You want to go to Roger Russell's website about Mcintosh, and read about the ML and XR series speakers. All the specifications are there and the theory behind the design of the speakers and why the need of the EQ. If you think about it, all speakers depending on location need bass EQ. Where Mac speakers need 4 position of boost, Other SOB speakers might require two boost positions and two attenuation positions. Mcintosh built the set of speakers to seriously produce 20 HZ. They also produced 20,000 hz with out being irritating. Though designed a point source speakers at close listing distances they can reveal whats recorded very faithfully.