The wall separating CR and LIVE room!?

[Sen]

Hi Steve and everyone else,
My first studio plans are being submitted to the council for the building permit. In the plan we specified that we'd have a double brick wall between the CR and live room. Now my question is:
If I have the double brick wall (one wall 2-bricks thick) and frame and plaster wall on the each side of it (with insulation inside of course), how would this compare and hold against the "2 leaves - 1 air gap" rule? Would it be considered a "no no" because I'm technically having two air gaps??

Sorry I haven't got any sort of drawing s/ware available at the moment to clarify things a bit, but I hope you'll understand what I'm talking about.

Thank you guys

[knightfly]

Sen, yeah it's a no-no. If you could actually test the construction you're considering, vs. the same amount of mass distributed in two leaves/one air gap, you would find that the third leaf actually LOST you a few dB of isolation.

All these comments of mine are based on research into what OTHER people have done, because it is very difficult and expensive to actually DO these tests - for one thing, how do you know that part of the isolation used AROUND the test wall isn't the limiting factor? Still, of all the published test results I've seen since I became aware of this phenomenon, they ALL show similar results - you can get at least 20 dB of difference in STC using the SAME AMOUNT of materials, just by changing the order of things.

You'd be better off to just furr out and panel ONE side of the wall, or better, do a free-standing stud frame with only one side paneled, so you can isolate the double glass panes of your CR/Studio window... Steve

[Sen]

You'd be better off to just furr out and panel ONE side of the wall, or better, do a free-standing stud frame with only one side paneled, so you can isolate the double glass panes of your CR/Studio window... Steve

I imagine this "panel one side" suggestion would mean to leave let's say the live room side brick and drywall the CR side, with a signifficant gap between the brick and the framed wall filled with insulation.
Not sure though what you meant by the "free-standing" stud frame....would it be something like this :

[Sen]

And would I do the window like this then:

[knightfly]

Sen - You've got the right ideas as far as isolation, if you notice the drawings you refer to all have only two mass leaves and one air space (a space is an air space, even if it is full of insulation)

However, unless you're just in love with brick you can get BETTER sound attenuation with less money (assuming similar cost ratios as US), and have an easier time of remodeling at a later date if you need to.

I'm going to try something here I've not yet tested as to using images, so I may end up editing this a time or two, but here goes: Nope, didn't work...

From the STC charts on the same SAE site, note the ratings of the brick + framed wallboard, vs. double steel stud walls with triple wallboard.

Now, picture yourself re-locating or removing the wall 5 years hence - which way would you prefer to have used?

On the subject of splaying layers of glass in a control room window, let me first say that I've not done this and John has; however, I came across this source a while back; the writer is(or was, not sure) employed by the Russ Berger Design Group, which is pretty well respected in proffessional circles, so I thought I'd "stir the pot" and see what John thinks about his comments as well

(John, I'm not trying to "sandbag" you here, just trying to learn wherever I can...)

http://www.acousticalsolutions.com/educ ... _Myths.pdf

If that link doesn't work, go here and click the Acoustical Myths link -

http://www.acousticalsolutions.com/education/index.asp

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OK, the STC #'s didn't come with the pix - the brick/frame is STC 56, the double steel stud/triple wallboard is STC 60, when both have insulation. Have you ever built a brick wall? 'Nuff said... Steve

[Sen]

Hi Steve,
Thank you again for much appreciated help. I'm more and more realising that I should take the things a little slower and with more caution, so I'll probably hold onto my plans for a week or two longer to reconsider all the options once again. Man there's so many theories and opinions to consider ....
I did however read the Richard Schrag's acoustical myth and there's a lot of logic in there. But In one part of the article he says:
"In a cavity wall, transmission loss depends on the mass and STIFFNESS"!
OK, makes enough sense, but for a moment what came back to me was the "flexing" of the drywall under the low frequency sound waves, so that flexing actually helps absorb these. Is this flexing prefered on the actual walls or just on the sound treatment panels?

Hehe, no I'm not in love with bricks, but I built a few with my father some years ago when we built our house. And I can tell ya , they were some massive blocks which I'd love to do my outside walls with, but don't think I can afford it now.

Interesting story (in Richard's article) about the windows as well, eventhough it didn't give me any new ideas that I could try in my studio, except for the one with parallel glass panes and relevant room treatment and lighting system to minimize the negative effects of the parallel glass.....which I'm not gonna get into building either ....

I couldn't find the STC ratings for different types of walls on the SAE site and I can remembner seeing them there before. They're not under "walls"...where are they?
Youre right about modifying the wall too. I am certainly going for the double stud drywall. What sort of air gap do you think I should go for? About 15-20 cm?
I will try to do some floor plan nad post it tonight to bring the things a bit "closer"!

Thanks!

[Sen]

After a couple of hours of hard work I finally finished this drawing. This is the floor plan witht the discussed double stud between the CR and LR. If there are any suggestions about better utilization of space or any other comments please feel free....Do you think I should have an iso booth? I was trying to come up with something in that LR corner with the big air gap....any ideas??

Thanks, please let me know what you guys think

[knightfly]

Sen - first, since I was recently accused of making fun of people just let me say that I find these little quirks just as funny when I myself am on the receiving end, which happens often enough to keep me amused - Have you ever read Poe's The Purloined Letter? If so, grin and bear it - the STC ratings of walls are under the link called STC charts... :=)

Next, there's a good reason why John asked me to moderate the CONSTRUCTION forum, and kept the DESIGN forum for himself - he's done a TON more of them, and he's quick and insightful.

