Have you tried running Pd using Jack osx and Jack mode?
pd's jack backend should perform way better than the coreaudio backend ...
I can get latency down to 7ms without crackles - this is on a meager
old g4 powerbook
7ms measured round-trip or setting in pd's audio dialog (which is merely a suggestion for the driver and iirc is completely ignored by the jack backend)
tim
-- tim@klingt.org http://tim.klingt.org
Who need fossil fuel when the sun ain't goin' nowhere Amiri Baraka