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.
Contrary to popular belief, the sound processing/producing parts of the Leslie 122 and 147 are identical. The difference in the models lies in the switching. Any variance is due to cabling, effects of age, condition of tubes, and overall condition of the cabinet.
Please refer to the Leslie Model 122XB product page for sound demonstration.
The Video below delves a little deeper into the “nuts and bolts”