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Old 28th August 2012, 07:24 AM   #1
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Smile Effects of changing BL of drivers

Hi everyone, this is my first posting. I've read some papers published by the AES suggesting that, by increasing the BL of a given size (by changing its ceramic magnets to neodymium of the same physical size), produces a significant efficiency in the mid to high frequency output of the driver. Has anyone experimented to test the viability of this? I plan to do just this on an old woofer that need rebuilding. Any help, suggestions and research materials will be very much appreciated. Thanks
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Old 28th August 2012, 12:28 PM   #2
IG81 is offline IG81  Canada
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It is an accepted fact that drivers with strong motors will often have an apparent rise in midrange and high frequency sensitivity, but I think it's actually the other way around, where the strong motor acts as an electro-magnetic brake for low frequencies, when the cone has more travel.

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Old 28th August 2012, 12:29 PM   #3
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I have two drivers, ostensibly the same, one of which has a neo plug that increases the Bl by about 20%. Mids and highs may be about 1 dB louder. But the neo version has a Vas almost 3/4s the size of the other, and a 12% higher Fc (slightly lower Qts, as well). My thought is, the biggest difference will be in the cabinet size needed.
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Old 28th August 2012, 08:50 PM   #4
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Research has been done on this.
"Direct-Radiator Loudspeaker Systems with High-Bl"
by John Vanderkooy, Paul M. Boers and Ronald M. Aarts
It's an AES Convention paper, available for free download.
Search the Web for "aar03c4.pdf".
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Old 28th August 2012, 09:15 PM   #5
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by lyedavide View Post
Hi everyone, this is my first posting. I've read some papers published by
the AES suggesting that, by increasing the BL of a given size (by changing
its ceramic magnets to neodymium of the same physical size), produces
a significant efficiency in the mid to high frequency output of the driver.
Has anyone experimented to test the viability of this? I plan to do just
this on an old woofer that need rebuilding. Any help, suggestions and
research materials will be very much appreciated. Thanks
Hi, Viability versus the bog obvious, take the latter any time, /sreten.

Attempts to improve drivers by motor changes usually fail miserably.
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When your only tool is a hammer, every problem looks like a nail - Abraham Maslow
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Old 28th August 2012, 09:58 PM   #6
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Thanks for the link to that article, Don.


It's always comforting when my observations coincide with the work of respected theorists. It's all too easy to measure a fluke and think it's the whole whale.
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