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View Full Version : Port length calculators????



mendon mafia
12-06-2009, 01:49 PM
Which one is the best.

carstereo, RE, and 12volt all yeild the exact same results. 3 cubes net 48" area yeild 31.5" length for a regular port. Is there another calc thats better?

carstereo has a feature to account for a slot port. Yields 29.5 length for the above box parameters.

Is the calc on carstereo accurate when accounting for a slot port? Is this why the RE calc is said to be way off, since it only allows you to design a slot port but they dont shorten the port accordingly.

IIRC for a slot you can extend the effective length of the vent half the width of the port longer that the actual length, on both sides. IE for a 4" wide port you would add 4" in length (2" on for each opening)

Please correct me if im wrong.

Now for a kerned port how do you determine the length? IIRC its half the length of the flared section.

Again please correct me if in wrong.

RAM_Designs
12-06-2009, 01:52 PM
I personally use the carstereo.com calcs, and cross reference them with the winISD program....they're within 1" of each other 99% of the time. I believe higher tuning(50hz+) starts to make the carstereo.com calc get a little off course.

S.B.C.
12-06-2009, 01:54 PM
I personally use the carstereo.com calcs, and cross reference them with the winISD program....they're within 1" of each other 99% of the time. I believe higher tuning(50hz+) starts to make the carstereo.com calc get a little off course.

OMG!! its the guy from million dollar listing!!

RAM_Designs
12-06-2009, 01:56 PM
OMG!! its the guy from million dollar listing!!

Whenever I'm not selling real estate, I like to dabble in car audio...in my Bentley, of course.

S.B.C.
12-06-2009, 01:57 PM
Whenever I'm not selling real estate, I like to dabble in car audio...in my Bentley, of course.

I always knew you were a highclass pimp!

sub-FATHER
12-06-2009, 02:01 PM
http://www.mobileinformationlabs.com/HowTo-1Woofer-Box-CAL%20Port%20lenth%201.htm

mendon mafia
12-06-2009, 02:06 PM
I personally use the carstereo.com calcs, and cross reference them with the winISD program....they're within 1" of each other 99% of the time. I believe higher tuning(50hz+) starts to make the carstereo.com calc get a little off course.

thanks yea i forgot about winisd. For me all 4 come out within 0.1" of each other. unless I uses the slot port feature on carstereo.com which is 2" shorter than all the others.

mendon mafia
12-06-2009, 02:08 PM
http://www.mobileinformationlabs.com/HowTo-1Woofer-Box-CAL%20Port%20lenth%201.htm

Same exact as carsterso.

I dont trust any of these. Why do ppl say the re calc is off? so far there all the same for me.

RAM_Designs
12-06-2009, 02:14 PM
http://www.mobileinformationlabs.com/HowTo-1Woofer-Box-CAL%20Port%20lenth%201.htm

I like this one, but it's nice having a box volume and solid object calculator as well, like at carstereo.com, to be able to calculate box volume and port displacement at the same time.

mendon mafia
12-06-2009, 02:29 PM
I like this one, but it's nice having a box volume and solid object calculator as well, like at carstereo.com, to be able to calculate box volume and port displacement at the same time.

Its the exact same as the carstereo.com. calc which means its the same as all the others.

Why do ppl say that one calc is off or better than another when there all the same? Obviously you need to account for driver displacement in all cases but just cuz you forgot to do that doesn't mean the calc is off. Im guessing this is where most people have issues with the RE calc.


Now can anyone answer any of my other questions?

IIRC for a slot you can extend the effective length of the vent half the width of the port longer that the actual length, on both sides. IE for a 4" wide port you would add 4" in length (2" on for each opening)

Please correct me if im wrong.

Now for a kerned port how do you determine the length? IIRC its half the length of the flared section.

Again please correct me if in wrong.

sub-FATHER
12-06-2009, 02:36 PM
its a mathmatical equation they all use, that equation is set in stone. they should all be very similar

mendon mafia
12-06-2009, 02:46 PM
Ok so its settled the calcs are all the same.

Now help me out here:

IIRC for a slot you can extend the effective length of the vent half the width of the port longer that the actual length, on both sides. IE for a 4" wide port you would add 4" in length (2" on for each opening) or is it just for the opening on the inside of the box for just 2" added.


Now for a kerned port how do you determine the length? IIRC its half the length of the flared section but this may be for flared i forget.

mendon mafia
12-06-2009, 09:57 PM
IIRC for a slot you can extend the effective length of the vent half the width of the port longer that the actual length, on both sides. IE for a 4" wide port you would add 4" in length (2" on for each opening) or is it just for the opening on the inside of the box for just 2" of effective port added.


Now for a kerned port how do you determine the length? IIRC its half the length of the flared section but this may be for flared aero port. Please Remind ME

Mitch86
12-09-2009, 11:10 PM
http://www.mobileinformationlabs.com/HowTo-1Woofer-Box-CAL%20Port%20lenth%201.htm

Question... When using a calculator such as this, is the "box volume" the NET volume or do you have to account for displacements? For example, if I want a NET volume of 4.5cf how do I account for port displacement if I dont know how long the port will be?

mendon mafia
12-10-2009, 09:40 AM
Question... When using a calculator such as this, is the "box volume" the NET volume or do you have to account for displacements? For example, if I want a NET volume of 4.5cf how do I account for port displacement if I dont know how long the port will be?

the volume used is after all displacements (subs and port) which is NET volume. Gross volume would be box volume with port and subs added.

When you enter 3 cubes it assumes that is after port and sub displacement.