As a first step, please give a look to this article first :
It describes the good practices concerning routing in DAW to avoid sync issues with Spat Revolution.
Logic specificities :
As Logic will stop processing a track if it finds no sound at its input, you will not receive any sound sent back by Spat if you don't route any audio to this track.
The good practice with Logic is to route the 'send' track dry signal to an aux bus, then insert the 'return' plugin on this aux bus. This way, Logic will detect some audio at the aux bus input.
Of course, enable the 'override' option in the 'return' plugin (to bypass the dry signal) and enable the 'thru' option in the sends plugins to make sure that dry signal is sent to the 'return' tracks.
Here is a basic Logic Pro X project with 8 audio 'send' tracks and 2 stereo 'return' track:
Please note the use of a 'Dummy' bus track, to make the audio tracks easier to setup. (just route your audio tracks to 'bus 1' and insert a 'send' plugin with local audio path option enabled.)
This 'dummy' bus track has 2 aux send (pre-fader) to route the signal to both the 'return' tracks.
Simply put an audio file in one of the send track and connect the input and outputs objects in Spat Revolution.