Variable Port Lengths/Diameters? Like a pipe organ...

[justinzane]

@sreten: I think I understand your point. I do wonder, though, I thought that multiple ports worked like parallel resistors/inductors (roughly). That is, the pressure change caused by the motion of the driver will find equalization by all available paths based on the instantaneous resistance of the paths. That would mean that with proper balancing of the diameters and lengths of the different ports, they should respond to the driver differently under different frequencies and volumes. Make sense?

[sreten]

Originally Posted by justinzane

@sreten: I think I understand your point. I do wonder, though, I thought
that multiple ports worked like parallel resistors/inductors (roughly). That is,
the pressure change caused by the motion of the driver will find equalization
by all available paths based on the instantaneous resistance of the paths.

That would mean that with proper balancing of the diameters and
lengths of the different ports, they should respond to the driver
differently under different frequencies and volumes. Make sense?

Hi,

Basically wrong. They are much more like series LCR's in parallel.
Consequently the highest tuned port dominates the low rolloff, by
providing the lowest impedance to ground at all low frequencies
preventing any other lower tuned port having any useful effect.

rgds, sreten.

[justinzane]

@sreten: Thanks. Exactly what I needed to know.

Just for others who might be curious: https://en.wikipedia.org/wiki/RLC_circuit

[baskiria]

Thank you for the explanation Sreten!

[head_unit]

Originally Posted by sreten

Hi, Its been done, by the[...] marketing who don't [CARE ABOUT] the physics.

Take a speaker tuned to 50Hz by one port and 25Hz by a much bigger port.

The 50Hz port depressurises the cabinet below 50Hz so the 25Hz port has
next to no effect...[/QUOTE]
I'd be curious to hear your comments about David Weem's design. In case you're not familiar, that's where you have 3 ports all the same size. One vents from the main chamber to outside, one from the main chamber to a second chamber, one from the second chamber to outside (was trying to find an image on the internet, but no luck).

I simply can't wrap my head around what will happen, if it really works or not. If I had more time ha ha I should build one and test it...

[tinitus]

if you tune two ports just a small bit different, I think it broadens the ressonance peak
but that may be all there is to it
maybe it also have influence on possible upper port peak(midrange)