I do, however, have a couple of comments on your preliminary drawing -

You have the basic idea down pretty good, and have drawn a couple of nice-sized rooms that will not make you feel cramped - The control room, while comfortable, isn't large enough to worry about using diffusion at the rear, at least not in its easily recognizable form - any time there is less than about 11 feet from the mix engineer's head to the rear wall, absorption is the way to go. This is because your ear can detect anything longer than about 20 milliseconds as a discrete echo, so under those conditions if you diffuse the rear wall those echoes are broken up and scattered, getting to your ears quite a bit later and disguised as reverb of sorts.

With a shorter path, if those echoes are allowed to return to your ears they are too soon and will cause comb filtering, which smears the stereo image you hear and gives you a free "phaser pedal" that's not appreciated...

When walls are splayed so as to get rid of parallelism, flutter echoes stop being a problem - however, room modes are still there, just spread out into more of a "gentle bell curve", so to speak - because of this, and the fact that more room cubic volume generally makes rooms sound better, if you stay with the size control and tracking rooms you've drawn I would recommend an AVERAGE FINISHED ceiling height of 13 feet. This would give a very smooth sounding room even for a rectangle, but with splayed walls it should be wonderful.

The other thing I noticed is that you have rooms on opposite ends of the building that both require plumbing. There are two reasons I would NOT do this - one is economy - it costs more to run plumbing that far when you can design so the rooms are adjacent, and can use a common wall for pipes, etc -

But the MAIN reason I would change this, is that you shouldn't have ANY plumbing any closer to your TRACKING room than absolutely necessary, and even when in the same room it should be oversized by one step for supplies, and isolated from any structure with rubber. This keeps you from having to do another take just because a guest flushed the toilet and washed his hands during the one time the guitarist actually NAILED his solo...

Unless you expect to be doing acoustic recordings in the Control Room itself, putting ALL the facilities requiring plumbing in the corner on the control room end makes more sense.

There is one of John's designs already being built that is in a space almost exactly the size of your proposed one, albeit with low ceilings - it has smaller rooms, but might be of interest - check this out -

http://www.johnlsayers.com/Studio/Pages/Bluebear.htm

Take your time with this phase - once you stop doing it virtually, and start mixing mortar, it's much harder to change your mind... Steve

[Sen]

Thanks Steve....OK so just straight wall at the back of CR with good ABSORPTION, rather than diffusion...
About the ceiling: I've been told that by the regulations I can go only 3 metres (10') high....I still thought that was better than 7,5 - 8 '.
The two rooms at the ends....I know, that's what I've been thinking about as well, but how can I do 'em?! I can't have people through the toilet yo make a cuppa, or have people going for a wee and coming back through my kitchen... ...unless I made major movements within the given area.....
In the "design" forum John has just told me that I shouldn't be angling the walls but achieve the non-parallel surfaces by just treating the walls with panels and traps....which confused me a bit.....
I'll see what more he has to say.....oh well, every beginning is hard...

thanks steve

[knightfly]

John isn't saying not to splay walls, and the peak in the center of the rear wall is fine, may even help some - what he's saying, is not to WASTE the air space created by angled walls, by not UTILIZING that space for traps, absorbers, etc -

On the plumbing front - are you locked in on the actual dimensions of the overall building, and is that where the entrance NEEDS to be? It would help if we knew what is "cast in stone", and what is negotiable. You need to somehow be able to put the kitchen and bath BESIDE each other, with separate doors and a common, double-framed utility wall between, as far from the tracking room as it can be.

What's this crap about only being allowed 10 feet of ceiling height? I've never heard of such a restriction, is that because of the brick wall height restriction?

If so, these guys claim they can go 16 feet with 8" walls, and still meet US Class 4 earthquake specs (think San Francisco, 1906)

http://www.polysteel.com/

This what I plan to use for my next facility - not sure if something like this is available in Oz, but if it is you get 52 dB STC with just a single layer of 1/2" drywall inside - imagine when you do a free-standing inner leaf on studs, with 6" air gap...

[knightfly]

Just a thought - if you could widen the whole structure by about 2 meters, (yeah, I remember you're on a budget, sorry) you could get both the bath and kitchen to fit beside each other at the control room end, and that would give you enough room at the tracking room end for a nice drum booth... Steve

[Sen]

Steve, you're a mind reader I must admit, but at the same time I am a poor guy who's studio is cramped between his house and the back fence neighbour ...That's exactly how I was thinking I could have maybe even two booths by that live room...
I'll try a bit of a different drawing and post it to see what you say..

thanks

[Sen]

Steve, Here you can see I shifted the toilet ant kitchen to the same side and increased the width of the foyer area on that side (so you can walk to the toilet), that's why I ended up with a 10" narower CR, which I don';t think matters a lot coz the CR is still pretty comfy I reckon...
this is without Johns changes to the CR.
I think the live room idea with the two isos could be good because most of the parallelism is broken and there are to booths...(and more work to drive my self nuts, as Im lost already )
Let me know what You think

[knightfly]

Better, but you still need to reverse the splay angles in the front half of the control room - the idea is for any reflections from the front half are reflected BEHIND you, to be either absorbed (short room) or absorbed and diffused (long room)
Same with the ceiling - low in front, high further back so any paths from speakers reflect BEHIND the mix position so they don't interfere with the direct sound from the speakers... Steve

[Sen]

with Johns CR it would look sth like this: