Are induction efects eliminated when using current drive...

[454Casull]

as opposed to voltage drive?

If so, what about flux modulation? Or is that source of distortion still present with current drive?

[ThorstenL]

Konnichiwa,

Originally posted by 454Casull
Are induction efects eliminated when using current drive...as opposed to voltage drive?

Yes, with perfect current drive they are completely eliminated.

Originally posted by 454Casull
If so, what about flux modulation? Or is that source of distortion still present with current drive?

Flux modulation is caused by the interactions of two magnet fields. It can only be resolved in the magnet design. If you saturate the Magnet structure and ideally use a fieldcoil magnet with sufficient negative source resistance to overcome the fieldcoil DCR flux modulation will diappear too.

Now just imagine a High Quality Radio from the 1940's... It had usualy a zero feedback output stage with tetrodes/pentodes (PP or SE) thus giving current drive and usually a fieldcoil magnet with a saturated magnet structure. And a dipole enclosure.

And guess you what? Guess you what! These things can sound darn realistic if low bass and high treble is not the issue and the signal feed is of sufficient quality.

Sayonara

[454Casull]

Thanks for clearing that up. But is it even possible to saturate an entire motor?

[ThorstenL]

Konnichiwa,

Originally posted by 454Casull
Thanks for clearing that up. But is it even possible to saturate an entire motor?

Possible, of course. It makes for a bloody big and powerfull magnet system which almsot invariably makes for a (very) low Qt Driver. Some Lowthers have saturated magnet systems.

Sayonara

[454Casull]

I've read that the response of a driver with a high source impedance is proportional to its impedance. Any way to combat this, besides EQ?

http://home.insightbb.com/~stephenwm...s/image014.gif

[ThorstenL]

Konnichiwa,

Originally posted by 454Casull
I've read that the response of a driver with a high source impedance is proportional to its impedance.

That is not entierly accurate. But yes, if you have a driver that has a flat response with voltage which does not have a flat impedance curve and you drive it with current the frequency response will show overlaid over the classic FR the Impedance response....

Originally posted by 454Casull
Any way to combat this, besides EQ?

Design a driver that has a flat response with current drive? Should actually be easier than the other way around.

Sayonara

[454Casull]

Current drive seems too good to be true. =/ The only drawbacks I can see are that it's difficult to design an amp with high current output _and_ high output impedance, and loss of damping near resonance (both of which can be designed around).

I've found a material that's almost ideal for use in a driver motor: FINEMET. High saturation induction, high magnetic permeability, and high electrical resistivity (to eliminate those pesky eddy currents). Drawbacks? Probably price, and the fact that you can't process it in the shapes/sizes required for a motor (it is possible to form a top plate out of laminated FINEMET, though).

[454Casull]

Anybody want to translate this?

http://www.hilberink.nl/codehans/tannoy91.htm

[ThorstenL]

Konnichiwa,

Originally posted by 454Casull
Current drive seems too good to be true. =/

Yup. Kill compression and distortion....

Originally posted by 454Casull
The only drawbacks I can see are that it's difficult to design an amp with high current output _and_ high output impedance,

You can always use NFB to get the high output impedance, no sweat.

Originally posted by 454Casull
and loss of damping near resonance (both of which can be designed around).

Treat that problem the Einstein way. See it as opportunity, not as problem.... ;-)

Sayonara

[ThorstenL]

Konnichiwa,

Originally posted by 454Casull
Anybody want to translate this?
http://www.hilberink.nl/codehans/tannoy91.htm

I can read that straight away.

Funny, I had these pictures (THESE EXACT PICTURES) and the Funkschau scan posted in my Yahoo Group for ages (since April 2003). I recently posted the details and pictures on AA.

http://db.audioasylum.com/cgi/m.mpl?forum=hug&n=80261

And promptly Mr. Hilberink swipes the Files (arguably placed in the public domain), places them on his site, with first of all no aknowlegedment of the source and secondly a fake "modified" date and all...

Goodness gracious me, I must have really put the bee under his bonnet (Do you know his "I hate Thorsten" Page? I just love it)....

This guy cracks me up....

Sayonara