Long Throw Speaker

by Anthea Caddy
Fieldtest with SR-S4 long throw speaker at Tempelhof Berlin. photo by Anne van Waveren

Introduction:

The long throw speaker project will investigate sound as a physical, energetic body within space through amplified cello performance. An exploration of the current technology surrounding long throw sound will be investigated with a means to create a controlled spatial projection of sonic energy.

The research:
This research aims to connect and complete the components of the expanded energetic cello system; the modal system of the cello, its electro acoustic projection through speaker systems and the environment. It details the design of a speaker that explores expanded spatial projection shapes within alternative performance environments. The research is undertaken through an artistic and technical process of researching, field work, design and building and the testing of a number of different long throw speaker designs and environments, culminating in a final art piece.

The cello:
A musical instrument uses its interior energetic vibrational qualities to create sound that is projected into the exterior performance space. Within this space, projected sound will travel and develop before it meets the ears and bodies of the audience. This process is through a complex and highly designed system of vibration of the physical internal and external parts of the instrument. This research will explore the different elements of this sound behaviour, its subsequent projection and phenomena and its direct physical and spatial relationship between performer, instrument, audience and environment.

The speakers:
Up until now there are three different designs of speakers I am looking at; line array, a large parabola and wave field synthesis. Each system has a different approach to harnessing energy; one using a carrier frequency, the other using a parabola to reflect and focus energy and software based to cancel out frequencies to create spatial reflections (research yet to be done).

Research questions:

  1. How far can sound be projected from a long throw speaker?
  2. What is the spatial pattern or distribution of sound by the speaker?
  3. How does the frequency and performance effect the sound projection?
  4. How does the environment effect the projection of the sound signal: what environmental factors such as wind, trees, walls, room effect the sound reflection, absorption, propagation or expand the signal?
  5. Can the signal be controlled?
  6. What are the differences in environments for sound projection, propagation?
  7. Where is the audience positioned? Do they need to see the performer or the speaker?
  8. What effects will the lack of proscenium have upon the sound and its subsequent experience?
  9. Which speakers control sound and cover required frequency bands whilst still maintaining a long throw over a substantial distance?
Fieldtest with SR-S4 long throw speaker at Tempelhof Berlin. photo by Anne van Waveren

FIELD TEST 1

Tempelhofer Feld | Berlin, Germany (former airport) | Speaker test #1 with the TOA Long Throw model SR-S4L

SR-S4L (long-throw) comprises speakers, each with eight 4" cone drivers and twenty-four 1" balanced dome tweeters, all aligned to form a continuous linear sound source. Weather resistant.

Other equipment: Power generator, amplifier, mp3 player, sound recordist.

I tested the TOA SR-S4L Long Throw model, which was generously supplied by TOA Europe to support my artistic research. A line array is a loudspeaker system that is made up of a number of usually identical loudspeaker elements mounted in a line and fed in phase, to create a near-line source of sound. The distance between adjacent drivers is close enough that they constructively interfere with each other to send sound waves farther than traditional horn-loaded loudspeakers, and with a more evenly distributed sound output pattern.

I chose to use cello samples to initially test the projection capacities of the SR-S4L. These samples comprised of different frequencies and timbres of a performed cello which would cover the majority of the frequencies I would use in performance. I chose the Tempelhofer Feld, the former airport which is now a park to test this speaker. I chose this environment as I knew there would be no physical obstacles to potentially interfere with the sound projection of the speaker.

There were two specific areas I was looking at for this speaker; firstly, how far it projected (and what) and what the spatial projection was like, for example did it disperse widely etc.

I found that the speaker threw the higher frequencies (440 Hz and up extremely well). In fact, so successfully that I could not find the end of the signal. What was interesting about this speaker was that it maintained the finer details of the sound it was projecting for a substantial distance. I would estimate this speaker threw a signal of around 660 Hz for over a kilometer across the flat terrain of the airport. (See map).

In collaboration with Australian Council for the Arts, National Institute of Experimental Arts, UNSW, Australia Sound, Energies and Environments Research Group, UNSW, Australia, TOA Europe