For MACThe CDJ aggregator from Pioneer makes all the CDJ's attached via USB look like 1 soundcard, so that you can select it in Cross and route the output to each CDJ individually. Without aggregation, you are only able to select 1 CDJ as a soundcard in Cross, which was what was causing his issue of only 1 output.
Link to aggregator
http://Pioneer.jp/support/download/dj-e/popup/agri.htmlFor WindowsWindows Sound drivers can automatically "aggregate" sound sources. BUT, you have to install the drivers for your device before this can happen.
Link to Pioneer website for Drivers
http://www.pioneerelectronics.com/PUSA/DJ/CD-DVD-Media-Players