Hi guys, for your information. This is what tech support told me. I'm sure someone will be interested in this data:
"Using both loops with Constant Latency will result in approximately 15 ms latency plus added latency if digital devices are patched into the loops.
Without Constant Latency the latency with both loops is approximately 9 ms plus added latency if digital devices are patched into the loops."
...Add latency from digital devices in the loops (not my case), plus latency from any audio interface used, or latency from digital console in a live situacion (minimum 1.5 ms) plus latency if digital in ears are used (2 ms minimum)...