Once again there are two things in sound re-enforcement there's plenty of, reflections and opinions. The Bose L1 a derivative of the BosePro MA12/MB4 system which I dealt with and has the same characteristics as the L1, plenty of lobing (Bose White paper and specs). There is no way to eliminate comb filtering only reducing it. Using just one L1 is not going to eliminate it. JBL and others have several solutions such as CBT, DSS and other sound beam forming arrays to reduce this effect. Avoiding dual mono (same signal in both arrays as Dave Rat demoed) will reduce it. Early reflections will provide plenty of comb filtering. As in most small venues reflections are the norm (very little if any acoustic treatments). So as always in this business the solution is compromise depending on what your sound objective is. IEM's are the solution to performer listening. Yes, to do the job right takes $$. A aged but valid technical review of what's going on to address this is here.
http://www.zainea.com/raschlistener.htmDefinition or spaciousness are your choices or a compromise.
Happy New Year
