Hemispherical loudspeakers for laptop orchestras

 

hemispherical loudspeaker
A hemispherical loudspeaker as currently used by the Princeton Laptop Orchestra. © Scott Smallwood, Lawrence McIntyre, Dan Trueman, and Perry Cook

With the rise of laptops in music in the 1990s, and more and more musicians using laptops on stage, it did not take long before the first laptop orchestra was founded. Nowadays there are many of them and there is even an International Association of Laptop Orchestras. They are often associated with universities and open not only for music majors, but for all students who want to make music with computers and delve deeper into making music with new technology.

Taking inspiration from the traditional orchestra, one of the aims is to make every laptop diffusing its sound similar to how acoustical instruments do this. To achieve this, every member of the orchestra gets their own loudspeaker and in this way their sound is diffused from one spot in space, similar to how a violin or a trumpet does this. It also makes it easier for the musician to distinguish their own sound from that of the others, and thus have a hierarchical relationship to your own sound in relation to that of others, similar to what is the case in traditional orchestra playing.

Dan Trueman and Perry Cook founded the first laptop orchestra in 2005, calling it the  Princeton Laptop Orchestra (or just PLOrk). To amplify the sound of each player through an individual loudspeaker they used hemispherical loudspeakers designed to diffuse sound from one point into all directions. The history of these hemispherical loudspeakers starts twenty years ago with Dan being unsatisfied with a guitar loudspeaker for his electric violin and looking a more appropriate loudspeaker set-up in the form of a spherical speaker in 1997.

spherical loudspeaker
The first spherical loudspeaker used by Dan Trueman to amplify his electric violin. © Dan Trueman

This was developed further into an instrument called  BoSSA (short for the Bowed Sensor Speaker Array). This instrument  “includes elements of both the violin’s physical performance interface and its spatial filtering audio diffusor, yet eliminates both the resonating body and the strings” as Dan and Perry described. Besides sensors to control the instrument and software to process the sound, this instrument contains a spherical loudspeaker for sound diffusion.

Bossa Dan Trueman
Dan Trueman plays the BoSSA, using a spherical loudspeaker to diffuse the sound. © Dan Trueman

By the time PLOrk was founded, these experiments had evolved in several kinds of hemispherical and spherical loudspeakers. Nowadays they are constructed in such a way that each member just needs two elements to perform in the laptop orchestra: his or her laptop and a hemispherical loudspeaker (with built-in audio interface and six channel amplifier).

PLOrk Princeton Laptop Orchestra
A typical rehearsal of the Princeton Laptop Orchestra: each student’s laptop is connected to a hemispherical loudspeaker, or to a “hemi” as the orchestra members calls them. This is a picture from 2006, and as you can see, the amplifiers were not integrated in the loudspeaker cabinets yet. © Dan Trueman

As Jeff Snyder, current co-director of PLOrk, explained to me why the hemispherical and not the spherical loudspeakers are used for the orchestra. After playing around with both hemispherical and spherical speakers, the hemispherical seemed the most practical, since they can just be placed on the floor, next to the player (and they cost half of the money of a spherical loudspeaker, of course). The acoustical difference between hemisphere and sphere was not very relevant for this kind of application. The loudspeakers nowadays use six loudspeakers but are connected to a mono signal, so each speaker diffuses the same audio signal. Also, to add some power to low frequencies, the “hemis” are placed on a subwoofer.

hemispherical loudspeaker on subwoofer
A “hemi” placed on a subwoofer. In between you see the audio interface attached to the bottom of the hemispherical loudspeaker. © Jeff Snyder

Dan Trueman and Perry Cook on founding the Princeton Laptop Orchestra:

A detailed construction guide has been written by Scott Smallwood, Lawrence McIntyre, Dan Trueman, and Perry Cook, in case you are interested in building one yourself. Other laptop orchestras use slightly different ones, as can be seen from the manual for building loudspeakers for SLOrk (the Stanford Laptop Orchestra). These are still based on IKEA salad bowls, as some of the earlier Princeton versions did as well.

hemispherical speaker
Mounting the loudspeakers in the hemispherical speaker construction. © Scott Smallwood, Lawrence McIntyre, Dan Trueman, and Perry Cook.

