# Bass trap questions



## Hakka (Sep 10, 2006)

I'm planning to make some corner bass traps this weekend, i'm trying to smooth out the 100 - 200hz region, i cant post a graph at the moment.

I have 3 room modes bunched up around 120 - 140hz, and a deep null above that. 

I will make triangular floor to ceiling solid chunks. I can only place these in the rear corners. Any suggestions on the ideal size of the traps? 

My projector screen covers a window 2m x 1.2m, there is around 4 inches between the screen and the glass. Would there be any point filling this cavity with rigid fibreglass? 

Thanks.

Hakka.
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## Prof. (Oct 20, 2006)

Hakka said:


> I will make triangular floor to ceiling solid chunks. I can only place these in the rear corners. Any suggestions on the ideal size of the traps?


If you make the faces 600mm. wide, you'll get 32 pieces from a 1200 x 2400 sheet..
That should be an ideal size chunks for a bass trap..

It wouldn't hurt putting fibreglass behind the screen area..
Do you ever have to access the window behind the screen?


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## Hakka (Sep 10, 2006)

Thanks Prof.


I need to take the screen down to access the window, which is a 2 person job, so it never gets opened.

I've started consruction of the frames for the bass traps, is there much difference in performance of the trap if i close off the backsides with MDF vs just using dowells and leaving it open?


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## Prof. (Oct 20, 2006)

There probably isn't a lot of difference between solid sides and open frame, but the open frame would be the way to go for max. efficiency from the chucks..
Let us know how it turns out..


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## Hakka (Sep 10, 2006)

I went with open frame but I'm thinking I might add some wood panels to make them more rigid, one will be in front of the door so it will be moved around a bit. It might make it easier to attach the fabric too. 

The batteries are flat in my camera so no pics yet.

Hakka.


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## Hakka (Sep 10, 2006)

I just went to collect the rigid fibreglass, i got a sheet of 2 inch but it seems to be a lower density than the stuff i used previously.

Should i use this or look for a higher density?

I have a bit more than i need so i could compress it a bit.

Hakka.
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## Prof. (Oct 20, 2006)

Are you using Bradfords Supertel.?


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## Hakka (Sep 10, 2006)

Prof. said:


> Are you using Bradfords Supertel.?


Dont think so, not sure who makes it.
Its not the same type i got last time, this stuff is yellow, not pink.
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## Prof. (Oct 20, 2006)

For the bass traps, you need the yellow Supertel..similar to the US OC703..


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## Hakka (Sep 10, 2006)

Prof. said:


> For the bass traps, you need the yellow Supertel..similar to the US OC703..


Just had a look on the bradford website, the supertel comes in 4 or 5 different densities, the stuff i got looks like the lightest one, i might order some of the high density one from bunnings.

Hakka.
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## Prof. (Oct 20, 2006)

In the 50mm. thick there is only type that comes in a 1200mm. wide sheet..
That's the one I used..It's the R1.5


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## Hakka (Sep 10, 2006)

Prof. said:


> In the 50mm. thick there is only type that comes in a 1200mm. wide sheet..
> That's the one I used..It's the R1.5


Thanks mate, that helps a lot.

The sheet i have, if i pinch it between my thumb and finger, it compresses down to around 5mm. I might give it a go compressed in one absorber and use the supertel in the other, if there is a big difference i will change it to supertel.

Hakka.
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## Prof. (Oct 20, 2006)

I just tried the finger press on mine and it only compresses to about 15mm. thick..and when I let go, it springs straight back to the original thickness..

I think you might have Gold Batts, which are not in the same category as Supertel..and I wouldn't advise you to use that as a substitute..
If you got it from Bunnings, then I would say it's definitely not the same...They don't carry Supertel..

I got mine from a specialist Insulation Company..


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## Hakka (Sep 10, 2006)

Prof. said:


> I just tried the finger press on mine and it only compresses to about 15mm. thick..and when I let go, it springs straight back to the original thickness..
> 
> I think you might have Gold Batts, which are not in the same category as Supertel..and I wouldn't advise you to use that as a substitute..
> If you got it from Bunnings, then I would say it's definitely not the same...They don't carry Supertel..
> ...


I got my sheet from an aircon place. It was actually a roll, there was around 5m left on it, not sure how long a full one is. The guy said it was the same material as the 1200x2400 sheets.

It looks identical to the pic on the bradford site, there's no markings on it though, and i didn't think to ask at the time.

