# Why won't my HH resonator work...?

Discussion in 'Archived Threads 2001-2004' started by Dennis B, Aug 18, 2002.

1. ### Dennis B Stunt Coordinator

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Hi,
I've built a Helmholtz resonator according to ETF's calculations, have placed it in the appropriate corner, but I can neither feel nor measure (with ETF) any effect at all. It seems to be 'dead'.
My feeling is that while the math in the program works, the dimensions I've used are too extreme, leading to a very high theoretical Q (?). Please advise.
Dimensions of the completed unit:
Tube diameter = 12"
Tube height = 23"
Duct diameter = 2"
Frequency = 30 hz
Calculated duct length = 4.5"
Calculated Q (theoretical) = 895...
Thanks,
Dennis

2. ### Dennis B Stunt Coordinator

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anyone...?

3. ### Chris Tsutsui Screenwriter

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I was under the impression that adding a single resonator wouldn'd do much. At least compared to say 2 stacked resonators in each edge of the back wall. Or a resonator in each of the corners of the room.

So is 30hz the frequency you wish to absorb? Do you have a link on more info about the resonator?

4. ### Dennis B Stunt Coordinator

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Chris,
Thanks. Yes, 30 is one of them. The resonator's dimensions were designed by ETF's built-in calculator. See www.acoustisoft.com for the program, but I don't remeber if their page actually shows this part of the software. They have a free demo version that you may want to download to try out.
But I don't have to stick to that formula, if you could point me towards a different approach I'd appreciate. I was trying to understand why the one I built didn't work...

5. ### Chris Tsutsui Screenwriter

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Could you post your room dimensions or better yet, and subwoofer location/mic location? I'm just wondering if you have approx a 20 foot wide room? If you did then it would make sense to have a 30hz room mode.

I'm also wondering how an HH at 30hz would work when most of the DIY ones I've read about are effective at 80hz and above.

So do you have a noticeable spike or dip in the 30hz region that needs fixing?