Cheap Bass Trap?

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dyermaker8

New member
25 bucks buys an 18" Diameter x 6' roll of 6 lb foam carpet underlay.

I've read the same stuff as everybody else regarding using proper room treatment, but I can't seem to shake the thought that the mass/density of this stuff should come in handy somewhere. That and I keep looking at the conglomerate pattern of the foam thinking that should bring some form of diffusion into play as well.

I'm planning on throwing it in the one exposed corner In my room and putting a material drape/cover over it,.. how to they test things like this for effectiveness? Speaker/pink noise/Mic/analyzer (before and after) good place to start?

Thoughts?
 
If you already have it give it a shot but I wouldn't expect much. Fiberglass and rock wool is used for a reason and it is just as cheap.
 
Oh and room eq wizard would be the best way to monitor these changes in acoustics.
 
Putting a roll of carpet foam in one corner of a room isn't going to do anything useful.
 
Not to mention you could put a proper bass trap in all four corners for under 100 bucks
 
so by common logic I should also assume that commonly available acoustical foam bass traps are also suspect of functionality? or Is the type of foam that different?
The carpet underlay i'm speaking of is bonded urethane, Its is made from scrap high density foam, same as whats used in furniture and car upolstry. I could certainly see cutting and stacking(spray adhesive?) to make wedges or whatever if the shape is that important. I could let the roll unwind and increase the interior air gaps, of which there could be several,,, I look at this stuff and see the raw material for a readily available acoustic foam project.

Does having furniture in the room not help either?
 
I assume you are going to leave it in roll form? I doubt it'll do anything for bass trapping at all. Better to buy some rolls of fiberglass unfaced insulation and stack those in the corner, if you don't want to make/buy real bass traps.
 
Honestly, any diffusion helps. A bookcase with the books set in and out at different levels will do great diffusion. But the question becomes, does that really help your acoustics. The use of diffusion in small rooms is debatable. I bought some foam bass traps (cheap--$40 for 4) on clearance at a local shop. They were worth just about what I paid for them. Putting up 6" OC705 bass traps in the same corners really pulled the bass out. Superchunk traps would be better, but it's enough for my needs. It's funny, because I can go into the next room (bathroom) and hear really pumped bass, but in my studio, it's just nice, flat sound.

I'm sure there are professionally designed rooms that want to keep some of the ambiance and use foam, and furniture, etc. What I've seen of Chickenfoot's studio time (and others) are large rooms with very little acoustic treatment besides heavy curtains. They are acoustically designed rooms. That doesn't mean my 12x10x7.5 room will sound good that way. Sound waves being what they are, you have to do a lot more to control them as rooms grow smaller and dimensions enhance bounces...
 
dyermaker8 said:
25 bucks buys an 18" Diameter x 6' roll of 6 lb foam carpet underlay.

I've read the same stuff as everybody else regarding using proper room treatment, but I can't seem to shake the thought that the mass/density of this stuff should come in handy somewhere. That and I keep looking at the conglomerate pattern of the foam thinking that should bring some form of diffusion into play as well.

I'm planning on throwing it in the one exposed corner In my room and putting a material drape/cover over it,.. how to they test things like this for effectiveness? Speaker/pink noise/Mic/analyzer (before and after) good place to start?

Thoughts?
Click to expand...

Here's the main issue: you're convinced that the density or mass of an object is what gives rise to it's absorptive properties. But this is actually here nor there with absorbent materials. The absorbers resistance to air flow is what really determines the absorption. And carpet underlay will have very high resistance, making it a very poor absorber. All current models of absorption use the resistance parameter as the main parameter for estimation (along with thickness). It is mainly known in the literature as GFR (Gas Flow Resistance) (but sometimes air instead of gas, and sometimes resistivity instead of resistance).
To test efficacy, if you have a microphone, you can use REW which is a free program to measure the sound before and after installation. We've got a video on how to set it up and get going on our site here: Room EQ Wizard Tutorial - GIK Acoustics

BroKen_H said:
Honestly, any diffusion helps. A bookcase with the books set in and out at different levels will do great diffusion.
Click to expand...

Not to be too negative, but this myth is really detrimental so I would like to set the record straight: random books don't diffuse in the slightest. What they will do is scatter sound in different directions, and often this can be better than a flat wall, but it can also cause comb filtering that wasn't present before, so not always worth doing (no harm in trying of course). Often people have the idea that all diffusion does is shoot sound in different direction, but this isn't the case. A proper diffusor evenly distributes sound in the entire 180 degree span left to right, for sound coming in at any angle, and also does this not just in direction/space but also phase/time and also in amplitude/intensity. This is not a small distinction at all, and makes a huge difference compared to a 'random' scattering device. One is guaranteed to actually reduce problems due to comb filtering, mix the sound field better in the room, etc. The other method has such a small chance of achieving this, it is not really a useful spend of time.
How Diffusion Works - GIK Acoustics
 
Well,. I'm glad I ask,. if nothing else its caused me to research more and change my entire room plan. ., and to beat it all I find out I can get roxul at lowes! its amazing how quick the money goes.

That last bit about GFR is exactly the kind of info I like, thanks Alex.
 
Thanks. Always wondered about the ACTUAL of the bookshelf thing. Always heard the myth, good to know it's junk.
 
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