DIY Tube Bass Trap

nukmusic · Post by **nukmusic** » Sun Nov 02, 2003 1:22 pm

Just stacking up ideas and knowledge. What do you think?

here: http://www.teresaudio.com/haven/traps/traps.html or http://ic.net/~jtgale/diy2.htm

also read throught these sights:

http://www.ethanwiner.com/basstrap.html
http://www.realtraps.com/
http://www.silentsource.com/efs/tubetra ... betrap.htm

Todzilla · Post by **Todzilla** » Tue Nov 11, 2003 3:48 am

Most of the pros (of which I am not one) don't think too highly of the tube trap approach, especially those DIY tube traps. The wad of high density fiberglass in the corner is much better bang for the buck. The Ethan Wiener traps you reference in your link (both the DIY solution and the RealTraps products) are quite effective down to a pretty low freq. (something like 90Hz or even less). The corner wad has the nice extra benefit of being broadband, so yeah, it traps bass, but everything else above it too. The panel traps of Ethan's are deliberately reflective on the surface, so they're dedicated bass only traps.

Your Mileage May Vary.

Bill · Post by **Bill** » Wed Dec 03, 2003 1:17 am

I've only noticed a few disapproving remarks regarding this type of trap, but only in that they aren't particularly space efficient. Anyone know (from experience) whether they are good despite this problem, or if indeed they do need to be place 1/4 wavelength away from the corner walls?

Jon Risch seems to be their greatest advocate. Does anyone know what his credentials are?

They sure do look cheap and easy to make!

Bill.

Ethan Winer · Post by **Ethan Winer** » Thu Dec 04, 2003 4:32 am

Bill,

> I've only noticed a few disapproving remarks <

Give it time.

The main problem with the type of tube traps I've seen is they don't have enough absorbing material to do much at low frequencies. There's nothing magical about a tube shape either. A flat panel of thick rigid fiberglass placed straddling the room corners is a better approach for bass trapping.

> Does anyone know what his credentials are? <

I have no idea, but this sentence from his site sure leaves me wondering:

"Be sure to squirt some silicone rubber or Liquid Nails in between the roll edges and between the fiberglass roll and the endcaps, so there are no ready air leaks."

There is no point to making those things air tight, so why does he say you should bother?

--Ethan

Andrew Steel · Post by **Andrew Steel** » Sat Jan 10, 2004 11:50 am

Hi Ethan,
Just a quick question re: sealing the top and bottom of tube traps - If the trap were in a place where the pressure outside is greater than inside, then the gas (air) will try to flow from high to low i.e. from outside to inside the tube trap. This the converts pressure to velocity with a drop across the resistive fibreglass and hence some abbsorption. I have no idea how well it works but I think it would work that way - do you? If this is the case and considering the nature of low frequency sound propogation, unsealed ends would defeat the funtion wouldn't they?

Andrew

DDev · Post by **DDev** » Sat Jan 10, 2004 12:02 pm

There has been a lot of discussion about these DIY tube traps recently over at HR.com, also. If you think about the material used for the tube section, which is basically just a tubular form of rigid insulation, then you realize that this material is porous, so sealing the ends really does not provide an airtight seal, it just makes the ends look better.

Darryl.....

Ethan Winer · Post by **Ethan Winer** » Sun Jan 11, 2004 2:15 am

Andrew,

> If the trap were in a place where the pressure outside is greater than inside <

I'm with Darryl - the porous nature of rigid fiberglass prevents a pressure difference from developing in the first place.

--Ethan

knightfly · Post by **knightfly** » Sun Jan 11, 2004 2:18 am

Andrew - tube traps, by dint of the fact that they are a porous material, don't work on pressure like a panel trap - they work on velocity, same as other porous membrane type absorbers. Because of this, they should be placed at points of higher velocity at the desired wavelength that is to be absorbed.

Darryl, the REAL reason for the nice solid tops - it's a much safer place to set your beer than on top of the console :=) Steve

Andrew Steel · Post by **Andrew Steel** » Sun Jan 11, 2004 8:55 am

Hi Guys,
The beer theory sounds good. Thanks for the replies.

Andrew

nukmusic · Post by **nukmusic** » Thu Jan 15, 2004 1:43 pm

pass the Bud Light!

They do work. I'm basicly finished the studio, just a few minor things here and there. Folks get lazy when the cr room is finished.

I built (4) 16" bass tubes(2 each in the front corners) using 1 1/2" pipe insulation(rigid fiberglass), each 3ft high, and they do work. While testing the control room with a few different commerical cds, mackie HR824's, and radio shack db meter, I found that the tubes SEEM to do a pretty good job with the mids, and an nice job with the bass. The Mackie's sound so dam good IN and near the sweet spot (on and off axis I should say) . I spent a few hrs listening to severals cds of all types of music. I only get bass build-up in the deep bass around 45hz, and that's in the rear-right corner(no tube trap). But the mixes still sound pretty good with it, kinda like turning on a subwoofer. When I did move the tubes in that corner, they reduced the bass buildup about -4db(radio shack meter). The sweet spot also sounds pretty good with a pair of Hafler M5's. I'll try to get someone do do a professional test of the CR room if a can.

Ethan Winer · Post by **Ethan Winer** » Fri Jan 16, 2004 2:20 am

Nuk,

> They do work. <

No question that tube shaped rigid fiberglass absorbs. The issues are 1) there's nothing special about a tube shape that makes it better than a flat panel, and 2) there are better types of traps you can buy or build for less effort.

--Ethan

nukmusic · Post by **nukmusic** » Mon Jan 19, 2004 12:22 pm

wonder what would happen if the tubes where filled with 703?

maybe absorb too much bass?

Jon Best · Post by **Jon Best** » Tue Jan 27, 2004 3:29 pm

Probably the same as backfilling a piece of 703 straddling a corner- my feeling is that it may increase the efficiency a little bit, maybe widen out the Q a little (although I'd think this would be more pronounced with a 703 trap that was a uniform depth off a flat surface).

Without any emperical evidence, it's filed in my brain in both cases as 'worthwhile if you've got extra insulation lying around, probably not worth buying more for.'

Speaking of absorbent bass trapping, I'm shutting down the studio mostly, to be restarted in spring/summer as strictly hobby. So, last night, as I was finishing up the second to last session before some of the important gear gets sold, I decide to move some of the absorbent material in from the live room. I stuck 2 each 2x4', 2" thick pieces of 703 across each back corner, lined up four 1x4', 4" thick pieces across the back wall about a foot off, and did the same thing above my control room window in the front. All things I had intended to get around to.

Dammit, I shoulda done that two years ago....

nukmusic wrote:wonder what would happen if the tubes where filled with 703? maybe absorb too much bass?

nukmusic · Post by **nukmusic** » Mon Sep 20, 2004 9:13 am

Just a thought` WOnder what wouls happed if u added 3 hangers inside the 3 ft x 16" bass tubes instead of filling with 702 or Pink stuff? 3 hangers as in:

(III) 3 hangers, 1 in the middle(maybe 12" x 2.5ft) and 2 on each side of the middle hanger(maybe 6" x2.5ft) all hanging from the top cap of the tube using something like picture wire.

just a thought while i was looking at the bass hangers at the bottom of a few speaker soffit designs.