So, it seems you may be grounding the driver frames?
Thiel drivers since CS2.2 in 1990 use Faraday networks / shorting rings in the voice coil / pole piece structure which should cancel stray fields. But, stray residual eddy currents are possibly in play. Please report your findings.
Thiel drivers since CS2.2 in 1990 use Faraday networks / shorting rings in the voice coil / pole piece structure which should cancel stray fields. But, stray residual eddy currents are possibly in play. Please report your findings.