Leslie Speaker

leslie speaker

The Leslie speaker is a specially constructed amplifier/loudspeaker used to create special audio effects using the Doppler effect. Named after its inventor, Donald Leslie, it is particularly associated with the Hammond organ, an electric organ invented by Laurens Hammond in 1934 and manufactured by the Hammond Organ Company. While the Hammond organ was originally sold to churches as a lower-cost alternative to the wind-driven pipe organ, in the 1960s and 1970s it became a standard keyboard instrument for jazz, blues, rock music, church and gospel music. The Hammond/Leslie combination has become an element in many genres of music. Both brands are currently owned by Suzuki Musical Instrument Corporation.

Unlike a high fidelity loudspeaker, the Leslie is specifically designed, via reproduction of the Doppler effect, to alter or modify sound. Although there have been many variations over the years, the classic Leslie speaker consists of two driver units – a treble unit with horns, and a bass unit, and a crossover that divided the frequencies between the horn and the woofer. The key feature is that both the horns (in reality one working horn with a dummy to counter-balance it) and a sound baffle or scoop for the bass are electrically rotated to create ‘Doppler effect based’ vibrato, tremolo and chorus effects. The rotating elements can be stopped, switched between slow (chorale) and fast (tremolo), or transitioned between the two settings.

To stop a Leslie’s rotor, a special brake circuit was added to the Leslie motor controls that incorporated a tube relay, which sent the rotors into chorale before cutting power from the rotors to bring them to a quicker stop. Solid state relays now make this possible. A three position switch must be used to allow the rotors to ‘brake’ on a two speed Leslie. Some other model Leslies had no slow motor and were basically one speed, ‘fast’ or ‘off.’

Much of the Leslie’s unique tone is owed to the fact that the system is at least partially enclosed, but with linear louvres along the sides and front so that the unit can vent the sound from within the box after the sound has bounced around inside, mellowing it.[citation needed] . The tone is also affected by the wood used. Tone differences due to cost cutting using particle board for speaker and rotor shelves instead of the previous plywood, are evident in the Leslie’s sound. The thinner ply of the top of the cabinet adds a certain resonance as well. Like an acoustic instrument, a Leslie’s tone is defined by its cabinet design and construction, the amp and speakers used, the motors, and not merely by the spinning of rotors.

Don Leslie, at the outset, was refused hire by the Hammond Organ Company, but did work for the local electric company, in a contract with Hammond, to replace the old fifty cycle rotor tone generators with the new sixty cycle units, in customers’ homes. The speaker’s first name, in 1941, was the ‘Vibratone’; the name was used later by Fender Guitar Company for a speaker system and effects unit containing a Leslie rotating speaker. Fender also used the name ‘Leslie’ after Leslie sold his company, in 1965, to CBS, which had also acquired Fender.) From 1941, when the first units were produced, the speaker went by several names including ‘Brittain Speakers,’ ‘Hollywood Speakers’ and ‘Crawford Speakers,’ before returning to the name ‘Leslie Vibratone’ in 1946. Seventeen years after it had rejected him, Leslie offered to sell the company to Hammond, who again declined.

In 1980, the Hammond Corporation finally bought Electro Music and the Leslie name from CBS. To this day it remains part of Hammond under Hammond Suzuki, USA .

Leslie never advertised his speakers. After demonstrating a prototype (a rotating baffle in a hole in a small closet with a big speaker in the closet near Leslie’s home organ) with Bob Mitchell, an organist with radio station KFI near Los Angeles, a contract was made to install another prototype in the station’s studios, where Mitchell would be the only organist authorized to use it. Soon afterwards, Mitchell became an organist with the Mutual Broadcasting System, and played a Hammond with the Leslie on its shows. Organists, professional and amateur alike, wanted to have ‘that sound.’

Jazz organist Jimmy Smith helped to popularize ‘that sound’ among rock-n-roll musicians in the late 1950s and early 1960s. The Leslie of that time was over sixty inches tall (about the size of a modern refrigerator), and was named the 30A. Don Leslie made a whole series based on the 30A, called ‘Tall Boys’ (31 series). In the 1950s, Leslie introduced the 21H for use in homes, concert hall venues and smaller radio sound stages.

Today, Leslie parts are available from a number of sources. There are also websites with plans (and photographic examples) for constructing a Leslie speaker, with much improved electronics and speakers. The classic Leslie is still made and sold to this day, though similar effects can now be obtained via analogue electronic devices and digital emulation. Chorus and phase shifter devices can mimic the sounds produced by a Leslie speaker; in fact, early phase shifters like the Uni-Vibe were specifically marketed as low-cost Leslie substitutes for guitarists, and used a foot-operated fast/slow switch. Although the sound of a Leslie speaker heard in person is quite distinct, some digital emulations of the Leslie Doppler effect have become virtually indistinguishable from the sound of a recorded Leslie speaker.


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