SPL Expansion Rack - Rack Mount for Phonitor 2 and SMC 7.1 (Black)The SPL Expansion Rack is a Rackmount for Phonitor 2 and SMC 7. 1. The Expansion Rack also increases the number of active speakers or power amplifiers that can be connected from one to four. Installed in the Expansion Rack, a Phonitor 2 or an SMC 7. 1 can be mounted into a 19 inch rack. The installation is the same for both devices. The Expansion Rack is equipped with a rotary switch that passively routes the stereo output signal of Phonitor 2 or the