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Rotary Speaker MKIII - isolation cabinet - Part 1

Part 1

First, a little background...

If you don't know what a rotary speaker is, Google "Jimmy Smith" or "Leslie speaker".

Constructing rotary speakers is an intermittent hobby of mine. In 2011 I built my first from salvaged parts - a motor from a tape deck spinning a coffee filter over an old Fostex speaker, the speed adjusted by a PC fan controller. Here it is:



It garnered a favourable response on YouTube, so I embarked on a more elegant approach, still using salvaged parts but with a little more thought and care going into the design. It took a couple of years to get round to making it but here's the result:


It hasn't received as many views or comments as the first - not that surprising since I make next to no effort to promote my online presence but I feel it was a step forward...

One issue with these things is they have to be mic'ed up to record the effect. So I got to thinking that some kind of isolation could be a solution. Now, some six years later, I find myself ready to move on the next stage - a rotary speaker enclosed in an isolation cabinet. Quite frankly, this is a fool's errand - much easier, and probably much better sounding, would be to use a rotary effects pedal, for which I already have several options. But my hobby is making things so that's what I'm doing.

Although the build is nearing completion, I'll be posting it in instalments as it's been quite an undertaking and I'd like to keep things more manageable. For now, here are the early stages, showing some prototyping along the way.

Here's the rotary mechanism and speaker built into a box. I seem to recall the motor came from an ink-jet printer - it's rated for 12 volts DC. It's rotating a 'tube' mounted above the speaker. The 'tube' (for want of a better word) is an assemblage of plastic parts including sections of a cotton reel, cap from a wood glue bottle and 35mm film canister. At it's heart is a short length of ABS pipe which slides over an aluminium spindle centred over the speaker. Silicon grease helps it spin smoothly and somewhat silently.



This is the box viewed from below showing the motor on the left and speaker to the right. This was still at a prototyping stage - the speaker here has since been upgraded to one that can better handle the frequencies and volume anticipated.



Again, some prototyping. The cone shown here mounted on the tube is an entirely paper construction but I've since opted for a piece of PVC duct pipe which has a wider diameter and seems to improve the overall sound.


Part 2 to follow soon - it involves concrete!

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