Capacitors

But the OP asked for "other not-polarized." Wouldn't they have said with other "bi-polar electrolytics?"
But good point on the size.

Depends how old, and where.

In series = Safe
Going to ground = Dangerous
Old = High ESR
Newer = Low ESR


If you are replacing a series cap, relatively ( < 10 years) new, you are fine.

If the cap is old, it probably has higher ESR, and that should be taken into account, but in series it's not much of a problem.
The problem is in shunts ( 2nd component in low pass)  where loosing a couple of ohms can dump the speaker impedance to 2 Ohms, and cause you to loose amplifier output.

Maybe not. The crossover design probably required the high capacitance of the polarized cap and the designer took into account the high ESR into the overall impedance. Replacing that cap with a lower ESR film may throw things out of balance and may require a series resistor.

Hi, I report the data of the crossover scheme:

in high pass band
bennic 26uf - 7 watts in series;
bennic 8uf - 7 watts in parallel;

in low pass
bennic 85uf - 7 watts in parallel.

I proceed step by step to avoid unbalancing the speaker.
Thank you all for the detailed info.

I forgot ..

the speakers date from 1992

Thanks!