Quarter Wave Resonator? Helmholtz?

[BARRY]

hey guys...

i haven't been able to find exact information online on this calculation. many forums say one thing, but the formula doesn't match other forums. have any of you tried calculating tube length to eliminate drone? Helmholtz is a better device, but also harder and more time consuming to build. I did read that Helmholtz resonators can target a frequency range, whereas a quarter wave resonator can target a specific frequency.

the center point of my exhaust drone is at 2,750rpm, and according the spectrum analyzer android app my annoyance is a frequency of around 83-86hz. not sure how accurate this is as a cell phone isn't really considered high end audio equipment. using these values as a reference point calculations are recommending a quarter wave resonator of 1.04 meters. this sounds pretty long to me.

any help would be greatly appreciated. Thanks!

[Biged243]

Check the b7 forum. Somewhere in there a guy did it and he I believe has a dyi. I don't think there is a formula in the dyi but it is adjustable.