Less – a simplified Leslie style cabinet

[henrim]

I always wanted to have a Leslie. And I have an extra G12H lying around. So let’s stuff the Celestion, a motor and some other parts into a box and that should be it.

Started by making a box. It’s not glued yet. Only kept together by some hand cut box joints. Did them by hand because I didn’t feel like adjusting the router jig in the cold cellar. Needless to say it would have been faster. But the saw and chisel method is kinda therapeutic. To an extent.

Next I should figure out some kind of spinning baffle and decide how to spin it.

Unlike a real Leslie this will be just a speaker cabinet. No amp inside. And only one speaker.

[curtisa]

Neat little project! I have an old Fender Vibratone that I restored from a semi-destroyed state a number of years ago that is essentially what you're doing - a single 12" speaker firing into a Leslie-style rotating baffle with no amp. Leslie also made their own version of it simply called the '16' or 'Model 16'. Stevie Ray Vaughan was a well-known user of it on the tune 'Cold Shot'. 

Any thoughts on how you're going to make the rotary baffle? That and the mechanical arrangement of motor, pulleys and speed control (if you're going that way ) will likely be the most difficult part of the job.

[henrim]

5 minutes ago, curtisa said:

Any thoughts on how you're going to make the rotary baffle? That and the mechanical arrangement of motor, pulleys and speed control (if you're going that way ) will likely be the most difficult part of the job.

I thought I’d test first with a sewing machine servo motor I have. It has a driver for speed control and can be operated with foot pedal. Although it may be too noisy, it’s an easy solution for testing. 

Also the 750w motor is an overkill as I’ll make the baffle out of EPS foam, which doesn’t weigh much.

Anyway foot controlled speed is something I really want to try. And it would be great if I could make the thing to return the baffle to the front position when spinning stops. I can’t do that with the controller I have but if I change to a closed loop motor I’ll use a controller I can program freely.

 

[curtisa]

1 hour ago, henrim said:

Also the 750w motor is an overkill as I’ll make the baffle out of EPS foam, which doesn’t weigh much.

Same as the Vibratone, then. It uses polystyrene foam for the baffle too, The motor is some kind of specialised 2-speed AC synchronous thing running direct from the 240V mains. 

Really keen to see how yours comes out. If you need me to provide any details on my unit just shout out. It's been a while since I fired it up. 

[henrim]

5 hours ago, curtisa said:

If you need me to provide any details on my unit just shout out.

Thank you!

[Professor Woozle]

I'm watching with interest now, since I've got a 50W 10" Trace Elliot Celestion kicking around doing nothing that maybe could get used in a future project, when I've finished some of the ones that are on the go!
The footpedal speed controller reminds me of one of the mods Van Der Graaf Generator organist Hugh Banton made to his Hammond - he put a pedal-operated speed controller on the rotor motor circuit so he could alter the sound while playing. He used to make some crazy kit for himself and the rest of the band...

I looked up that SRV track on Youtube, and loved the official video - I think we can all relate to this (and our partners too)
 

 

[MiKro]

16 hours ago, henrim said:

I thought I’d test first with a sewing machine servo motor I have. It has a driver for speed control and can be operated with foot pedal. Although it may be too noisy, it’s an easy solution for testing. 

Also the 750w motor is an overkill as I’ll make the baffle out of EPS foam, which doesn’t weigh much.

Anyway foot controlled speed is something I really want to try. And it would be great if I could make the thing to return the baffle to the front position when spinning stops. I can’t do that with the controller I have but if I change to a closed loop motor I’ll use a controller I can program freely.

 

@henrim, I would think that if you have a sewing machine motor, say a Consew CSM 1000  or similar and have maybe the needle position set.  If you enable the needle stop up or may be down to coincide with the baffle pointing out that would suffice. I hope that makes sense? You may have to have the actual positioner for that as well? That would be an add-on to the motor as a clutch I think.

mk

[henrim]

49 minutes ago, Professor Woozle said:

he put a pedal-operated speed controller on the rotor motor circuit so he could alter the sound while playing

Yes that’s what I had in my mind too. Although I have no idea if I’m capable of using it that way. But the idea is tempting.

