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Old 10th June 2013, 05:58 PM   #301
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There are a couple of ways to go spider less. One way is to have a pole piece the same width as the inner diameter voice coil and have them lubed with Teflon. Though this will cause rubbing at low volumes. The second is merely the addition of ferro-fluid with the right centering force. If the motor has a high magnetic flux this isn't too much of a concern.
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Old 10th June 2013, 06:13 PM   #302
Hentai is offline Hentai  Romania
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Yes, but ferro-fluid is not an option for field coil units.
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Old 10th June 2013, 06:16 PM   #303
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Oh yeah sorry I forgot who I was talking to. There more ways try a patent search for some ideas. I have heard of active restoring force. I also know of a company using a center rod which is attached to the voice coil? which pushes on a spongy material to act as a restoring force. maybe you guys could experiment with fiberglass rods attached at specific points for a restoring force
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Old 11th June 2013, 11:42 PM   #304
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Quote:
Originally Posted by Hentai View Post
Yes, but ferro-fluid is not an option for field coil units.
Why not? The gap will have the strongest field, right?
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Old 11th June 2013, 11:58 PM   #305
nhuwar is offline nhuwar  United States
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Ah maybe because field coils are electro magnets. Once they were turned off you'd have a bit of a mess.
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Old 12th June 2013, 12:03 AM   #306
kevinkr is offline kevinkr  United States
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Nick hit the nail on the head, no field, no containment. Ferrofluid beats a hasty retreat with some help from gravity..

IMLE some of it escapes over time anyway. I've seen it wick out of the gap some drivers.

Drivers with large displacements (xmax) may also have problems with ferrofluid pumping out of the gap.
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Old 12th June 2013, 04:45 AM   #307
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Quote:
Originally Posted by kevinkr View Post
Nick hit the nail on the head, no field, no containment. Ferrofluid beats a hasty retreat with some help from gravity..

IMLE some of it escapes over time anyway. I've seen it wick out of the gap some drivers.

Drivers with large displacements (xmax) may also have problems with ferrofluid pumping out of the gap.
Did you seen it with drivers where it is placed only between the polepiece and former? Or only if there is fluid on both sides? The inner side is very smooth the outerside is not that smooth because of the windings. Also need good venting holes because of building up pressure under the gap. You can combine field coil with normal magnet so if the electro magnet won't work there is just enough flux to held the fluid in place. just a thought.

Hentai, Sorry I looked for the paper about 1khz distortion but couldn't find it anymore. I'm sure I read it is from the spider or surround but was the author correct? that's the question...
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Old 12th June 2013, 07:50 AM   #308
Hentai is offline Hentai  Romania
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From my test i believe that spike was caused by transition between former and cones. I have tried different surrouds and spiders but still showed the peak at around 1khz but masses of vc and cones were always very close. The glue i used at those joints created a small compliance between the cones. when i made that compliance larger i was able to shift the peak in frequency indicating that the assumptions are correct.
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Old 14th June 2013, 04:49 PM   #309
Frank40 is offline Frank40  Denmark
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I have made some changes for the spring system. With the other system I would get tension energy at the joints, due to the twist of the spring when moving up and down. This is massive reduced with the new two loop springs, this will keep the two spring- joint close to 0 angle when moving becouse most of the flexing will be between the two loops. See picture.

Take care
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Last edited by Frank40; 14th June 2013 at 04:52 PM.
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Old 6th July 2013, 12:16 PM   #310
Frank40 is offline Frank40  Denmark
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Hi, just a little update.

Just pick up the parts for the basket for the unit, man I am exited.... It is made from 10mm aluminium and the spacers made of stainless steel, they should be able to hole the field coil. Here is some pic's.

Take care
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