The Scamp+ represents the latest refinement to my alternate dipole compensation build, adding the Usher 8137A woofer for additional bass duties. Mounted low to address floor bounce, this 3rd driver is plate amp powered and handles frequencies from ~90Hz down. This Kevlar driver is surprisingly resilient and has great speed. A variable phase is implemented and seems to sum best somewhere between zero and +20 degrees.
Can't understate the significance of being able to dial-in additional resistance to the mid woofer in the passive circuit above. The parallel resistance extends the lower register by more than a half octave in dipole alignment. The corresponding efficiency loss is factored into the design, as the B&C pro sound driver is already several dB more sensitive than the other drivers.
The additional woofer compliments more contemporary musical genres but isn't required to achieve a satisfying presentation. It does add authority to a design that is already smooth, fast and balanced.
