Hi all!
After days of frustration I found a solution that might help some people.
Problem:
I recently installed Yosemite 10.10.1. on my 21.5-inch mid 2010 IMac.
I have an mbox mini (3rd generation) and Pro tools 11 (not hd or hdx).
After a clean install of PT 11, I could not make PT play through the mbox, although I could play music or movies with vlc or quicktime etc, and it was appearing in my sound preferences.
Every time I was opening Pro Tools, I was getting the message "Could not create a new document beacause Assertion in "/........./", line 1549" and would not open a new session. This message had to do with the playback engine. So I set the playback engine (setup-> playback engine) on built in audio, opened a new session and tried to change it back to avid mbox mini. I got the "Current Playback Engine does not support sample rate...." error message and it either crushed the session or restarted it with the built in audio as a playback engine. This drove me nuts for days. There is no avid mbox mini update for yosemite, but by experimenting and reading a few things I made it work. Here is how.
Solution:
1) unplug Mbox
2) Uninstall all the Mbox drivers that you have. If the uninstaller gives you an error message do it manually. Instructions
here . Also delete it from the applications, and look through your library and system/library for any extra files with the word mbox.
3) Download and install pacifist (free).
4) Download
here the version 1.2 and the initial release.
5) Open the version 1.2 with pacifist. click on the dropdown menu of the .pkg and manually put all the folders in the right place (drag and drop). If you cannot find the right place, right click on the file or folder and choose "install in default location". Close pacifist.
6) Open the initial version pkg with pacifist. click on the dropdown menu of the .pkg. Now move
ONLY the files that do not already exist in your mac in the correct place (drag and drop). Again, if you cannot find the right place, right click on the file or folder and choose "install in default location". Close pacifist.
7) Restart mac.
8) Plug in mbox
9) Go to Applications/utilities/audio midi setup
10) Select Pro Tools Agreegate. Right click and select "use this device for input" and "use this device for output". Under use and drift correction tick only the boxes of built in mic and Avid Mbox mini (or the input of your preference). Set the clock on Mbox mini and the sample rate at 48KHz (or your preference)
11) Open PT 11, go to Set up and set the playback engine on Pro Tools Agreegate!
Thats it, now pro tools 11 is using mbox mini on yosemite 10.10.1.
If you click on the MBox app it still looks like it not connected with a sample rate of 44.1KHz but since it works I'm happy. Share this if you find it useful.
Cheers