Mac users interested in Pcsx2 mac zerospu plugin generally download:
ZeroSPU - is one of the best Pcsx2 sound plugin for mac.
ZeroSPU - release version of ZeroSPU2 plugin, recommended sound plugin. Portaudio package mandatory.
The sound is synchronized with the P.E.Op.S. SPU2 1.9.0, however, aside from the "robotic" sound issue.