John Sayers' Recording Studio Design Forum

It's not a matter of whether you use mineral wool or rigid fiberglas (703, etc) it's a matter of DENSITY. The specific Roxul you pointed to has too high a density (PCF) for proper Balance of attenuation in walls, so if those two are your only choices, then the 703 is much closer to the correct Density for balanced Transmission Loss in a wall.

Lower than 2.5 to 3 Pounds Per Cubic Foot (PCF) causes the wall to attenuate lows more, and higher Density than that attenuates the highs more. USG did a study of this, and that's why their Sound Attenuating Fire Blankets (mineral wool) are 2.5 PCF.

When you unbalance Transmission Loss in a wall, then certain frequencies get through easier than others. This sounds "un-natural", and so it causes you to hear things coming through as if they were louder. This makes the whole wall seem less soundproof.

I hope this helps make sense out of it for you... Steve

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Soooo, when a Musician dies, do they hear the white noise at the end of the tunnel??!? Hmmmm...

Well, I just called Roxul directly and asked their technical guru's on what product they make. They make it all. Now it's just getting the local guys here to custom order the product and wait 3 weeks for it.

I wish I knew this $600 question earlier (before I found this site). Then again, maybe the 2 different densities will be of some benefit for freq's.

Thanks for the tip Steve. I do remember reading that in the USG handbook about the 2.5 pcf awhile back.

By the way...getting back to the floating floor issue. I was just reading some other threads. I've got someone working on the drawings in autocad, and also getting me some weight measurements. I was reading in a thread about where if there are too many pucks, it defeats the purpose, and vice-versa, not enough, the same thing (you told me this too). It's about finding that happy medium of springiness (is that a word? or just mispelled).

Anyway, as far as the sub floor goes, what is the preferred 3/4" material to use? I don't want to use partical or mdf due to possibilities in moisture or condensation. That stuff will absorb like a sponge. Should I go w/ OSB? I know the insulation issue was mentioned earlier, but should I use the 2.5 lb or 4lb mineral wool in the flooring since I'm not using sand.

Aaron the only two Roxul Products I'd recomend are the AFB and the RHT-40

AFB for inside the walls and RHT-40 for the surface. If you read the lit on the RHT-40 the density is 3.5pcf at 2" or greater. Not sure if it's in the online stuff or in a pamphlet I got from my local supplier

AND, I would not use a thickness greater than 3" in the walls (on either wall assy. and 2" on the surface)

Bryan Giles

Any particular reason on the 3" vs. 4"? I take it the theory of thicker is better doesn't apply in the world of acoustics?

When you're talking about the 2", are you talking about inside the control room as the surface absorption? Wrapping them in cloth, etc. making panels?

By the way, for some reason, I no longer receive notifications when someone reply's. On either one of my posts. Is there a server issue?

Thanks,

Aaron

Roxul Specs 3" AFB in their wall designs, here is a link

http://199.202.236.133/usa/pdf/afb_sell_sheet1.pdf

I used 4" in the angled walls of my control room. (The dead end of the control room) see studiosn under construction Patricks den. the cloth covered angled exposed wlls was where I used 4" Mainly because I didn't want to build hanging bass traps. My Crude work around.

And yes the 2" is exactly what I meant.

Bryan.

So is it ok to still use 4" for filling the floor, or should I also use 3" here?

Aaron, as long as it's not tightly packed it will be fine. 2.5 PCF density has been tested as being best weight for walls, and I'd think that would also apply in floors, The main thing is not to pack it tight or it will cause the wall/floor to "short out", or flank sound through. Some light/medium pressure is OK, in fact it helps damp the panels and minimise resonance... Steve

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Soooo, when a Musician dies, do they hear the white noise at the end of the tunnel??!? Hmmmm...

Hello again,

Been too busy trying to finish off a keg the past few days. Had a house warming over the weekend. That Australian beer is good...

Anyway, another question about the floor. It appears that the floor in the basement isn't "level". I haven't shot it w/ a laser yet to find out how bad, but it's off some. Any recommendations on how to shim this floor up if and where it may need it?

Thanks,

Aaron

What you just said. Use them shims.

place em under the neoprene pads. and use that level well.

Bryan Giles

Thanks Bryan. So that would be: Concrete, shim, neoprene, 2x4 in that order if I read that correct.

Knightfly (Steve), on page 2 of this thread where we discussed the walls some, I need to ask this...

