port length

dave k · 13th July 2003, 05:33 AM

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?

SY · 13th July 2003, 06:22 AM

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.

kelticwizard · 13th July 2003, 07:12 AM

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.

SY · 13th July 2003, 01:08 PM

KW, don't you remember that old saw about giving a man a fish?

7V · 13th July 2003, 01:12 PM

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?

SY · 13th July 2003, 01:19 PM

Hmmmm, water-filled enclosure.... 'Scuse me, gotta call my patent attorney.

AudioFreak · 13th July 2003, 01:20 PM

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."

SY · 13th July 2003, 01:22 PM

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."

pinkmouse · 13th July 2003, 01:26 PM

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.

SY · 13th July 2003, 01:29 PM

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.

13th July 2003, 05:33 AM	#1
dave k diyAudio Member Join Date: May 2003 Location: B.C	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?

13th July 2003, 06:22 AM	#2
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	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. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

13th July 2003, 07:12 AM	#3
kelticwizard diyAudio Member Join Date: Sep 2001 Location: Connecticut, The Nutmeg State	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. __________________ "A friend will help you move. A really good friend will help you move a body." -Anonymous

13th July 2003, 01:08 PM	#4
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	KW, don't you remember that old saw about giving a man a fish? __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

13th July 2003, 01:19 PM	#6
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	Hmmmm, water-filled enclosure.... 'Scuse me, gotta call my patent attorney. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache


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13th July 2003, 01:20 PM	#7
AudioFreak Warp Engineer On Holiday Join Date: Oct 2001 Location: Queensland, Australia	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." __________________ - Dan

13th July 2003, 01:22 PM	#8
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	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." __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

13th July 2003, 01:29 PM	#10
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	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. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

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