During the piece Twilight by Ge Wang—a former PLOrk member, and founder of SLOrk—the members of the Stanford Laptop Orchestra (SLOrk) control their laptops with sensors, and each of them is amplified by a typical SLOrk loudspeaker:

If you want to hear PLOrk live, your next chance is on May 3, 2017. The Princeton Laptop Orchestra (PLOrk), directed by Jeff Snyder and Jason Treuting, presents their spring concert, featuring guest artists HPrizm and Iarla O’Lionaird. Taplin Auditorium, Princeton University, Princeton, NJ.

Doppelbelichtung by Carola Bauckholt

Carola Bauckholt has written several pieces in which the imitation of bird sounds plays an important role. Examples are Lichtung (2011) for string quartet and Zugvögel (2011/2012) for five wind instruments. In her piece Doppelbelichtung (2016) for the first time these “photographic imitations”—as Carola calls them—are confronted with real recordings of singing birds. This piece is for violin and 12 loudspeakers, among them several “violin loudspeakers”: by placing tactile transducers on violins and hanging them in the concert hall, sounds are transmitted through the corpuses of violins.

A tactile transducer violin ceiling
A tactile transducer attached to a violin, hanging from the ceiling. © Carola Bauckholt

Carola brought both worlds of violins and birds together in this composition and both have to be transformed to be able to approach each other. To imitate the bird songs, it is necessary that the violinist listens very carefully to the birds and searches for appropriate playing techniques to be able to imitate the birds as good as possible. But also the birds have to move closer to the violin:  their songs are slowed down, resulting in lower and slower songs. Both bird and violin sounds are notated very precisely in the score:

score Doppelbelichtung Carola Bauckholt
A fragment of the score of Doppelbelichtung by Carola Bauckholt. All bird names as well as the speed change of the recording are notated. © Carola Bauckholt

The twelve audio tracks of transformed bird recordings are played through twelve loudspeakers. Two of these loudspeakers are normal PA loudspeakers. Four of them are small loudspeakers placed in the audience, another small one is used as a monitor for the violinist. Most remarkable are the five “violin loudspeakers”, as mentioned above these violins have tactile transducers attached to them and the audio is sounding through the violin.

set-up violin loudspeakers Carola Bauckholt Doppelbelichtung
An overview of the set-up for Doppelbelichtung with the five violin loudspeakers (violin loudspeaker 5 is playing Specht sounds, which is a woodpecker). © Michael Acker, SWR Experimentalstudio
Violin loudspeakers Carola Bauckholt
The set-up in the concert hall, with the hanging violins, the PA loudspeakers on stage behind the violinist Karin Hellqvist and the small loudspeakers (the metallic objects next to Karin Hellqvist belong to another piece). © Carola Bauckholt

Double exposure—the english translation of the title Doppelbelichtung—is the technique of taking two pictures on one frame of film. In this piece every sound seems to be a sonic double exposure of a violin and a bird: the violin is imitating the bird sounds, which are in turn modified to resemble the violin. By transmitting these sounds through tactile transducers attached to violin corpuses hanging in the air every bird recording acquires spectral characteristics of a violin. The piece is a thoughtful conversation between these new creatures.

Doppelbelichtung has been performed by Karin Hellqvist and the SWR Experimental Studio:

 

Tonewood by Hugo Morales Murguía

Tonewood Hugo Morales
A tactile transducer as used in the Tonewood pieces: 2 cm cork on top, and some felt to not harm the instrument. © Hugo Morales Murguía

Tonewood I (2011) and Tonewood II (2015) by Hugo Morales Murguía are using small tactile transducers with corks attached to their cone. Five musicians play their instruments with these transducers. The transducers are not sounding at all, as long as they are not pressed to any surface. During Tonewood they are pressed against the wood of the soundboards of violins, guitars, violas, violoncellos, double basses or pianos. In this way, their soundboards become a kind of membrane for the transducers. As Hugo describes in the score:

The term “tonewood” generally refers to any wood which may be used in the construction of a musical instrument, specifically string instruments. An intrinsic characteristic of these instruments is the use of a resonant chamber, or sound-box, which not only projects the sound of the instrument but provides personality and quality to the overall sound of the instrument depending on its size, architecture and different kinds of wood used in its elaboration. This piece explores the internal resonances of each instrument and the way these correlate with the external performance space. For this, each instrument is continuously “scanned” through a series of impulses, exciting several resonant modes and projecting different overtones resulting in complex harmonic relationships.

