I can't find information on this anywhere. Does port volume effect its efficiency?
e.g. A cabinet contains a 50mm round port 100mm in length representing a tuning frequency of 50hz. Port volume = 196.25cm3.
To maintain the same tuning frequency using a 100mm round port I'd need to increase the port length to 600mm. Port volume = 4710cm3. The second resonator has almost 25 times the volume of the first. Does this make it more efficient in the way larger drivers are more efficient than small drivers. Or does just enable the vent to handle greater SPLs, or both?
I have another bizarre question with regard to port material. Our first experience of a Helmholtz resonator is when we blow across the top of a glass bottle . . . try it with a plastic one - it doesn't work so well.
e.g. A cabinet contains a 50mm round port 100mm in length representing a tuning frequency of 50hz. Port volume = 196.25cm3.
To maintain the same tuning frequency using a 100mm round port I'd need to increase the port length to 600mm. Port volume = 4710cm3. The second resonator has almost 25 times the volume of the first. Does this make it more efficient in the way larger drivers are more efficient than small drivers. Or does just enable the vent to handle greater SPLs, or both?
I have another bizarre question with regard to port material. Our first experience of a Helmholtz resonator is when we blow across the top of a glass bottle . . . try it with a plastic one - it doesn't work so well.
A larger vent will be no more efficient at low power, but will not be "blown out" at higher displacement volumes.
The effect of a "too small" port is generally known as "port compression", like any type of compression (or limiting) a certain threshold needs to be crossed before the compression occurs.
Plastic bottles have more damping effect than glass or ceramic bottles, so their Helmholtz resonant frequency is both harder to excite and lasts a shorter time.
The effect of a "too small" port is generally known as "port compression", like any type of compression (or limiting) a certain threshold needs to be crossed before the compression occurs.
Plastic bottles have more damping effect than glass or ceramic bottles, so their Helmholtz resonant frequency is both harder to excite and lasts a shorter time.
