Euphonic Studio Hammond

Hammond A-100 with modified Leslie 251

Ask any pop or jazz keyboardist to name their ultimate organ and you will undoubtedly get an answer of “Hammond B-3”. The Hammond-Leslie speaker sound is inextricably tied to popular music and the list of Hammond artists and bands seems endless. Just about any pop music recorded with an organ track will use a Hammond; they are found in the best recording studios worldwide.

There is some confusion regarding different models of Hammond organs. My studio has an A-100. To help clarify, a Hammond A-100 has every part in it that a Hammond B-3 has, and more.

The A-100 has two additional features not found on a B-3. First, it has an internal amplifier and speakers so it can be played without any additional equipment. A B-3 requires an external amplifier and speaker system. Second, the A-100 has a separate reverb channel not provided on B-3s. The reason why A-100s are rarely seen on the stage is the extra weight added by having 3 speakers, an amplifier, and additional cabinetry. B-3s are already heavy enough.

Hammond creates its unique sound by an electromechanical system.  There is a motor turning a shaft with "tone wheels", or "tonewheels", which are toothed metal with varying numbers of teeth.  These spin past electromagnetic pickups which create pitches based on the number of teeth on the wheel.  Each tone wheel has its own volume control, and different timbres are achieved by adding and subtracting harmonics.  The sound is distinctive... often imitated but never reproduced.

The Hammond sound is further defined by Leslie speaker systems. There are many different models of Leslie speakers but the one thing they have in common is a method to rotate the direction of sound output from the speaker cabinet. The keyboardist can change the speed of the motors that rotate the sound to create different effects.

The least expensive version of this machine/instrument is a foam baffle that rotates in front of a coned speaker. This version of Leslie (e.g. Model 120) requires an external amplifier. This design was licensed to manufacturers of home organs and despite its limitations it improves the sound of the organ by an order of magnitude.

The most desirable Leslies have a two output amplifier and two speaker components. The bass output is sent to a 15” woofer facing downwards in the cabinet. Beneath it is a rotating wooden baffle that directs the sound as it rotates. The treble channel speaker is actually not a speaker at all; it’s a horn driver connected to a plastic rotating horn. There are two rotating horns but one of them is plugged and serves to balance the two horns. The most common models of this Leslie type are 147 and 122.

With the proper motor controls, Leslie speakers can produce 5 distinct effects: stopped, accelerating, rotating slow (chorale), rotating fast (tremolo), and decelerating. What the Leslie actually does to the sound is beyond the scope of this website (see my links page). In a nutshell, the Leslie modulates amplitude (loudness) and frequency (pitch due to the Doppler Effect). This gets to be a complicated topic due to the variations of rotating speed and what notes are being played (high and/or low pitches). More interesting complications… the horns and baffle turn in opposite directions and they accelerate and decelerate at different rates. It should be intuitive that when the Leslie is stopped, there is no Doppler Effect. At chorale, the Doppler Effect is present but the amplitude modulation is much more of a factor. As the speaker rotation accelerates the Doppler Effect becomes more pronounced. With this brief description, you may have an appreciation of how difficult it would be to model this with a synthesizer through a fixed speaker.

My Leslie is a Model 251, specially designed to work with a Hammond A-100. In addition to the bass and treble speakers, it has two fixed speakers for the reverb channel. Originally, the speaker motor controls had a two position switch for only slow or fast. I upgraded the motor controls with solid state relays to eliminate the loud metallic contact clicking noise when changing speeds (this was very annoying when recording). The kit contained a 3 position motor control switch for chorale, tremolo, and off.

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Euphonic Studio digital recording services and music lessons

Mount Vernon, Iowa serving Cedar Rapids, Marion, Solon, Mechanicsville, Ely, Springville, Anamosa, Iowa City and surrounding area

For information about music lessons and digital recording at Euphonic Studio, call Bill at 319.895.8002 or 319.329.4527