Center frequency of Ethan style membrane traps?

[RiomirG]

Hopefully this will be my final question before I actually get to build my traps. I nearly have all of the materials, and those I don't yet have I will be able to buy this weekend.

What is the "center" frequency absorbed by Ethans low bass traps? How about the mid high bass traps? What would you estimate to be the range of effectiveness for these?

I'd also like to offer a sincere Thank You to all who have helped myself and others, and continue to do so here and on other forums.

It's kinda stange, a couple of months ago I was not even aware of the presence of acoustic distortion, and now, not only do I hear its influence in "my room", I actually "listen" to every room I go into, if that makes sense...

A thousand Thanx!!

[Ethan Winer]

Rio,

> What is the "center" frequency <

The low-bass traps are centered around 100 Hz and the high-bass traps are about 200 Hz. Each absorbs over a range of a little more than one octave, so together they trap the most important range of 80-300 Hz.

--Ethan

[RiomirG]

Hmmm...

What would you recommend if I wanted absorption down to 60Hz? Deeper trap or thicker membrane/both???

[knightfly]

Just intuitively, I would think that a deeper trap (with the same thickness membrane) would be more efficient, since the thinner membrane would be more easily excited -

The operational theory of panel traps is that the pressure at the membrane vibrates the membrane, which then converts the air in the trap to moving air, which is then partially absorbed by the inner insulation material. You lose energy in the panel's conversion to motion, and again with the resistivity of the absorbent converting the motion to heat.

No proof of the first part, just gut feel... Steve

[RiomirG]

Thanx Ethan and Knightfly. That was what I thought/hoped for.

I'm going to build one with a depth of 6", in hopes of taming the grumbling 60Hz troll in my corner. He really is obnoxious.

[dymaxian]

A couple of the traps I had built were out of 1x6 instead of 1x4s. Otherwise they were identical to Ethan's posted plans- 1/4" membrane, 1" rigid fiberglass inside. I did some pretty remedial tests (playback of loud sine wave and feeling the front panels for vibrations). It seemed to me that the deeper traps centered on 75 or 80Hz. If their absorptive range is as Ethan describes, this would probably absorb at least some of the 60Hz sound you're having trouble with...

Kase
www.minemusic.net

[RiomirG]

Any guess as to what effect the substitution of 2" 703, instead of 1" 703 might have?

[Ethan Winer]

Rio,

> Any guess as to what effect the substitution of 2" 703, instead of 1" 703 might have? <

Not a clue. But these traps work very well with one inch of 703, so just build them that way and your success is guaranteed.

--Ethan

[RiomirG]

Unfortunately, I already bought the 2" with the "more is better" frame of mind (it's been almost 2 months ago)...

Would you advise I used these for mid/high absorption, and buy some more 1" 703 for the bass trapping???

Thanx.

[Ethan Winer]

Rio,

> I already bought the 2" <

For all I know the 2-inch stuff is better. But I doubt it. My fear is that will lower the Q so much that the overall absorption suffers as a result.

> Would you advise I used these for mid/high absorption, and buy some more 1" 703 for the bass trapping??? <

Either that, or maybe you can slice the 2-inch panels in half?

--Ethan

[RiomirG]

Thanx.

Guess I'll have to save my pennies to buy some 1".