I don't suppose anything would stop a guy from buying a PE buyout woofer (12" $15) and cut the magnet off it.
That is half price from a 12" PR.
That is half price from a 12" PR.
That sounds like an lot of money to spend on a PR experiment. I just wait until I find a pair of speakers on the side of the road and mod the woofers out of them for passive radiators.😀😛
Peace,
Dave
A copy of Adire's RDO paper is here:
http://stereointegrity.com/Files/RDOOperation.pdf
"The math behind RDO is fairly simple; the best explanation/set of equations we've seen comes from Ron
Ennega, and was posted at Brian Steele's DIYSubwoofer site:
First you need the original Rms:
Rms = 2 * pi * Fs * Mt / Qms
Next calculate:
Rms'=Bl^2 /(Re + R) where R is the shorting resistor
Rmt = Rms + Rms'
The new Qms is:
Qms' = 2 * pi * Fs * Mt / Rmt
Qes does not change:
Qts = 1/(1/Qes+1/Qms)"
To which I would make the correction that:
Qts = 1/(1/Qes+1/Qms')
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Dan Wiggins did some of the preliminary math but, as been pointed out here, Ron Ennega did the really "deep" math (as was usual on the the old "Bass List"). I was being too hasty in replying and forgot to mention Ron's vital contribution.
Best Regards,
TerryO
I generally leave the magnet on.
I do cut off the voice-coil below the spider joint (remove the dust cap, pull the cone up, and cut the coil former with an exacto knife, yank the coil out with pliers).
I do cut off the voice-coil below the spider joint (remove the dust cap, pull the cone up, and cut the coil former with an exacto knife, yank the coil out with pliers).
Usually you will need to add mass to tune the PR. Removal of the magnet gives you somewhere to put it.
question: why not leave the magnet/vc on.then you could tune the pr with a (variable)resistor between the poles?
"Removal of the magnet gives you somewhere to put it. "
Removal of the dust cap gives you a better place to put it, between the surround and the spider.
"question: why not leave the magnet/vc on.then you could tune the pr with a (variable)resistor between the poles? "
I would wonder about the excursion capacity. Cheap woofers will slam the coil-former against the back-plate, and you will probably be adding a bunch of mass too. The coil could also pop out of the gap in front and get hung up too, especially with some added mass.
Removal of the dust cap gives you a better place to put it, between the surround and the spider.
"question: why not leave the magnet/vc on.then you could tune the pr with a (variable)resistor between the poles? "
I would wonder about the excursion capacity. Cheap woofers will slam the coil-former against the back-plate, and you will probably be adding a bunch of mass too. The coil could also pop out of the gap in front and get hung up too, especially with some added mass.
"That won't "tune" it. The resonant frequency will stay the same, it will just reduce output. "
True, it can only damp the cone (reduce the output), changing the mass changes the tuning frequency.
True, it can only damp the cone (reduce the output), changing the mass changes the tuning frequency.
Well, I wouldn't say it was all that deep, but at least it was right, if not fully simplified 😉 I wasn't begging for recognition, FWIW, just pointing out a fact. Dan Wiggins and David Hyre were good guys and I used to have lots of productive side conversations with a lot of bass list members back then.
Ah, the basslist - I miss it sometimes, but I used to spend way too much time on it.... 😉 Funny there were 7000 members subscribed, and only ~150 moved to the new list - the other ~6850 were all probably too confused about how to unsubscribe 😉
I didn't even know they had moved, as AOL's "upgraded" spam filter began blocking the Bass List and I was never able to figure out how to get around it.
When I finally got on the new forum, there weren't many of the former member's left. It was a real shame, as they had some real characters on the old "List".
Best Regards,
Terry
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