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.

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 ).

Bandoneonbook by Hans W. Koch

Hans W. Koch performing Bandoneonbook for laptop
Hans W. Koch performs Bandoneonbook, using the acoustic feedback between the internal microphone and loudspeaker of the laptop.

In Bandoneonbook (2003) by Hans W. Koch the acoustic feedback between the small internal microphone and loudspeaker of a computer is played by opening and closing the laptop, similar to how one would play a bandoneon. Computer software (a MaxMSP patch) is controlled by the keyboard of the laptop and by pressing some keys the feedback will be filtered in different ways. A piece which can only be performed with a titanium-powerbook series of 2001!