inside out wall construction / double windows

[fretless]

hi,

could any of you please comment my wall construction plan? i´m thinking of using it for control and live room.

my studio will be built inside an old brick house (probably from the 20s) where one wall connects to a neighbors garden wall. most of the traffic noise from the main street of our little town gets caught by the "front" wall on our lot just alongside the sidewalk. the neighbors aren´t THAT susceptible to noise since they sometimes produce some themselves which is in fact not much of a problem. the auxiliary fire brigade´s siren in the vicinity is kismet - i will live with it.


the inside out construction for the inner layer seems suitable for me since space is limited and acoustic measures can be placed easily. until now two concrete plates (each appr. 6,8 x 3,9 metres ~ 22 x 12,5 feet) have been poured out (the building had no base plate) and wait for the inner walls to be put on. because of limited budget i will for now only start with the control room so that my girlfriend gets her will and our bedroom can be used as such this very year. guess where my equipment resides now! construction of the live room will start next year.

the music will range from rock over funk to jazz, i intend to use mostly real instruments so the live room will be multifunctional and be having a drum kit set up permanently. i want to be able to play, record and mix in evening and night hours, however i don´t necessarily plan to do business with the studio.

is this wall construction sufficient for my needs?!? should the air gap be bigger? are the studs the right size? are 60cm (~ 24") the right stud spacing in this case?


before this i thought about doing a staggered stud construction inside the brick walls, but this would be 3 layers and therefore probably not effective!?

what also confuses me are windows to the outside as i plan to use 1 standard window in the control room and 1 small window in the live room. would it be better to put a window in each layer - one on the brick wall and another on the timber/gypsum wall? everywhere there´s talk about double doors when it comes to going in and getting out of the studio, but speaking in terms of letting daylight into the studio i never hear/read of double windows!?


i appreciate every help i can get!


cheers

fretless

[knightfly]

The physics of sound isolation are the same, whether for windows, doors, walls, ceilings, floors, whatever - you want two centers of mass (leaves) with an air/insulation gap between them. No more, no less. Additional leaves and air gaps will possibly improve isolation in the midrange, but at a serious cost to low frequency isolation.

You want to come as close as possible to matching wall mass to window mass for best results - a glass in the bricks should match the TL of the bricks, and likewise for the second glass in your inner leaf -

With the walls actually CONNECTING, you will need to do a floated room to get much isolation. Otherwise, flanking will keep you from achieving very good results.

From your comments, I'm assuming that the brick walls are now hermetically sealed, correct?

Sorry, gotta get to work in a couple minutes - more tomorrow... Steve

[fretless]

does this mean that if i´m using modern standard windows which itself are constructed with 2 layers of glass with an air (or whatever gas) gap in between i may only install one piece on only one wall layer?!? would then another window on the second layer leave me correspondingly with 4 layers of glass in total and therefore be a no-no?

about the brick walls:
there are no holes between bricks - everything´s filled with more or less mortar like it should be - you cannot see light coming in if you know what i mean! only the inner render is not very continuous any more, the outer will be "refreshed" anyway. is this enough for a hermetic seal?

the two concrete plates are in fact already decoupled from the outer brick walls - since initially there wasn´t a real base but rather clinker (bed ash?) we laid out the borders with styrofoam to not get a connection in the first place.

thank you for your help!

fretless

[fretless]

here´s a plan i just finished - what do you think?

greetings!

fretless

[fretless]

ups - it seems that didn´t work!
here´s another try

fretless

OK, except for too big - I resized it to under 800 wide... Steve

[knightfly]

Not bad, other than the CRT's both being on one side will mess with your stereo imaging if they're high enough to see - also, if doing "inside out" walls you'll probably want to use slats on about half of them and maybe reverse the angle of the rear wall (the left side) to make a deeper broadband trap wall there - that's all I'd change at first glance... Steve

[fretless]

i can see that the crt´s are really an important factor for correct stereo imaging but they will be replaced by tft´s anyway - maybe next year. and since those are much handier i will surely find a better solution then - maybe just attach them to the left wall ...?!? however, the single 19" rack on the other side is 1,30 meters (4 1/3 ft.) high itself, with cd player and hifi amp even over 1,60 meters (5 1/3 ft.) - this aids a little bit in terms of symmetry!

did you read my 2nd post in this thread? how do you think about those double pane glass windows?

should i go with the slats like this or should i put them all on one side of the room - like only on the front half or only on the sides? should the monitor walls have slats too?

