@Jojo-Lapin Just tried a beta of Jack Audio, and that did the trick, I can now change block size. Also removed the sound glitches that I had previously, even when keeping the block size at 64.

The beta of Jack Audio for newer versions of OS X can be found here btw:
https://github.com/jackaudio/jack2/issues/144#issuecomment-207788137

@Jojo-Lapin I'm using PortAudio, Jack Audio for later versions of OS X seems to be in beta still. I'm using the default, built-in audio device on my Macbook.

I cannot set the audio blocksize of Pure Data. It defaults to 64, which works.

If I open the settings and change it to e.g. 256, pressing save does nothing, and I cannot close the window and have to force-quite Pd.

I am running Pd-0.47-1 on OS X 10.11.5 on a Macbook. I have tried both the 64 bit and 32 bit versions of Pd. No libraries installed.

I have also tried running Pd from command line with option -blocksize 256, in which case Pd does not start (the icon just jumps up and down in the launch bar).

I have also tried changing the default value of 64 to 256 in the .plist file. Pd does boot in this case, but if I enable DSP, it stops responding.

Any hints?