[henrim]

Just now, MiKro said:

I would think that if you have a sewing machine motor, say a Consew CSM 1000  or similar and have maybe the needle position set.  If you enable the needle stop up or may be down to coincide with the baffle pointing out that would suffice. I hope that makes sense? You may have to have to the actual positioner for that as well? That would be an add-on to the motor as a clutch I think.

mk

Unfortunately mine doesn’t have the needle position feature. When I bought that motor for my old sewing machine I didn’t think I need the feature because I had never had it before. My current machine has it and now I finally understand why it’s handy for sewing. But I’ll use the motor as is for sound testing and change it afterwards if I feel I need to.

[MiKro]

10 minutes ago, henrim said:

Unfortunately mine doesn’t have the needle position feature. When I bought that motor for my old sewing machine I didn’t think I need the feature because I had never had it before. My current machine has it and now I finally understand why it’s handy for sewing. But I’ll use the motor as is for sound testing and change it afterwards if I feel I need to.

No problem was just trying to help with a solution. I use the Consew types on small equipment. Convert the  hall sensor pedal or lever to a POT for speed control. They make great consistent torque for there size and weight over a range of RPM. You may still be able to program in the feature though.

mk.

[henrim]

Not the first time, and unfortunately probably not the last time in my life, that I realize I should have drawn something before I started. But I think I can just fit the motor in.

Found a length of 10 mm ground shaft and matching bearings from the house. And a random pulley with 15 mm bore. I machined an adapter to fit the pulley to the 10 mm axle.

I thought I had some pieces of polystyrene insulation board but apparently everything has gone to use. So I’ll probably make a plywood baffle then. Anyway the non-existing design (what I have in my mind) should allow the baffle to be changed easily.

[henrim]

And yet it moves!

Doppler effect is clearly there but not too pronounced with fully open cabinet frame and a makeshift rotating baffle. But I already love it!

Maybe I make openings to the front and sides so that they can be blocked/opened individually.

I need to change the motor as that servo motor is too noisy. I guess I need to find a silent dc motor.

[curtisa]

Nice work! FWIW, the Fender Vibratone has a fully-sealed cabinet with 'letterbox' openings at the top, both sides and along the bottom on the front baffle. The speaker in the Vibratone faces forward and the rotating drum directs the sound outwards towards the floor/ceiling as it spins, whereas yours is more like the original Leslie with the drum directing the sound outwards towards the walls. Your cutouts would therefore make the most sense on the sides and front of the cabinet.

[woodfab]

Very nice, I've always loved that sound of the Leslie and worked on a few.

I feel it's more of a natural sound than an effect unit.

Similar to, that I love an acoustic piano as compare to a to the sound of a digital piano, close but no cigar!

[mistermikev]

On 3/8/2023 at 3:25 PM, henrim said:

And yet it moves!

Doppler effect is clearly there but not too pronounced with fully open cabinet frame and a makeshift rotating baffle. But I already love it!

Maybe I make openings to the front and sides so that they can be blocked/opened individually.

I need to change the motor as that servo motor is too noisy. I guess I need to find a silent dc motor.

really hopeful to hear this.  that sound srv gets is lovely.  have never seen that vid but have seen/heard that song a million times.  a while back I had an h and k rotosphere that i played all the time... instant "late night with david letterman" sounds.  cool project, enjoyed your share and hope to see a demo someday!

[Bizman62]

That single photo of the open cabinet opened my eyes to understand how it works! For some reason I had had the impression that the entire speaker rotates which kept me wondering how the wiring had been done. You can also imagine how puzzled I was thinking about inner structures made of EPS foam and similar materials carrying the weight of a 12" speaker!

Having now seen what a "baffle" is and how it works, I got this idea of a noiseless fool proof rotating system: Combine the baffle to a potter's wheel! No EMI issues and fully adjustable speed.

[henrim]

Thanks guys! I have glued the cabinet together. Also checked the alignment of the drive shaft with a dial indicator. It’s now running fairly straight so there’s much less unwanted vibrations. Other than that I tried to insulate the noise the motor makes but can’t make it silent. I think part of the problem is the belt I’m using. Motor alone makes a buzzing noise but when the belt is engaged the noise is louder. I’m testing with other motors next. 

8 hours ago, Bizman62 said:

For some reason I had had the impression that the entire speaker rotates which kept me wondering how the wiring had been done.

What I have done here is how the original Leslie has bass speaker installed. However it also had a pair of rotating treble speakers. I’m not familiar with how the wiring was done. I’d guess brushes maybe. There are other implementations like rotary welding tables and such that has to pass current while spinning, so there are ways to do it.

