subwoofer enclosure, port conversion
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=89341
Printed Date: May 09, 2024 at 2:24 AM
Topic: subwoofer enclosure, port conversion
Posted By: damper
Subject: subwoofer enclosure, port conversion
Date Posted: January 22, 2007 at 1:47 AM
i recently purchased a pyle sub the(plw12bl) but i do not know what size cubic foot box it requires on the specs it says 800watts peak pwr.,4-ohms,voice coil 2inch,magnet 90 oz.,fs26.2,qms5.81,qes 0.90,qts 0.78,spl 85.5,vas 4.146cuft.does anyone know what size box this sub. requires
Replies:
Posted By: damper
Date Posted: January 22, 2007 at 5:00 AM
how do you convert round port measurments(4 inch diameter x 6 inch lenght tuning is 36 hz) into slotted port measurments w/ the same 36hz tuning
Posted By: geepherder
Date Posted: January 22, 2007 at 6:02 AM
Read this- that way you can design your own enclosure to your liking. ------------- My ex once told me I have a perfect face for radio.
Posted By: DYohn
Date Posted: January 22, 2007 at 10:01 AM
Calculate the area of the round port opening (pi times radius squared) design a rectangular port with the same area for its opening (width times height) make the length the same as the round port calculator tells you. ------------- Support the12volt.com
Posted By: stevdart
Date Posted: January 22, 2007 at 6:55 PM
This is a reprint of an answer I gave previously to this question: pi r^2 to find the area of a circle pi is 3.14
r is radius, or half the diameter of a circle
^2 is squared, or the number times itself
pi r^2 is 3.14 X the result of radius squared
pi r^2 gives you the square inches of a circle You want to change the shape of the opening but keep it the same square inches. The length of the port is not a factor and you will leave it exactly the length it already is. Find the square inches of your circle using pi r^2 (ex. a 6 inch diameter circle yields 28.26 square inches)
Decide on the longest side you want your square or slotted port opening to be
Divide the total square inches of the circle by that long side, in inches (ex. 28.26 / 11.5 = 2.46)
The result is the measurement of the shorter side of the port opening In the example, the 6" round port equals a slotted port 11.5 X 2.46 inches. Round measurements to the nearest Imperial or metric value. 2.46 would be 2 7/16 to 2 1/2. You should keep the ratio of length to width of the slotted opening at no greater than 8:1.
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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: conseit68
Date Posted: February 13, 2007 at 10:31 PM
Ok I feel like a dough-head...but what if I have the dimensions for a ported box volume (1.75 cu ft.) and that design has a slotted port of 1.375"W x 12.5"H x 23.75"L which says the tuning would be at 30.3Hz. Do I reverse the procedure to get a round port? Also, would I assume that the primary box dimensions would change if the port was mounted partially external? Reason I ask is that I am considering building a box for (1) JL Audio 12W3v2 but having the port aimed (if not directly) in the existing subwoofer hole in the rear deck. I am thinking that way I can get maximum sound response since the design would be similar to having the box within the actual listening area as opposed to the trunk which I have always felt would make the box act more like a poor quality bandpass (box in a box). Please help I am confused at this point and want to get all of my deminsions exact prior to building
Posted By: aznboi3644
Date Posted: February 13, 2007 at 11:25 PM
Im most trunks the subs sound the best with both port and woofer rear firing...the volume of the port does it account for the internal volume the woofer sees...so if half of the port is internal and half external...than you would only subtract half of the ports volume from the total useable area.
Use WinISD for tuning and port lengths and such...all of those variables can be adjusted there
Posted By: conseit68
Date Posted: February 14, 2007 at 6:47 AM
I understand that most cars sound good with rear firing sub and ports, why woudl be the wuestions I have there...and I still need some information on the round ports if I do stick with my plan please. Thanks
Posted By: DYohn
Date Posted: February 14, 2007 at 8:29 AM
If you know the inside net volume of your enclosure and the target port frequency, simply use the port calculator on this site (click on "woofer Calculator") to find the proper port length for whatever diameter you'd like to use. I suggest a 4" port diameter. This is simplified, but the reason most subs sound better to the driver if they face backwards is due to the wavelength of subwoofer frequency sounds. Facing backwards allows the sound energy to reflect off the rear of the car before it gets to the driver's seat, allowing low frequency waves to develop to their max SPL before you hear it. ------------- Support the12volt.com
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