I would like to run an extra set of sub speakers on the same amplifier output, but the speaker impedances are different, will this work?
No, when the PA-CP amplifiers are set to the 8ohm constant power setting, each SpeakON output is designed to be connected directly to a single 8ohm passive speaker.
When the PA-CP amplifiers are set to the 4ohm constant power setting, each SpeakON output is designed to be connected either directly to a single 4ohm passive speaker or to 2 x 8ohm passive speakers.
A workaround is to run the 2 x 8ohm PA speakers from one SpeakON output and run a single 4 ohm sub speaker from the other SpeakON output although this will mean that the speakers are running in a Mono configuration.
To run 2 x 4ohm passive subs and 2 x 8ohm passive speakers in a stereo configuration an additional amplifier will be required.