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The Leslie HL-722 is a 2-channel solid-state 215-watt Leslie with 11-pin input introduced in 1978 with the Hammond B-3000 organ, an instrument ostensibly intended to replace the venerable B-3. It is electrically identical to the models 715, 815, and HL-822 ?Leslie822. It has "pillar" moldings on the front edges designed to harmonize with the cosmetic accoutrements of the B-3000 console.

A breakdown of these four otherwise identical models is as follows:

The HL-722 has two input channels routed via an electronic crossover to four internal amplifiers. Bass frequencies from both the rotary (below 100Hz) and stationary channels (below 220Hz) are routed to the Pedal amplifier board (delivering 70 watts) which drives a 4-ohm 15" bass speaker. The midrange and treble frequencies from the Stationary input (above 220Hz) route to the Keyboard amplifier board (delivering 65 watts) which drives three 6X9" speakers, each housed in a styrofoam sub-enclosure. Rotary channel frequencies above 100Hz are split into two bands. The band from 100Hz to 450Hz is sent to the Drum amplifier board (40 watts) which drives a heavy-duty 6X9" speaker housed in a RotosonicDrum. Not only is this driver beefier than earlier Rotosonics the output "throat" is deeper than that of the 710's drum. The band from 450Hz on up is sent to the Horn amplifier board (40 watts) which drives a Jensen or Rola V21 16-ohm treble driver (early units) or an 8-ohm horn driver from either Jensen or Atlas (the author's personal HL-722 ca. 1985 had an 8-ohm horn driver with a Jensen EIA code and a date code indicating manufacture in 1985. This was replaced with a late Rola-manufactured V21 from a 720 to suit the author's tastes in tonal balance.) All four amplifier boards are the standard Leslie solid-state 4-transistor amplifier with interstage transformer and rear-panel-mounted output transistors. Later versions of these models use larger aluminum heat sinks on the rear panel as opposed to simply using the sheetmetal rear panel as a heat sink as in the early versions of this series, 710, 760, and other solid-state Leslies. There are separate gain trimmers accessible by screwdriver for each amplifier board allowing the organist to "voice" the Leslie to his/her personal preference. These models also feature "Treble Response Control" (TRC), a pair of switches on the side of the cabinet allowing the user to select from three levels of "brightness" for both the Rotary and Stationary channels.

The HL-722 uses standard 2-speed motor stacks mounted in the later style of mounting which eliminated the horn belt tensioner pulley. As in all 41" Rotosonic Leslies the rotors both spin in the same direction (some of the "shorty" Rotosonics like the 315 and 415 have reversed horn direction due to the above-shelf mounting of the later solid-state-controlled motor these cabinets used)

Schematics and the service manual for this line of Leslies can be found at .

The HL-722 is reportedly notorious for blowing speakers, due to users adjusting the gains to too high a level. When setting gains, users are advised to check for audible distortion as maximum organ volume is reached and re-adjust levels accordingly. This is especially critical for the rotary channel as excessive volume can blow the Rotosonic speaker and the treble driver, especially in earlier units using the V21 driver. This Leslie is capable of high volume and there is a temptation to turn it up as far as it will go, which will result in blown drivers.

While the usual opinion of many players of the Rotosonic-equipped cabinets is not very high, this series of Leslies does have many satisfied users and admirers, and is capable of fine, rich sound, especially for the playing of more "theatrical" music. Excessive spin-up/spin-down times can be somewhat ameliorated by correct adjustment of lower-rotor belt tension, and replacement of the belt if it is worn. The biggest trouble spot in these as well as all Leslies equipped with the RotosonicDrum is the Mercotac slip-ring contact. If the lower rotor exhibits static or noise in the audio as it rotates, the Mercotac is worn or stuck and needs to be replaced. Replacement of the Mercotac is a simple, plug-and-play affair.

A blown or poor-sounding treble driver can be replaced by the current Hammond-Suzuki "ferro-fluid" treble driver. Anecdotal field reports suggest this to be a worthwhile and effective replacement driver for these cabinets, and is capable of handling higher power levels than the V21 driver, especially at the lower crossover point used for the horn channel in these Leslies.

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