How to fix sync issues in multi-output device? When I'm listening to music (iTunes) during the day, I'd like to have sound all around me.  So I've created a multi-output device out of my main audio interface (Propellerhead Balance) and my portable Bluetooth speaker (MagicBox II).  Unfortunately there is a significant sync issue between the two.  I'm not surprised that the audio signal would be delayed slightly with Bluetooth, but then I had hoped that the hardware interface would match the delay to compensate.  This is clearly not the case.  I have tried enabling drift compensation but it made no difference at all.

Is there a way to make this setup work with both output devices in sync?
The only solution I've found is to use the third party app AirFoil Speakers and use my iPad as the receiver for my "rear channel" audio (the BT Speaker).  I found an article documenting some debug settings that include per-device sync adjustments:  


  To enable the sync adjustment, follow these steps:
  
  1) Quit and re-launch Airfoil while holding down the option key. This
  will bring up the debugging window.
  
  2) Turn the Sync Adjustment debugger to On, and click Done.
  
  Now each remote speaker will have an additional slider below the
  volume slider - that's the sync adjustment. The center is 0 offset,
  and the ends are +/-1 second. Adjustments only take effect when
  connecting, so if you're experimenting with it, you'll need to
  disconnect, adjust, and then reconnect to see how well it worked.


Very handy and works well once dialed in!  It's unfortunate that in addition to the BT speaker already purchased, this solution also needs both a commercial 3rd party app as well as an expensive iOS device, but unless there is an option somewhere within the Mac OS to adjust sync in a similar fashion but for hardware audio devices, this is going to have to do (and I'm fortunate to already have the iOS device).