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:


A sympathetic piano by Gökhan Deneç

The electromagnets attached 2 mm. above the piano strings to create a sympathetic piano. © Gökhan Deneç

In Chapter Three of my book I discussed several early attempts of creating electric piano’s during the end of the nineteenth century. Often these efforts made use of electromagnets and feedback to keep the piano strings in vibration. The Neo Bechstein was one of the first commercially available results, but did not use any feedback anymore. During recent years new compositions and systems using electromagnets or tactile transducers and feedback for sound shaping and diffusing have been developed, for example by Per Blond, Andrew McPherson and Rama Gottfried (I’ll post about them in the future). Also Wave Train (1966) by David Behrman is related to these kinds of electric piano’s.

The hand-wounded electromagnets, with the permanent magnets inside the plastic reel.
The hand-wounded electromagnets, with the permanent magnets inside the plastic reel. © Gökhan Deneç

Gökhan Deneç has developed a sympathetic resonance system for a piano using electromagnets and feedback through its strings. He developed his own hand-wound transducers for this, using a simple but effective combination of wire, magnets and plastic reels. These electromagnets are placed in a grand piano and hung approximately 2 mm above the strings. The piano strings are attracted and repelled by the magnetic fields caused by these electromagnets. By sending the same signal through all electromagnets each piano string will start to vibrate, depending on how much its partial tones relate to the spectrum of the signal sent through the electromagnets.  A contact microphone (a model similar to an AKG C-411) is attached to the soundboard of the piano. In between this microphone and array of electromagnets a Pure Data patch is controlling and shaping the signal to the electromagnets. As Gökhan explains:

”My first intention was to create feedback to excite the piano strings and then by manipulating it I would create textures. Then I decided to define some possible regions for feedback to occur by sending an initial sound and also accompany the feedback by these textures. Also, I have a filtering algorithm that keeps the feedback under control. […] The sound creation is realised in PureData; there is a generative algorithm that I designed to create a very specific type of sound world. […] What you hear in the video is the generated tones that are created to vibrate the piano strings and because of its nature, they are unique in their own time. I can not repeat the same sounds, there are tons of randomization going on to construct this generativeness.”

This sound processing is controlled by the amplitude of the feedback signal coming from the contact microphone. Gökhan created an algorithm which is generating clusters of ten pitches, relating to the number of our fingers. A detailed explanation about how this all functions can be found in his PhD research. His PhD is entitled Creating sound mass using live sound processing and feedback with sympathetic vibrating strings and was defended in 2015 at Istanbul Technical University.

Gökhan Deneç is continually developing this project, so if you are a composer or sound designer interested in this system and would like to experiment or even compose a piece for this, please feel invited to contact him!

The Pure Data patch with a ten pitch cluster.
The Pure Data patch with a ten pitch cluster. © Gökhan Deneç

An active loudspeaker by Hermann Scherchen

The rotating loudspeaker ball with 32 loudspeakers developed by Hermann Scherchen (source http://www.studiodabbeni.ch/exhibitions/20/hermann-scherchen:-alles-hörbar-machen-i).

Due to his intensive occupation with recording and reproduction of music the conductor Hermann Scherchen (1891-1966)  became aware of the enormous increment of people listening to music through loudspeakers. He was concerned about the difference between the complex sound diffusion during a concert by the whole orchestra and the very poor representation of the music through one loudspeaker (at that time sound diffusion was often still mono). Scherchen aimed for a recording to sound as if performed in the (acoustic) space, in which it was reproduced and in which the listener of the recording was present. To achieve this, loudspeakers should diffuse sound in such a way, that they “trigger” the acoustics of the space. The recording is not anymore a reproduction of a musical event, which had happened in another space and another time, but the recording now becomes a musical event in itself, sounding as if the orchestra plays in your living room.

To achieve this effect, Scherchen invented a rotating loudspeaker ball, or, as it was called by him, „Der aktive Lautsprecher“ (the active loudspeaker). Scherchen looked for an alternative for stereophonic reproduction, which in his opinion could not reproduce the sound perception in a space. The rotating loudspeaker ball was developed to distribute the sound in such a way, that each member of the public would sit inside the „sweet spot“ or actually no sweet spot was existing anymore. This loudspeaker was developed in 1959 and consisted of 32 speakers (215 mm diameter) placed on a 70 cm ball. The weight of the whole construction was 150 kilogram. This ball was placed on a stand and able to rotate in all directions. The music played on this loudspeaker ball was not experimental at all, but for example J.S.Bach’s St. Matthew Passion. (I would love to experiment with these loudspeakers though!)

I only have a very bad picture but apparently listening to this loudspeaker was also done outside (in Gravesano, Switzerland, where Scherchen lived). In the second picture you can see the loudspeaker ball in the middle and the audience sitting around:

A beautiful documentation of an exhibition on Herrmann Scherchen’s electroacoustic research has been made by Luca Frei. Bruno Spoerri wrote a detailed history on Scherahen’s studio in Gravesend (see the article Hermann Scherchen und das Experimentalstudio Gravesano (1954–1966) in the book Musik aus dem nichts).

In this video the loudspeaker ball can be seen in rotation (the music heard in the video seems not to be diffused by the loudspeaker ball though):


More information on this loudspeaker ball can be found in the archive of the Akademie der Künste Berlin and in several volumes of the Gravesaner Blätter:

“Fünf Jahre Gravesano“ (1954 – 1959) in: Gravesaner Blätter No. XIV Volume IV 1959 p. 2.

Technical aspects at the Fifth Anniversary of Gravesano, F. A. Loescher, Gravesaner Blätter No. XV/XVI Vol. IV 1960, p. 6 – 7

Annea Lockwood’s loudspeaker ball  also diffuses monophonic sound through many loudspeakers.