GoodSoundClub - Romy the Cat's Audio Site

In the Forum: Horn-Loaded Speakers
In the Thread: Vitavox S2 with Electromagnets

Post Subject: Re: quicker rise time with higher voltagePosted by cv on: 2/28/2010

I still say you will get the same "effects" if you current source a low voltage supply. Or, easier, put an inductor in series with the windings after your filter cap.

The way I look at it is that the voice coil is the primary of a transformer; the core is the motor iron, and the secondary is the field coil, which is loaded by the power supply. The loading of the secondary will be "seen" by the voice coil to some extent, and thus potentially affect the driver damping.

If you have a perfect voltage source for the field, then the "secondary loading" is essentially the DC resistance of the field coil.

If you current source the field, then the DCR difference between coil types becomes negligible - the "secondary load" is an open circuit, in which case I will claim the field coil impedance will make little difference.

For similar reasons, I'll also claim that if the driver has a shorting ring, then that will dominate the field coil/PSU design.

This is theoretically related to the broader question of what the best driving impedance is for any kind of traditional speaker to get the optimum damping for rise time etc.

In short - the flux is determined by the current. The voice coil may be damped to a degree by how it "sees" the field coil and power supply.

That's my theory anyway, and should all be quite readily measurable in an impedance sweep of the driver.

I would be interested to hear Romy's consultant's reasoning for his claims.

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