This may not be the right place to ask this question but I'll give it a shot anyways. Maybe someone here is an audiophile. 

I'm using a DSP called Audison Bit One HD which uses FIR filters for crossover and EQ. They recently included all-pass filters which allows me to adjust the phase of the crossover point. I'm wondering if anyone here knows how this will benefit for room correction. 

I know what an all-pass filter does but I'm not sure how it could be useful with FIR filters which is a linear phase filter. Why would I want to adjust the phase of the crossover point for?

The manufacturer is no help.