Let's say we have the outer walls floating on the floating floor. There will be metal studs at 24" centers, filled w/ 2.5lb 3" Roxul (mineral wool). Should I then place 2 layers of drywall prior to building the interior angled walls?

On the interior angled walls, especially where I will have the bass traps in the corners, etc, do I cover these w/ drywall too, or just fill the studs w/ insulation and then cover w/ a cloth or something similar? When I build the bass traps in the corner, do I leave a hole for sound to enter, or how does this work? If there's a thread that covers this in detail, let me know.

Thanks

"Concrete, shim, neoprene, 2x4 in that order " - Unless your shims are made of plastic or other waterproof material, I would put them above the neoprene. If necessary to keep them in place, a dab of construction adhesive won't hurt.

On the number of "leaves" used, I tried to make this clear with this comment - "Basically, between any area and the area you want to isolate, there should be only ONE airspace - this can be (and should be) insulated with either semi-rigid or regular fiberglas insulation. What you do NOT want to do is to have 3 separate centers of mass (leaves) between any two places you're trying to isolate. So, if one wall has wallboard on its frame on only one side, and the other wall (or other side of the same frame) has wallboard on it too, you're DONE. All you can do from there, without making things WORSE, is to add LAYERS to the same LEAF. Period. "

What this means is that between ANY two areas, unless you have more than maybe 50 FEET of air, you ONLY want two leaves. If you draw a plan correctly, then pretend you're a noise that's trying to travel, you should have to go through TWO, and ONLY two, centers of mass (leaves) to get from one area to the other area that it's supposed to be isolated from.

From outside in the driveway, through mass, then air/insulation, then mass, and DONE. From control room, thru one center of mass, then air/insulation, then one center of mass, and you're in the Live room. Same for ANY room to ANY OTHER room, as well as any room to outside.

This means that if you have TWO wall frames between any two areas, there should only be paneling on ONE side of EACH frame. If you're doing any of John's "inside out" walls, this paneling can be AWAY from the room side of the frame, then the insulation/absorbent, etc, can be toward the room. This does NOT violate the above rule, since absorbents act as an AIR space.

It would probably take anywhere from 40 to 100 feet of air space OR MORE between walls before you should EVER violate this rule.

Easiest way to ALWAYS get this right, is to just say "One, two" as you virtually travel from one area to another - if you have to say "three" before you're there, it's WRONG... Steve

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Soooo, when a Musician dies, do they hear the white noise at the end of the tunnel??!? Hmmmm...

Sorry, missed a few questions -

"One of the things he was talking about was putting 2 layers of 40lb felt (I believe he said roofing felt) and overlap by at least half way. Staple/tack them between the 2 layers of drywall. Any validity to this? " -

Sure. Roofing felt is flammable, but between two layers of drywall it isn't as susceptible to fire. It will add a dissimilar mass layer between drywall layers, and probably gain you at least 2-3 dB of STC, plus likely even better Transmission Loss at a couple of different frequency ranges.

"What if the speakers are not soffit mounted? I have the JBL LSR28P monitors. I was looking at the other site that had pictures of your finished/under construction studios, and had noticed that Sjoko's Studio was designed w/ these monitors. Would it be best to use these speakers as near fields on stands, or soffit mount them? How does he like those monitors being soffit mounted?" -

If speakers aren't soffited, they have a different response and need different compensation. Some speakers have built-in switches that give a 6 dB rolloff on the low end to balance out the results of soffit mounting - however, not very many speakers offer this and I'm not sure if the LSR's do or not. What I DO know is that Sjoko LOVES his LSR's soffited - he posted that he participated in a mastering "competition" a while back, and came in second only to some major "guru", don't remember the details.

All speakers will image better when soffited, it's just the physics of the thing. Soffiting forces the speaker's elements to ALL radiate ONLY in the forward hemisphere, so there are no nearby walls causing early reflections that smear imaging by phase cancellations/reinforcements - so as long as the REST of your room is properly laid out the sound that arrives at your ears is more coherent.

Noticed a few pipes in your pix - while they're still exposed, I would recommend re-doing all your hangers with flexible, sound deadening ones before your ceilings go up. Also, you may want to think about adding a couple extra layers of drywall between the ceiling joists to beef up that mass before insulating and adding the inner ceiling leaf.

Hopefully I caught any "stragglers" this time... Steve

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Soooo, when a Musician dies, do they hear the white noise at the end of the tunnel??!? Hmmmm...

Thanks Steve,

The last paragraph you wrote about the pipes. Are you talking about the plumbing pipes, or the structural posts holding up the house? What do you mean by redoing hangers? You lost me on that one.

