Interview with Godfried Willem-Raes — 20/03/2019
DF: Can you go back to the first project where you used piezo?
GWR: or the predecessors of piezo! I came in contact with piezo actually in an indirect way. The first piezo element was seignette salt, it was very hygroscopic. If it gets wet it’s lost forever. These old elements you won’t find anymore because they wouldn’t work. Because of humidity, they deteriorate after a while. But those are the first ones that were used as contact microphones, as headphones also, cheap earphones, crystal radios. These are old headphone pieces with seignette salt that are actually broken (fig.1).
DF: Have you done artistic projects with them?
GWR: Yes because we used them as contact microphones at the beginning of Logos, at the end of the 60s. And then only, I think, by the end of the ‘70s, piezo disks with the copper came. Only at the end of the ‘70s. We can look it up, this is the book by one of the producers, and it gives applications of these piezo disks, so if we look at the dates, …’68, but the second edition of '74. And this is the report from the producers, from the factory. I was studying these materials (fig.2). The brass-bond piezo was not on the market when this book came out. It just describes the piezo electric material itself, the new ones that are not hygroscopic. As soon as they came out they started experimenting with it. Contact microphones were sort of trivial application, but my research was very much into what you could do with piezos if you go beyond audio, because they are very good for ultrasound. I used them a lot in the range of 20kHz and 70kHz.
DF: When have you started with the project on ultrasonic?
GWR: Mid ‘70s I think. ’74/75 must be my first project in that realm. And the first big result was the Holosound production, and that was somewhen early in the '80s. So this was a complete artistic full evening production, completely based on ultrasound and ultrasound demodulation. I used piezos a lot. Actually this is a component of it (fig.3). You see these four piezo encapsulated in silicon, this is the preamplifier. And I attach big springs and metal chimes to it, very long ones, and they get into resonance.
DF: So this is not for the ultrasonic?
GWR: Well, it was driven by the ultrasonic signals from the movements that trigger these things: those are the pickups. It was all a feedback system. The space becomes magic, because you move into the space and the sound changes automatically, because of the ultrasound. And the ultrasound gets demodulated and triggers the objects that I attach here on these piezos.
DF: The use of the springs reminds me of some works of Hugh Davies…
DF: So you have made several installations with this kind of thing: How long were the springs attached to it?
GWR: Around 3 meters.
DF: Springs are attached at these piezos, and what is on the other side?
GWR: There are electromagnetic exciters, coils that bring the spring into motion, excited by the audio. So it's an inductive coil to which you send audio… And all these things are reversible. In fact, if you send electricity to it, you can use it to activate the spring. And if you move the spring you make electricity, you'll get a signal.
DF: Does this project have a title?
GWR: Yes, it was applied in Holosound. Holosound exists as a performance, as an installation. as a concert version. But I did many things before that. There was also another piece, called Montage, with all springs installed in here, and people activate all the things just by moving.
DF: How long have you worked to develop all these ideas and installations?
GWR: Well, it’s hard to say, because I'm always experimenting in the lab. I think it's quite long... I did almost nothing else than researching it, making circuits how to pre amplify good… it was not so straightforward. You cannot use just about any pre-amp: impedance matching is important. Then I’m trying to get rid of the resonant frequency. All these ancient things have an inconvenient in that they have a resonant frequency which generally has a peak between 2 and 3 kHz, which makes it sound very metallic and harsh all the time. The thing is dividing circuits to get rid of this proper resonance of the piezo material.
