The model 147a is specifically designed for single-channel organs with self-contained speaker systems, such as Hammond Organ model A-100 and spinet models such as M, M-2, M-100 and L-100. Please refer to the Leslie Model 122XB product page for demonstration
It is widely assumed the Leslie Models 122 and 147 are intrinsically different in tone and response. This is not accurate. They are essentially twins, save for the switching. Vintage Leslies are subject to environmental and upkeep-related forces; both of which can color a Leslie’s tonal makeup. The Modern 122’s and 147’s are made of the same stuff, save for the manner in which they may hook up to each particular Organ.