active crossover and passive?

[Michael Chua]

This configuration is often used in Satellite with Active Subwoofer.
Satellite woofer is passive LP. Tweeter is passive HP.
Subwoofer is active LP and HP to satellite.

 

[Milsdrewbulch]

If you are 100% certain that the amp won't pop when switching on or off you don't need the protection cap for an actively driven tweeter.

That's a very dangerous answer.

Any transistor amp can fail to present full DC rail voltage to the load. Of course any amp worth its salt will have a speaker protection system to minimise the risk to drivers, but many don't. For this reason alone any tweeter in an active system ought to have a series protection cap tuned to around 2 or more octaves below the intended high pass corner of the active crossover (or tuned to form part of the intended high pass filter). The presence of such a cap also protects the tweeter from inadvertent connection of say the mid or woofer amp with low frequency output that could fry a fragile tweeter very quickly.

 

[AllenB]

or tuned to form part of the intended high pass filter

Yes, this means a smaller cap and it will be neatly counted in the response unless the DSP is done 'without measurement' style or similar. It can also reduce amplifier load current.