Sony MDR-ZX770DC or MDR-ZX770BN and AptX (Apt-X) bluetooth and OS X

We just purchased a Sony MDR-ZX770DC and Sony MDR-ZX770BN BlueTooth / noise-canceling headsets. (Note: the difference between DC and BN models seems to be about $100 and not much else).

These models support the AptX codec, but by default seem to choose the SBC codec.

Getting the AptX codec involved two steps - it's not clear which was the magic step, but once both were done the AptX codec was selected:

• Do the magic "Sony Press" to prefer the higher quality mode: https://us.en.kb.sony.com/app/answers/detail/a_id/55060/~/switching-the-sound-qu ality-mode
• Use Apple's Bluetooth Explorer - you have to download the correct version for your OS: https://developer.apple.com/downloads/?name=hardware
• Launch Bluetooth Explorer, choose "Tools" / "Audio Options" and click the "Force use of aptX" button

You may need to quit the app, un-pair, then re-pair your headphones.

At some point, in both 10.10 and 10.11, it works!