As Larry said, there should not be any trouble using a Motor Start / Run Capacitor for High Pass Filter components, in Audio System Passive Crossover Networks... at least Harmonic Damage,...
But
These Capacitors might not sound very good - especially if they are the ones in Series with Tweeters; in which case using something in the Mylar or Polypropylene (sp???) flavors is better sounding.
The Standard Electrolytics, such as a Motor type Capacitor, might not have an effect on the sound, when placed in Parallel to the Loudspeaker ("drains" out a certain upper frequency ones), which is likely where you plan to use these types anyway - since they come in larger sizes per individual device, the need to Parallel 2 or more devices is eliminated.
(last part added to cover reasoning for "oddball" Capacitor usage).
Scott35
p.s. we have some Schematics of Passive Crossover Networks in the Technical Reference area.
You will find it "between" this forum section and the Computers/Internet forum section. Just click the link for the "Menu", and search near the end of the list.
