at least 3/4", with 1/2" and 5/8" being the most common. US price for 5/8" 4 x 8 panels runs around $5 per sheet. It is heavy, and hard to beat for sound control at a reasonable cost.

About the one wall between two rooms - read back through this thread to my comments of mar. 17 - more is sometimes less. check the STC chart above.

The STC 62 was an estimate of one filled block wall with two layers of 5/8" (15mm) gypsum wallboard on resilient channel. If you were to build two of these walls between rooms, you would probably either not gain anything or at most maybe 2-3 dB. It would make more sense to build a wall such as the STC-63 example in the chart above, since it would be tons lighter and just as effective as the concrete block - it would also be easier to modify should you change your mind at a later date.

At this time, I have no idea where on the Internet you can buy real Acoustic caulk - if anyone does, please post in the Building Materials section for all to see.

Sound lock doors are better when farther apart, and all surfaces between the two doors should be absorbed. Also, the two doors should not be parallel to each other, which would require a deeper area between them. Ideally, if the sound lock was a 4-sided enclosure, the doors should NOT be across from each other. Parallel walls are best avoided too, so there is no single frequency that can excite a standing wave within the sound lock.
So, 15 cm is kind of small for the best case since the lock would need to have all dimensions large enough to mount a door, which would mean more like a minimum of 100 cm if the doors are to be 36", or 915mm.

Resilient Channel - read this short thread -

http://www.johnlsayers.com/phpBB2/viewtopic.php?t=122

As to using RC in two adjoining walls, sure - One of the two links to US Gypsum I posted earlier in this thread has recommendations as to how to do this - basically, you stop the RC about an inch short of the adjoining wall, and run both layers of wallboard beyond the intersecting RC, then attach the layers of wallboard to the remaining wall leaving about 5-6 mm gap from the edge of the wallboard to the surface of the adjoining wallboard, making sure to thoroughly caulk EACH LAYER joint completely.

Another school of thought on adjoining wall construction is to alternate layers of wallboard so that the corner joint is rabbeted, caulking as you go - the downside of this is that the two wall surfaces aren't as isolated from each other, but the joint itself is better performance.

Your comment - "I get good STC (a lot of mass) or I get good bass trapping..." - isn't really true. The STC 63 wall in the previous illustration will give as good sound control as a concrete block wall, maybe even a double concrete block wall, but with MUCH better bass trapping due to the added flexibility. I personally would NOT use concrete block walls except on the exterior, and even then I'd probably use stuccoed and filled block outside, and maybe 3 layers of wallboard furred out 6" on Resilient Channel for the inner leaf. Otherwise you may not have enough room inside for enough bass trapping to compensate for those stiff walls... Steve

[AWS]

Right! Here we call it Durlock (brand).

I will check the thread on Mar. 17

Ok… your tip is very good!!! It saves me a lot of bucks!

I´ll try to find some caulk dealers.

So… you´re saying that I´ll need 1 meter (deeply) to put both doors in the same frame, right? What happens If one door will open for the inside and the other for the outside? This would work?

About the RC… as you say… I have to built until I arrive to the end of the wall, I left 6mm gap, and continue to built the perpendicular wall? Later I caulk the gap? Do I understand it right?

I think that we´re going to use concrete on the exterior walls, filled with sand or caulk, inside RC, with two or three plasterboards. In the intersection wall between the control & the recording room, we´re going to put 2 Gyp 15mm + RC + Concrete filled + RC + 3 gyp 15mm. Do you think that this “system” will be a little “hard”?
There´s something that I cannot figure out… the glass wool, where I´ve to put it? Between the concrete and the plasterboard (in the RC space)?

Sorry for the delay... I had some net problems

Thanks again!
Fernando Musarra
AWS

[knightfly]

My recommendation for the 1 meter (or more) depth for a sound lock (vestibule) wasn't so that the door could swing into that space - it is so that the interior of the vestibule can be completely absorbed with thick 703/705 type board, covered with cloth, and still leave room for a person to enter thru one door, close that door, and exit thru the other door so that at no time are both doors open (assuming there is either noise inside or a recording happening, or both.) Ideally, the two door frames should NOT be rigidly connected to each other just the same as the two halves of a double wall between studio and control room should not be rigidly coupled to each other.

Yes, I think your wall between control and recording room would be quite hard. Plus, you're not remembering my warning against triple leaf walls, which is what you just described. If I were building that wall, I'd put the (filled) concrete block wall up, then put a separate wood or steel stud frame up on the control room side, and either build the frame wall "inside out" (see the SAE site or John's site, I forget which) or fill between the studs and then put 2-3 layers of sheet rock over RC. Either way would soften the bass somewhat - the "inside out" wall would also give you some absorption behind the console to lessen early reflections.

As to the gaps between adjoining walls - you want a break so there is no metal-to-metal contact between adjoining RC's - when mounting wallboard, I would alternate layers - put a layer on one wall, leave a small gap and put a layer on the adjoining wall, CAULK well, put the second layer on the first wall, CAULK, put the second layer on the second wall, etc - That way, the corner between the walls will have a zig-zag joint with multiple beads of acoustic caulk. That should make an excellent seal and still separate the two walls acoustically.

You're right about where the glass wool or rock wool goes - except, as I said above, I'd NOT do that on both sides, instead do a separate frame on ONE side of the block wall ONLY, put the Glass wool between the studs (or tack it behind them if there's room), put the RC on that frame, then 2-3 layers of wallboard.

