...
"The series resistance will also change the TS-parameter of the tweeter maybe this makes the difference.
Also the damping factor of your amplifier reduces due the series resistance."
That is true, but frequency dependent damping factor is
also affected by the series capacitor, which has a much
higher impedance than the tweeters Rg in the crossovers
rolloff range and the crossover frequency is typically fairly
above the resonance of the tweeter.
Every circuit has to be investigated individually,
concerning the resulting Qes ... it depends on the
tweeter's properties and the whole crossover
circuit.
But it is impossible to make the tweeter "see" the
amplifier in the rolloff region of the crossover, there
will always be a high impedance in series,
with resistive component or not.
The question - besides going active - may be:
Where do we get damping ?
One option is to make Qm lower and apply mechanical
damping (e.g. by a large rear chamber and a flow
resistance behind the membrane) to the tweeter to get
the desired effective Qts.
Another option is to provide some low electrical
impedance in parallel to the tweeter especially in
the rolloff region of the crossover, which provides
some damping by back EMF. For purposes of
back EMF solely it is not important, whether the
current induced by the tweeter's moving voice coil
flows through the amplifier
("which is ideally a wire with amplification")
or through a (low) impedance parallel to the tweeter.
But you won't get that impedance very low - just
as low as possible.
If one does not want to compensate the resonant
impedance peak of the tweeter using an LCR in
parallel to the VC terminals, also a resistor
in parallel can be used to make the load more
resisitive and damping more frequency independent.
You can use that even without series resistor, which
means without padding the tweeter down ...
That will cost some efficiency ( not voltage sensitivity)
but the crossover slope will be closer to the "resistive load"
case. Especially with a tweeter of relatively high impedance
this may be an option.
Kind Regards