Stud spacing

[murphy]

Hello,

I'm planning to build a control room in my studio. The studio is our former rehearsing room which is a concrete bunker ( 24 x 36 ft ) with three concrete pilars. One of the 24' sides is open.

I want to build the control room in 1/6th of the total room. The design is determined by the concrete pilars and the concrete ceiling construction.

I'd like to know what is the best spacing between the studs of the frames?


Tanks in advance,

Murphy

[John Sayers]

Murphy - first: why the square room for a control room??

aslo - if you want isolation the idea is to build the columns into the cavity between the new walls. Could you give us a drawing of the whole space??

cheers
john

[knightfly]

Depending on how ambitious you are and the level of isolation you need, there is more than one answer to this.

Closer stud spacing stiffens a wall, making low freq isolation better.

Wider spacing lets the wall flex more, improving mid-high freq isolation.

Wider air space is better. Insulation density should be about 2.5 pounds per cubic foot according to US Gypsum. That's the weight of their SAFB's (Sound Attenuating Fire Blankets)

Identical wall constructions back to back will share a common resonant frequency, which will pass through easier. I've read of cases where an extra layer of wallboard had to be added to an otherwise symmetrical construction, because 44 hZ went right through it. (resonant frequency of both sides)

Due to all the above (and probably several more reasons) the most effective double wall will use dissimilar stud spacing (16" one side, 24" on the other) - different materials on each side (maybe 1/2" for one layer on one side instead of 5/8" - and, for insulation, rockwool or mineral wool or SAFB's (at least 3") with some of the "fluffy stuff" tossed in, in contact with one of the inner wall surfaces (panel damping)

If you don't want to go to the trouble of figuring out two different fastener patterns, etc, use same spacing (16" if you have heavy bass) and OFFSET the studs sideways in the two frames - this will stiffen the wallboard on one side, right where the emanations from the opposite side panel will be trying the hardest to vibrate it.

If you're using wood studs, putting Resilient Channel on the studs on one side ONLY will improve Transmission Loss at all but low bass frequencies - at frequencies below 125 hZ, it appears that RC actually WORSENS performance slightly.

If you use light weight (25 gauge) steel studs, you don't need the RC because the studs themselves flex enough to decouple between wall leaves. If you need the partition to be load-bearing, you need heavier gauge steel studs (20 gauge) - these can benefit in all but the lowest frequency ranges with the addition of RC.

It never hurts to run your plan by the local building inspector (assuming he KNOWS about your project :=)

Where your wall frames touch the concrete pillars, you could improve isolation a bit more by isolating the frames from the pillars with a strip (per stud) of homosote/celotex/sound board (3 names, same product) that is well-caulked, between the end stud and the concrete pillar. Since sound travels in concrete at nearly 10 times the speed it does in air, doing this would lessen the coupling between parallel leaves of the same wall AND the coupling between intersecting walls.

Hope that helped... Steve

[murphy]

Murphy - first: why the square room for a control room??

aslo - if you want isolation the idea is to build the columns into the cavity between the new walls. Could you give us a drawing of the whole space??

cheers
john

Hi John,

First of all I've got a very small budget ($ 2000 ).
Second; I don't have any construction experience and I want to finnish the room in one month..... with a little help from my friends
Third; the ceiling construction pretty much imposes the square room. I've added a little drawing which gives an impression.


Thanks,

Murphy

[murphy]

Depending on how ambitious you are and the level of isolation you need, there is more than one answer to this.

Well, let's say it will be a private non commercial studio. I want a control room in which I can put my portable recording grear. Most of the mixing will probably be done at home.

Closer stud spacing stiffens a wall, making low freq isolation better.

Wider spacing lets the wall flex more, improving mid-high freq isolation.

Thats the info I needed. I predict we will have most problems with the low frequenties so I'll go for the closer stud spacing.

Wider air space is better. Insulation density should be about 2.5 pounds per cubic foot according to US Gypsum. That's the weight of their SAFB's (Sound Attenuating Fire Blankets).

I've got about 3" air space. That's not pretty much.
Do you know any usable types of Rockwool ( mostly used in The Netherlands )

Identical wall constructions back to back will share a common resonant frequency, which will pass through easier. I've read of cases where an extra layer of wallboard had to be added to an otherwise symmetrical construction, because 44 hZ went right through it. (resonant frequency of both sides)

Due to all the above (and probably several more reasons) the most effective double wall will use dissimilar stud spacing (16" one side, 24" on the other) - different materials on each side (maybe 1/2" for one layer on one side instead of 5/8" - and, for insulation, rockwool or mineral wool or SAFB's (at least 3") with some of the "fluffy stuff" tossed in, in contact with one of the inner wall surfaces (panel damping)

Hmmm, I don't understand the insulation part. Is there some drawing somewhere that explains how that's done?

