Calculating Port Length with PVC Elbow?
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=96025
Printed Date: May 14, 2025 at 1:31 PM
Topic: Calculating Port Length with PVC Elbow?
Posted By: Alpine Guy
Subject: Calculating Port Length with PVC Elbow?
Date Posted: July 29, 2007 at 3:21 PM
I am in the process of building a box that consists of 2 4" round PVC ports, but to get the length I need I have to use 90 degree elbow's, does's anyone know how to measure/calculate how many inches of the port length the elbow will take up?
Thanks
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2003 Chevy Avalanche,Eclipse CD7000,Morel Elate 5,Adire Extremis,Alpine PDX-4.150, 15" TC-3000, 2 Alpine PDX-1.1000, 470Amp HO Alt.
Replies:
Posted By: DYohn
Date Posted: July 29, 2007 at 3:29 PM
Measure the length inside the elbow as close to the middle as possible. Just stick a ruler into the opening from both directions. Port length can be off by 10% and still have good results, so you just need to be close. ------------- Support the12volt.com
Posted By: Alpine Guy
Date Posted: July 29, 2007 at 5:19 PM
What about taking a piece of string and hanging it in there so it's right in the middle around the whole bend then measuring it? Will that work also?
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2003 Chevy Avalanche,Eclipse CD7000,Morel Elate 5,Adire Extremis,Alpine PDX-4.150, 15" TC-3000, 2 Alpine PDX-1.1000, 470Amp HO Alt.
Posted By: i am an idiot
Date Posted: July 29, 2007 at 6:38 PM
If you want an accurate way to figure it out, try this. Take 2 pieces of pvc 4" long each, fill them with shipping peanuts, pour the peanuts in a bag then insert the 2 pieces of pvc into the elbow, pour the peanuts back into the pvc. Measure from the top of the peanuts to the top of the tube and this will give you the length of the elbow. Depending on the size of the pvc you may have to use something smaller than a peanut. Maybe bb's out of a bean bag chair.
Posted By: stevdart
Date Posted: July 29, 2007 at 7:13 PM
Alpine Guy wrote:
What about taking a piece of string and hanging it in there so it's right in the middle around the whole bend then measuring it? Will that work also?
A regular steel tape measure is very accurate; it will bend through the elbow and you can play it back and forth a bit to find center. First, construct the port with the desired length of the first straight leg, and attach the elbow. The first leg is the part that opens to the front of the enclosure. For the second leg, insert a length of straight tube that you know will be longer than what is desired, as it will be cut after you measure. Don't glue the PVC at this time, just insert fully. Use the tape measure to find the length of this port, then cut off the excess inches from the second leg to the desired length. Match the piece lengths of the second port to the one that you measured. Note: paint the inside of the PVC tube that will show on the finished box. Do this before assembly and glue. Placing the business end of a shop vacuum at the other end of the tube will pull the spray paint through and give a drip-free finish. ------------- Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
Posted By: Alpine Guy
Date Posted: July 29, 2007 at 10:09 PM
That sounds so simple now! Thanks for the advise.
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2003 Chevy Avalanche,Eclipse CD7000,Morel Elate 5,Adire Extremis,Alpine PDX-4.150, 15" TC-3000, 2 Alpine PDX-1.1000, 470Amp HO Alt.
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