Leslie 760 Rotating Speaker


Last Update 02-05-2021

First Toy
You own HOW many?
Micing a Leslie

What's a "rotating speaker"?!?  When the electronic Hammond Organ was invented in 1934, Don Leslie was working as a radio service engineer at one of the first Hammond Organ franchises and he bought one.  To save money, he passed on the companion speaker that came with the organ, believing he could build his own speaker.  While the organ sounded great in the store, it sounded bad in Don's home.  Don was aiming to reproduce the sound of pipe organs in large churches, which was a target market for Hammond Organs.  When it dawned on him that the source of sound from a pipe organ moves around the room, he experimented with mechanically rotating the speaker.  Between 1937 and 1940 he perfected the design then he marketed his rotating speaker product.

The rotating speaker, better known today as the "Leslie" speaker (the brand is a trademark), initially consisted of two speaker drivers - one for bass, one for treble - installed in rotating baffles that directed the sound around the room.  These are the "Rotosonic" models.  Later models, which are the more familiar ones, used fixed drivers whose output was directed to ports in the rotating baffles.  The original name for Don's speakers was "Vibratone" but by 1949 the name was dropped as the market consciousness with "Leslie speaker" was too ingrained.  The effect of sound being rotated around the room produced a stereo animation that sounded great, especially with the Hammond Organ.  Upon introducing it to the market in 1940, Don demonstrated his speaker to Hammond representatives and about 50 organists.  The organists all loved the rotating speaker, but Don overheard the Hammond representative going around whispering in their ears not to let him know it is any good.  Don told Hammond that he was going to start making and selling his speakers, and they had 30 days to talk to him about it.

Hammond brushed off Don, which was what he wanted.  If they had acquired the Leslie speaker, they would had just cast it aside to be forgotten and refrained from marketing it.  The Hammond company was furious that Don built a better sounding speaker, launching a rivalry for decades.  Don brushed off the animosity and bristled in their rivalry, believing he was Hammond's savior to sales.  History proved him correct.  Customers loved the Leslie speaker and most Hammond franchises also bought a Leslie franchise.  Hammond introduced new organ models that defeated the connection to a Leslie speaker, but the resourceful Don Leslie quickly designed adapters so his speaker could still be used with them.  Hammond tried to forbid their dealers to sell Leslie speakers in the same stores, but they defied that policy.  Hammond Organs had to be sold with a Leslie speaker.  Hammond artists would not perform without a Leslie.  While the upper brass at Hammond detested Leslie products, the other employees were more rational and embraced the Leslie speaker.  The irony of Hammond's constant campaign against Leslie speakers is that the speakers sold themselves and Don never had to advertise his products!

Hammond did develop their own rotating speakers but they sounded nowhere near as good as Leslie speakers.  Key features of the Leslie speaker were protected by patents, which competitors had to evade.  Other organ manufacturers built their own rotating speakers but the sound was never as good.  Most of them succumbed to selling Leslie products with their organs.

Much of the anti-Leslie policy was driven by Laurens Hammond, the inventor founder and president of the Hammond Organ company.  Laurens retired in 1960, and as his loyal executives faded from the company the policy became history.  By 1965 Don Leslie's speaker company was acquired by the megaconglomerate CBS Incorporated.  In 1966 a Hammond executive contacted CBS to inquire on purchasing Leslie modules for use in Hammond Organs.  The secretary at CBS heard the name "Leslie" and directed the call to Don Leslie himself, who was working with CBS as part of the acquisition.  When the executive realized who he was talking to, he sheepishly said "I don't know how to say this, but we want to buy your speaker units."  Don retorted "Why don't you say we want to buy your LESLIE speaker units?"  Hammond was very late to the market of integrated Leslie modules in their organs, but the reluctance had finally come to an end and Hammond stopped selling their own speaker cabinets.