is the back now more like what you meant? how deep/with wich angle would you attach the broadband traps? i suppose you mean (rigid) fiberglass behind cloth on another stud frame? couldn´t for this purpose the back wall be even non-angled?

questions over questions ...

thanks again for your time and expertise!

greetings!

fretless

[fretless]

i´m such a dumbass, sorry! this time i tried to make it perfect but must have mistaken height for length ...

fretless

[knightfly]

I resized it again - that's more what I meant at the rear, but now I'm wondering - your splayed walls (the inside out ones) are your inner leaf of a 2-leaf wall system, right? if so, the rear won't be any more trap than before. You'd need to accomplish your double leaf first (for isolation) and THEN do a deep trap inside that; otherwise, you'll lose a LOT of LF isolation there... Steve

[fretless]

... but now I'm wondering - your splayed walls (the inside out ones) are your inner leaf of a 2-leaf wall system, right? if so, the rear won't be any more trap than before. You'd need to accomplish your double leaf first (for isolation) and THEN do a deep trap inside that; otherwise, you'll lose a LOT of LF isolation there... Steve

i know - therefore i asked how this trap should look like (angle, depth) in my case!? so i come to think it would be possible to just let the rear wall straight without angling and build what is seen now inside!?

... and what do you think about those double pane glass windows? is one of those to be seen as a 2-leaf system in itself and has therefore only one to be used?

how do you comment my slat placing?

excuse my curiosity, i want to be sure of what i do!

thanks a lot!

fretless

[knightfly]

Sorry for the delay; my ISP has been dead for three days, just now getting back online -

You're right that those double pane windows make up a mass-air-mass system all by themselves, so if you put in two of them you would have a quadruple-leaf system.

Since the things that improve isolation are (largely) mass and distance between the masses, something such as a double paned window is not the best way to go for good isolation - you're much better off with two separate panes of glass, separated by a larger air space and properly sealed. Using more than one of those double glass windows will only worsen your low frequency isolation for the most part.

Are those brown things your slats? If so, you'll want to eliminate the ones beside the mix desk; they will likely cause early reflection problems at the mix position. YOu'd be better to have straight absorption at those points, basically any place you can put a mirror against and see your speakers in that mirror, should have absorption placed there.

The trap in the rear should be as deep as you can spare the room/materials for, and should be done with different absorptive materials at different depths - if you put 4" mineral wool about 4" off the rear wall, then do some bass hangers(do a search here on bass hanger) in front of that, and finally put some normal weight fiberglass batts closer to the room, covering it all with cloth (fire treated), you'll end up with a smooth wideband trap at the rear. If you want to build the trap straight instead of peaked in the middle, it will work - but if you have the space, the peaked center will widen the response of the trap even more, making the room sound more natural because of a more even reverb time. Your other treatments need to be calculated also, in order to not have any glaring differences in reverb times for the room. The overall depth of the rear trap should be at least two feet, more if you can spare the space.

You can use the reverb calculator here -

http://www.saecollege.de/reference_mate ... m#verbcalc

Hope that helped... Steve

[fretless]

You're right that those double pane windows make up a mass-air-mass system all by themselves, so if you put in two of them you would have a quadruple-leaf system.

Since the things that improve isolation are (largely) mass and distance between the masses, something such as a double paned window is not the best way to go for good isolation - you're much better off with two separate panes of glass, separated by a larger air space and properly sealed. Using more than one of those double glass windows will only worsen your low frequency isolation for the most part.

so if i want to enjoy a little dailight inside my control room i would have to use custom-designed single (heavy) pane windows in each leaf, wouldn´t i? everything you can get window-wise ready made from retailers is double pane style!

you have to know that i lived the first 25 years of my life in a very dark apartment and moving into a house 2 years ago finally shed some (day)light on me and i don´t wanna miss it anymore ... and since i do have 2 double pane windows for this room in spare and cost is an important factor i think i´m in a dilemma ...

however, thank you very much for your help!

fretless

[knightfly]

Yes, unfortunately you're right about what you would need to do - the only exception I've ever seen was some very expensive custom windows at a home show about a year ago, they used double glass with about an inch of air space between and actually had made one of the two glasses heavier than the other - I think they were claiming about STC 42 or so. The windows were so expensive I didn't bother to get any literature for my files.

I don't blame you for not wanting to lose your light or view; I'm just not sure what to suggest other than what I already have, and I don't want to tell you something will work when I think you'd be disappointed... Steve