Score Tonewood Hugo Morales
At the beginning of the piece the instruments slowly fade in. © Hugo Morales Murguía

Very minimal material is diffused through the transducers: just a pulse repeated each 80 ms and a sine wave of 659 Hz (pitch e). These are generated by a MAX patch. To scan their instruments the musicians follow a score in which three different aspects are notated. First of all, the volume of the sound diffused by the transducer (thus being the volume of the 80 ms clicks or the 659 Hz). They control this with a volume pedal. The second aspect is the amount of pressure the player uses to push the transducer against the instrument: low pressure, normal pressure and overpressure are the indications mentioned in the score. The last aspect is the placement of the transducer on the instrument, which is indicated by 4 (Tonewood I) or 9 (Tonewood II) numbers.

tonewood Hugo Morales
The nine different spots used for pressing the transducer against the instrument in Tonewood II. © Hugo Morales Murguía

This piece is not played on the strings of the instruments and neither fingers nor bow movements are producing the sounds. For this reason, the five musicians playing this piece turn their instruments around. This allows them to easier access the soundboard of their string instruments.

Ensemble Vortex rehearsal Tonewood Hugo Morales
Double bass player Jocelyn Rudasigwa during a rehearsal of Ensemble Vortex: she has turned her double bass around and is scanning her instrument with a transducer.
Tonewood Hugo Morales
Tonewood II starts with quick changes between normal pressure and overpressure,  a crescendo of the pulses controlled with the volume pedal and the transducer placed on the middle of the instrument. © Hugo Morales Murguía

This is a video documentation of Tonewood I performed by ensemble Modelo62 . Just having the same pulse repeated till nearly the very end of the piece opens your ears for a miniature world of sonic changes, all caused by the resonating bodies of the instruments themselves.

The system of Hugo reminds me a little bit of Ute Wassermann’s Windy Gong, for which she uses a loudspeaker with a cork placed on top. And indeed: Hugo confirmed me that he had been influenced by Wassermann’s loudspeaker after reading about it in Nicolas Collin‘s great book Handmade Electronic Music. This is—by the way—an indispensable book not only for those interested in hardware hacking in general, but also for several hands-on microphone and loudspeaker technologies. Chapters such as How to make a contact mike, The celebrated jumping speaker of bowers county, or Turn your tiny wall into a speaker are great sources of inspiration.

Tone wood II is going to be performed on the 30th of March in Geneva, so if you are close by, you can attend the concert by Ensemble Vortex during the Archipel Festival.

Klangflug by Lara Stanic

Lara Stanic Klangflug flying loudspeakers
Lara Stanic performs Klangflug. © Lara Stanic

In her performance Klangflug (2006 – 2013, several versions) Lara Stanic looks for ways to transmit the airiness and volatility of sound itself to the heavy loudspeakers, needed to produce sounds. By simulating sounds of an airplane taking off on her flute, she sets the loudspeakers free and they start to fly.

This is done by attaching four big helium balloons to four loudspeakers. Lara puts sugar on top of the loudspeakers to keep them on the floor. She starts to play glissandi on her flute now, simulating airplane departure noises. These glissandi are picked up by a microphone and sent to a computer software (a Max-patch), using pitch shifter to  transpose and enlarge the glissandi.  These sounds are diffused through the four loudspeakers with sugar on top. As can be seen in this short demonstration movie, at certain frequencies, especially low ones, the movements of the loudspeaker membrane cause the sugar to fall off. The helium balloon will now ascend into the air, taking the loudspeaker with it:

During the performance the pitch shifters prolong Lara’s glissandi on the flute more and more, enlarging the possible glissando range of the flute. Lara explained to me, that the balance of the weight of the sugar piles, big enough helium balloons and right pitches on the flute is very delicate. The amount of time it takes to free each loudspeaker is variable for each performance, and the height of their flight is depending on how much sugar is left on the loudspeaker. When I attended this performance, exactly this unpredictability was so fascinating: the big balloons and the rising pitches built up the tension, whereas the final taking off of a loudspeaker always came as a surprise.

The movement of the loudspeakers is only visually perceivable in the movie documenting the performance. Evidently, when hearing this performance live, an important aspect is also the upwards movement of the sound. (And if you are curious why sugar is used: I asked Lara and she told me it was just a result of trial and error with different kinds of sand, sugar and other material.)

Lara has created many works for microphones and loudspeakers, another example is Open Air Bach. Other artists have focused not so much on the taking off, but especially on the flight itself of loudspeakers. Works by Lucio Capece, Fabrice Moinet and Genoel Lilienstern are interesting examples (and I will write about these works in the future ).