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Need speaker/crossover help - modifying Leslie cabinet? Answered

I have a Leslie 125 that contains a 20W tube amp and a 12" full-range Jensen.

What I want to do is to add a horn to the cabinet in order to get more punch on the high end. I hope to do this without replacing the Jensen, but I will if I need to.

What I don't know how to do is to pick a speaker and crossover that will be correct for the 20W amp and the speaker I currently have. 

Looking for advice in choosing parts to buy. See image for what I want to do


I have a vintage tremolo unit model 14 L 2S I bought off Ebay from a Lowrey HR 25 organ. What parts, capacitors do I need for making a crossover for it?


7 years ago

Why no use the Hammond crossover circuit from a leslie with the the horn? Try the 122 for instance: Leslie schematics.

Or even easier, buy a crossover on ebay. I just searched for "leslie crossover" and three are for sale right now...

Good luck btw. Mechanically this will be more of a challenge than electronically (I'd just buy a leslie horn/driver unit).

I was looking at crossover design some time ago and found some pretty useful info HERE with a crossover calculator.  You'll need to know the response of your existing speaker and choose a horn to complement this.
(Are leslie speakers the ones with the rotating baffle?)

Thanks Andy, I'll check out the link. The problem Is I know nothing of response, etc. and don't have the tools necessary to find out.

Hmmm . . . Leslies appear to be pretty complicated beasts and there's a LOT OF THEM. Are you looking to fit a rotating horn?
The existing Jensen should have the impedance on the label, or at least a model number on it (or be traceable from one of the Leslie enthusiast sites) and you should be able to find the impedance from that.
As the Jensen is a full-range speaker, I'd not alter the signal to that, but use  a non-polarised capacitor in series with the horn, which will only let through the higher frequencies.  From THIS table you'd  use a 20uF capacitor to give a rolloff from 1000Hz, which would be reasonable.  The horn would not have to be rated at the full 20 watts as the capacitor limits the power to it.

I hate to say this, but I don't come close to understanding the design of crossovers - it gets really complicated really fast. I am hoping someone can point me to one that will work :)