Organ Donor Gives Up A Leslie Speaker


It was about ten years ago that [Richard] received an old musical organ. Moving to a new house meant it would be cumbersome to move the organ with him, so he opted to harvest some interesting components instead. Specifically, he kept the Leslie speaker.

A Leslie speaker is a special kind of speaker mechanism that creates a tremolo effect as well as a vibrato effect. You can hear this effect in [Richard’s] video below. Simple effects like this would be easy to do on a computer nowadays, but that wasn’t the case several decades ago. Before digital electronics, musical effects were often performed by analog means. [Richard’s] Leslie speaker is a small speaker behind of a Styrofoam baffle. The baffle spins around the speaker which changes the reflection angle of the sound, producing the musical effect.

[Richard] tried hooking this speaker up to other musical instruments but found that turning off the electric motor created an audible pop over the speakers. To remedy this, he build a simple “snubber” circuit. The circuit is just a simple 240 ohm resister and a 0.05 uF capacitor. These components give the transients a path to ground, preventing the pops and clicks when the motor is powered up. Now [Richard] can use this classic piece of audio equipment for newer projects.

23 thoughts on “Organ Donor Gives Up A Leslie Speaker

    1. Interesting link. Many years ago (40?) I played bass in a rock band. The keyboard player had a Hammond L100 with a Leslie. I think it was the original Type 122. He also had a Farfisa, and I remembe for one gig I played through the Lesie. I had 2 150W tube amps and fed one to a clone of a Marshal 4 x 12 Celestion cab and the other to a 1 x 18 Goodmans cab, and fed the Leslie direct. With the Leslie on the other side of the stage it was an interesting effect. We were doing a cover of Zeppelin’s “Ramble On”. Those were the days! I know all this can now be done with digital filters, but it’s not as much fun.

  1. That’s not much of a Leslie speaker, probably 8 inch speaker and just single speed. Those small motor jobs were meant to run full time and the audio was switched to a straight channel. Usually the pop cap is a .1uf with line safety ratings. One advantage of the single motor is you can easily run it horizontally like the big boys. Have fun!

  2. This is different than the Leslie speakers that I’ve seen. Those actually rotated a plywood disk that had three 8″ speakers on it, and a commutator for the speaker wiring. I think these might have been from Allen organs, but I’m not sure. Too many intervening years.

    Either setup is pretty interesting.

    1. Yes those were Allen gyrophonic. A CYA workaround on the Leslie patents. Because the speakers were parallel to the shaft no real Doppler effect happened unless you were way off to the side. Solid silver sliprings. Church organ tends to not want much vibrato, that’s theater organ sound. I have a small one with 2 8inch speakers. I want to gut it and run a neodymium tweeter horn on the rotor. More power than stock or modified Leslie horns. Less rotating weight than regular magnets. I have many bottom 2 speed rotors.
      I listened to the video and looked too.
      The Leslie should come out of the box and be in free space, but the backside of the speaker covered with sound muting stuff needs to be in a box so the non shifted sound doesn’t water down the front shifted sound. Most of the built in models in better years had a full box covering the back. If you want the (chorus) sound then pot up a channel with the straight sound in a different speaker. Black or with cream.

  3. I made an all analog Leslie-like amplifier with 6 channels for 2009 Maker Faire BA. The hexagonal column speaker was driven by 6 amps with analog control of amplitude and phase. For some reason Google does not find the project page :-(

  4. Leslie speakers are not exactly like a tremolo or a vibrato in that they are also a spacial effect. The way that a leslie can throw the sound around the room in 360° is hard (I dare not say impossible) to replicate using only a stereo setup of 2 stationary speakers. Using a true leslie brings out the ‘coloration’ of a room in a very different way which we can’t really hear using my cellphone a home theater system.

  5. Piling on — there a lot of subtle details in the sound of an authentic Leslie that get left out of attempts to reproduce the original. As Scissorfeind points out, it’s not really tremolo (amplitude modulation) but a combination of amplitude, phase and room interference effects that are fairly complex to model accurately. Regarding the single speed devices, those also eliminate the possibility of my favorite Leslie effect: the exciting crescendo effect as the Leslie accelerates from low to high speed. A great Hammond player (like Spooner Oldham) can work this with amazing results.

  6. i always wanted a leslie.

    you can easily (manually) sample the expierence fpr all who have never heard one!

    spinn (back and fourth) a really small mini radio with your hand, get the kind with a strong handle or it will break, after you realise how much you like the sound and keep doing it.
    only catch is you only get to hear <1 rotation worth of sound, then you have to reverse direction.

    after a while you get a sore/injured wrist depending on total weight and degree of rotaion.

  7. A styrofoam Leslie (cheesewheel) in an external enclosure is an easy project that has been done hundreds of times. It’s a fun thing to do, but really isn’t a traditional Leslie. A real Leslie is a different animal, in that there is a crossover to split the highs and lows at 800hz. 800 and above go to a compression driver and horn (none of this in the cheesewheels) that is turning one direction. Below 800hz goes to a stationary 15″ speaker, that is blowing down into a wooden rotor that is turning the other direction. There are two speeds, 40 rpm for chorale and 400 rpm for tremolo.

    The Allen Gyrophonic, and the Rotosonic drums were different takes on rotating sound, but are not the traditional Leslie sound.

    It’s difficult to use any servo because the Leslie isn’t that precise. The wooden rotor weighs 10 pounds, the horns weigh 7 ounces. When you change speeds, the horns do it almost immediately. The big wooden rotor spends some time, accelerating or coasting. It’s all belts and motors, the belts are designed to slip a certain amount. Since they are turning opposite directions, very complex phasing and AM components come into play. A single styrofoam rotor is very lightweight, and cannot do these things.

    As mentioned, you cannot really replicate a real Leslie with stereo speakers. It is a 3d thing. All the best recordings sometimes have many mics set up, sometimes they have only one. The original wooden Leslies only had a 40-watt amp, so they were usually miced into the PA (in a live setup) to be heard. The first time you are physically a few feet away from a Leslie will be a startling experience, it’s more than stereo. Later Leslies had 100-watt amps and the cabs were made of particle board. They’re louder, but don’t sound the same. Nothing wrong with that, the best sound is the one that you like!

    And? Electronics is a wonderful thing. They quit making wooden Leslies about 40 years ago. There are great emulators, the Neo Ventilator and the GSI Burn are the best external ones, but you’re looking at $400-ish dollars (but a good wooden antique Leslie is a kilobuck. Because there is nothing like it). Both of these devices will be limited to stereo only, but they sound wonderful.

    I rebuild Hammond organs and Leslies for fun. I have a 1962 FrankenLeslie that I have played out 75 times in the last two years. Hauling it is a moderate bitch (150 pounds), but there is nothing like it.

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