Leslie 760 Rotating Speaker
Last Update
02-05-2021
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
Maintenance
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
Simulators
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 II 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
Epilogue
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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