I've been trying to figure out resistive damping of dual voice coil woofers.

First I went to Adire:

http://www.adireaudio.com/Files/TechPapers/RDOOperation.pdf

I put the eq.s into Excel, but the higher the damping resistor, the closer you get to the original Qts and no higher. At Rl=0 the Qts is halved (more or less)

Then I went here:

http://www.geocities.com/kreskovs/Dual-VC.html

Same story. Either there's something fundamentally wrong with the eq.s as written, or I'm so far out in left field I cant see the plate from here.

Has anybody fooled with this before?

This is in parallel with the output impedance of the amplifier. Less impedance makes more damping, lower system Q. Higher output impedance makes less damping, higher total Q.

Thanks, Wayne.

But if you read the references they claim the exact opposite - they talk about doubling Qts with a couple of hundred ohms across a second 8 ohm coil. From the Adire paper:

"It allows you to vary the Qts of the driver over a range of nearly 2 to 1, from the "nominal" Qts up to nearly double that value."

How can they get it so 180 out?

I did some considerable web crawling on this and I have Adire's engineer saying explicity that the technique allows you to double the driver Qts, going from 0.38 with both coils driven to 0.76 with one coil driven and one coil shorted with the appropriate resistance.

There just doesn't seem to be any way that's possible given the derivation I found, which looks pretty consistent to me (but dynamics was never my long suit).

• Derivation