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Old 1st August 2008, 07:11 PM   #1
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Default Passive radiator

My brother and I were recently in a bad auto accident and his dayton reference 12'' subwoofer was destroyed. The magnet and the voice coil ripped off from the back of the subwoofer. The cone and spider are still in perfect condition except for a small dent in the dust cone, so I was thinking about trying to use it as a passive radiator. Using WinIsd I am not sure how to transfer the parameters of the whole subwoofer driver to what is now a passive radiator.

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Old 1st August 2008, 07:55 PM   #2
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You need to know the cone mass and surface area as the main ones. Excursion is also worth knowing.
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Old 2nd August 2008, 03:18 PM   #3
Ron E is offline Ron E  United States
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Default Re: Passive radiator

Quote:
Originally posted by Chris8sirhC
Using WinIsd I am not sure how to transfer the parameters of the whole subwoofer driver to what is now a passive radiator.
Vas = Vap
Fs = Fp
Qms = Qp

From Fs and Vas you can calculate Cone mass
Search wikipedia for Thiele Small and you will find some equations
(watch out for units)

Cone area is just pi * diameter^2 / 4
for diameter use half of the surround width.

If the voice coil former is gone, you will have to consider how to attach mass to the cone - you might have to use caulk and put it on the front or back of the cone. Otherwise just out it inside the VC former.

The easiest way to design a PR box is to design a ported box with a port the same diameter as the PR, your program will spit out a port length. Add about 3/4 of a port diameter to this length, then calculate the mass of the air in this port. Subtract from this mass the mass of the PR cone and you have the amount of mass you must add.
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Old 5th August 2008, 10:21 AM   #4
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I hope you and your brother are both OK. I am nominating you for DIY Audio Guy of the Year, for turning a serious auto accident (major bummer) into another DIY project!
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Old 5th August 2008, 05:49 PM   #5
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For the most part we are both fine. Both cars were totaled, and ive got some hairline fractures in my ribs that are still bothering me, and my back is still giving me some issues. Other than that we are ok. First i will have to finish my tapped horns then I will start on the PR sub.
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