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Variable Port Lengths/Diameters? Like a pipe organ...
Variable Port Lengths/Diameters? Like a pipe organ...
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Old 29th December 2012, 09:33 PM   #11
justinzane is offline justinzane  United States
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@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?
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Old 29th December 2012, 10:04 PM   #12
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by justinzane View Post
@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.

Last edited by sreten; 29th December 2012 at 10:12 PM.
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Old 29th December 2012, 10:23 PM   #13
justinzane is offline justinzane  United States
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@sreten: Thanks. Exactly what I needed to know.

Just for others who might be curious: https://en.wikipedia.org/wiki/RLC_circuit
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Old 30th August 2013, 11:25 AM   #14
baskiria is offline baskiria  Hungary
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Thank you for the explanation Sreten!
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Old 31st August 2013, 07:18 PM   #15
head_unit is offline head_unit  United States
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Quote:
Originally Posted by sreten View Post
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...
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Old 31st August 2013, 08:11 PM   #16
tinitus is offline tinitus  Europe
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Variable Port Lengths/Diameters? Like a pipe organ...
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)
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