Remember - put ALL the mass you're going to use in a wall, in only TWO layers with only ONE airspace between and you will get the most isolation for your money. Then, leave room for traps/absorbers, etc, as a separate system. Otherwise, you could space one of the wall leaves out even FURTHER, put some bass hangers in the space, and kill two birds with one stone.

If you have the ceiling height, one good reason (forgot to mention previously, sorry) to float the floor would be to allow space for cable trays for power and signal, depending on how much of each you will need... Steve

[J.J.McLeod]

Sorry to interrupt but does this:

Otherwise, you could space one of the wall leaves out even FURTHER, put some bass hangers in the space, and kill two birds with one stone.

mean that hangers can work behind drywall, even double drywall? If so, would bass passing through a normal wall of drywall to the room next door (say a kitchen that the control room doesn't need that much isolation from) get rid of bass buildup as well as, say, building hangers and a false wall in front of the drywall in the control room?

Thanks,

J.J.

J.J. McLeod
Different Drummer Studios
www.differentdrummerstudios.com

[knightfly]

Hey JJ - After re-reading that, I came to the conclusion that I was still in need of more rest after a recent bout with pneumonia -

In reality, the answer to your question would be, "sorta"...

By that, I mean that inside a wall that is panelled with drywall, there is still appreciable sound energy even though it would be LESS than if the front surface were made of more absorptive material, such as 703. So, yes, hangers inside a drywall, much as rockwool or 703, will add to the absorption and reduce the amount of sound going through.

However, it would not be nearly as efficient for bass trapping in particular, as having a 3-4 foot deep bass trap, faced with 3-4" of 703, AND hangers spaced inside the trap. Under these conditions, the hangers would both broaden the range of absorption AND improve on the QUANTITY of absorption.

Think of it this way: Air, by scientific definition, behaves very similar to water, and because of this, both are sometimes referred to as being fluids. If you hang some fine mesh netting on frames in a tank of water, then cause a disturbance in the water on one side of the meshed frames, if you look at the surface of the water behind the first frame, it is calmer than in front - as you progress thru more of these frames (assuming they are one behind the other) you see less and less disturbance in the water.

This is pretty much how bass hangers work inside a trap - however, the less disturbance you START with, the less effect these "impedances" will have.

Always keep in mind that absorpton of any kind works by converting a portion of the sound energy into HEAT energy - since you can't hear HEAT, the level of sound is reduced.

Another major factor in absorption is the position of the absorbent away from a solid barrier, versus the 1/4 wavelength of the sound to be absorbed. This is why absorbent traps, in order to absorb low bass, would need to be several feet deep.

And, this is why other methods of absorption are used for low bass unless there is an abundance of space available somewhere in the room design.

Sorry for any false hopes I may have raised, I'm going to try to force myself to get more rest which will hopefully reduce the incidence of "brain farts"... Steve

[J.J.McLeod]

No worries Steve Thanks for clearing that up, and for all your other great posts as well.

J.J.

J.J. McLeod
Different Drummer Studios
www.differentdrummerstudios.com

[knightfly]

I'm feeling much better lately thanks - Damn, now I'll have to find a different excuse... :=)

[John Sayers]

you could have a relapse:D

[knightfly]

Certainly tempting, under some conditions...:=)

[wildplum]

I am new to this forum and have been reading back posts. The diagram John posted on Sun Mar 02, 2003 is a real eye opener. One would have thought that two completely separate walls, faced on both sides and built on separate floating floors (that is how I am interpreting the double isolated stud, STC 40, example) would have performed better!? So much for common sense.

Regarding the STC 63 example, do the two stud walls rest on one bottom (sole) plate and have one, common top plate? Or do the two stud walls have separate plates?

I can't get my mind around this, so I clearly am not understanding something. In the former case, the plates would have to be at least 8 inches wide and would sit on both of the floating floors (assuming the walls were build on the floors). doesn't seem right to connect the floors in this manner. Also to get more than a very small space between stud walls, the width would have to go up from 8 inches.
But in the later case, the air cavity between the stud walls would be all the "free" air space in the studio (ie, all the space not inclosed by the stud walls- all the space outside of the control room, live room, isos, etc.) because the stud walls, being open between them at top and bottom, form a channel connecting all non-enclosed space in the studio. This doesn't seem right either (very odd spring).

Like I said, I am not understanding something hear. Some one please steer my out of the woods. Thank you.

[knightfly]

First, the 63 dB example uses separate frames entirely - their only connection to each other would be if both were sitting on the same floor, in which case if they are wood frames you would benefit by a few dB if Resilient Channel were used on one side.

The wierd spring you refer to (all that air) is a GOOD thing - factors that improve isolation (assuming you're sticking to the proven mass-spring-mass model of a 2-leaf wall) are more mass, wider air space (softer spring), decoupling between leaves , stiffer leaf (better bass rejection) proper density of insulation between leaves (2.5-3 PCF is considered optimum for music), insulation touching at least one inner panel (damping improves Transmission Loss), there are probably others I've missed but those are the main ones.

Best isolation overall is to completely float each room, with separate frames for each leaf - one frame on one floated floor with one leaf (multi layer, different thicknesses in layers) (the other leaf in that wall would be on the other floated floor)- then, suspending ceilings inside the walls using isolators on each suspension wire.

All this is a waste of time unless you use double doors with an air lock between rooms, because any openable partition takes a lot more work to achieve those levels of isolation so you need two in tandem, the more air space between them the better - it also helps to put lots of absorbent in the air lock.

Hope that cleared up some of your questions... Steve