After the patents expired, organ companies could copy the Leslie speaker without worries of infringement.  But without the Leslie trademark - which does not expire unless abandoned - product recognition was a problem that hampered sales.  The Leslie name was too well associated with good organ sound.

Hammond Organs and Leslie speakers were marketed to worship, educational, and home organ markets; in the 1950s jazz players embraced the new Hammond B-3 with the Leslie 122 model, followed by gospel churches.  Their influences launched a new sound.  The Hammond company was too old fashioned to acknowledge their new proponents, but Don was eager to exploit the new market.  The Hammond/Leslie found acceptance with the birth of rock-n-roll, blues-rock, rhythm-and-blues, and progressive rock which continues to this day. top

My First Toy

I’ve been a happy Leslie 760 owner since 1981. I bought my first Hammond organ (Porta-B) and first Leslie (760) from my piano teacher - good purchase for a budding 18 year old musician.  For many years the 760 was dismissed by Hammond snobs because they weren’t a 122 or 147.  Leslie made many different models which all sounded different; it wasn’t until about the year 2000 that the 760 has been accepted as a good sounding Leslie with Hammond organs. Rotating speakers require periodic maintenance and used models will require replacement belts and components as they are over forty years old.  The solid state 760 won't crunch like a tube driven 122 or 147 but the 760 is a louder Leslie that can compete with a loud band on a stage.  The 760s are built with plywood cabinet which will sound different from the hardwood cabinet of a 122/147.

The Leslie 770 is the home organ version of the 760 with hardwood cabinet - same drivers, same electronics.  I never heard one so I can’t comment on its sound.

I won't deny that the 122 or 147 are essential for jazz and gospel-influenced music.  Blues/rock players prefer the 122/147 because the tube amplifiers can be driven into distortion.  The 122/147 hardwood cabinet has a pleasant “thunk” when percussion is used on a Hammond organ.  But they aren’t loud enough to compete on a stage with a loud band, and their furniture-grade hardwood cabinets will show their road wear quickly.  Because they use a passive crossover, you have to substitute both the crossover and the power amplifier if you want louder volume.

I liked the 760 because they are road-ready rugged cabinets with higher power solid state amplifiers.  Unlike the 122/147 the 760 comes stock with wheels and handles.  Unlike the single amplifier and passive crossover in 122/147, the 760 has an active crossover and independent amplifiers for upper and lower drivers.  It is also a taller cabinet with better bass output.  The 122/147 had a 40 watt tube amplifier that was sufficient for traditional use, but the 760 with its 90 watt solid state amplifier could keep up with a loud secular band on stage.

One of the best attributes of the solid state Leslie models is that the amplifiers were designed to sound like a tube amplifier.  Don designed the amplifier using current feedback as opposed to voltage feedback of other designs, and he received a patent for it.  An interesting component is the output transformer to couple to the speaker; traditional solid state amplifiers did not need output transformers like tube amplifiers did.  To my ears, the 760 sure sounds good.

If you’re a drawbar artist like me who uses much more than just 888000000, the 760 sounds sweeter than the 122/147.  With higher power they can be loud and still sound clean, so they can keep up with loud stage volume.  Because I used the 760 from the start, they became “my sound”.  They WILL distort if you push them too loud, but it isn’t the cool tube distortion of the 122/147.  I did blow the upper V21 driver in Leslie #1 once, luckily the fix was simple; the wire at the speaker post broke, so all I had to do was carefully unwind the coil wire one revolution and solder the loose end to the post. top

You own HOW many Leslies?

I now own three 760s.  The one I owned since 1981 is now firmly planted in my studio.  It is road worn but still sounds great.  I stopped gigging it because I was tired of moving it in and out of the studio, especially up basement stairs!  The 760 can be really loud but I don’t run it full bore - only use enough to keep up with guitar players with loud amplifiers.

