Onther basstrap thread

Hi guys,

So already a lot of discussions have been had about bass traps and what materials to use for DIY versions. Only I can’t realy find anything about hard foam isolation panels. Not the accoustic foam panels, but the one’s you also use in building construction. Example below.

I’m wondering if this could be a good bass trap material since a good bass trap has a lot to do with the density of the material. At least for as far as I understand.

Any thoughts or experience?

They are available in 30cm thick panels

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“a good bass trap has a lot to do with density”, well it’s not that simple… The performance of a bass trap relies on several parameters, the most important being:

  • Thickness
  • Air flow resistivity
  • Air gap behind the bass trap
  • Its placement in the room (room modes are highly localized)
  • Backing material and fabric (or whatever) material used to cover it

The density itself actually has little to do with the bass trap performance. The resistivity is the key parameter, but there is no one simple rule like “the higher the better”… There is, however an ideal resistivity for a given bass trap and you can calculate it with this fantastic website: http://www.acousticmodelling.com/porous.php

If you play around with the values, you will see that for thin panels a high resistivity is better, but for thick panels the trend is reversed.

It’s hard to tell if these foam panels would be any good without knowing their flow resistivity. Maybe you can contact the manufacturer and ask if they have tested them for resistivity and can give you the value? However, if this material is cheap I think it’s safe to assume that it is not as good as the material bass trap are usually filled with, which to my knowledge is mostly glass or mineral wool.

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I think the DIY panels I made out of rockwool are classed as broadband absorbers rather than bass traps. When you play around with the equations, you’ll sometimes come out with panels that have to be 80cm thick or so to trap the bass. Now, he/she who as 160cm spare space in the perimeter of their room, please speak now!

In the end, my panels (as far as I understand) absorb a broadband of frequencies (high and high mids definitely), and diffuse / trap / redirect the lower frequencies. I have built a fair amount of space in the frames with the understanding that bass frequencies will go through the panel losing some of it’s energy, bounce off the wall and have to make the same journey back to my ears, again losing energy on the return leg. I have enough of them to have taken out all the boominess of my 80hz problem that used to plague me. As I’m not an EDM DJ, I’m not hurling sub bass around my room regularly and when the mood does hit me, I grab my headphones for a second opinion. Not a perfect room by a long shot, but I couldn’t live without the treatment I’ve got in that room.

:sweat_smile: Yeah there are probably a lot of us in the same boat. However, you really only need bass traps (those devices that can properly absorb frequencies under 200 Hz) in the corner and angles of your room. With the “tri-trap” shape (GK acoustics vernacular) or what is commonly known as super-chunks, you can decently treat a small room without sacrificing too much of the space. In my small room, I have 4 superchunk bass traps that are 24 inches (60 cm) deep and they’re making a dramatic difference.

If you can locate the primary reflection points on your walls that might need some bass absorption too accurately enough, you can place thick panels that don’t need to be huge as well. I have made 4 “BBC like” wideband absorbers, 25 cm thick, 60x60 cm in shape. I used these studies as a reference: http://downloads.bbc.co.uk/rd/pubs/reports/1992-11.pdf

Back when I got serious about recording at home coming up on 7 years ago now, and not being DIY kinda guy by any stretch of the imagination, I bought a set of GIK Acoustics absorbers that one of their very helpful staff worked with me to select given the weird dimensions of the room I had then. It ended up costing almost US$1300, but it was the best investment I have made by far. I have two of those tri-traps and a bunch of panels in two sizes.

After moving here to Virginia last year, they now cover nearly all the walls of the basement room I’ve made into my studio – that room is smaller than the one I had before, but they just fit. They are visible in the 1-take guitar videos I’ve been posting, e.g. here. Very happy with how my primary recordings sound with these babies.

Here’s mine:

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