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Bass traps in room

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Re: Bass traps in room

Postby Danny_79 » Mon Nov 04, 2019 9:28 pm

Hugh Robjohns wrote:A door/window will reflect HF very strongly, like a wall, and also most midrange frequencies. But unless it's a really heavy, solid, door with an airtight seal it will tend to leak low frequencies, so it effectively becomes a low efficiency bass trap.
I was thinking of hanging a broadband absorber by hooks and ropes in front of that door. As close as it would be to a wall. But i don't know if that would be a good idea tho(?). The door isn't very airtight
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Re: Bass traps in room

Postby Hugh Robjohns » Mon Nov 04, 2019 9:57 pm

It's a good idea. I have a broadband panel on the back of my door. It's there to stop mid and high frequency reflections.
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Re: Bass traps in room

Postby Danny_79 » Sun Nov 10, 2019 6:19 pm

I have purchased 2 of these now: https://www.thomann.de/se/the_t.akustik ... InN2In0%3D

I think i understand most of it now. But one thing that could be good to know is, is there a minimum and/or a maximum on how much space that should be left between it and the wall for the sake of getting out the best effect of it? In cm...i don't understand feets :lol: Thanx in advance anyone
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Re: Bass traps in room

Postby Sam Spoons » Sun Nov 10, 2019 6:34 pm

Those are 100mm thick so I'd probably put them 100mm from the wall, or less if that takes up too much space. I haven't read anything about the theory of it but making the space the same as the thickness seems to be the most recommended and it seems to make some sense.
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Re: Bass traps in room

Postby Studio Support Gnome » Tue Nov 12, 2019 10:30 pm

typically best bang for buck is make the offset the same as the thickness, as a rule of thumb... but anything over about 20mm is worth doing...

it moves it out of the edge of the boundary zone, where there's zero movement for the panel to act on...

it can be shown that in some cases, it can be worthwhile going further than the same thickness for thinner panels , up to 2 x depth can be effective, but it is dependent on the material and the room.

but the simple " same distance as thickness " is a sound basic starting point.

(ha ha see what I did there ?? eh ? eh ?? )
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Re: Bass traps in room

Postby Danny_79 » Sun Nov 24, 2019 12:54 pm

Studio Support Gnome wrote:typically best bang for buck is make the offset the same as the thickness, as a rule of thumb... but anything over about 20mm is worth doing...

it moves it out of the edge of the boundary zone, where there's zero movement for the panel to act on...

it can be shown that in some cases, it can be worthwhile going further than the same thickness for thinner panels , up to 2 x depth can be effective, but it is dependent on the material and the room.

but the simple " same distance as thickness " is a sound basic starting point.

(ha ha see what I did there ?? eh ? eh ?? )
Mine are constructed in such a way that if i hang them directly at the mounting clips(included in the package) it only leaves 11mm from the wall. Could it be that the designers have just made it simple without caring so much about the best effect of it all?
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Re: Bass traps in room

Postby Wonks » Sun Nov 24, 2019 1:24 pm

With those panels, looking at the picture of the rear, they seem to have some form of hardboard or plywood panel at the back of the trap.

Image

This will stop sound waves from passing through the back and allowing the reflected waves to re-enter the trap. So mounting the trap further away from the wall won't have any benefit here, as it basically takes its own rear wall with it.

You could remove the rear of the trap, put some suitable fabric at the back and then mount it off the wall for better performance, but you'd have to make up your own brackets.

You need to be really careful with what you buy. DIY traps are almost always the cheapest and effective solution. You can buy good, well made traps that you can hang away from the wall, but they do cost more than the DIY solution.
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Re: Bass traps in room

Postby Hugh Robjohns » Sun Nov 24, 2019 2:18 pm

Wonks wrote:With those panels, looking at the picture of the rear, they seem to have some form of hardboard or plywood panel at the back of the trap. This will stop sound waves from passing through the back and allowing the reflected waves to re-enter the trap. So mounting the trap further away from the wall won't have any benefit here, as it basically takes its own rear wall with it.

...unless that hardboard is designed and intended to serve as a membrane absorber for lower frequencies... Probably not in this case, but that approach was a popular solution in the BBC's bespoke modular absorber panels.

H
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Re: Bass traps in room

Postby Wonks » Sun Nov 24, 2019 3:24 pm

As the mounting points are on the rear panel, I doubt it too in this instance.
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Re: Bass traps in room

Postby Wonks » Sun Nov 24, 2019 5:23 pm

As I understand it, the BBC A10 modular had 3.2mm hardboard at the front and 9.5mm exterior grade plywood back and sides, with a loft insulation filling (Supawrap 600). Size 580mm x 580mm x 184mm. Rockwool filling was tried, which had a smoother absorption profile but the overall absorption level was significantly less.

http://downloads.bbc.co.uk/rd/pubs/reports/1992-10.pdf
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