Pipe Dreams … 50hz Helmholtz resonator out of PVC pipe. Bass trap or money trap?

[nwickliff]

The nozzle is critical to the design. As I commented earlier somewhere the nozzle is the most important part, more important than the volume because both diameter of the nozzle and the length are parts of the Helmholtz resonator equation, which I also posted earlier.

I measured each resonator to see what frequency it was operating at. If I wanted a lower frequency, I cut a longer neck.

 

[NoviceTunes777]

Hello,
I've registered to this forum just to be able to share my personal experience, and hopefully to disprove some of the stuff written above.
I have a bad problem with a room mode, the room is irregular and not sealed (it's just a living room with some speakers, no studio). By measuring with REW there's a very clear peak in frequency response at 139.7Hz with a looong decay time. Then I played a sine wave with that frequency on one speaker and went around looking for intensity peaks (i.e. max pressure points) by hearing: in some corners the resonance is crazy..
I have 2 empty wine bottles laying around so I tuned them by adding water and put them in the problematic spot. The difference is clearly recognizable, sound intensity in the corner goes down a lot by just putting the tuned bottles there (yes, I will do more quantitative measurements with REW when I have time).
TLDR: even if the bottles don't magically suck energy from the room, placing them at the right spot has some very noticeable albeit local effect.

 

[Turbowatch2]

After sucking two bottles of wine I start to hear audible differences two. Just never realized it came from the empty bottles...

 

[NoviceTunes777]

 

[geoffkait]

I built a nine foot long folded S PVC 4” diameter pipe with nozzle attached on one end, sealed at the other. I used straight pipes, elbow joints and end caps. This resonator stood about 4” tall and was positioned in the room where a 75 Hz standing wave was located.