Dear friends : The OP thread answer is:
the best Capacitor or Inductor in a crossover speakers is NO CAPACITOR/INDUCTOR. Please let me explain.
Even that I ask for help on the thread and gave characteristics of the crossover speakers and everything I did not took advises on the overall subject.
Things were and are that I decided to make a change in my external crossover and in specific at the corssover filter for the speaker woofers that crossover around 400hz and what I decided and did it is to take out the all silver ribbon ( 2.5kg. ) inductor along the Kemet capacitors down there.
So now both woofers at each speaker are hard wired directly to the monoblock amps and know what: this non-orthodox change makes an incredible/outstanding quality improvement into the whole room/system performance listening levels.
A major improvement. Yes, I'm way satisfied and I want to share here that before this last speaker changes around two months ago I made another change that when I did it I really did not thinking of any quality improvement in the room/system.
Due that my 20.6 ML amplifiers where builded 30+ years ago and even that in all these years the amps were running just fine I decided ( just for common sense. ) to change the power supply filter capacitors in each amp, these are 4 caps each amp ( 70K uf. ).
The originals were Sprague that today is out of the market, I think Vishay bougth it, and I find out exactly the same ones by Vishay ( these were the higher uf caps ) and the others I have no other choice to use Kemet.
Well, I said that I did not expected for any improvement but wrong I was because those capacitor changes in the amps made it a formidable an unexpected quality overall improvement.
Yes, I always said that each single day is a learning one and my both changes experiences were and are a important and critical audio learning lessons to me.
R.