I love the sound when employed with an Organ ( Jimmy Smith) and on Little Wing(SRV) - I vaguely remember seeing Kings X live once and I believe Ty Tabor had a pair of Leslie speakers that sounded awesome. Anyway, any "homemade" ideas so I don't have to shell out $1,500 for a pair?
The others have already said yes and then listed time and money, I'll say yes but also tell you that it's actually not that hard if you take a different approach.
First, I'll say that nothing comes close to a true rotating speaker in the room. Chorus is nice. Emulators are nice, especially if you can run them in stereo, but the Doppler effect can't be had any other way than physical motion and there is nothing quite like your first rotating speaker experience. It's a bit transcendental really.
I have a friend who, in addition to being very handy, also fell in love with the rotating speaker and wanted to build something portable that got pretty close to the real deal. A real Leslie setup rotates both the upper frequencies via a horn-type speaker that spins, and the lower frequencies via a down-firing cone-type speaker and a rotating wooden drum. See:
That's a fairly large setup. What my friend did was adapt the lower frequency portion of the classic Leslie design to make a more portable setup that was specifically tuned for use with guitar (where a lot of high frequency content isn't necessarily wanted). He took a traditional 1x12" guitar cabinet design, doubled the depth and instead of firing the guitar speaker in to a cloth grill, he fired it in to a rotating disc made from styrofoam. I'm sure he's got pictures of the whole setup, I'll see if I can get him to post them. The light styrofoam means you don't need a particularly beefy motor to rotate it. He used an Ernie Ball volume pedal to do speed adjustments. The whole thing weighs a little more than a regular guitar cabinet and it can fill a room with sound that moves so well it's quite heavenly.
As @Jduv said, it's possible to make them but I doubt you'd find it economically worthwhile, besides the bigger problem with possibly stomping on patents.
If you're committed enough to the idea that you'd want to spend money making one, take a look at some of the dedicated rotary stomp-boxes first. Boss, Line6 and TC-Electronics come to mind as having units.
Having played with organists with Leslies, I can vouch for how heavy they are, and how much work it is to travel with them. Having it on a small pedal would be SO nice.
Well, yes you could--if you had the time, money, and roadies to carry it. Here's a great technical link to how they work, so you could theoretically use this to build your own solution.
If you want to emulate a Leslie, why not go with a chorus or vibrato set to a high speed? I have an analogman BiChorus with one side set to a leslie sound and the other to a slower chorus. It works great for all my leslie emulation. The Retro Sonic Chorus also does a nice leslie.
<Shameless self promotion> I did a review on my personal site of the Analogman BiChorus vs. the Retro Sonic Classic Chorus complete with sound clips, and the conclusion is located here. You can perhaps use this to see that chorus units are indeed good for emulating Leslies. </Shameless self promotion>
FWIW, Fender made (and may still make) a Leslie style thing for guitar.
I haven't seen them new in quite a whlie, but they've popped up on used craigslist here and there for anywhere from $250 to $700 IIRC. I'm still kicking myself for not buying the $250 one when I had a chance.
They're not nearly as heavy as the real thing and sound better than a Univibe/Rotovibe to me.
I as well salvaged the rotary speaker and I had a transformer 240 down 100 volts, my question what sort of box you built to resemble the organ enclosure which had a small square opening at the front! Still I can't notice any difference see my entry under arpolwest1 under kawai rotary speaker! The sound combined with a left channel Advent 10' two ways sp. Maybe mounted on top of a round column with a slit down in a corner as a omnidirectional project
Adding to the "get a pedal" list, the Leslie/Hammond combo has a speed control switch. The Univibe has as new optional expression pedal which you can use to control the speed. Not perfect but lighter and cheaper than a real Leslie.