Leslie speakers are fun. I have one ripped from an old organ which i need to fix up a bit to make it more easily usable (add legs/a box, plus I need to wire up a switch to change speed; it has two separate motors rather than any actual speed control electronics!) but my quick test sounded great. It’s basically a large down-facing speaker over a spinning polystyrene scoop, would actually be easy to build. some kind of motor/turntable and weird-shaped styrene or other material constructions to create different sounds could be interesting
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Salut Harold 
Fascinating topic; I’ve been exploring unconventional speakers in a studio and performance setting for a while now.
My findings so far – except for what has been cited already – revolve around speakers with a diffusor: take a regular speaker, mounted in a regular enclosure or on a large plate (open-back), and put a plate of metal/wood/acrylic on top of it, so as to block all sound (must be airtight). Then pierce a large hole in this plate, more-or-less aligned with the center of the speaker, but smaller than it. The sound diffuses at 180 degrees (like radio waves in a radar), and gives a very different feeling than traditional unidirectional speakers. I’m experimenting with hole numbers, sizes and placements and getting very varied frequency responses.
Also interesting (to me): dropping/attaching various objects (metal, cardboard…) directly on loudspeakers cones, or blocking the travel of the coil in various ways to create distortions/rattlings. Requires some assiduous dumpster diving to find old speakers to experiment with 
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Oh, bonjour Matthias ! I was just reading your interview on Hannes’s blog.
Horns didn’t cross my mind but they’re indeed a great solution. + I guess you’d need less power to get the same dB. Reminds me of this great festival that took place for a few years in the French Alps called Echo, maybe some of you know it. I got some images for you :
12 tons horns. In the mountains. Here’s their website. I found the pictures on the 2015 page, which is also translated in English.
Wow that’s some great ideas. I’d love to hear how it sounds.
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I’ve been reading about the various speakers used with the Ondes Martenot and I really want to try creating something similar to the Palme speaker. Has anyone tried anything like this? It looks like the transducers are somehow connected straight to the bridge that the strings are connected to, so they get a stronger excitation signal than if they were relying purely on sympathetic vibration.
I imagine a zither could work really well for this, but I’m going to try some experiments with my guitar and cello once I get ahold of a properly sized transducer.
EDIT: forgot to post this article as well–goes into much more detail about the Palme itself and mentions an instance of someone who seems to have created a similar device from a zither.
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I’m not sure this answers your question but I hope it’s interesting enough for this thread to share:
For a few years now I’ve used a Vibesware GR-1 Junior, which is this magnetic transducer on a gooseneck that you set up on a mic stand. The way it’s supposed to be used is as a hands-free EBow, although more realistic in the way it feeds back since it has a wider magnetic field and vibrates several strings at once. How I tend to use it is plug a synth into it and then resonate some other string instrument (or a sheet of metal, it can give you some very interesting results as well).
I tend to use a squareneck dobro as the resonator, mostly because it’s what I have lying around but I also think its trebly metallic tone is very suitable for this type of application and also since its strings are further away from the fretboard, it doesn’t cause fret buzz as easily, which I’ve noticed this type of setup is very prone to with fretted instruments.
I also, just personally, prefer the diatonic tuning.
One thing I’ve noticed that is very prominent is that depending on the transducer’s position across the string it emphasizes very different harmonics, very similar to playing harmonics with your finger. I tend to find positioning it around the 4th fret to give the richest sound in terms of higher frequency harmonics, but that is totally a personal preference.
Here is an example of a synth by itself and then it going through the dobro’s strings, picked up by a contact mic (there is some bleed from a harp being played but I hope it’s fine for demonstration purposes), both completely dry otherwise:
I hope you found that useful. The sound I’ve been going for is very different from what I’ve heard of the Palme speaker (what I’ve heard of it has been imo too subtle in its effect to my purposes and I’m also not really a fan of its chromatic tuning) but the techniques are at least similar.
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There must be something in the air. I’ve been recording lately with a guitar & transducer setup that was originally inspired by the Palme (but also by David Tudor’s Rainforest, and sustainer technologies like @oot is using), and @tristan_louth_robins recently posted a nice transducer- & guitar-based piece for the latest Junto.
I’ve used transducers / bass shakers to resonate electric guitar before too, which yields a less Ondes-y sound since, as with @oot’s setup, the resonated instrument isn’t inherently acting as a speaker, so you have the option to completely eliminate the “dry” signal and record or listen to the strings alone.
I also have a cheap electric lap steel that I initially bought to use with transducers as a compact set of sympathetic strings, but so far I’ve been too distracted playing it as a lap steel to use it that way yet. I’ll get around to it eventually.
Oh, and cymbals are amazing too. For the Métallique diffuser sound.
Out of curiosity, how, uh, “fiddly” is the GR? Do you find you have to place it very carefully and leave it there, or can you get nice results from changing the position while playing? The clip sounds great, by the way – I’d love to hear it in context with the harp. Have you released recordings with this setup?
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Baking trays with water sound really interesting!
The way I use it is usually to place the guitar on a stand and then adjust the GR-1’s stand against it, which is fiddly in the way goosenecks very often are – you turn it and find a sweet spot only for it to immediately slouch that cm or so from that position when you let go. I tend not to touch it once I’ve set it up simply because I always have some other instrument in my hands.
