While devices have compatible PoE implementations the problematic part is PoE out power limit on hAP ac. hAP ac will always output same voltage as supplied. Provided PA uses 24V, combine that with 700mA limit and calculate max output power to be 16.8W. Possibly this would barely enable audience to work as its rated power draw is 17W ... if there was no voltage drop on UTP cable. In reality audience would receive less power and while it might even work most of time, some sporadic instabilities might happen. Cable voltage drop is lower if higher voltage is used. Both hAP ac and audience support up to 57V, but PoE out on hAP ac is limited to 300mA at higher voltages, which barely comes to the required power @57V but not at lower voltages.
Which means you won't be able to get rid of second PA. You can still use PoE to power audience using separate PoE injector such as Mikrotik's RBGPOE
which allows up to 2A meaning you can use PA supplied with audience.