Please, a few questions, and I won't bother you again

[TerrorFiend]

Hi.
Ok, here's the situation. (You might remember me).

Basic studio, with the second room built completely independent of the outer shell. (Diagram below) Thick concrete floor right on top of the ground. In a very quiet, rural area. Moderate budget. I've read a fair amount of material and know the basics.

The questions...

- Does concrete, especially thick concrete transmit sound out of the room? I.E. Would you recommend a floating floor?(I was thinking about just having regular carpet on a thin layer of flooring foam, right on top of the concrete.

- The thickness of the wall (and ceiling) coverings obviously makes a difference, and I was planning on using thicker than average plasterboard for the INNER wall of the INNER shell, and the INNER wall of the OUTER wall.
I've heard about using multiple wall and ceiling coverings, but get conflicting results when I look it up. What do YOU think is a good covering, or coverings? How would you attach multiple coverings to each other? Keeping in mind that I have an above average budget for a small home studio.

- I was just going to put regular fibreglass insulation batts in the inner walls and ceiling. But I'm uncertain if they're any good for sound absorbtion. (Due to conflicting stories I've heard). Do you think I should use them?

- Is it true that wider stud spacing in the inner wall (say at 24" instead of the normal 16") increases the transmission loss? And...If you made the frame out of thicker timber, (90mmx45mm instead of 75mmx35mm) would this yield a higher TL?

- Is there an ideal width for the air gap? If it were to be built at 1", would this be less favourable than at, say 3"?

- Is it OK to have a reflective surface (I.E. the plasterboard) on the INSIDE of the OUTER wall?

- What's the best way to fasten the inner wall to the floor? I've seen diagrams where 'caulk' was shown, squished under the walls. I don't know what this is (apart from the dictionary meaning), but I was just going to squish some rubber underneath and use masonary screws into the floor.

- In the diagram below, the one with the red arrows, this indicates the door opening that points across the street at the closest neighbours. It's currently closed with a normal wall frame and we were originally planning on covering the outside with weather boards. Now, it's possible that the opening will be filled in with bricks (which would be good because it would stop most of the lows from going across the street).
The red arrows are pointing to two areas where I was planning on building bass traps to help stop the lows from going across the street.
Will I need them if the brick wall is constructed? What about if it isn't? Can I just hang the insulated planks from the ceiling INSIDE the air gap like that?

Any other comments or suggestions on the design or on anything would be appreciated.

Thanks a million!

- Brad

[knightfly]

Not trying to ignore you, just a lot of stuff to cover here - I'll try to get you some answers by tomorrow night, sorry... Steve

BTW, if I thought questions were a bother I wouldn't be here; no apologies necessary...

[TerrorFiend]

Thanks dude, I appreciate it

[knightfly]

Well, it's becoming plain that the stuff keeping me from this won't go away, so I'll just have to ignore it for a bit (you've waited patiently long enough, thanks)

Floating floor - Yes, concrete conducts sound but only to connected rooms, not so much to the rest of the world - if you're looking for total isolation so you can play drums in the middle of the night next to crotchety old ladies with excellent hearing, then yes... I wouldn't carpet a sound room - they work better with live floors/absorbent ceilings, you can always use a couple throw rugs to change liveness.

Walls - what is there now, exactly? spacing, thickness, insulaton, framing, etc -

Regular fiberglass batts are fine for in-wall use, perhaps some of the newer "quiet batts", which are a bit denser, would be better - somewhere between 2-3 PCF is best overall.

Stud spacing has not been demonstrated to make any real difference in TL - mass does, and heavier frames will (only because they increase the air gap) - air gap noticeably increases TL up to about 8-10 inches, where it takes several more inches to make a noticeable difference - Air gap is measured from the inside of one leaf to the inside of the other leaf, regardless of whether using single or double frames, RC or not, etc - an air gap of less than a couple inches isn't worth much at all.

"Is it OK to have a reflective surface (I.E. the plasterboard) on the INSIDE of the OUTER wall?" - by this, do you mean the inner layer of mass on the outer wall leaf, or do you mean a layer of plasterboard on the inside of the outer wall stud frame?

