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-   -   DIY Bass Trap....Will it Work ? (https://www.hometheatershack.com/forums/home-audio-acoustics/3198-diy-bass-trap-will-work.html)

Marks57 01-24-07 08:38 AM

DIY Bass Trap....Will it Work ?
 

Hi, I have an 11' x 13' room that I have converted to just a 2 channel listening room with some pretty nice equipment, i.e. Marantz, Musical Fidelity, Tannoy Saturn S10 towers. I have treated the side walls with 2' x 4' 1" thick 703 Owens in wood frames covered with burlap. The wall/ceiling are treated all the way around with 2" thick 703 Owens with 14" wide panels and are angled between the wall/ceiling area. The front wall has a 2' x 4', 2" thick panel on each side.

Now I am ready to start treating the corners. I read on a DIY site to use Sonno Tube (concrete forms) and fill them with sand for bass tubes. Then, I read a reply from Ethan Winer that this would have no positive effect at all.

I bought 2 of the Sonno Tubes anyway....12" in diameter. I heavily duct taped each end and inside of them I put a 2" thickness of 703 Owens in a + (plus sign) configuration and capped each end with a round cut of 2" 703 Owens, then duct taped it air tight.

I have only made one of these so far and don't really know how to tell if it is effective or not. I do not have an SPL meter, nor the software to measure the room. Furthermore, when I look at the examples of the EQ readouts on some sites, it's like a monkey doing a math problem. I don't understand it, therefore have not downloaded the software and bought a meter.

Has anyone tried this method with the Sonno Tubes and have you found them worthy? In theory, they are similar to the bass trap drawings Ethan Winer shows on his website, but may not be doing a thing for me. If not, I haven't wasted much $$. :crying:

Thanks in advance for any input.

Mark

bpape 01-24-07 09:46 AM

Re: DIY Bass Trap....Will it Work ?
 

Don't bother with the Sonotubes. The sand filled thing doesn't work at all - not sure where they ever got that idea but whoever did it, I'd never hire them - they obviously don't understand how things like that are supposed to work. The bass absorbers on Ethan's site operate as a membrane absorber - a completely different principle and very effective - though not broadband.

If you want tube shaped absorbers, get some pipe insulation and fill it with fluffy fiberglass and cap the top and bottom. Just understand that with a tube design, you'll need to be looking at 16" diameter minimum to get into the subwoofer range.

One other suggestion... For the panels on the upper horizontal corners, you'd get a lot of good broadband bass control if you doubled the thickness to 4". In a small room like that, you'll need a proportionately higher amount of bass control.

Good luck,

Bryan

scott 01-24-07 08:00 PM

Re: DIY Bass Trap....Will it Work ?
 

i originally posted about seeing the sand-in-a sono diy. it was shot down quickly.since then i have seen several other sites and people filling their stage with sand, their risers and more sono tubes. john mellencamp's personal recoring studio has tons of tubes, risers and a knee wall filled with sand. something is being dampened, their not to keep the floor from jumping up.

there is a reason for this i think some of us would like an answer to, not just "sorry, no, won't work"

not being rude...just why not?

Marks57 01-24-07 10:01 PM

Re: DIY Bass Trap....Will it Work ?
 

Bryan, since I am not using sand and am using 703 Owens would that not give it some type of a membrane type of absorber? Mark

bpape 01-24-07 10:17 PM

Re: DIY Bass Trap....Will it Work ?
 

The tubes with 703 might do something though without testing them, I have no idea how much or in what range.

Sand in stages, walls, risers, etc. is to damp them and deep them from resonating, not provide absorbtion. At most, they'd act as diffusers down to a few hundred hz


Bryan

drf 01-25-07 03:58 AM

Re: DIY Bass Trap....Will it Work ?
 

They probably got the idea for filling sonotubes with sand from an old speaker design style, which has the bottom filled with sand to stop them from resonating and to give them a heavy physical grounding.
however as stated once sound is airbourne (so to speak) sand will do very little.

Anthony 01-25-07 08:29 AM

Re: DIY Bass Trap....Will it Work ?
 

I think the sand/Sonotube idea came (or at least was reawakened) through the DIY Network mini-series on Home Theater. I remember watching the episode on room acoustics -- it had a lot of good tips like wall isolation, hat channel, floating floor, panel absorbers at the reflection points, etc. But I remember scratching my head when I saw the sand/tube arrangement. I'm pretty sure it was on that show, but alas, most of my audio/HT knowledge gets jumbled together now :)

I believe you can make an absorber by bending the rigid fiberglass over a hollow inside form (chicken wire comes to mind) and then covering it, but unless you just want diffusion, the sound wave has to be able to travel through the absorber, otherwise it can't effectively slow down the air being moved by the waves.

This is why the sonotube won't work -- the wave will travel through the outside layer, but then reflect off the hard surface of the sonotube and come back out. When waves reflect off a hard surface, they are usually at minimum air movement (but highest pressure). The fiberglass works best resisting the air movement. Since the air isn't moving much at all at the sonotube bass trap, it can't trap much bass.

Ethan Winer 01-25-07 03:44 PM

Re: DIY Bass Trap....Will it Work ?
 

Scott,

> john mellencamp's personal recoring studio has tons of tubes, risers and a knee wall filled with sand. something is being dampened, their not to keep the floor from jumping up. <

Yeah, this is a huge problem - just because someone is famous does not mean they know anything about acoustics or any other aspect of audio science. Month after month the home recording type magazines interview one clueless musician after another, and each thinks he's an expert and is qualified to explain sample rates, bit depth, phase shift etc ad nauseum. It's pathetic. Really. It's gotten so bad over the past 20 years that most of the technical stuff I read in these magazines is just wrong. And Yes, I am serious! :rolleyesno:

> there is a reason for this i think some of us would like an answer to, not just "sorry, no, won't work" <

Not rude at all.

As Bryan explained, these are totally different issues. Sand can minimize vibrations in things like a floor that flexes and resonates. Or it can at least lower the resonant frequency to be below the important parts of the bass range. But it's not the same as absorption which is needed to reduce peaks and nulls and ringing in a room. Further, sand seems to me a poor choice for reducing resonance too. If I were building a riser for a home theater I'd make it from wood, with a rigid wood top, and then fill the cavity with fiberglass. That would damp the resonance and also add a small amount of bass trapping into the room.

--Ethan

scott 01-25-07 05:13 PM

Re: DIY Bass Trap....Will it Work ?
 

i appreciate the explanation of both ethan and bryon. i personally don't agree with the whole sand thing either, just looking for an explanation.

ethan.....just FYI, i didn't read read about john's studio. his second wife was my cousin. we are still fairly close friends, and get together every now and whip stitch for dinner at his place. but between you, me and the rest of the forum, i think he's a......never mind.

bpape 01-25-07 08:28 PM

Re: DIY Bass Trap....Will it Work ?
 

On a riser, I'd agree with the insulation. On a stage with a sub sitting on it trying to bounce the top plate all over, I'll take the sand. In that case, I want to stop the vibration before it starts as opposed to trying to absorb it after it's already vibrating.

Again, there is no single answer. Depends on the room and the application.

Bryan


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