Routing Audio on a Mac - :-) or maybe :-( - no, :-) !

I am using Apple's AULab to implement my first pass at crossovers for the A100s:

• Define an AULab document with one stereo input, two stereo outputs each 
• Input so far has been AUGenerator, which plays sound files; great as a first pass
• Outputs are set to my Focusrite Safire, channels 1-2 (woofer) and 3-4 (tweeter)
• Configure an AUCrossover on each of the outputs
• HiPass for the tweeter
• LoPass for the woofer
• Wire Safire
• Channel 1 to amp LH channel (woofer)
• Channel 3 to amp RH channel (tweeter)
• Play audio file to check configuration

AULab Document for 2-Way Crossover, Soundflower or MP3 input

AU Crossovers (currently Butterworth!)

This seems to work ok, as far as I can tell there are different signals coming out of the appropriate inputs.

However, on closer listening, ALL inputs are coming out of ALL outputs - not good if I'm looking for two separate sets of signals, especially for the tweeter!

How to fix this??

<<<<<<<< Long pause (many days!!) whilst I calm down, amongst other things >>>>>>>>

OK. I've located the Saffire Control application, and looked at that. I have to click on the "soundcard" button, which makes the Saffire behave just like a simple 8-way soundcard. Hurray! The button is down on the right hand side of the panel below.

Setting Soundcard mode in the Saffire Control panel

Now to get the REW software to route its testing signals to the AULab.

Lots of struggling with this... Hours, in fact! Until I notice that there is a choice in the AULab software for configuring the input, which has as its last two channels Soundflower 1&2... Sorted. Set REW output to Soundflower 1, job done. The other channels are from the Saffire inputs.

Selecting Soundflower as input in AULab

Next problem - got a great setup, lots of good equalised curves for tweeter, but some distortion on last couple of runs. Saved AULab document, exited AULab, restarted, reloaded doc -  and now it's lost the Saffire output!! Everything is via Soundflower - suboptimal. If I make the default Saffire, then I can't set the input to Soundflower. Bah!!