GWR: Well, I have an original Hugh Davies here: look (fig.4) there’s his signature and the date. It’s a real Hugh Davies’ springboard. An original one: I bought it from him in ’74. But this is not piezo. Hugh Davies almost never worked with piezo. He was always working with these magnetic transducers, and he gets them from this (fig.5). This is an old headphone, before the Second World War, and what is inside: there is a membrane in here, a very thin steel membrane, and here there are these two coils on the u-shaped magnets, and when you send the signal to it, because of the magnetism, the membrane starts to vibrate, and you can listen to it. But it’s reversible. It’s a perfect microphone. It’s the same microphone used here. He took them from these old telephones and used them as pickups. You just unscrew it, it’s easy to take it off. It works by induction, this is a permanent magnet, so a metal object that moves in front of the magnet induces an electrical current in proportion to the vibrations of the spring, and you get an electric voltage on the output immediately. The advantage is that it is a non contact device because it makes no physical contact with the spring. With the piezo you always have to make a physical contact, you have to attach something to it, whereas this works at a distance: basically it’s the same system of a microphone used on an electric guitar, it’s only much smaller and you can go to a tiny object with this. I know Hugh Davies had hundreds of these things because he bought them at the flea markets, always. From headphones, old telephones also had them…
Inside there’s the preamplifier circuit, just with the signal conditioning and the filter to make sure it doesn’t sound metallic and behind there’s the line-out that goes to the 4 loudspeakers in a quadraphonic set.
DF: Were you also controlling a sort of spatialization?
GWR: Well, it goes automatically in this case (the first piezo goes in the first speakers, and so on).
I have a mixer board, yes. But in principle it goes automatically, depending on the movements of the people and the sensors. In a certain corner you activate that speaker there, …
DF: How many sensors do you have?
GWR: Normally it’s 3. At first I had many more. But I came to the conclusion that three it’s the optimum: one, two, and the third suspended in a tetrahedron, and I always need an emitter. If you do ultrasound work, you have a tetrahedron, you have one emitter and three receivers, and from the receivers you go to a demodulation circuit, a sort of ring modulator, to bring the signal back to the audio realm. But at first I’ve tried with many more, but they don’t bring more information. With a little math you can just derive all the three-dimensional signals with just three transducers. But in an installation piece you are free of course to have as many as you like. I also made installations with many receivers that use just one ultrasound emitter - and it’s very magical! - just to amplify things like keys, or breaking glasses, or things like that. You can put keys here and by just touching the keys you make a strange noise. And this is because things as keys and glass have a lot of ultrasounds in their audio spectrum,, which we don’t hear, but the system allows to translate that into the audio realm and then it becomes magic, because you have a set keys, you do a “click click” (a small movement) and you hear a very loud sound, and you put them down and it’s gone. And you see no microphone!! That’s quite magic…We did it last November [2018], there were a lot of festivities for the 50th year of Logos, we did many installations, with old pieces… Look what I have here, did I show you this? This is a massive piezo material (fig.6).
All made of piezo-material. It’s heavy and very fragile. You cannot touch it because it has a coat of silver and if you touch it, it oxides immediately and then it becomes less sensitive. This is tuned to 65 KHz and gives an incredibly high sound pressure level, but you won't hear it. This can be used as an emitter, you cannot use it as a receiver. It comes from a laboratory, this is research material. Philips, all the electronic things that have a research department, before that goes into production, have to make prototypes, and all sorts of things. You cannot buy it, it's research material, it’s not supposed to be for sale.
DF: When did you meet Hugh Davies? Here or in the UK?
GWR: I think here, I met him many times. I visited him in England, and that was ’73, I’m sure, but I knew him already. He was involved in the experimental scene in England, after he worked for a while as technician for Stockhausen, in the late 60’s. I played with Gentle Fire - his group - here in Gent, I think it was '71 or something…. But he was also involved in that group around Cornelius Cardew, the Scratch Orchestra… I had contact with these people, also with Cardew, etc…
DF: Do you also have projects where you amplify objects?
GWR: Of course. I want to show you something…
Look, this is from ’71: It’s a monochord (fig.7), but look: it has electromagnetic transducer and piezo and two outputs, so you can have both things connected. One out is for the two piezos - they are mixed internally - the other one is for the microphone, a magnetic transducer, from an electric guitar. This is an early application and the bridge is just on the piezos, without touching in the middle. There’s a pre-amp in the circuit.
DF: Why do you choose to have two different kinds of microphone?
GWR: Because this one is very good for the bass frequencies, and this is very good for scratching sounds, for the high sounds. So it's a completely different sound core. So you can mix the two signals externally. You can also decide to plug only the piezo, or vice versa. The first model was from ’69, but it didn’t have piezos. It’s also possible that I put piezo disks later, as soon as they came out, but this is the very earlier thing that I did with piezos. You have two preamps - two different circuits - one for the piezo and one for the magnetic transducer.
