Hoffman Amplifiers Tube Amplifier Forum
Other Stuff => Cabinets-Speakers => Topic started by: G._Hoffman on January 12, 2011, 04:54:57 am
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A few years back, I started working on a Leslie/Vibrotone type speaker cabinet for myself. I ended up buying the rotor/motor assembly from ebay, and building a cabinet around it. I finally finished it this week, and wanted to share.
(http://farm6.static.flickr.com/5042/5348264843_ac08ed6a7c.jpg) (http://"http://farm6.static.flickr.com/5042/5348264843_d7323070c3_o.jpg")
(http://farm6.static.flickr.com/5245/5348874450_f6ed087f68.jpg) (http://"http://farm6.static.flickr.com/5245/5348874450_b5266dbb6a_o.jpg")
It still needs cabinet feet, but I think that is just going to be some nail in feet from the hardware store, so very simple. I've been using it "in-the-white" for the last year or so, but I finally got around to covering it in the last couple weeks. I had some really ugly cheap gold piping, and it was awful, but once I got the white piping for it ... well, let's just say I think it look great. :grin: :grin: :grin: I could have done a better job with the piping around the speaker grills, but other than that it turned out better than I had any right to expect. The tolex was all done with Hide glue, and I'm completely convinced hide glue is the way to go. Got a lump? Iron it! Easy as could be. (Of course, I already had experience with hide glue, and all of the equipment for using it, but still, I'm very happy with the results.)
Gabriel
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Looking good.
Tony
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Very Nice ! :wink:
How heavy is it? Bet it would sound great at a gig.
Brad
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Very Nice ! :wink:
How heavy is it? Bet it would sound great at a gig.
Brad
It's not bad. There is no amp in it, so it's just the speaker, motor, and the rotor. Maybe 30ish pounds or so? The handle isn't in the best place, but other than that it isn't a problem.
Gabriel
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Very well done, Gabe. Are you playing guitar or keyboards through it? Or both? I saw a blues guitar player use one and it was pretty cool. Anyway good to see such excellent craftsmanship. Thanks for sharing.
Al
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single rotor?
2 speed?
wood or Styrofoam rotor?
what kind of speaker (s)?
Damn it looks good!
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Very well done, Gabe. Are you playing guitar or keyboards through it? Or both? I saw a blues guitar player use one and it was pretty cool. Anyway good to see such excellent craftsmanship. Thanks for sharing.
Al
Guitar. Just guitar. It doesn't have a built in amp, so I can just use my normal amps to run it. Well, one of them. I need a higher wattage speaker if I want to use my other amp. If I'm completely honest, I made it because I wanted to play Joan Osborne's song Spiderwebs. I use it for a lot of other stuff, though. I've been playing through it for about a year, but I only just got around to covering it and making the grills.
single rotor?
2 speed?
wood or Styrofoam rotor?
what kind of speaker (s)?
Damn it looks good!
Single speed, single rotor. Its a Styrofoam rotor and motor I bought off of eBay. You can usually find the speaker/rotor/motor/mounting assembly from some kind of old home organ in eBay. I replaced the baffle board it was all mounted to, and replaced the old 10" speaker with a new 12" Celestion Greenback, which is what I have in the amp I use it with. It's just a bit quieter than the speaker in the amp (not too surprising, since the Leslie is essentially a closed back cabinet, and sound goes through the rotor and all, which reduces the efficiency of the speaker just a bit), but it's pretty close.
My plan is to eventually make a variable speed drive for it, but because it is an AC induction motor, it's pretty complicated. I basically know what I need to do, but the implementation is a bit more challenging than I'm up for at the moment - at least until I've got a bit more free time. You can't just use a resistor, because induction motors speed is a function of the frequency of the AC power supply. So, to change the speed, you have to vary the frequency. Easy, except for one thing - as you lower the frequency of the AC, you also lower the impedance of the motor's coil, and Ohm's Law applies, so the excess current a lower speeds can easily burn out the motor. Not good. So, in addition to changing the frequency, you need to increase the impedance of the power supply. Or you can lower the voltage, of course. Either way, while it isn't impossible, it is something I haven't done before, and so it is challenging. I've read about it, but that's not the same thing, you know? Now, I'm getting better at programing microcontrollers, so I'm probably going to go that route, which is easier than trying to do it any other method I can think of (and lighter in weight!).
Here's the rotor/motor/speaker baffle, after I got rid of the crappy particle board baffle it came with:
(http://farm3.static.flickr.com/2797/4025319368_faf5419b4a.jpg) (http://farm3.static.flickr.com/2797/4025319368_37d5b06ac6_o.jpg)
Gabriel
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I put a DC motor on one of mine and built a real simple pulse width modulator. 555 timer circuit that drives a 3055 transistor that drives the motor.
I used the expression pedal from the organ that donated the Leslie to control the speed.
DC motors give their maximum torque nearly instantaneously, unlike an AC motor that winds up.
The result is where you put the pedal, the speed follows. well there is some belt slippage, but if I switched to one of the styrofoam rotors, less mass would equal less belt slippage.
as it is it's unnoticeable, but being the machine guy that I am, I actually considered a cog belt LOL
I'll finish it one day,now that I've seen your cab, it may look VERY similar :angel
I've never even considered making my own baffle board and using a 12. Just might throw that in there too!
Ray
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I put a DC motor on one of mine and built a real simple pulse width modulator. 555 timer circuit that drives a 3055 transistor that drives the motor.
The only problem with that is finding a motor that I KNOW would work, and be quiet enough. DC would certainly make the speed control easier, to be sure. I'd probably still use a μC, just so I could store settings and have the program change be MIDI controlled, but as of yet I've not found a cheap motor that would be both reliable and quiet.
Gabriel
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Nice looking unit
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AWESOME! That's a win!
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That's badass, Gabriel!!
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Thanks for all the positive comments.
Now I just need to find somewhere to put it. It's getting a bit crowded in here!
Gabriel