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Old 15th January 2009, 02:30 PM   #1
Clipped is offline Clipped  Thailand
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Default magnetic poles of a speaker motor

can a speaker operate if the voice coil interacts with only one pole of the magnet?
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Old 15th January 2009, 06:30 PM   #2
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Wouldn't that mean that the cone only moves in one direction ? I mean both north and south poles are required for both positive and negative wave cycles (and polarity changes based on the AC wave cycle or how far along the wave cycle is)

So then I take it that the waveform wouldn't be reproduced. But I'm sure someone more knowledgeable will tear my words down.

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Old 15th January 2009, 07:09 PM   #3
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No a magnet always have two poles.So the the voicecoil will interact with both.
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Old 16th January 2009, 01:25 AM   #4
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you only need 1 pole for the voice coil to move.
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Old 16th January 2009, 01:34 AM   #5
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you answered your own question.
Audio is AC and does the change of attraction/repulsion in the voice coil.
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Old 16th January 2009, 10:04 AM   #6
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just wanted to double check before i drop $200 on NEO bars to make a sub.
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Old 16th January 2009, 10:19 PM   #7
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Quote:
No a magnet always have two poles.So the the voicecoil will interact with both.
Exactly so.

But you may be planning to have the coil only near one pole; the other pole far away - which in effect give you a really HUMONGOUS air gap, compared to conventional driver construction.
Result = low magnetic flux = poor effieciency & low power handling.
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Old 16th January 2009, 11:15 PM   #8
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There are a variety of transducers that use only 1 pole of a bar magnet such as the ribbon tweeter on this page:
http://www.lautsprechershop.de/hifi/aka_hoch_en.htm
http://www.visaton.com/bilder/sonsti...utsprecher.gif
Audio Magazine had a construction article ( 70's ) orienting neo bars magnets in V's on both sides of the membrane.
Click the image to open in full size.

Perhaps an unconventional design is in mind?
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