John Sayers' Recording Studio Design Forum Archive

I have a basement that I'm using as a practice/recording space. The basement is concrete built, no blocks. The walls/ceiling/floor isn't transmitting anything to the rest of the building. The only problem iis the doorway. There're two doors. One is a hollow-core(more like hive-core) door, and the second is a solid-core door. The inner door is the hollowcore door and the outer door is the solidcore. The distance between the doors is 15cm. Every slot between the doors to the ground/frame is sealed.
I was thinking about putting some rockwool on the outer door's inner side(still with me?), would it help? I can only get 60Kg/pcm 2" thick Rockwool sheets. How many sheets should I put on this door? would it help?
I'm not putting anything on the inner door since it's going to be acoustically treated soon, so I prefer handling the outer door first.

Thanks,

Bump.

Sorry..

http://www.johnlsayers.com/phpBB2/viewtopic.php?t=3231

You missed the part about including location in your profile - please re-read the above for more... Steve

Hi, I read the reference area and included my location in my profile(Israel).
I'm still confused about how soundproof my door..

Thanks,

Putting 2 or 3" rockwool on the outer, solid door wil help a bit, but your main problem is that your inner, hollow core door is making the overall doorway into a 3-leaf situation which will actually WORSEN the isolation anywhere near the several resonances caused by multiple leaves.

It's possible you could improve the door by REMOVING the inner hollow core, at least at some frequencies. The only way you'll get noticeably better isolation is to replace the inner door with another solid core one, so you have a true mass-air-mass system.

Ideally, you would have two WELL-SEALED solid core doors in two separate frames, with their individual casings caulked under any moldings (usually this space just has shims in it to adjust the casing for smooth operation of the door) -

There are a few door-related links in the REFERENCE section that may also help... Steve

I can't afford another solid-core door right now. But I guess there few methods to thicken the current door. I've heard about making two holes at the top profile of the door, and putting sand inside. It seems like a good idea, but I'm not sure the hings could take care of that.
Another idea I was thinking about was to put plywood on the hollowcore door, and that way it'll be thicker. The question is if I have any chance to reduce the noise significantly without installing another solidcore door.

Thanks,

Most hollow core (and honecomb) ones I've seen are only thin veneer, sometimes the honecomb stuff is just cardboard glued in place. IF your hinges are designed for that door, sand will break things for you. IF the door is honecombed, you couldn't get the sand to go everywhere anyway. Beefing up the existing veneer sides of a hollow core door will STILL leave you with 3 leaves; the solid core and both sides of the hollow core.

Easy experiment - pull the pins out of the hinges on the hollow core, and see if the isolation gets better or worse (it may be a "toss-up")

If you were going to beef up both sides of the hollow core, you should use something like 19mm MDF both sides - you would then need heavier and MORE hinges, longer screws for the hinges, and possibly more wood in your framing (hard to do after it's enclosed) -

That would STILL leave you with 3 leaves, and you'd probably end up removing the SOLID door temporarily til you can afford the second solid door.

Those are the only options I know of. If removing the inner hollow door doesn't help (I know this seems impossible, but try it) then you may have to wait til you can afford the second solid door... Steve

I tried removing the hollow core door and it didn't help. It seems weird that thickening the hollow core door wouldn't help. As I see it, there's another boundry for the waves to pass through.
I wouldn't loose anything from thickening the door(except for the money i'd spend for the MDF), so I guess I'd try that out anyway.

btw, I won't loose anything from putting rockwool on the solidcore's inner side, so I guess i'd try that out too. Should I use the densest? In case of 60Kg/pcm 2" thick rockwool sheets, how many layers I should put on the door.

(I know that some of the stuff I say contradict what I've read in the refernce area, but I've seen this stuff work, and Knightfly said that the roclwool sheets might help).

2" dense rockwool on the door will damp it a bit, as well as absorb air movement between the two doors - that's its contribution.

If you add MDF to the hollow door, try it ONLY on the innermost surface - this may lessen the effects of multiple leaf construction. Here's a pic of what happens with different constructions - walls work same as doors, and as you can see (these are actually TESTED results) it's more in WHERE the layers go than how THICK, and TWO leaves ALWAYS beats more leaves... Steve

Perhaps what might be very helpful (and maybe even deserving of a "sticky" is a cut away view of a hollow core door. Over and over again I see people mistaking a HC door as a single assembly when in fact it is two layers separated by air (mass-air-mass). If Knightfly's drawings of wall construction were put right next to a cut away view, people might finally "get it" and understand the physics of what's going on and why less can be more.

By the way, one thing I didn't understand in the "testing" discussion is why the HC door had to be removed from it's hinges? Couldn't you just open the door and see if the isolation increases? Seems a lot easier than removing the door and has the added advantage of having the A and B of an A/B compare a little closer in time.

Just a thought...

len

Len, my thoughts on the "hinge" thing were that it's possible if you open the door all the way, the neighboring wall would become 2 leaves BIGGER due to the proximity of the door, and that might skew the perceived/measured result. Paul Woodlock discovered the reality of this phenomenon and documented it about 40-50 pages back in his infamous diary on studiotips.

Good idea about combining these, I'll add it to my (looooong) list... Steve

Good point. I'm planning to use Paul's demonstration when the studio is finished to amaze the ignorant and prove to the uninformed that I know at least a LITTLE about what I'm talking about.

len

Just another thought: If these hollow core doors are so flimsy, wouldn't it be fairly simple to use a chisel around the edge of the door to remove one of the layers? You could then remove any "honeycomb" that's between the veneer and fill wil say 703 (or nothing) and then cover the side with cloth. This would allow you to beef up the remaining side and get back to a m-a-m situation.

Granted, this really only works in the situation where you have 1 hollow core door and one solid core door but I've seen a lot of these. I guess you could also make a case that two closely spaced hollow core doors modified this way (with the cloth sides facing each other) could give you a bit more air space between to closely spaced HC doors.

len

I would think that the integrity of a hollow core door with one face removed would compromise its integrity tremendously, let alone beefing up the opposing side.

Oh well -- if the door is the problem and can't afford a door (we're not talking freakin' $3,000 Overly here), I'm at a loss to recommend anything.