When i originally did the pinch test i did it on the end which was a little knocked around, i cut some and tried it again and it was closer to 12 or 13mm. I've just finished one frame and i will have to wait for the supertel to arrive so might as well give it a try. I've got plenty of it so will squash it down as much as i can. 
When i finish the second one i can switch them and use rew to look for a difference.

I also noticed on the bradford site the different densities have different names, eg ultratel, flexitel. Missed that the first time, thought they were all supertel. Thats what i get for web browsing on a 5cm screen.
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## Hakka (Sep 10, 2006)

Supertel is 32kg/m3, ultratel is 48kg/m3. Would there be any point using the denser one?
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## Prof. (Oct 20, 2006)

Hakka said:


> I got my sheet from an aircon place. It was actually a roll, there was around 5m left on it, not sure how long a full one is. The guy said it was the same material as the 1200x2400 sheets.
> 
> It looks identical to the pic on the bradford site, there's no markings on it though, and i didn't think to ask at the time.


It sounds similar except the supertel only comes in sheets..Possibly it's a lighter weight type ..




> I also noticed on the bradford site the different densities have different names, eg ultratel, flexitel. Missed that the first time, thought they were all supertel. Thats what i get for web browsing on a 5cm screen.


Yes..there's a whole range of different weight insulation materials..


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## Prof. (Oct 20, 2006)

Hakka said:


> Supertel is 32kg/m3, ultratel is 48kg/m3. Would there be any point using the denser one?
> _Posted via Mobile Device_


I was originally advised to get the Supertel, as it was very similar to the OC703..
I suspect that the heavier weight Ultratel would have a little more reflective qualities than the Supertel..and would have a slightly different broadband range..
Whether that makes any difference or not, probably depends on your individual acoustic environment..


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## hakonfl (Feb 9, 2008)

Hello Hakka. 

I have been working on acoustic treatment of several recording studios, control rooms and at the moment two practice rooms for bands and a complete stage with 120 seats. 

My simple advise is like this. 

Use as much bass trapping as you can afford. The more broadband absorbers/bass traps you can put in to your room the better the low end responce will be. But filling the complete corner is a bit waisted. Here's my way of saving a few bucks and still making a lot of low frequency absorbers. 

I have built bass traps from compressed plates of rockwool (135 kg/m3). Here in Norway they are 120 x 60 x 5 cm. Theses plates are ment to be put under houses and are quite strong. For each trap I use three plates. 

One of them is cut in half, making two plates at 120 x 30 x 5 and one is cut off by 10 cm making one plate 120 x 10 x 5 and one 120 x 50 x 5. From these 5 plates i now build a tower. At the bottom, the 60 cm plate, next the 50 plate, next a 30 AND a 10 (making a 40 plate) and at the top the remaining 30 cm plate. This i simply place in the cornes, using som canvas to cover it and som wood to support it. Works perfect and saves you a bit of rockwool. 

These traps absorbs almost any sound above 100 Hz and is absorbing well down to 50 Hz. 

For the rest of the room i use the same rockwool plates, wrapped in canvas, and place them 5-15 cm away from the wall. This way they absorb almost twice as good as if you place them direct on the wall. 

As a test you could simply put the plates in large plastic bags and place them in your room. Or even easier, don't even unwrap them at all. Thin plastic film does not reflect bass sound. 

And remember: It's more important to treat a larger area of the room (specially the corners) than making fewer 'perfect' traps. 

HF


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## Prof. (Oct 20, 2006)

Hakka said:


> I got my sheet from an aircon place. It was actually a roll, there was around 5m left on it, not sure how long a full one is. The guy said it was the same material as the 1200x2400 sheets.
> 
> It looks identical to the pic on the bradford site, there's no markings on it though, and i didn't think to ask at the time.
> 
> ...


Hey Hakka...What did you finish up using for your bass traps.? Did you use the chunks or the flat panels.?


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## Hakka (Sep 10, 2006)

Prof. said:


> Hey Hakka...What did you finish up using for your bass traps.? Did you use the chunks or the flat panels.?


I used the big sheet that I got from the aircon supplier, I didn't really see much imrpovement so I plan to change it for supertel when I get around to it (been busy with more hardware upgrades). I just have the one trap around 1.5m tall in one of the rear corners, I have another frame ready to go just need to fill it.

I had some pics but can't find the memory card, I will take more when i finish the second trap.

Hakka.


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