On 3/3/2023 at 6:04 PM, MiKro said:

have maybe the needle position set.

Actually I was wrong. The driver I have has needle positioning. I just don’t have the hardware that would be needed for implementing the function for a sewing machine. Anyway I need to use an other motor because of noise. Although I wonder whether the motor itself is noisy of if it is the driver that makes it noisy. I don’t have much experience with servo motors but I know that with stepper motors the driver can make all the difference.

14 hours ago, mistermikev said:

hope to see a demo someday!

I’ll def make a clip once this is done.

[Bizman62]

4 hours ago, henrim said:

What I have done here is how the original Leslie has bass speaker installed. However it also had a pair of rotating treble speakers.

So I wasn't wrong at all, there was speakers that rotated. Brushes, most likely. Something that they use in curling irons to prevent the cord from twisting.

[curtisa]

4 hours ago, henrim said:

it also had a pair of rotating treble speakers

In the original Leslie the treble speaker operates on the same principle as the bass - a fixed speaker firing into a rotating diffuser. The difference with the treble speaker is that the diffuser used looks kinda like two trumpet bells pointing away from each other, but only one is hollow and transmits sound. The other one just acts as a counterbalance for the rotating mechanism.

[curtisa]

4 minutes ago, Bizman62 said:

So I wasn't wrong at all, there was speakers that rotated. Brushes, most likely. Something that they use in curling irons to prevent the cord from twisting.

There are examples out there of *rotating* speakers (I think Conn used to make one for their organs), but they're more unusual and rare. The speaker electrical terminations were indeed brush connections on a slip ring. I suspect they're less common because the brushes would probably require regular maintenance and replacement as they wear out.

[henrim]

1 hour ago, curtisa said:

In the original Leslie the treble speaker operates on the same principle as the bass - a fixed speaker firing into a rotating diffuser. The difference with the treble speaker is that the diffuser used looks kinda like two trumpet bells pointing away from each other, but only one is hollow and transmits sound. The other one just acts as a counterbalance for the rotating mechanism.

Thanks, I stand corrected. I always thought it wrong. Never seen the element up close. Although I have seen and even played with a Leslie cabinet ages ago.

But like you said there have been some  other cabinets with rotating speakers. I’m not familiar with any of them but saw some pictures when I did “research” for the build.

[henrim]

Decided to use a stepper motor for now. I may change it to a DC motor a some point but since I have steppers it’s a good way to figure out what speeds I need. Maybe even add some odd patterns if I feel like trying. Like acceleration and slowing down. Now I have a potentiometer for speed control.

I bought some new stepper motor drivers to try out and the one in the picture (TMC2208) drives the motor completely silently at low speeds. The belt I have will add some noise so I may need to change that. I‘ll see. Maybe a rubber band would do.

[curtisa]

Now you're using a stepper motor with a TMC driver, any reason you wouldn't use direct drive instead of belt drive? If you limit the acceleration/deceleration ramps you'd avoid any issues with excess torque as the rotating drum speeds up/slows down upsetting the stepper/driver

[henrim]

1 hour ago, curtisa said:

Now you're using a stepper motor with a TMC driver, any reason you wouldn't use direct drive instead of belt drive? If you limit the acceleration/deceleration ramps you'd avoid any issues with excess torque as the rotating drum speeds up/slows down upsetting the stepper/driver

No other reason but the fact that the belt is already there. And the stepper was not meant to stay there. Anyway, the stepper is in place now and the cabinet is much less noisy. Belt noise isn’t too bad either. I would prefer a dc motor, but wanted test with a stepper because I have them. So it may stay there for a while.

I’m starting and stopping the motor gradually. Which is now just a linear ramp, but I’ll change that to a logarithmic curve. 

Edited March 24, 2023 by henrim

[henrim]

I haven’t finished the cab yet but it has been hooked to an amp and I have played with it every now and then. It definitely needs side vents. Really boxy sounding as is, but I wanted to try before cutting the holes.

I found an old Accutronics spring tank while organizing my workshop. The driver I made years ago wasn’t working but apparently it was just a charge pump chip that had to be replaced. May not be the best ever reverb but way more spacious than the digital one on the DSL20. And that spongy spring sound is perfect fit with the spinning speaker. Too bad I didn’t think about that tank before I made the cabinet because now that tank doesn’t fit inside. Would have been a solid package.