HammondWiki - Leslie Modifications

From the OriginalHammondLeslieFaq:

With a Leslie, as with anything else, improvements can be made --- or so some people claim. On the other hand, some other people claim that they've never heard anything good out of a non-stock Leslie. Leslie modification (and Hammond too for that matter), is a subject that has the potential to generate lots of ire and bile among the devotees. Nonetheless, here are some of the things that can be done to modify or restore a Leslie's sound.

Removing the treble diffuser:

As is mentioned on the Leslie description page, a common modification is to remove the conical diffuser from both active and dummy horns of the treble rotor. This will cause an increase in the AM component and a decrease in the FM component of the sound. As you can well imagine, there are opinions on both sides of the value of this modification and you might want to listen to one before you hack away. On second thought, a new horn assembly is not too expensive, so you could buy a second stock horn and hack away at the one you own now. That way you'll own one of each.

Amplifier modification:

The stock amplifier produces 40 Watts. It's a great amp and has a terrific sound but it has a tough time competing on stage with a guitar amplifier at full honk. It's not surprising that a common modification consists of some method of achieving higher power. This usually involves replacing the amplifier or else powering the Leslie from an external amplifier. The increase in power will probably require a change in drivers as well. (You probably did that anyway when you blew up the treble driver).

Also see LeslieDriverReplacement.