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Old 17th September 2013, 07:26 AM   #361
Hentai is offline Hentai  Romania
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I was once thinking of a spider inside the voicecoil former and fixed on the center pole. It wont allow for huge xmax and will be troublesome for small diameter voice coils. But there wont be any sound radiating spider on the back of the cone and mass will be light.

Didnt pursue it tho...
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Old 17th September 2013, 08:27 AM   #362
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Quote:
Originally Posted by Jef Nuyts View Post
Hi RayCtech,

I did already make two models with magnetic centering like you mention (two directions winding) but... radial centering with ferrofluid. I found out this is not a good way, to much damping (was unable to apply the point of critical damping). Overdamped resulted in a not open stereofield, missed some "sparkle" in the music. Thinking of a solution for magnetic centering (axial and radial). But didn't found a (good) solution yet. The axial centering works very well so this is a good basis to go for (very lineair). Some help for the radial centering would be very much appreciated. If you have questions about my design please ask.

Cheers,
The minimalistic spider design are the only alternative to magnetic oil with my current mechanical design. And this will be evaluated as soon as I get time.

A redesign and building of new motor assemblies to incorporate a new non magnetic centering method are not anything I have time to do in the near future.
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Old 29th September 2013, 01:28 PM   #363
Frank40 is offline Frank40  Denmark
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Some updates

I did try a cloth surrounding. It was one that I removed from a unit, it was softened by adding some de solvent to remove all glues and resin. After removing the access glue the weight was 2,6 g, but it was still to stiff resulting in a to high resonances frequency...The foam surroundings was way better.

When using cones that are as light a 1,6 g I need a surroundings with a very high compliance, and this lead me to try leather. I got a small piece to play with, it had to bee joint due to the small size but it turned out OK. As you can see it is totally durable, one thing tow It increases in size when it is socked in water....So it is actually big big now.

Take care
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Old 29th September 2013, 01:38 PM   #364
nhuwar is offline nhuwar  United States
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That's a very impressive looking job you've done there.
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Old 29th September 2013, 01:42 PM   #365
Magura is offline Magura  Denmark
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Originally Posted by nhuwar View Post
That's a very impressive looking job you've done there.
Indeed it sure is impressive.
Good to see.


Magura
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Old 29th September 2013, 02:04 PM   #366
Frank40 is offline Frank40  Denmark
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Thank you guy's
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Old 29th September 2013, 04:02 PM   #367
nhuwar is offline nhuwar  United States
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How did you mold the surround?
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Old 29th September 2013, 06:46 PM   #368
Frank40 is offline Frank40  Denmark
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After making a full circle from two sheets of leather, I let it sock in water for about 30 min. For moulding the shape I used some nice big 8 spiders (as you can see in the picture), I put the leather in between the two spiders and added pressure and let it sit for 3-4 hours.

The leather I used was from a lam, and is about 0,5 mm thick. Hope this is the info you are looking for, other vice please free to ask.

Take care
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Old 30th September 2013, 12:40 AM   #369
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Wow that leather surround looks sharp! Nice idea to form it using a spider.
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Old 12th October 2013, 01:01 PM   #370
Frank40 is offline Frank40  Denmark
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Quote:
Originally Posted by Jef Nuyts View Post
Hi RayCtech,

I did already make two models with magnetic centering like you mention (two directions winding) but... radial centering with ferrofluid. I found out this is not a good way, to much damping (was unable to apply the point of critical damping). Overdamped resulted in a not open stereofield, missed some "sparkle" in the music. Thinking of a solution for magnetic centering (axial and radial). But didn't found a (good) solution yet. The axial centering works very well so this is a good basis to go for (very lineair). Some help for the radial centering would be very much appreciated. If you have questions about my design please ask.

Cheers,
Did you feed your centring coil from a constance current source, I think that is what you should do.
If you remember I thought if you use a voice coil former as a shorting ring, it would work. But in fact it turned out to have some funny effects.

If you feed your coils with a normal power supply, then the coil will see it's self as shorted. But if you use a constance current source, it will see it's self as a open loop.

Just some thoughts any way.
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