If you don't want to go to the trouble of figuring out two different fastener patterns, etc, use same spacing (16" if you have heavy bass) and OFFSET the studs sideways in the two frames - this will stiffen the wallboard on one side, right where the emanations from the opposite side panel will be trying the hardest to vibrate it.

I'll go for this option. Very good advice!

If you're using wood studs, putting Resilient Channel on the studs on one side ONLY will improve Transmission Loss at all but low bass frequencies - at frequencies below 125 hZ, it appears that RC actually WORSENS performance slightly.

If you use light weight (25 gauge) steel studs, you don't need the RC because the studs themselves flex enough to decouple between wall leaves. If you need the partition to be load-bearing, you need heavier gauge steel studs (20 gauge) - these can benefit in all but the lowest frequency ranges with the addition of RC.

I don't need load-bearing. So, I think the light weight steel studs are the best option, right? Will they improve Transmission Loss of the low bass frequencies over wooden studs.
At least it's a lot cheaper than wood.

It never hurts to run your plan by the local building inspector (assuming he KNOWS about your project :=)

I don't know any local building inspector.
I do have friend who knows pretty much about contruction. He offered me to look at my drawings and purchase the materials.

Where your wall frames touch the concrete pillars, you could improve isolation a bit more by isolating the frames from the pillars with a strip (per stud) of homosote/celotex/sound board (3 names, same product) that is well-caulked, between the end stud and the concrete pillar. Since sound travels in concrete at nearly 10 times the speed it does in air, doing this would lessen the coupling between parallel leaves of the same wall AND the coupling between intersecting walls.

I understand that it would improve isoaltion but how much? Is it worth is?

Hope that helped... Steve

That helped a lot. I know now that I don't know much and have a lot to learn before I start....

Thanks,

Murphy

[knightfly]

OK, sort of in order;

"I've got about 3" air space. That's not pretty much.
Do you know any usable types of Rockwool ( mostly used in The Netherlands )" -

If that's 3" between frames, that will do fine. As far as the Rockwool, I'm not well-versed on availability of particular materials anywhere but the US as yet, but gaining on it - maybe John has a a better idea of what's available in the Netherlands. The weight you need is 60 KG/square meter, which translates to 2.5350170353144773132875452923044 pounds per cubic foot. (Close enough for rough carpentry :=)

Here's a drawing that sort of shows insulation placement -

http://www.saecollege.de/reference_mate ... stics3.htm

scroll down to the drawing of the floated floor and walls to see where the insulation is placed.

you would be using 50mm or 75mm, 60 kg rockwool (if that's what's available in your area) - Rockwool is a semi-rigid board, so you can cut pieces to size and fit them in between studs. You don't want them too tight, or you may restrict the flexing of the studs. That could reduce the effectiveness of the wall slightly.

If you use 75mm rockwool in one half of the wall, you could do the same in the other side or you could use up to 100 mm spun fiberglas insulation in the other side, which would extend from the surface of the wall panel to the beginning of the space between the two frames.

You would fasten the paper backing on the fluffy fiberglas insulation directly to the studs between the cavities it gets stuffed into. When using wood studs, this is done with a staple gun or a staple "hammer" - for steel studs, a good, sticky duct tape works - just use pieces of tape about 75mm long and tape the backing to the inside edge of the studs at intervals of about 300 mm. In this particular case, you DON'T want an airtight seal.

"I don't need load-bearing. So, I think the light weight steel studs are the best option, right? Will they improve Transmission Loss of the low bass frequencies over wooden studs. " -

Right. The TL down to about 125 hZ would be about the same as wood studs with RC - below 125, wood studs WITHOUT RC might beat the metal ones slightly. I would still offset the studs sideways in either case, as I mentioned before.

"I understand that it would improve isoaltion but how much? Is it worth is? " -

Probably not, for what you're doing there. However, you do need to find a source for REAL acoustic caulk and use it everywhere.

One more thing - you didn't mention what the ceiling height of your control room will be - the room isn't TOTALLY square, just close. Your ceiling height could make a lot of difference in the modal problems you may have to treat, so we need to know that measurement as well... Steve

[murphy]

However, you do need to find a source for REAL acoustic caulk and use it everywhere.

Unfortunately I do not know what you meen by acoustic caulk. Could you explain this?

