The Leslie 520 speaker was to be used _along with_ a model 705 or
model 720 speaker, to extend the amplification to a 4-channel organ
(two model 520's for 6-channel organ, etc.).

They have two amplifiers, a power supply , and two high-pass networks
at 100 Hz, to keep the low frequencies out of these little speakers.

Hope you didn't pay much for it.  The Leslie speakers are now made by
Hammond-Suzuki near Chicago.  (Actually their offices are near Chicago.)

Scott Olson
Missoula MT