building a reactive load. question about phase of 2 series coils

[SoulFetish]

I'm about to breadboard a high power reactive load (8ohm nominal impedance.) It's based on Mike Sulzer's speaker circuit model.
The circuit has 2 HF inductor coils of the same inductance wired in series. I remember some talk about these kinds of components being problematic for mechanical vibration and radiating noise under load. I'm potting these air coils in a repurposed motor case for acoustic damping and magnetic shielding.
My question is: What effect would it have if these were connected series out of phase with one another?

Here is the original schematic-

[Chuck H]

My own experience with air coils in an attenuator build was that radiant field could be problematic with single coil pickups within ten feet of the unit causing instability. Since the phenomenon didn't happen with humbuckers I came up with the idea to wire two air coils of half value in series and out of phase so that there would be a tendency for the radiant field to cancel itself. Sort of like a reverse humbucker. I put a copper plate between them in hopes of minimizing mutual inductance. This worked a treat, BUT... I'm sure there was some loss of inductance due to proximity anyway and since the unit I made "sounded" good I never bothered to measure for it. I suspect the value of the two series, out of phase air coils would need to be bumped to achieve the original intended spec but I don't know for certain.

And that's all I can say about it.

[Helmholtz]

Using 2 coils with individual damping resistors is based on a proposal by Zollner.

I experimented with mounting plates of different metal and thickness.
As expected plates of copper or aluminum lower coil inductance by Eddy currents. The effect increases with frequency and plate thickness
Also effective damping resistance changes.

A steel mounting plate otoh increases inductance but seems to give best decoupling of coils.

In any case L and Rp at 10kHz should be monitored with an LCR meter.

I recommend to use a steel case for magnetic shielding of the reactive load.

[SoulFetish]

im potting them in this enclosure

[g1]

Teac motor?

[SoulFetish]

Teac motor?

Winner Winner, chicken dinner!