I rescued a 2nd one from a 15 year storage in a barn.  Bass driver and rotor belts needed to be replaced, electronics needed repair.  Motors were fine, knock on wood. The original tolex would no longer adhere to the cabinet so I stripped the tolex and had it painted black. The cabinet looked a little bare and needed something... so I bought a Marshall logo and installed it.  That’s my gigging Leslie.

The “Marshall Leslie" is the best prank I ever did.  Guitar players see it and remark “when did Marshall make a rotating speaker?!?”  It messes with gear spotters and really turns heads. Organ players - who have long fought losing volume wars against Marshall guitar amps for years - bust a gut when they see my "Marshall Leslie".  Fits right in with Marshall guitar stacks too!  I love setting FOH guys up for a surprise when I tell them I am bringing “the Marshall”.  I showed a picture of it in a Hammond discussion group, and before I could finish posting the story behind it some members were already on Google searching for "Marshall Leslie".  I’m going to have a good laugh when I see people on gear discussion forums asking where they can find a “Marshall Leslie”.  They’re very rare… LOL

The 3rd 760 became the rehearsal room Leslie.  Having another one fixed for the rehearsal room means less hassle setting up especially in winter weather.  It is the cleanest one I own, never gigged.  A friend knew a warehouse where there had to be 30 Hammonds and Leslies in there, I bought it from him.  When I opened it up to check the motors, I immediately noticed that the upper driver was not stock.  It was a University Sound ID-60 driver, 60 watt 16 ohm.  They were later acquired by EV.  Back in those days, it was a popular replacement or upgrade for the original V21 driver.  Atlas or JBL driver were also popular replacements.  All of them need a throat adapter to fit the Leslie.

A 60w high frequency driver is more than I will ever need - even at 30w it is LOUD.  The ID60 driver has a reputation of being bulletproof, and the original specification sheet claims it is weatherproof.  They were designed for outdoor PA in ballparks, racetracks, fairgrounds, etc.  Since my gigging 760 already has a bulletproof EVM bass driver, I moved the ID60 there and put the V21 driver in the rehearsal room 760, where it is unlikely to endure abuse with loud stage volume.  Now my gigging 760 is truly bulletproof.

Like many gigging organ players, I painted the horns on the top rotor for visual appeal.  I applied white paint on my 1st 760, the stage 760 got gold paint.  It enhances their stage presence.  Even to patrons unfamiliar with rotating speakers, they spot the spinning bright colored rotors and it arouses their curiosity.

EVM 15B speaker is a good substitute for the original Jensen C12 bass driver.  In a 760 the bass driver MUST be 4 ohm coil or the balance between upper/lower driver will be off.  You can still get EV cones wired for 4 ohms.  Placed next to a stock 760 - very little difference in sound. top


Any Leslie in original condition will likely need aging components replaced.  760s were built between late 1960s to early 1980s so capacitors and other components will be past their expiration date.  Belts can stretch or become frayed over time and should be replaced.  The rubber O-ring for the choral wheel on the motors wears with use and should be replaced.

Leslies need periodic maintenance.  The top rotor, bottom rotor bearings, and motor bearings need oiling.  Usually once a year is sufficient, if they are used very frequently they will need more frequent oiling.  Do not use WD-40, use light viscosity motor oil such as 3-in-1.  You have to perform some disassembly to oil the bearings on the motors.  The owner/service manual can be found online with directions.

A common error is adjusting the belt tension for the lower rotor.  You MUST follow the procedure in the owner/service manual.  DO NOT set the belt tension too tight or you will damage the motor bearings and/or burn out the motor.  Replacement motors are not available; you have to find NOS or scavenged ones and they won’t be cheap.  During transition from choral to tremolo speed, the belt acts as a torque converter and belt slip is actually essential for correct operation.  With correct belt tension, the belt will gradually “grab” on the motor pulley more and more until full adhesion and full rotation speed is acquired.  This gradual transition of speed is an essential component to the Leslie sound, and when applied right can be a dramatic effect.  If the belt tension is too loose then the rotor will never reach full rotation speed; too tight and you risk damaging the motor.  Once adjusted it should last a long time; if adjustment becomes frequent then the belt is stretching and should be replaced.  Only use a cloth-impregnated belt designed for Leslie systems - new third party replacements are available online.

