Helmholtz Resonators


Anyone here have a good bit of experience with Helmholtz resonators? I'm thinking of building a large one, thinking that having one with  variable openings could help me tune it to absorb a frequency range in the bass. Looking to filter out some one note bass but not sure the frequency range, hence the need to have a variable option.
dentdog
I have a little bit of experience with Helmholtz resonators. The biggest one I built was a fifteen foot long folded resonator, 9 inch diameter with a 2-inch long 1/2" diameter nozzle. It was used to ameliorate a nasty low frequency standing wave in one corner.
Exactly what I'm facing. I have an alcove about 4' by 5', 7'high behind the left side of my listening position, full of deep bass. I have tri-trapped both corners but this situation persists. As I see it my options are either a Scopus tuned membrane trap or build a resonator. 
Could you give me a hint on how you went about the process? Much thanks.

Dentdog wrote,

"Exactly what I’m facing. I have an alcove about 4’ by 5’, 7’high behind the left side of my listening position, full of deep bass. I have tri-trapped both corners but this situation persists. As I see it my options are either a Scopus tuned membrane trap or build a resonator. Could you give me a hint on how you went about the process? Much thanks."

There is an equation for Helmholz resonators somewhere on line. The equation includes volume, diameter and length and diameter of the nozzle and velocity of sound in air. 

https://en.m.wikipedia.org/wiki/Helmholtz_resonance

All materials can be obtained at Home Depot including large diameter PVC pipe and purple prep and cement for the PVC pipe sections some of which are 90 degree elbows so you can construct a large S or Z shaped resonator. As I recall I used short sections of PVC between elbows and three four foot sections of PVC. PVC end caps are used to seal both ends of the large S or Z shaped resonator. Remember to insert about a grapefruit size ball of natural hollow wool inside the large S or Z shaped resonator before cementing the last end cap. The nozzle can be a brass fitting threaded on both ends. You will need a drill and reamer so you can screw in the brass fitting into one of the end caps. Stand the finished resonator in the room corner with the nozzle located in the spot where bass energy is greatest. 


Thanks. I'll let you know.