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DIY Bass Traps

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Re: DIY Bass Traps

Postby Digipenguin » Tue Sep 28, 2004 2:44 pm

Thanks, Mike. Glad you're enjoying it. 8-)
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Re: DIY Bass Traps

Postby Digipenguin » Tue Sep 28, 2004 2:46 pm

Well the left tweeter just went out so measurements are on hold until I get a new set of monitors or get these fixed. :frown:

Feckin' Samson. :madas:
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Re: DIY Bass Traps

Postby cc. » Tue Sep 28, 2004 10:11 pm


Ah someone else trying to squish insulation - I built some acoustic screens the same way, but only managed to fit in half the fluffy stuff you did!

I'd be interested to see the measurements, from what I understand of the theory (from ethan's site mostly) this type of trap shouldn't really absorb much bass - because to absorb efficiently you have to have the absorbing material at least 1/4 wave length from the wall (because that's where the air is moving most), and for low frequencies that's a long way! Which is why ethan goes for the panel / membrane type trap... but then again simplistic theories like this (ie ones I can understand) are often wrong :headbang:
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Re: DIY Bass Traps

Postby MPBStudio » Wed Sep 29, 2004 12:05 am

Furthermore, Ethan's mid/high absorber design (the one with just burlap on the front side, ie the way you did) requires a 2" air gap between the insulation material and the back panel (or wall).
This is the most highly tuned of Ethan's designs.
I'm a bit sceptical about the effectiveness of your traps on bass frequencies, even though this is a theoretical assumption.
The deep bass trap and the high bass trap design work on the resonator principle: you need a rigid front panel that vibrates and a sealed box with dumping material inside in order to absorb that energy and transform it into heat.
Maybe you could try to put a front plywood panel on your traps ( Ethan bass trap page )
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Re: DIY Bass Traps

Postby Digipenguin » Wed Sep 29, 2004 12:53 pm

CC, yeah, actually 'bass trap' is a misnomer pointed out by someone on another forum. This design is technically a broadband absorber. :blush: It will probably only be effective down to 125Hz. I've just found out though, that filling the cavity behind the trap with acoustic foam type bass traps will maintain it's mid high absorption qualities while boosting it's bass absorption coefficiency. 8-)
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Re: DIY Bass Traps

Postby Digipenguin » Wed Sep 29, 2004 1:02 pm

MPBS, yes, Ethan's design does work that way however, an air gap like that in a corner is as effective if not more. The distance is figured as an average of the total distance of the corner cavity. The larger the cavity, the more average distance, the better they work. Mine figures out to be about 3" average (I tell my wife it's 9" :).)

Oh, and thanks for the link, but if you look a few posts before this one or just look at the photos on the website you'll see I'm fairly familiar with Ethan's designs as I have already built a few deep bass membrane traps that are in use in my studio now. :)
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Re: DIY Bass Traps

Postby Digipenguin » Sat Oct 02, 2004 7:03 pm

I've contacted Samson support about what I can do to fix my monitors. Hopefully I can get the measurements done this year. Sorry to make you guys wait so long. I need the time to figure out some better testing procedures anyway.
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Re: DIY Bass Traps

Postby MPBStudio » Mon Oct 04, 2004 12:15 pm

MPBS, yes, Ethan's design does work that way however, an air gap like that in a corner is as effective if not more. The distance is figured as an average of the total distance of the corner cavity. The larger the cavity, the more average distance, the better they work. Mine figures out to be about 3" average (I tell my wife it's 9" :).)

But it sould be a sealed cavity, if I'm right. From your description and your pictures I supposed you haven't sealed the cavity. In this case, I think the only difference is the corner positioning (ie more bass energy to absorb) and the double surface extension (ie bass freq coming from the front and the back of the box).


Oh, and thanks for the link, but if you look a few posts before this one or just look at the photos on the website you'll see I'm fairly familiar with Ethan's designs as I have already built a few deep bass membrane traps that are in use in my studio now. :)

I've pointed out Ethan site only in order to underline the need of a sealed box to absorb bass frequencies.

