Simple (hopefully) speaker port question

bm_mode · 22nd November 2001, 11:44 PM

I've calculated the internal volume I need and also the dimensions of the port. Do I have to increase the volume of the box by the amount of space the port tube occupies (if it were imagined to be solid and not tubular)? Hope you get what I mean.

Thanks.

Ignite · 22nd November 2001, 11:59 PM

Yes, just as you would account for the lost volume due to drivers, crossover, bracing, etc.

Super · 23rd November 2001, 12:45 AM

I don't believe you have to compensate for it as though it were solid, but you should take into account the length and thickness of the port.

ThomasW · 23rd November 2001, 05:17 AM

Treat the port as if it were a solid cylinder.

bm_mode · 24th November 2001, 09:13 AM

Ok, so it's 2:1 in favour of treating the port as a sold cylinder. Any further opinions? Anybody know as a matter of fact?

Super · 24th November 2001, 03:32 PM

Sorry, I seem to have misinterpreted your question. Yes, the port tube should be treated as a solid cylinder.

P.Lacombe · 24th November 2001, 03:54 PM

bm_mode,

Ignite is right. Doubtless.

Regards, P.Lacombe.

pkgum · 25th November 2001, 07:56 AM

why is the port be treated as a solid cylinder when it is hollow? dont you only take into account the space occupied by the actual port tube, instead of treating it as a solid cylinder?

f4ier · 25th November 2001, 08:11 AM

pk,

.... because the air inside the port acts as a "lump" of mass that is attached to the "spring" that is the net air volume in the enclosure. Together, the spring-mass system form a resonant system.

You really should buy the LDC of Vance Dickason, or at least skim through it when you happen to see one at a bookstore

Isaac

[Edited by f4ier on 11-25-2001 at 10:25 AM]

Eric · 25th November 2001, 03:06 PM

What is critical about the port is NOT its lenght, its diameter, or its wall thickness. The importance of the port is the MASS OF AIR that it contains. This mass acts as a braking system for the driver and works to tune the box. Therefore, your calculations of enclosure size, as determined by your software, will then need to be increased by the ENTIRE VOLUME displaced by your port, by your driver, by any bracing, and by the presence of an amplifier that resides inside the enclosure.

Thus your total volume for wood cutting purposes should be: Volume calculated by software + volume of port + volume of driver + volume of bracing + volume of amp.

23rd November 2001, 12:45 AM	#3
Super diyAudio Member Join Date: May 2001 Location: Connecticut	I don't believe you have to compensate for it as though it were solid, but you should take into account the length and thickness of the port. __________________ Bryan

24th November 2001, 03:32 PM	#6
Super diyAudio Member Join Date: May 2001 Location: Connecticut	Sorry, I seem to have misinterpreted your question. Yes, the port tube should be treated as a solid cylinder. __________________ Bryan

25th November 2001, 08:11 AM	#9
f4ier diyAudio Member Join Date: Sep 2001 Location: Sydney	pk, .... because the air inside the port acts as a "lump" of mass that is attached to the "spring" that is the net air volume in the enclosure. Together, the spring-mass system form a resonant system. You really should buy the LDC of Vance Dickason, or at least skim through it when you happen to see one at a bookstore Isaac [Edited by f4ier on 11-25-2001 at 10:25 AM] __________________ Crossover/Subwoofer Simulator

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22nd November 2001, 11:44 PM	#1
bm_mode diyAudio Member Join Date: Oct 2001 Location: New Zealand	I've calculated the internal volume I need and also the dimensions of the port. Do I have to increase the volume of the box by the amount of space the port tube occupies (if it were imagined to be solid and not tubular)? Hope you get what I mean. Thanks.

22nd November 2001, 11:59 PM	#2
Ignite diyAudio Member Join Date: Jul 2001 Location: Toronto, Ontario, Canada	Yes, just as you would account for the lost volume due to drivers, crossover, bracing, etc.

23rd November 2001, 05:17 AM	#4
ThomasW diyAudio Member Join Date: Oct 2001 Location: 5280'	Treat the port as if it were a solid cylinder.

24th November 2001, 09:13 AM	#5
bm_mode diyAudio Member Join Date: Oct 2001 Location: New Zealand	Ok, so it's 2:1 in favour of treating the port as a sold cylinder. Any further opinions? Anybody know as a matter of fact?

24th November 2001, 03:54 PM	#7
P.Lacombe diyAudio Member Join Date: Jul 2001 Location: Orleans, France	bm_mode, Ignite is right. Doubtless. Regards, P.Lacombe.

25th November 2001, 07:56 AM	#8
pkgum diyAudio Member Join Date: Oct 2001 Location: sydney	why is the port be treated as a solid cylinder when it is hollow? dont you only take into account the space occupied by the actual port tube, instead of treating it as a solid cylinder?

25th November 2001, 03:06 PM	#10
Eric diyAudio Member Join Date: Nov 2000 Location: Central PA, USA	What is critical about the port is NOT its lenght, its diameter, or its wall thickness. The importance of the port is the MASS OF AIR that it contains. This mass acts as a braking system for the driver and works to tune the box. Therefore, your calculations of enclosure size, as determined by your software, will then need to be increased by the ENTIRE VOLUME displaced by your port, by your driver, by any bracing, and by the presence of an amplifier that resides inside the enclosure. Thus your total volume for wood cutting purposes should be: Volume calculated by software + volume of port + volume of driver + volume of bracing + volume of amp.

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