I think the best way to answer your question is to create a simple situation and discuss it. By simple room I mean something that is relatively well behaved, i.e normal reverb and reflections for is size. Here is a step by step analysis.
Lets measure one side only.
Pick House Left. We measure the transfer function, set cross-overs and delays within the cluster, set gain levels and use some eq. Now listen to the system and lets say its getting close to show-time. What this means is that the 2nd cluster will look like correlated noise. Before a crowd comes in you can measure this effect by measuring the cluster that is slightly closer to you and looking at the coherence function.