Isn't that like an EQ used for headphones mainly? Why would one use it with a BDP?
EDIT: Ah I get it. Room correction for speakers.
Well, it goes for headphone use as well. I was currently doing BDP -> DAC/Headphone amp -> HD 800
Now, the BDP is replaced by MacBook Pro (Audirvana Plus running Sonarworks). Before Sonarworks, I preferred the fidelity of the BDP-1. However, now the Sonarworks fixes too many things about the HD 800 that it's actually worth it over just BDP-1.
For speakers, I'm still using the BDP-1, as GOOD room correction is a LOT more trickier.