If the top rotor has a rubber belt then replace it with the correct cloth-impregnated belt, available online.  Rubber dries with age and they break.

Also beware of potential electric shock hazards in the power supply.  The metal tabs on the SCRs or Triacs have line voltage on the tabs (120VAC or 240VAC depending on domestic power).  From the factory these tabs have shrink plastic tubing on them to prevent accidental electric shock, but when they come from a repair shop the tech may not have replaced the tubing!!!

Beware of the original 9 pin cables.  The wires can break with age.  Since they carry high AC voltage the wrong wires can be a shock or fire hazard.  The US agency - UL Labs - outlawed high AC voltage in multiple signal cables, which is why succeeding Leslie models used 11 pin cables.  Replacement 9 pin cables can still be acquired online but they are not cheap.  A popular (and cheaper) replacement is large six-pin XLR interconnects.  I never liked the 30 foot lengths of those cables as they were too long and were bulky to pack up. top

Micing a Leslie

Micing a Leslie for live music is a challenge. Choice of mics is very subjective as everybody has their tone preferences. Everybody has preferences to mic distance to balance chorale vs tremolo effects and the changes in tone further alters the choice of mic.  You would be shocked how various microphones sound different on Leslie cabinets.  Many micing techniques have been developed over the years, all resulting in unique sounds.  After experimenting in the studio I settled on these mics:

Top AKG D321 @ 12" distance
Bottom Sennheiser e609 @ 16" distance

"Distance" is relative to the port of the baffle.

The AKG is long out of production, the e609 is still available as of 2020.  Neither of these are expensive.

Like gospel players, I'm a drawbar artist who uses much more than just 888000000. So the top rotor is crucial.  To my ears the D321 sounds better than SM57/SM58 on the top rotor. I thought my professional quality SDC (small diaphram condenser) mics would sound great but that was not the case.  Whatever you use you might need a windscreen; when the rotor is on tremolo it generates a lot of wind.  When the top rotor is in chorale speed I do not want to hear much tremolo.  Believe it or not it does take the right microphone, and not always expensive ones.  Some players install the mics right inside the cabinet; while this is convenient from gig to gig, it limits the choice of mics and they were too close to the horns for my preference.

Unless you're playing left hand bass on the Hammond, the bottom rotor doesn't need a LDC (large diaphragm capsule) like an AKG D-112.  A LDC can reproduce the bass frequencies very well but you don't need all that bass in a band context. LDCs may not reproduce the mids in the bottom rotor - the Leslie crossover is set to 800hz so there’s lots of midrange in that bottom rotor.  The e609 won because it didn't sound "woofy" and has even frequency response, sounds just like the bottom rotor is supposed to sound. When playing “smears” on the low end of the Hammond manual for dramatic effect they don’t get bass heavy and the relative volume is the same.  Some mics (such as condensers) had too much tremolo on chorale speed (even at 16" distance) but not the e609.  Condenser mics can be too sensitive and will pick up too much stage volume from drums guitars and vocal monitors.  Some mics (such as the SM57/58) will pick up 60hz hum from the power amp, the e609 doesn’t do this.