One more thing - you didn't mention what the ceiling height of your control room will be - the room isn't TOTALLY square, just close. Your ceiling height could make a lot of difference in the modal problems you may have to treat, so we need to know that measurement as well... Steve

The ceiling height is 9.35'. It has a particular shape. I've added two pictures of the concrete frame.

Acoustical treatment will be done at a later stage. I will probaly purchase Studio In A Box from RPG. http://www.rpginc.com/products/studioinabox/index.htm


The latest idea is shown in the third picture:
Move one of the double walls to a different location. The other walls will be single stud walls with gypsum board on both sides.

This way I'll probably improve insulation between the live room and the control room because the sound has to pass three walls now. Also the insulation between the live room and the rest of the building be improved.

However my main concern is that the sound of the live room will dramaticly change because the sound will be trapped inside the room.

Any advise?


Thanks,

Murphy

[John Sayers]

Murphy - I appreciate what you are saying about the concrete ceiling beams but you have but you can build around them and a false ceiling below will cover them completely visually.

Here's another approach getting away from the square rooms and hiding the pillars in the design.

cheers
john

[knightfly]

John - Once more, "from a sow's ear"... Man, do you ever sleep?

'Bout the only caveat (not for you, I know you wouldn't do this) is to make sure you keep that upper wall intersection so that the concrete pillar only contacts one (or none) of the walls in that section to avoid "shorting out" the isolation given by two wall leaves...

Murph, pay attention - you're in the presence of the Master...:=)

[John Sayers]

Yeah steve - you have to box the columns out and never touch them, but you can hide them within the construction between the walls.

cheers
john

[knightfly]

Yeah, John, that "caveat" was for Murphy - it wasn't obvious to me from the drawing, and I'm learning that "obvious" is a relative term :=)

Murph, sorry I missed your question on the caulk - When you're caulking sound construction, it needs to be air tight (hence the caulk) but, more than that, it needs to STAY airtight. This doesn't always happen with "normal" caulk, even the 50-year guaranteed silicone or butyl - sooner or later, the stuff dries, shrinks, and may develop small cracks.

These cracks aren't big enough to cause problems in NORMAL construction, because heat transfer is strictly a RATIO thing - if you have a one square foot opening in a perfectly insulated, 100 square-foot wall, your heat loss (no fans involved) would only be 1%, since the hole is 1% of the total area. For SOUND, however, a miniscule crack a couple of feet long will drop your wall rating by anywhere from 10 to 25 decibels.

Acoustic rated caulk is designed to be heavier bodied (better sound attenuation) and NOT SHRINK or harden, so that if you make a joint airtight today it will STILL be that way many years later.

The real stuff can usually be found (with some effort) at local drywall/insulation contractors. It comes in 5-gallon buckets, or in 29-30 ounce tubes for use with a contractor size caulking gun. If you can find it locally, it is usually around $4 USD per large tube. It is available on the web for $7.50 if you can't find it anywhere else. Remember, that's $7.50 US for a tube that's THREE TIMES the size of a normal tube of caulk, so even if you have to pay web prices it's the equivalent of $2.50 per tube for the home owner size.

Here's a couple of links to what I'm talking about - usually, though, you can get better deals locally as I said -

http://www.osisealants.com/proseries/PS ... /sc175.htm

http://www.owenscorning.com/around/soun ... /caulk.asp

http://www.builderschoice.ca/pictures/14111.htm

http://www.doityourself.com/store/0511931.htm

I can't stress enough how important caulking is to soundproofing - without it, it's just another room (but with more expensive walls)

As to "Studio In a Box", I'd spend 1/3 of that money on a bunch of Knauf or 703, and the rest on a good chair or signal processor or pre-amp... Steve

[murphy]

John,

That drawing looks really great. I wish we wouldn't have so many restrictions.
But we un-officially rent the space from a company that rents the whole building from the owner.
So, there are a lot of uncertainties. The company could break up our agreement or they could go out of business. Bang.. We’re on the street...

My partners and I have gone over this a dozen of times last couple of days and we have agreed that we'll keep it as simple as possible and most of all LOW-budget.

Thanks for the great input anyway!!



Steve,

Thanks for the elaboration on the acoustic caulk. Now I understand what you meant. I'll look around for stuff like that over here or order it from the website you mentioned.

So the "Studio In a Box" isn't such a good idea?


Man, are ya'll helpful.

Thanks again,

Murphy

[John Sayers]

The company could break up our agreement or they could go out of business. Bang.. We’re on the street...

not if you build the studio in a modular construction so if that happens you pull it apart and move it somewhere else. It can be done.

cheers
john