Leslie 18

[osing]

Howdy,


I just acquired a Leslie 18 off of Craigslist. The previous owner plugged it in and played it briefly so I could tell it was operational. Before testing it at home (still not done), I decided to open it up and look around and also learn how to adjust the motors/belts.


Anyway, as many of you might know, the Leslie 18 is a variation of the Leslie 16 and Fender Vibratone cabinets. It has a 12 inch speaker instead of 10 inch, and it does not have the crossover network. Based on what I can tell online, the logic was that the 12 inch speaker has an extended range and does not require the crossover. Instead of the crossover network (part 012377) used in the Leslie 16 and Vibratone, the Leslie 18 uses an adapter (part 065227) which basically just allows you to plug the pedal assembly together with the plug that contains the speaker plug for the amp and the female 1/4 jack to which the amp's main speaker should be connected. I have attached a diagram "Leslie 18 adapter and 16 crossover" showing this adapter circled in blue (the yellow circle shows the crossover network). As you can tell, it is just a straight through wire adapter.


In the control box of the Leslie 18, there is no 200uF capacitor as found in the Leslie 16 and Vibratone - my understanding is that this is also part of the crossover network in those other cabs.


When the crossover network is used in the Leslie 16 and Vibratone, my understanding is that when the "Leslie" switch is engaged, part of the signal from the amp is sent through the crossover network and back to the amp's main speaker. The remaining signal is sent to the Leslie speaker (on its way it goes through the 200uF capacitor). When the switch is pressed again, the signal from the amp is sent right to the amp's main speaker, bypassing the Leslie. In other words, regardless of whether the Leslie speaker is in use, there is always some signal sent to the amp's speaker. There will be a change in speaker impedance seen by the amp as you engage or disengage the Leslie speaker, but there is always a load.


With the Leslie 18, however, it appears that you either choose the amp's speaker or the Leslie speaker, but never both. In the "Leslie 18 adapter and 16 crossover" diagram, you can see that in the switch (SW3) position shown, the signal in from the amp flows to the left through the wires labeled "red" which then ultimately flows to the control assembly and the internal Leslie speaker (see second diagram attached). When SW3 is in the other position, the signal from the amp flows in through pin 4, but then gets sent right back out pin 1 to the amp's main speaker.


Should there be any concern that when you are switching the Leslie 18 in and out, that you are momentarily leaving the amp with no speaker load as it changes from the Leslie speaker to the amp's speaker? From what I can tell, the foot switch is not a make-before-break switch. I suppose if you are not playing there would not be an issue, but if you are playing the amp at high volume and switch while playing, isn't that bad for the amp? With the Vibratone and Leslie 16 I do not think this is an issue as there is always a speaker load present (albeit you are changing the load).


Thoughts?

[Raybob]

I have a Leslie 18 that I restored and it had no pedal.  i built a two button pedal, one switch for speed, other uses both amp speaker and leslie or just amp.  I wired the crossover into the pedal housing.  Works great, just heavy as hell.  My belt had torn places.  Found AES now carries those cloth belts.  I recall putting both caps in that pedal.  Didn't know the 16 came with one of the caps on the unit, not in the pedal.

[osing]

Thanks Raybob,

Mine did come with the cable assembly but I find it a bit messy (see pic). I might make myself a different one with a crossover to see if I like that approach. I did finally play the cab today and loved it - so far I preferred having one amp power the Leslie while also playing through a second amp as opposed to just playing through the Leslie.

By the way, I am curious if your control assembly looks like mine (see pic)? I think everything is original, but I was surprised how clean it looks and thus am not entirely sure. As far as the cables are concerned, I am not sure if the brown lamp cord is original as other photos I have seen have grey wires.

Did you change the power cord to a grounded one?

Edit; changed, shortened spacing. Willabe

[Willabe]

I don't think that's fully correct.   

I used to own a 16 and I seem to remember that the round cylinder in the hook up cables has a cross over in it.

And the metal box in the 2nd pic, is that inside the cab of the 18?

[osing]

Hi Willaby,


The Leslie 16 is supposed to have a round cylinder with a capacitor and inductor in it (part 012377 circled in yellow in the diagram in the first post above), but there is also supposed to be a 200uF capacitor in line with the speaker inside the control box (see other diagram above, also circled in yellow). I believe these all are part of the filtering of audio going to the Leslie speaker vs amp speaker.


The picture of the metal box is indeed the box inside the Leslie 18 cab. Basically, from what I understand, it contains three caps to reduce pops, a transformer and relay (to switch between the fast and slow motors), and the fuse and power switch. I believe the only difference from the similar box in a Leslie 16 is it would have included the 200uF cap mentioned above.


The Leslie 18 does not have the cap and inductor in that round cylinder - just a straight through connection (part 065227 circled in blue)

[Willabe]

My 16 had that same wiring harness set up. 

What does it say on that round cylinder? 

[osing]

Mine actually says the part number (065227) which is how I found that wiring diagram in the first place. From the pics I have seen online, the Leslie 16 cylinder is longer (presumably because it contains parts not just wires). The other clue is that I can only choose the Leslie or the amp speaker - they are never both on at once as they would be if there was a crossover network in place. That was also what triggered my original post - it seems like it is not ideal to switch between speaker cabs in this manner as the amp will have no load for a brief moment, but perhaps in practice it is not a big deal.

[Raybob]

By the way, I am curious if your control assembly looks like mine (see pic)?

No mine is a two button Marshall style box with capacitors inside. It has cable to the leslie and two shielded cables taped together with plug and jack to go between amp/speaker.