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Multi-Way Conventional loudspeakers with crossovers

port length
port length
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Old 13th July 2003, 05:33 AM   #1
dave k is offline dave k  Canada
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Angry port lenght

need help.the project requires a port of 2.5 dia and 4 inches long.i can get a port of only 2" dia, but what leght shoud it be?
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Old 13th July 2003, 06:22 AM   #2
SY is offline SY  United States
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port length
dave, the general vent formula for a flush mounted vent is:

L = {(1.463x10e07xR^2)/(fb^2xVb)} - 1.463R

where L is length, fb is box tuning frequency, R is port radius in inches, and "^" is exponentiation. The algebra should be pretty straightforward.
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Old 13th July 2003, 07:12 AM   #3
kelticwizard is offline kelticwizard  United States
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port length
Or you can run a quick simulation on WinISD to find that the length of the 2" tube should be 2.29 inches long to equal a 2.5" tube 4 inches long.
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Old 13th July 2003, 01:08 PM   #4
SY is offline SY  United States
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port length
KW, don't you remember that old saw about giving a man a fish?
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Old 13th July 2003, 01:12 PM   #5
7V is offline 7V  United Kingdom
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Quote:
Originally posted by SY
KW, don't you remember that old saw about giving a man a fish?
How big should the fish be and should the water just be in the port or does the bottom of the enclosure need to be filled as well?
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Old 13th July 2003, 01:19 PM   #6
SY is offline SY  United States
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Hmmmm, water-filled enclosure.... 'Scuse me, gotta call my patent attorney.
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Old 13th July 2003, 01:20 PM   #7
AudioFreak is offline AudioFreak  Australia
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port length
7V,

I'm sure this is a moot point but I believe SY was referring to the old adage "Give a man a fish, feed him for a day; Teach a man to fish, feed him for a lifetime."
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Old 13th July 2003, 01:22 PM   #8
SY is offline SY  United States
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I think Steve got it, but the adage I was thinking of goes, "Give a man a fish and you feed him for a day. Teach him to fish and he'll sit in a boat all day drinking beer."
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Old 13th July 2003, 01:26 PM   #9
pinkmouse is offline pinkmouse  Europe
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port length
Quote:
Originally posted by 7V

How big should the fish be and should the water just be in the port or does the bottom of the enclosure need to be filled as well?
I think what SY is suggesting is a cunning variable damping system, the water filled box providing a stiff coupling system to the driver, with the fish causing variable damping due to two factors. Their bodies will act to break up large scale standing waves, (depending on the size/age of the fish), and the eddies in the water caused by their movement providing micro diffraction to reduce high frequency resonances.
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Old 13th July 2003, 01:29 PM   #10
SY is offline SY  United States
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By means of implanted electrodes in the fish, you can actually use them to provide motive force to the cones each time you administer a shock. Or you can use the shock/wiggle technique, carefully phased, to provide damping. PETA might have a problem with this, though.

Then again, water dampens everything.

Sorry, I'll behave now.
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