mid/bass driver with dual voice coil?

I'm pretty new to higher end stuff :) I have a pair of Energy Veritas 2.2 which have dual voice coils in each 6.5" woofer. The woofer is 3db down at 40hz (ported cabinet) and crosses over to a 2" aluminum dome midrange at 550hz. They are pretty transparent in the mids (edit: including the lower midrange spectrum that's covered by the woofer).

I'm planning on running them with a servo sub, crossed over at 80-85hz. The two voice coils are connected internally, so there are two wires brought out to connect to the crossover. Dual voice coils are supposed to help lower distortion at low frequencies and are used in some subs. I've seen dual VC midrange units for high power car audio, but I haven't found anything yet in the mid-high end audiophile market.

Here are a few details in a review of the Veritas 2.4 (3 of these mid/woofer units) from https://www.soundandvision.com/content/energy-veritas-v24-surround-speaker-system:

"The Veritas V2.4's 6.5-inch woofers have dual voice coils wound in opposite directions (thus the designation Dual-Hyperdrive). Each coil is situated in its own magnetic gap; operating them in tandem is said to significantly reduce distortion. The cone is made of a special composition designed to optimize weight, stiffness, and damping. A phase plug of solid aluminum eliminates the dustcap—a possible source of coloration—and helps dissipate heat."

So would a dual voice coil setup also improve the accuracy of the lower midrange? Or is it just mainly for the bass region?
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I know Focal made some midranges in the 1990s or so with dual voice coils on the same former and gap. Their thought process is you may want to compensate for baffle step or some other thing and use the second voice coil for compensation.
In he case of the sound and vision link I think the advantage is you get to call them "Dual Hyperdrive woofers". Not sure if they are really any better or not.

Edit - another though is this speaker has a review from 2004 and this is the first time I have heard of Dual Hyperdrive woofers at diyaudio.com. Maybe the idea did not catch on so much.
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I second the old Focal drivers with dual voice coils. Any part ending in DBL had dual coils. I used a bunch of them back in the day. They had two versions of each, small magnet and large. The small magnet wasn’t able to take much power without burning the VC.
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Another word would be 4 layer voice coil.
Adding more layers to the coil for numerous reasons.
Usually yes in a very generalized manner improve bass.

I dont know every driver in the world.
But yes far as what 6.5" modern drivers can do in
the bass department.
There is many woofers, mid/bass with 4 layer coils.

Automotive world or subs can add extra external connections
to wire the layers parallel / series.
Otherwise normal 4 layer is just in series on the former
with one connection.

So blanket statement is Yes.
You can make small Bookshelf speakers with pretty
incredible bass.
Or yes likewise in a 4 way system have very good " mid bass"

usual tradeoffs for engineers to deal with.
Larger Gap for the larger winding.
Or increased inductance

So you see larger magnets, neo magnets.
Copper sleeves, copper rings. maybe flatter
aluminum wire etc etc.

another approach for 2 layer coils
is more open basket, or vented spiders
for thermal / heat dissipation
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So would a dual voice coil setup also improve the accuracy of the lower midrange? Or is it just mainly for the bass region?

In most instances, NO (absent specific conditions).

One of the better uses is a "2.5" or "3.5" design where the ".5" (2nd coil) is compensating for some baffle-step loss (either passively or preferably actively). This literally improves the linearity in the baffle-step loss region (absent a baffle-step compensation filter, which necessarily reduces efficiency).

Here is something more exotic (and "sounds" a lot like the Energy Veritas solution) though I doubt that it substantively improves the passband of the lower midrange (depending on how you determine that pass-band):

(..as you go higher in freq. - yes, as you go lower in freq. - maybe. In both instances owing mostly to improvements with Inductance.
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The dual-gap inversely wound voice coils is also how JBL did their version known as differential drive, IIRC. That is vastly different than the average DVC setup with a split coil in a single gap. One coil is behind its gap, and the other is in front of its gap. This means there is a constant number of turns within the gap of the driver, and keeps excursion linear and distortion low.
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I'll be crossing them over on the low end at around 85hz to a servo sub (currently a Velodyne ULD12, maybe a ULD15 if I can fix one of the two amps it came with), and they would be crossing over to some older Veritas 3" aluminum dome midranges at a low, low 380-400hz ish.
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