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In last weeks hangout I was asked “Is it a good idea to stick Acoustic Foam to walls?” Well our foam has a self-adhesive back and if you were wanting to do that, we would have offered that to you. It’s a peel-and-stick system that works really well but that said once you stick to a surface it’s gone, you won’t move it, it won’t change, you can’t peel it off, the foam will just tear so you’d need to buy more.

It’s open-celled foam so that means that every cell in the foam is open so what you have to first do is fill each cell full of adhesive so that it’ll stick and that’s going to require a thicker application process than just spraying something out of a can.

So you’re going to need to buy an adhesive, just a general adhesive, construction adhesive, it doesn’t need to be crazy but you need to roll it on the surface so that it’s thicker and the first thing is you have to fill the holes in the foam with adhesive. So you have all these little holes, because it’s open-celled foam, that at first must be filled with adhesive. I would put adhesive on the foam and on the wood surface, both that you’re trying to attach the foam to and then, that said just remember that it’s a permanent installation. You will never get the foam back off of that wood.

Ali: And an additional performance reducer.

Dennis: Well yes it’s a performance reducer because you’re only going to absorb on one side of the foam.

Ali: So what’s your recommendation for hanging the foam?

Dennis: Well I like the foam cabinets that we have because they allow for the kind of air movement that is needed. Also it helps in finding the correct positions for reverberation and reflection management in your room as it is a tuning process. I can’t really sit here and tell you “put a piece of foam six inches above this spot and four inches above that spot” as it’s a tuning process that you have to figure out kind of on your own.

Room tuning is a process

I can give you some great general guidelines but how much reverberation time you want to control and how you want to control it is really a subjective thing. So we like to give people pins. We have these big thumbtacks, these plastic thumbtacks that we send with our foam and they’ll work on any wall surface except concrete. And then you put the foam off in areas that I suggest to start with and then try moving in different positions because managing the reverberation times is really a subjective thing.

I can tell how much foam in what size room to achieve the correct reverberation time. That said finding the correct position for the foam within the room to suite your individual room usage and preferences, I can’t. you have to do that on your own and I’ll be more than happy to help you do that but you need to decide how much of what surface you’re going to absorb, how much energy at and that’s something that you do through a room-tuning process and that’s why we like our big colored thumbtacks, we call them ‘clown tacks’ because they all have these colors. But they help you have the ability to move the foam around in your room and not have it stuck permanently.

Now once you get the positions that you like if you want a more permanent installation then you can glue the foam to the surface or you can put it into a cabinet, put some fabric across it make it look very attractive. So all kinds of options to go once you really know where the foam is.

Watch that comb filtering off your desk

We’re working with a costumer right now who just does voice. He sits at a desk but it’s a glass desk, okay we all know how I think about glass and now we have the microphone sitting on a glass desk. What kind of sound are we going to get that that microphone is going to hear? Glass sound because even sitting in front of the microphone and sitting into it you’re going to get a comb-filter bounce off the glass into the microphone. So now you have vocals and glass vocals. Yikes we don’t want that so probably a good piece of foam on the desktop is the way to go there.

So everybody’s usually just different. Reverberation times are Physics they’re easy to figure out ‘how much of this material that absorbs at this rate and level do I need in this size room and volume’ I can tell you that number all day long. I can’t tell you where you like to listen at in terms of reflection management, that’s something you have to figure out on your own and it’s not complicated but the pins give you the ability to move the foam around and do it on a temporary basis and it just puts a really little hole in the wall, so it’s not, people don’t freak out too badly about it.

Ali: Well funny enough just behind your left shoulder there’s the pins demonstrated and just before we came on air we had the sun blaring through that window thenas a demonstration. Unfortunately we didn’t record that one that is easy it’s just moving them in and out.

Dennis: Yeah I think, hold on a minute I have some here. Here they are, they’re just big thumbtacks, we call them ‘clown tacks’ because they’re really big. So they will almost go through a one-inch piece of foam. Now they won’t go through a two-inch but they will almost go through a one-inch so you just simply angle them at a 45-degree angle on the side; that way you don’t put a hole on the front of the foam. So, and it doesn’t matter because the foam fills in the hole in anyway it’s you know, it’s dense but the one-inch foam will pretty much take the tack, the two-inch you come in at an angle and two to three tacks per piece and I always include those.

In North America you buy them in OfficeMax, Office Depot or whatever it’s called, that’s where we get them but they’re great temporary attachment devices if you will for foam.

Dennis Foley

I am an acoustic engineer with over 30 years’ experience in the business. My technology has been used in Electric Lady Land Studios, Sony Music of New York, Cello Music and Films founded by Mark Levinson, and Saltmines Studios in Mesa, Arizona, along with hundreds of others.

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