Wayne Parham Messages: 18787 Registered: January 2001
Illuminati (33rd Degree)
The three π model is slightly larger than the four π, that's true. Both have similarly sized baffles though, and they're large enough that baffle step happens right about the Schroeder frequency. So below the baffle step, we're in the room's modal region.
Instead of adding energy into the mains to compensate for baffle step - or worse yet, removing energy above the baffle step as it usually done with BSC filters - it's nice to be able to use a flanking sub approach. This provides simultaneous solutions to three important acoustic problems:
Provides baffle step correction (BSC)
Mitigation of Speaker Boundary Interference Response (SBIR) and higher-frequency room modes