Hi - Ferric what does it do? (BD-Design)

by GC, Wednesday, April 13, 2005, 18:25 (4662 days ago)

Evening All,

Well my question is as per the thread topic - I read the splurb over at the Lowther web site but it makes no sense.

So: Hi - Ferric what does it do?

Anyone care to comment?

Ta

Mark

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Hi - Ferric what does it do?

by GC, Wednesday, April 13, 2005, 19:09 (4662 days ago) @ GC

Hi Mark,

So: Hi - Ferric what does it do?

Anyone care to comment?

It sounds worse (to my ears) to start with...

Hi-Ferric is a metal paint applied to the coil of the driver. This pulls the coil back to the center position, you can feel that when you exchange diaphragm assemblies.

In other words, the coil will not be able to react freely to the current (music signal) like someone is hitting the break all the time.

The coil is quicker back after an impulse but on the other hand it will not reach the full pulse (dampened).

I do not see the advantage but it seems to sell better...

Ciao,

Bert

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Hi - Ferric what does it do?

by GC, Wednesday, April 13, 2005, 19:44 (4662 days ago) @ GC

Hi Bert thanks for your comments it ties up with my own conclusions!

Having just removed the Hi-Ferric from a pair of Lowther Diaphragms the difference is "Stunning" to say the very least.

My question is actually open ended in that I am looking for a way or for someone to justify the Lowther statement that the Hi-ferric helps acceleration away from and not only back towards the mean rest position - I cannot fathom that out as the Hi ferric is not encircled by or within a coil it is simply painted on a coil.

I agree - it certainly acts as a break and can only work as a restoring force towards the position of rest and not as an acceleration force away from the position of rest - and that is a big no no and in addition directly against what Voigt was trying to achieve?

Hell the stuff is a nightmare in terms of what is does to the sound - my ears are still battling to believe what I am now hearing!

Mark

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Hi - Ferric what does it do?

by GC, Thursday, April 14, 2005, 00:55 (4662 days ago) @ GC

Hi Ferric can also have a nasty habit of coming unstuck from the voice coil. When it does this, little chards of material block up the gap in which the voice coil sits. This leads to speaker distortion and necessitates a strip down of the driver.

Lowther do, of course, deny that this happens.

Cheers Chris

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Hi - Ferric what should it do?

by GC, Thursday, April 14, 2005, 10:45 (4662 days ago) @ GC

Hi!

Actually i think that the whole idea is very good, if you know how to implement it. The way Lowther has implemented it sucks, period. What they should have done is to modify the edge suspension and spider so that it does not apply any (or very little) restoring force to the cone within normal working conditions, say +- 1mm of travel or so. If one does that, all restoring force will be applied by the magnetic coating directly on the VC. Lowther also misses out on one of the most obvious benefits from using this type of magnetic suspension, namely increased linearity, since the magnetic coating on the units i have seen covers more than the VC. The way to implement this is to make the air gap, VC and magnetic material have the same axial length, if this is done you maximize the accelleration force you can apply to the cone. When parts of the VC travels out of the air gap the accelleration force decreases but so does the restoring force of the magnetic material and good linearity is kept. Exessive cone travel still should be limited by the machanical suspension. Unfortunatly it seems like all real knowledge went out the Lowther window together with Mr. Chave and all they have done since are raising prices and ruined good products.

Best Regards,
Anders

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