L1® Classic, Model I, and Model II Acoustical Output
In the L1 Classic, the L1 Cylindrical Radiator® loudspeaker is powered by two (2) 250 Watt amplifiers. In the Model I and Model II, the L1 Cylindrical Radiator® loudspeaker is powered by one (1) 250 Watt amplifier. The Classic, the Model I, and the Model II all use a second 250 Watt amplifier to power one or two B1 bass modules (update: or a single B2 Bass Module).
Although these numbers serve as a point of reference they do not tell the whole story. During the design of the L1 Model I and the L1 Model II the impedance of the L1 Cylindrical Radiator® loudspeaker was lowered. As a result of the lower impedance, a single 250W amplifier now powers the system to within 1.75 dB of the max SPL of the L1 Classic. Several other changes were made to the signal processing and acoustical sections to further reduce this small difference. Particular attention was paid to this change and many A/B comparisons were conducted by Bose to confirm that there was no significant audible difference between the two systems.
— Source: Ken-at-Bose, Neil-at-Bose