X

Chapter 15 Vintage B3 430
The Leslie cabinet
Don Leslie developed his rotor cabinets in 1937 and began marketing them in 1940. Laurens
Hammond wasn’t keen on the concept of rotating speakers at all.
Leslie’s approach was to simulate a variety of locations in the pipes (as in pipe organs), resulting
in a new spatial perception for every note. The rotor speaker cabinets could simulate this eect,
and the sense of space that they impart is incomparable, when placed side-by-side with any
xed speaker. The periodic undulations in sound and volume and the vibrato caused by the
Doppler eect (see below) aren’t all there is to the Leslie sound—it’s the spatial eect, too.
The “classic” Leslie speaker design features two drivers—a treble driver with horns (only one
works; the other simply acts as a counter-weight) and a bass driver. The horns of the treble driver
and the sound bae of the bass driver are physically rotated by electric motors.
Because the speakers rotate toward the front of the cabinet (the listening position), then toward
the back of the cabinet, you hear a “Doppler eect”—where sounds become louder and brighter
as their position changes. To give you an idea of this eect, it is much like the sound of a train
going past if you were standing on the platform. On approach, the sound is mued, but then it
becomes both louder and brighter as the train passes, and nally it becomes more mued as it
moves away from you.
The rotating driver/sound bae can be switched between two speeds—fast/Tremolo or slow/
Chorale (or stopped completely with a mechanical brake). The transition between the two
speeds, or the use of a xed speed, produces the characteristic “Leslie” vibrato, tremolo, and
chorus eects.
The rst Leslie, the model 30, had no Chorale—just tremolo and stop. The Chorale idea (which
came much later) was born of a desire to add a vibrato to the organ. Chorale, which oers far
more than a simple vibrato, was rst introduced to the market with the 122/147 models. At this
time, Leslie also added the “Voice of the pipe organ” label to his cabinets.
It wasn’t until 1980 that the two companies and brand names came together, six years after the
last tonewheel organ was built. Mechanical Leslie rotor cabinets are still being built today, by the
Hammond-Suzuki company.