The Leslie 16 is the functional equivalent of the Fender Vibratone. Leslie also built a Leslie 18. The Vibratone and the Leslie 16 were essentially identical except for cosmetics; they had 10 inch speakers. The Leslie 18 had a 12 inch speaker.
This is a Leslie 16, and I love it. There has been a lot of debate about pseudo replacements like phasers, chorus's, Univibes, and other kinds of Leslie simulators, but let me tell you, like Marvin and Tammy sang: Ain't nothing like the real thing!
It has two speeds, with a footswitch that chooses either fast, slow, or off. The speaker remains on at all selections. I wish there was a "medium" selection because sometimes the "fast" is too fast and the "slow" is too slow.
In the both the Leslie 16 and the Vibratone, there was a crossover built into the cable assembly. It sent the mids to the Leslie, and the lows and highs to the main anp driving the Leslie. A switching system would blend in the Leslie with main amp speaker. My Leslie 16 doesn't work this way. I drive it with a separate amp and the crossover has been eliminated. The full signal goes on through to the speaker, and I prefer it that way. In fact, the original Leslie 16 circuit had a 200mf cap which filtered some of the highs out, and I removed it and replaced it with a straight wire so the full unfiltered signal passes through.
Compared to a regular guitar amp, this thing much lower in volume simply because there is no direct radiation of sound, (The sound comes through ports on the side and top) and there is only one 10 inch speaker. I drive it my with my Blackface Fender Bassman, and there is a significant difference in volume between the Leslie and a normal guitar amp. I use a Morley A/B/Y box to switch them together or A/B. The Leslie sounds great by itself, but it sounds awesome when blended with my main rig.
I have replaced the original Utah speaker with a Ceramic California 10 from Ted Weber. The California 10 takes more power, is more efficient and brighter, and is an overall improvement to the sound. Some folks replace the 10 inch speaker with a 12 inch speaker, but that would require drilling holes, something I'm don't want to do. I don't think the difference would be significant anyway.
This thing is damn heavy, probably about 60 or 70 pounds, but once again I say it sounds so cool.
Click here to download the original Vibratone Manual.
Here is a very good site with lots of information on the Vibratone/Leslie 16-18.
Below is an internal shot of the Leslie 16. The speaker baffle is inset about half way into the cabinet, and the rotating drum is attached to the front of the baffle. The back part acts as a sealed cabinet for the speaker. In the Leslie 16, the six braces are removable, then you can remove the speaker baffle to get to the motor and drum section. The front panel is not removable. Right above the power and speaker input housing you can see a pulley and the belt.