Air Lock Doors

Hi everyone, This is my first post here. I have a problem with my studio, the live room is right next to the control room, the door separating both rooms were built on site because the frame is quite small and you can't really find doors that fit there. The size can't really be altered. Now the problem, as you may imagine is the extreme bleeding coming from the live room, it's so loud, it's impossible to monitor correctly, mainly drums and loud amps. I was testing this out and noticed the problem here seems to be the frame, whenever I placed my ears up and down along the corners I could hear as much as if I was standing in the room. I took a couple of pictures for better understanding of the situation. View from Live Room View from Control Room 1 Corner to illustrate how rubbish they are Another one Basically, I'm thinking of removing this door altogether and build 2 thinner ones but creating an airlock between them, so obviously this frame has to go, what I wanted to ask is, what's the best way of achieving this in this situation? What must be done to the frame, doors, stops, etc? The door dimensions are: D= 19cm , L= 88cm , H= 185cm Thanks in advance!

Hi "sptz". Please check the forum rules for posting: you seem to have missed something! :) Regarding your door: How is the REST of the room built? Is it built as a proper fully decoupled "room-in-a-room" MSM structure? If not, the door might not be the problem. But if it is built correctly, then the frame is probably creating a flanking path, or the seals are not sufficient. Please post some pictures of the seals around that door, with the door open. Also, is that a solid-core door, or hollow core? If it is not solid core, and very massive, that might also be an issue. One last thing: It looks like you have THREE panes of glass in that door! Is that correct? If so, that is DEFINITELY a large part of your problem. You should only ever have TWO leaves in any acoustic isolation structure. 3-leaves will always give you WORSE isolation than two leaves, especially for low frequencies, such as kick, snare, toms, etc.... It might not seem intuitive, but is absolutely correct that if you were to remove the middle layer of glass from that door, the overall isolation would increase by several dB, and most of that would be in the low end.

Basically, I'm thinking of removing this door altogether and build 2 thinner ones but creating an airlock between them, so obviously this frame has to go, what I wanted to ask is, what's the best way of achieving this in this situation? What must be done to the frame, doors, stops, etc?

That depends on several things, but the big question is: how much isolation do you need? You should put a real-world number to that, in terms of dB SPL Transmission Loss. With that number you can look at various types of door structures to find one that achieves the level you need. Anyway, please check the forum rules again for that missing item, then post more information about how the room is built, and photos of the seals around the door frame. - Stuart -

Hi Stuart, I'm not sure what I missed, was it the location or the hosting of the images? :oops: I addressed both in hope that was the problem. In terms of the room, no, it's not built as "room within a room", basically because we are not allowed to, as this is a really old stable and the estate owners won't let us. I'm not looking for complete isolation, I just don't want the bleed to overpower my monitoring basically and I don't like monitoring loud, at all. I'm 100% sure the bleed comes from the doors/frame, I have played around with a few absorbers around the frame while someone was playing drums there and the difference was night and day. Yes, you are correct there are 3 layers of glass in that door, I didn't have any say in that, I just saw the door when it was done, it's solid core as well I believe, I know there's some layers of rock wool inside, I'm not sure how they're placed inside it though. Also, the main thing that is leaking is not even low-end, but mids and high end, lots of it. I was thinking of replacing this door with two much thinner ones and create some sort of small air lock between them, I don't know how to go about with that though. Regards, Pedro

I'm not sure what I missed, was it the location or the hosting of the images?

Yep! :)

I'm 100% sure the bleed comes from the doors/frame, ... Also, the main thing that is leaking is not even low-end, but mids and high end, lots of it.