Be very careful of placement on the stage. When I was making a band demo from a live multitrack recording, I discovered that the stage bleed in the Leslie mics was so bad that I had to re-record the Hammond parts. To minimize bleed from stage noise I now place the Leslie as far as possible from the loud stage. With a 760 I can crank it and still hear it. Hell the guitar player on the opposite side of the stage furthest from the 760 can still hear it. top


Leslie cabinets are bulky and heavy.  Hammond players longed for a smaller lighter alternative that didn’t need maintenance.  For a long time, it was very difficult to simulate a rotating speaker electronically.  Don Leslie tried to design electronic simulators but was not successful.  The aural animation of a rotating speaker is a mix of phase modulation, pitch modulation, and amplitude modulation.  The balance and depth of these are crucial, are different for each rotor, and the balance/depth changes between chorale and tremolo speeds.  Guitar players could find pedal boxes that reproduced the tremolo mode but they weren’t close enough for the organ players especially the chorale mode.  Organ players are a much tougher lot to please.

Today you can buy Leslie simulators that do a respectable reproduction of a rotating speaker, even for Hammond players.  The first successful simulator was the Dynacord CLS-222 from the early 1980s (no longer made).  It was a BBD-based simulator that reproduced the crucial balance of phase/pitch/amplitude modulation for each rotor at each speed.  Leslie cabinets are also far from flat frequency response; the CLS-222 replicated this peculiar response (many others did not).  Because Dynacord is a German product they weren’t initially well known in the US until they landed a US distributor.  I had first read of them in touring bands.  When I read a product review I decided to find one.  While on a business trip in Los Angeles I stopped at a Guitar Center store (long before they became a national chain) who had a CLS-222.  After trying it out, I bought it.  With its compact 1U rackmount package and 8lb weight it packed easily in my suitcase for the return trip home on the plane.  It was a great alternative (notice I did not say replacement) for a real rotating speaker, especially for gigs where there isn’t much Hammond playing required.  Modern DSP-based simulators such as the Neo Ventilator and Stage 3 have been widely accepted by organ players.  They are a pedal format; I prefer a rackmount format for gigging, and the CLS-222 is the only rackmount simulator made so far. 

I have not tried any other simulators so I can't comment on their authenticity.

For young organ players who are not lucky enough to own a pickup truck or van to gig a Hammond organ and Leslie, a modern “clonewheel” organ and rotating speaker simulator is a great alternative.

So I only gig the 760 when the amount of Hammond playing warrants it.  Every band where I introduced them to the 760, the band enthusiastically welcomed it when they heard it.  They never complained about helping to move it.  The size of my pickup truck is also a factor - when I cart a 760, it consumes a lot of room and I can’t fit a lot of gear.

While simulators are much more compact and convenient, they don’t simulate the three dimensional animation of a real rotating speaker in a room.  Stereo outputs does not sound the same.   It is more than just stereo - the three dimension animation has to be heard to be appreciated.  That’s why I stressed that simulators are an alternative and not a replacement.

Another reason for simulators is that Leslies do not have any inputs for instruments with 1/4” interconnects.  Leslie made preamp boxes that allowed guitars and keyboards to be plugged into Leslies.  Vintage preamp boxes command a high price on the market today; modern preamps were made but as of 2020 they are out of stock. top


Leslie speakers and Hammond organs are a perfect match - like peanut butter and chocolate, like hot dogs and mustard, like guitar humbucker pickups and vintage Fender or Marshall guitar amps.  Other non-keyboard instruments were tried with Leslie rotating speakers, but not to much satisfaction.  Guitar players like them on tremolo speed; I did not care much for guitar through my 760 but it may sound better through a tube Leslie.  John Lennon even put his vocal through a Leslie on some Beatles songs.  Hammond organs seem to sound best through them.  My Porta-B has integrated spring reverb which I like through the Leslie.  At one jam session I even put my Simmons drums through the 760 and the drummer said they sounded good.

So what other keyboards sound good through a Leslie?  Just about any electric piano, especially Rhodes pianos.  The Leslie is far from a flat frequency response and is actually optimized for organ.  In my early gigging days the 760 was my only keyboard amp; I did play synthesizers through it until I decided they sounded better through a straight amp.  Couldn't had been terrible, as I played in a top40 band and played electronic piano, synthesizers and left hand bass all through the 760 - no one complained. top

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