On the ceiling/floor joists, I've got the joists filled w/ the 4" Roxul already. Are you saying to add a couple layers directly up on the joists, then I will also have the new ceiling frame w/ insulation and another layer or two of drywall? Sorry I'm not up to speed w/ all the construction lingo. It's a hit and miss. Some I know, alot of it is educated guess.

Yes, the LSR's do have switches on the back to compensate for low end. I've also got the sub that goes with these. I don't want to go into too much detail here on this thread about the monitors, but does the sub get soffit mounted too somehow in the wall, or just in the room somewhere.

Construction adheshive...any brands I should look for or use?

Thanks again for your patience in some of these questions. I greatly appreciate every answer I've been given.

Aaron

On the pipes I was talking about plumbing - both supply and drain pipes. The hangers I mentioned are the ones that support the pipes up under the joists - some of these are just metal tape or brackets, and will transmit any and all noise from water flow and valve shutoff, etc, right into the house framing. If there will be ANYONE in the house besides yourself (and whatever talent is playing) while you're recording, you need to hit the building supply and ask for isolation type hangers for those pipes to replace whatever solid ones have been used. Also make sure that wherever the pipes go thru a wall or framing member, that they don't directly touch the frame or wallboard, but instead have clearance all around, which you can then caulk with acoustic sealant.

For your ceiling, if you feel you may need more isolation (not Insulation, I'm very careful NOT to mis-spell since it clouds meanings) you can add more mass to the UPPER leaf of your "2-leaf barrier" known as a ceiling, by putting 1 or 2 layers of drywall AGAINST the bottom of the subfloor, up between the joists, and ABOVE the cavity insulation (Roxul in your case) - This doesn't violate the "2-leaf" rule, but helps improve both footfall noise and separation between upstairs and down. I've attached a pic that is similar to what I mean, other than the bottom part which has a layer of Celotex in place of one of the layers of wallboard -

On sub placement, I wouldn't soffit a sub unless I had two of them and could FLOAT them on isolated concrete pedestals inside the wall, which is very expensive to do. Otherwise, if you're lazy just stick it in an un-used front (preferably) corner, and adjust the level til you're happy at the mix position.

A better way is to place the sub in your mix position, sitting on a support that puts it at your ear level when mixing - then, play some "reference" mixes (something you're sure is well-voiced) and crawl around on your knees til you hear what you like, put a piece of masking tape on that spot, and move your sub there. That's a cheap trick I picked up from Floyd Toole, of Harmon. Haven't actually TRIED this yet, but his logic was sound...

On the construction adhesive, Liquid Nailz is readily found but is kinda thick for this - I'd ask for something a little thinner that's compatible with concrete, wood and rubber. I've not looked into what's available recently, so your local building supply would be your best bet. If you're stuck with the Liquid Nailz, put something heavy on top of the frame after you glue your shim/pad, maybe even stand on it for a couple minutes, so that it squishes down enough not to become an "extra shim" and screw things up.

HTH... Steve

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Soooo, when a Musician dies, do they hear the white noise at the end of the tunnel??!? Hmmmm...

That's interesting Steve. I never would have even thought of that.

Looking at the diagram, I would use the construction adhesive to glue the gypsum up again the bottom of the sub floor (2 layers), as far as the insulation (which I will have to pull back out...bummer) will the Roxul be ok? Do I need to add an additional compressed fiberboard since I already have the 4lb 4" Roxul? Then there is the "air space", and what appears to be the RC1 running parallel w/ the joists instead of across them? If that's the case, won't the screws going into the RC short out into the stud (joist) underneath? (just asking, that's what it looked like on the drawing.) Or is it just overhanging the joist and won't touch it?

The Celotex. I know I've seen it on this site somewhere. Same thing as Homosote?

And then 1 layer of 5/8 drywall. Is that glued or screwed? Will this be the final ceiling? Or can I still angle by framing, insulation and whatever I use for the ceiling (drywall, panels, etc.) Space will now be extremely limited.

On the plumbing (drainage), I just redid all that w/ pvc. It was that old cast iron stuff (and heavy). Unfortunately, the old vents are still cast iron and are not supported by anything other than those strong straps. Some of it I could do, but the part near the trap will drop if I pull that strap out.
The other pipes I can do though.

I finally went to the library and picked up some books. Started doing the book worm thing last night. They didn't have the books that were recommended though.

Awesome Steve. Thanks again.

Aaron