"What's the best way to fasten the inner wall to the floor?" - I'm assuming you're referring to a floated floor? If so, nails or screws are fine - any seals will be made by caulking with acoustic rated caulk in 1/4" gaps you leave at bottom, top, and sides of wall panels. Caulk is kind of like a thick, pliable glue you squirt into cracks to seal them - the acoustic kind never hardens, so it won't crack and leave minute gaps for sound to leak through. It comes in throw-away tubes like this -

http://www.acousticalsolutions.com/prod ... /caulk.asp

"Will I need them if the brick wall is constructed? What about if it isn't? "

- With the brick wall, you'll need MORE bass trapping inside because the wall will be stiffer and let less bass through, so it stays in the room - for isolation, though, the brick will help your neighbors. Keep in mind, though, that your other walls will need to be nearly as good or it's not going to help much - low frequency sound is pretty non-directional, so it doesn't matter WHICH direction it escapes, it still can be heard in ALL directions -

"Can I just hang the insulated planks from the ceiling INSIDE the air gap like that?" - Like what? Are you referring to "bass hangers", seen on another page?

Other comments - your room isn't symmetrical - if possible, you should re-do the area around the window, lessening the angle of the wall with the door in it, and increasing the angle on the opposite side of the window to make the room symmetrical. The extra depth that would be created on your left (as you look out into the larger room) could be used as a slat resonator, with bass trapping done mainly at the rear (opposite the window) - Just a thought... Steve

[TerrorFiend]

Thanks for such a detailed reply.

Floating floor - I don't know about playing drums in the middle of the night, with the crotchety old ladies , but as I said it's in a quiet area and it would be good not to make the neighbours too antsy. Their house is about 30 metres (100') across the road.

The internal walls are not built yet, except for the bathroom. As it is, the OUTSIDE walls are made of frames with plates of 70x45mm and studs of 70x35. We were planning on using regular 10mm plasterboard and fibreglass batts. I was planning on leaving a 70-100mm gap between the frames (Thus giving a 10-11inch air gap). The inner walls were going to be heavier frames, (90x45) with 15mm instead of 10mm plasterboard on the inside of the sound room. (Or maybe multiple coverings?, what do you suggest?)

I mean't a layer of plasterboard on the INSIDE of the OUTER wall frame. I suppose it lessens the air gap, but because of what I've got to work with, it's unavoidable if I want to get an airtight seal.

The bass hangers were what I was refering to. Is it effective to just hang them inside the air gap (like in the diagram), or should they themselves be contained seperately?

Im glad you gave me your opinion about the layout before I started building the inner walls for the sound room I'll try to come up with a better plan and then post it here.

Once again, thanks a million!

- Brad

[TerrorFiend]

Heres a couple of new plans I came up with. I know you're not the design guy, but do you like either of these better than my original design? They're both symmetrical.

Thanks.

[knightfly]

The upper one will give you a bit more room, and as long as your mix position is even with, or ahead of, where the walls get parallel, it should work fine - you might need a bit more absorption in that one because of possible flutter echo, but it should still work. Your door can still go on that wall, because the splay will keep it from reflecting back to the mix position -

Be careful on your walls - whether inner or outer, the TOTAL construction you want between you and the outside world (or another room) is only two leaves of mass, and only ONE air gap (with insulation) - anything else can actually WORSEN the isolation, especially at low frequencies. Heavy mass and wide air gaps are your friend here -

Also, I wouldn't use anything less than 12mm gypsum, and 15 is better - 2-3 layers of it per leaf is usually enough for normal amounts of isolation.

Whichever room your drums will be in is the first one that should recieve a floated floor - others are optional depending on how total your isolation needs to be - this is a typical cost cutting measure for project studios, although it makes things kind of wierd if you have different floor heights.

Check out the floating floor "sticky" for more on floors, and the "complete section" one for more wall construction hints... Steve

[TerrorFiend]

Thanks man.

Just want to clear one thing up. Is it the RECORDING room which is preferably symmetrical? Or just the CONTROL room? I think you may have mixed up which room I was to be using for which.

The standard designs in the manual seem to indicate that it doesn't matter if the recording room is symmetrical or not. Just that the control room has to be.

And since I dont really have a proper control room, is there still error with my first design?

[knightfly]

My bad - I automatically assumed the small room was the CR - and yes, it's the CR that should be symmetrical if at all possible. If that isn't possible, you need to find ways to baffle around the speakers so they "think" it's symmetrical -

The GOOD news is, if you're only going to float your recording (tracking) room floor, it's smaller than I thought and so would cost less to do... Steve

[TerrorFiend]

Yeah I thought so.

I was going to worry about the control room later. Hang up absorbant panels and such when mixing, to do just what you said. And maybe do the final mix elsewhere.

Thanks man.

- Brad