OK, in that case my prime suspect would be the seals. That is by far the most likely source of your problem. It's not 100% clear from those photos, but it looks like some of these seals are simply foam? That wont work. Foam does not stop sound: at best it might damp it, but cannot stop it. From image IMG_20110922_170048.jpg (looking down at the floor), it is clear that the seals up the sides of the door do not meet the floor seals: there is a gap there. This is a problem. IMG_20110922_170040.jpg shows two seals across the top of the door, but only one down the side. This is also a problem. Finally, there is only one floor seal, and it looks like a simple threshold weatherstrip. That is another problem. The key to door seals is simple: totally airtight. Hermetic. Foam is not air-tight: you need rubber, neoprene, or something like that. Putting that foam in might have helped a little, but it will not solve the problem, because air can move through it easily, and therefor so can sound. Here's an interesting fact: a tiny air gap around your door, just 1/32" wide and one foot long, lets through roughly the same amount of sound as the entire rest of the door (a bit more, in fact). So such a gap would decrease your isolation on that door by at least 10 dB. That's huge. In order for the door to work at all, there must be at least two complete perimeter seals, and they must both be totally airtight. I would suggest that, before going to all the hassle of replacing that door with anything else, it would be easier to first try replacing all those seals with two proper perimeter seals, made of neoprene, rubber, or something similar. The kind of seal used around the edge of car doors (on good cars!) is what you need. There must be two complete seals, each one must run around the entire perimeter of the door (top, bottom and both sides) with no breaks or gaps, and the door latch must hold the door tightly up against the seals. Try that, and I'm betting it will improve the situation greatly. If you still don't get the isolation you want after doing that, then it would be the time to think about the much larger (and far more expensive!) job of replacing that single door with a proper sound lock, with two massive back-to-back doors. (You could probably even re-use these new seals tha I am suggesting for now, if you had to go with the "double-door" path, since each of those doors would need its own set of double seals. So you waste nothing by trying this solution first.) But the key thing to remember here is: airtight. There must be zero possibility for any air movement around the edge of that door. Even the slightest gap wrecks your isolation. - Stuart -

To hazard another guess...you select the doors as the leak, but we have no evidence that the isolation was properly constructed. So while the foam could well be a leak...it may not be >the< leak.

Hi xSpace, I'm pretty sure the main culprit is the door. I shot a really quick video so you can see where the door is in relation to the rest of the room. http://dl.dropbox.com/u/617922/VID_20110923_104928.m4v When you're sitting in the mixing position you can perfectly pinpoint the bleed coming from the door, if you're sitting on the couch which is right next to the door, leaving the door to your left handside, it becomes unbearable. What comes through the left wall near the console is very very little.

Stuart, thank you so much for your really informative post, that was really helpful! Does anyone from the UK knows where can I get high quality seals etc?

Here is my thinking. The door(s) and the multi air spaced/glass are part of the problem. The seals are another part of the problem. Big part as always. But , all things considered, if who ever built this room allowed this type of construction, even if you get a better seal on the doors and alter the glass configuration, the rest of the room and all the weaknesses that surely are built into it, will show up. As time passes, this will show itself to be true.

Brien, You are absolutely right, but the thing is, I can tell you for sure it's coming from around the door, through the frame, I did loads of testing, moving rockwool back and forth etc, if this gets fixed, then what comes out of the actual wall + door will be completely minimal compared to this, because as it is, it sounds like I'm in the freaking live room and I know that it is impossible to makes both these rooms 100% isolated from each other, I just want to minimize it as much as I can

Sptz,an I think we ALL agree, post after post, that your doors are an issue...I get it, we all get it. So exactly what is your question? Is there a question or are we gonna beat this horse for a few more days ;)

My initial question was what would be the best thing to do. I got an answer for that, but the question now is, what kind of seals are the best in this case? Just regular neoprene seals? Double? etc

I think I already explained that: You need two complete independent seals around the entire door perimeter, and a door latch that puts enough pressure on them to seal tightly. Neoprene is fine, but most good quality, soft, flexible rubbery compounds will do. Do not get a hard, tough, inflexible rubber. One really good option is the type of rubber that you find around the edge of car doors. Look around your city for companies that supply rubber: where I live (down at the bottom end of the planet, in Santiago, Chile), there's a place called "The House Of Rubber" (in Spanish), that has a huge selection of many different types, sizes, thicknesses, shapes and prices. If there's a store like that here, I'm sure there must be something even better where you live! So find that store, and post a link to their website here, then we can help you choose the type of rubber that will do the job. - Stuart -