You have built nice looking traps indeed and I'm sure they are effective too. Mine are just theoretical notes. The rule is always the same: if it sounds good, it's good. :lol:
bye,
S.
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Re: DIY Bass Traps

Postby Digipenguin » Mon Oct 04, 2004 12:26 pm

Melting Pot Bedroom Studio wrote:
I've pointed out Ethan site only in order to underline the need of a sealed box to absorb bass frequencies.


Ah, gotcha, it was a reference. No, my design is not sealed. It is not a tuned absorber. I'm going to try some acoustic foam behind the traps after I take measurements but I want to do before and after measurements for that as well. Hopefully Samson will get back to me today.
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Re: DIY Bass Traps

Postby Adam Inglis » Wed Oct 06, 2004 9:17 am

Digipenguin wrote:
Melting Pot Bedroom Studio wrote:
I've pointed out Ethan site only in order to underline the need of a sealed box to absorb bass frequencies.

Ah, gotcha, it was a reference. No, my design is not sealed. It is not a tuned absorber. I'm going to try some acoustic foam behind the traps after I take measurements but I want to do before and after measurements for that as well. Hopefully Samson will get back to me today.

Guys, this is something that has been confusing me. As I understand it, bass traps do NOT need to be sealed, unless they're a part of a Helmholtz or other "tuned" absorber, is that right? They can just be broadband bass absorbers then?

.
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Re: DIY Bass Traps

Postby Digipenguin » Wed Oct 06, 2004 1:50 pm

I can't speak in absolutes when it comes to this because I am not an expert. I can say that all airtight bass trap enclosures I've seen were tuned to a specific range that was narrower than an open design. The tuned designs have all been lower than the average range of an open design. These are observations for panel type traps, both open and membrane, utilizing some sort of airflow inhibiting material such as insulation. It's really a comparison of apples to oranges though as a membrane trap works in part on a different principle than an open panel trap. Both designs work on the principle of slowing down the airflow and converting it to heat but a sealed design also relies on the cancellation of the reflected wave by the vibrating front panel.

Also, I just wanted to point out a Helmholtz resonator is not sealed and is not necessarily a panel trap although I guess in some configurations it could be considered so.

It's a complicated business this acoustic treatment thing. I doubt I'll ever understand it all.
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Re: DIY Bass Traps

Postby Ethan Winer » Wed Oct 06, 2004 6:42 pm

John,

> all airtight bass trap enclosures I've seen were tuned to a specific range that was narrower than an open design. <

You got it.

--Ethan
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Re: DIY Bass Traps

Postby Adam Inglis » Fri Oct 08, 2004 2:04 am

Digipenguin wrote:I can't speak in absolutes when it comes to this because I am not an expert. I can say that all airtight bass trap enclosures I've seen were tuned to a specific range that was narrower than an open design.

Thanks DP and Ethan.
One thing I get from reading these sites (such as Ethan's) is the impression that you can't have too much bass trapping. But if these things are not broadband absorbers, then surely you would skew your response?

I'm considering ordering four of Ethan's traps (around AUS$2000). Do we know just how broadband is the trapping? Are they sealed?

Related to this, I'm looking forward to your measurements DP!
"It's a complicated business this acoustic treatment thing. I doubt I'll ever understand it all. "
Man you got that right...


cheers
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Re: DIY Bass Traps

Postby Digipenguin » Fri Oct 08, 2004 2:35 am

In a small studio it's a safe bet you'll never be able to add enough bass traps to out absorb mids and highs. And if you did, mid and high treatment is relatively easy compared to bass taming. Normal foam panel and corner absorbers will fix that.
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Re: DIY Bass Traps

Postby Digipenguin » Fri Oct 08, 2004 2:40 am

Ethan can speak to his design better than I can. I can only say they have received rave reviews and are very highly regarded by most. If I could afford some, (read: if I could justify the expense to the better half) than I would have my walls littered with them. :)
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