DF: Which is the project that is more representative or more relevant for you?
GWR: With piezo material Holosound is one, and another piece that has a lot of piezo material is Hex, which is a sub-miniature robot orchestra. Instruments are all this size and there are a lot of piezos there, all computer controlled. The title Hex comes from hexadecimal, the composition is completely coded on a little computer. Originally it was a Sinclair ZX81. Hex is made of many boxes with pc boards, with little objects on them, and piezos. And they are directly amplified on the board. Piezos and the board are built together, completely integrated. The objects were driven through the computer with an electromagnetic thing, so you could see the movement of the object. It's a sub-miniature robot orchestra. The sound is amplified and the timbre depends on the tiny objects (little bit of strings, little bit of springs… super tiny things) that are moved.
DF: So did you first meet Hugh Davies and then Richard Lerman?
GWR: Yes I met Richard Lerman a little later (around the ’70). He was also working with piezo, as soon as they came out.
DF: There was a whole international scene…
GWR: Everybody used them, David Tudor, in the RainForest piece, there were lots of piezos in there. Takehisa Kosugi also used them, in the Cage’s production with Merce Cunningham.
There are the reports of the factory, experimenting with different shapes, describing the measurement results. I bought them in the early '70s. And this is also interesting: here there’s my correspondences with a Hungarian factory that produces piezos…I was at the University between '68 and '75.
DF: Did you get in contact with these factories through the University?
GWR: No, I knew people there, an engineer who worked there, was a friend of my parents. So I got, as a child already, many components for free, through this guy who was working at Philips. Because he knew that I loved to play with them, to solder them, so I got free components… The first electric component was given to me when I was a boy, 6 years old, and I got a resistor, from one of the laboratories from University. I was very proud. I got in contact with University people for many things, but University had no production facilities.
DF: Had University contact with those laboratories?
GWR: Not with Philips,.. well the technical high school in Eindhoven had connections because that University was almost erected by Philips, they lived there, there was close connection, but not here in Gent. There was a department of Philips in Brussels, that is where this family member of mine worked in the laboratories there… They were working on the development of loudspeakers basically, also with piezos. You know, these piezos, find applications 'til today in cheap loudspeakers… I also made some.
DF: Were you using different piezo material?
GWR: I checked all kinds of piezo material that I could put my hands on and see what they are good for. I also have piezo transducers which were produced for submarines to measure the distance. I have them also - on 200kHz, I have a complete set.
DF: How can you tune a thing like this?
GWR: You cannot tune it. I don’t have the machinery. You should cut it. And actually, if you read books on piezo you see that it’s a ceramic. That means it’s baked in the oven, and you first make them all, shape them, and you bake them. They solidify and they become this piezo material. So afterwards cutting it generally ruins the piezo. You have to make it right in that shape. If you take a piezo disk you can tune it but you have to be very careful… you see, if I break it, it’s broken! But if I take a grinder and I take off a little bit here [on the edges], I can make it smaller, I can tune them and the pitch goes up…. but you have to be very careful. Big pieces would break. For the Ultrasonic project, for receivers, I tend to tune them exactly to 40kHz by grinding them off. You have to choose one frequency. You can choose 60KHz, or 65, or whatever, but you have to make sure that all your system is tuned to the same frequency. The emitter and the receivers are both tuned at the same frequency. With submarine-thing that is around 200kHz… the problem is if you go up in frequency then the range you get through air becomes problematic, because the higher the frequency, the more dampening you get through the air. They use it on boats, because there the medium is not air, but water. Water is a good conductor for Ultrasound. But in the air, they have a sensitivity of maybe 20cm…which is what not was I need.
DF: So, is the choice of the frequency also related to the space to be covered?
GWR: Yes, yes.
DF: So you haven't done a project with this submarine component material, right?
GWR: No, no, I bought those components to do experiments with. I know someone who has done a project with them, actually, who used these microphones underwater to amplify movements of shrimps in the sea. If you have a decent ultrasound microphone you can get the shrimps’ sound. Warren Burt did that. He is a native American, he emigrated 30 years ago to Australia. He lives in Melbourne.
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