how to measure ports properly

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bigrank916

Member - Posts: 35

Joined: January 30, 2009

Location: California, United States

Posted: April 28, 2009 at 9:10 PM / IP Logged

how do you measure port length? Is it from end to end or from the inside of the box to the end? Im trying to get from 28hz to 33hz and cut my ports (2"x4") according to the info in the port calculations page. Im trying to get away from such low frequency bass and cut my ports considerably but it still is too low. Any ideas?

bigrank916

Member - Posts: 35

Joined: January 30, 2009

Location: California, United States

Posted: April 28, 2009 at 9:23 PM / IP Logged

oh ya...I have 4 hertz 12s in a 91 silverado pushed by a PG tantrum 1200.1. The boxes are approximately 2.01cuft. each.

cutlass013

Copper - Posts: 95

Joined: July 27, 2006

Location: United States

Posted: May 02, 2009 at 12:40 AM / IP Logged

maybe someone can back me up but if its round i would think 2" diameter and the 4" length .. if square then ur missing a demension?

boogeyman

Silver - Posts: 359

Joined: October 18, 2007

Location: Tennessee, United States

Posted: May 02, 2009 at 10:13 AM / IP Logged

you measure from end to end

aznboi3644

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Joined: May 01, 2006

Location: United States

Posted: May 02, 2009 at 1:04 PM / IP Logged

2 inch port is not enough....atleast a 4" round port

Custom Enclosure Design

bigrank916

Member - Posts: 35

Joined: January 30, 2009

Location: California, United States

Posted: May 02, 2009 at 8:01 PM / IP Logged

Yes it is a round port. A 4" port would require a 12.5" length if tuned to 33hz. I thought 4" was too big for a 12" woofer as well. I have two 15s in a box just slightly bigger than this one with ports at 2 9/16" diameter by about 4" length and the same frequency and it sounds perfect. It is in a geo metro though so that probably has a lot to do with it. Im just a little confused why a 2" port is not big enough. I thought it is all the same if the calculations are right.

aznboi3644

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Joined: May 01, 2006

Location: United States

Posted: May 02, 2009 at 8:24 PM / IP Logged

why...not enough port area. Simple as that. A small port with a large woofer will suffer from port compression with much less power than the proper port area. Essentially you will get port noise and the enclosure will act as a very leaky "sealed" enclosure and not like a bass reflex at all.

For each 12" subwoofer I recommend atleast a 4" round port.

Custom Enclosure Design

stevdart

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Joined: January 24, 2004

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Posted: May 03, 2009 at 10:12 AM / IP Logged

Re: your question of measuring port length:

The thickness of the face baffle of the enclosure (where the port extends through) will be included in the measurement of port length.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

bigrank916

Member - Posts: 35

Joined: January 30, 2009

Location: California, United States

Posted: May 03, 2009 at 12:37 PM / IP Logged

Ok. I think I will go up in port diameter. Now knowing the right way to measure it I should get this solved now. Thanks guys for the help.

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how to measure ports properly

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