Moving an instrument like a guitar around it as it’s intended does however work really well and while the amplitude is quite different across the string, the same is true with the frequency content of the input signal, as you heard in that clip. I like using it with a compressor as often inputs that are less consonant with the string’s root note is are more interesting.
It does crossfade cleanly between strings (completely different from something like an EBow), sounds very interesting to do with percussion.
Not yet.
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At my previous job I had the chance to listen to a pair of these Avant Garde horns with 4 stacked subwoofers (6 seen in the first photo here). Can’t remember exactly but I think they collaborated on some sort of audio installation recently as well? The horns sound amazing, but were very tweaky to dial in.
Wow, this is a fascinating topic of discussion! and thanks to @synthetivv for mentioning me and getting me involved in the chat. I’m looking forward to checking out some of the links that others have shared.
Yes, I’m a big fan of transducer/exciters for resonating surfaces. For the past year I’ve also be experimenting with the great DIY approach of ‘corked speakers’. I first came across this in Nicolas Collins’ wonderful book, Handmade Electronic Music many years ago.
All you do is find a decent sized speaker - say 8-10 cm in diameter - and affix a cork (ideally a fat champagne-style cork) to the centre of the cone. I made a few of these by fixing the corks with some hot glue to speakers of varying dimensions. Basically it’s a crude driver, whereby whatever signal/frequency you send through the speaker (depending on the amplitude/signal strength) will cause the cork to move/oscillate in tandem. You’ll get a great result by using pure waves at a frequency anywhere between 10-100 Hz, depending on the speaker, amplifier, etc.
I’ve had some interesting results by placing them in contact with resonant surfaces like baking trays, cymbals and wine glasses (be careful with this one though!) Aside from the resonance factor, you can place objects over the moving cork to create all kinds of rattling, shaking and sibilent sounds (alfoil and crumpled paper are particularly fun).
Best, TLR
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I have a pair of Vidsonix Ghost transducers that I added a pair of strong magnets to - so they could clamp on to large metal surfaces. Good fun!
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I too want to explore this, and have been designing a modular instrument of my own that will use transducers and strings inside its own case to turn it into something of an acoustic feeling instrument I want to use contact mics and piezos as well as spring reverb to be able to create feedback loops, as well as having a clean output from the strings themselves that can be mixed with the synth signal.
My question about transducers: what are people using to drive them? Would it be enough to use a VCA or output module straight to them?
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I have this question too!
When I was first experimenting with transducers, I used a Behringer bass amp that I had lying around, cut the wires that ran to the speaker, added alligator clips, and used that. That drove bass shakers & cymbals very well.
With guitars, I’ve mostly used battery-powered mini amps. The Dean Markley GT 1000’s headphone output can pretty easily be turned into an external speaker output by cutting a trace or two and replacing a resistor with a jumper, and that works very well if you’re going guitar pickup -> amp -> transducer (which you aren’t). The Marshall MS-2 contains a really similar-looking circuit (they’re probably both built by the same factory somewhere) but different voicing that I didn’t like as much for feedback.
For the Vulneraries albums I’ve been using a Blackstar Fly 3 with a 1/4" speaker output I added following these instructions: http://diy-fever.com/amps/blackstar-fly-3-review-mods/. It can provide more than enough power for our purposes, the batteries seem to last a nice long time, and it has a pretty flat frequency response compared to other mini amps.
But I’d love to find a solution that was a little more compact, flatter, or both, and if it was also a Eurorack module… hell yeah. Pulp Logic makes/has made a few different “driver” tiles, but I don’t have a case with 1U rows, and I think I’ve heard they’re not especially high-power.
(If an admin wants to move this into a transducer thread at this point, I’d understand.)
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It really depends on the transducer and how hard you want to drive it. If you want to drive an exciter or small speaker at audio rate then a small audio amplifier will work well. I often use the little 12V class-T (Tripath marketing for a class-D) amp boards that you can get on ebay for around $10. They are stereo, small, efficient and sound alright.
If you want something DC coupled the Koma Field Kit looks awesome.
If you are working with real small currents I have a DRV 1U Tile that will deliver a bit more than 50mA into a load. I use it to drive small speakers, exciters, meter movements, tiny motors etc… It works well with loads that have higher impedances than a typical 8 Ohm speaker since it will current limit on a pretty low voltage. HiWave was making a 32 Ohm exciter but I think it is no longer available.
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Thank you! Going to try out the Class-T amp board for this project. I think this could be very useful for people wanting to experiment with creating their own speakers, back on topic, too!
@synthetivv, I might try using something like the Blackstar for when/if I eventually make a set of portable “acoustic” speakers for electronic instruments a la Ondes. It sounds like a workable solution.
LOVE Vulneries by the way, I’ve felt very inspired by it and want to try something similar with my resonant case when it’s finished and a Celtic bouzouki!
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Do you place these snugly against the objects or just up next to them? My intuition tells me that if the cork loses contact with the object within the cycle, it would produce artifacts similar to clipping but I’d love to be completely wrong on that front.
Yep, more often than not I would make sure the cork is in consistent contact with the surface/object - which is easier to maintain if the signal is relatively stable or un-complex (i.e. set or drifting frequency; pure/sine waves).
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I’ve had a long-time infatuation with Stig Carlsson’s speaker designs, in particular the Sonab OA-5. Perhaps not too exotic if you are from Sweden. They were quite popular there.
Whilst they form a stereo pair, instead of directing sound toward a focused listening point they were designed to instead throw sound all around the space omnidirectionally.
Some of his other designs:
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