From Sewing Machine to Rotary Speaker

Guitar players have pedals, sewing machines have pedals. There must be something cool to make for playing guitar with a sewing machine. Sewing machine pedal goes slow to fast. Rotary speakers go slow and fast, and thus an idea was born. I don’t know if this has ever been done before, like most things I am sure it has. But the idea of making a rotary speaker out of an old sewing machine has been on my mind for a couple of years now.

The idea is simple enough but the execution is something else. So I got an old sewing machine and after brainstorming in my head I decided that it would be cool if everything packed up inside the sewing machine case. Once I knew that I thought about the general layout of the speaker, rotary baffle, and motor. Since the point of a rotary speaker is to create a sort of doppler effect in 3D space I knew that what I built should be fairly open to allow sound to travel in all directions. So the first step was to build a frame that was as big as possible while still allowing the lid to slide back over the bottom and latch.

I wanted to build this entire project out of a sewing machine but it became clear pretty quickly that a sewing machine motor was really not going to work. It basically spins too fast and is too loud. Luckily I had kind of figured that would be the case and I had an old fan that I rescued from the garbage. The fan has a small shaded pole motor that is perfect for this project. I removed the metal cage from around the fan and took off the fan blades and that was about it. I ended up just screwing the back panel to the top of my frame motor, switch, power cord and all. then I could just plug the fan into the sewing machine outlet labeled motor and that is all of the wiring done.

The motor drives the rotary baffle with an old turntable flat belt. This tracks nicely on a crowned pulley that I made for the motor shaft and a crowned disc that is the top of the rotary baffle. The difference in size helps the baffle to spin at around 400rpm at full speed, which is the maximum speed of a typical Leslie speaker cabinet. Once the top disc was made I could mount it to a dowel rod that spins inside two plates containing ball bearings from an old roller skate. Since there is a plate with a bearing above and below the top frame bars I can adjust their position to each other to make sure the dowel is perfectly plum and the belt tracks on my pulleys. This works very well however my cheap soft wood dowel ended up warping and that threw everything off. Everything still works for now but there is considerably more wobble to the rotor than when I built it. Simple enough to probably swap that out for a hardwood dowel and everything should work good as new again.

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Below my rotor disc I attached to squares of 1/2 inch thick wood with a piece of 1/4 inch acrylic mounted in between at a 45 degree angle. It would have worked just as well and been easier to just make this part out of wood, but I think the window looks a lot cooler as it spins around and looks are 50 percent of tone anyway.

I waited till the end to cut my baffle board to mount the speaker to. I wasn’t sure that the rotor would work well with just the two bearings on top and thought I would maybe need one on the bottom to stabilize everything, but once I saw it spinning well suspended from the top then I was confident that I could cut out the complete circle for the speaker.

Then I could mount the speaker with some T-nuts and attach a 1/4 inch jack on the side connected to my speaker. I have a Crate V5 amplifier that is perfect to drive the Warehouse Guitar Speakers G8C. Overall I am just happy that an idea in my head came to fruition and actually works, so my expectations were low. The speaker not only works but it also sounds pretty good as well. That being said there are already some improvements I could think to make if I were to build another one.

The biggest speaker that would fit inside the sewing machine case was an 8 inch speaker. This is not necessarily a bad thing but with everything just barely fitting inside the case I have a small speaker baffle and a tiny mostly enclosed space for the speaker. All of that combines to really not give me any bass or ompf from the speaker. Next time I really want to make everything bigger, especially since it would be cool if it worked with my Hammond E100 organ.

Overall a really fun project that is way more inspiring to play with than a pedal or plugin. If you want to watch me build the speaker and here it in action, watch the video below.

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