KTH Royal Institute Technology developed loudspeakers from wood pulp

Loudspeakers from magnetic cellulose membrane

7:02 AM, 23rd November 2013
KTH Royal Institute of Technology research on acoustic applications
The world’s first magnetic cellulose membrane loudspeakers produced from wood.

STOCKHOLM, SWEDEN: The world’s first magnetic cellulose membrane loudspeakers is produced from wood. These flat, sonorous and environmentally-friendly speakers are made with a new material derived from wood pulp – magnetic cellulose gel – which was developed at KTH Royal Institute of Technology. Unlike ordinary speakers, they require no heavy permanent magnets.

Richard Olsson, a KTH researcher in chemical sciences who supervised the doctoral research behind the magnetic cellulose gel, said the new material may open the way for innovations in such areas as acoustic applications for automobiles. 

Olsson and his colleagues at KTH, Lars Berglund, also a researcher in chemical sciences, and Valter Strom, a scientist in engineering physics of materials, recently demonstrated the speakers for the first time. Their paper is published by the Royal Society of Chemistry.

“This is, to our knowledge, the first reported magnetic speaker membrane. The sound quality is at least as good as in conventional speakers – possibly better because of the even distribution of forces created in the membrane,” said Olsson.

The idea is to show the potential of natural and environmentally-sustainable materials in everyday products. “We want to use this first prototype to see how the cellulose can be used in new applications,” he added.

The cellulose comes from renewable wood pulp and involves environmentally-friendly water chemistry. The gel is cast into a membrane which is then allowed to dry. The membrane’s strength is that it has a rapid reaction capability, which means a high degree of precision in sound reproduction.

Ordinary speakers include a large permanent magnet. The speaker cone’s movement, which creates sound waves, is driven by a voice coil that is wrapped around the permanent magnet and attached to the cone.

With the cellulose membrane speakers, the magnetic particles are part of the membrane itself. The KTH speaker has a coil, but it has no direct contact with the cone, so the only thing that creates sound is the movement of air. All of these components can be manufactured at a very small scale.

The technology has potentially other uses. “We want to look at applications for the material that are driven by magnetic fields. It may, for example, be a form of active damping for cars and trains.” It could also involve technology that cancels out noise.

© KTH News

Reference - http://www.kth.se/en/aktuellt/nyheter/nytt-material-ger-unika-hogtalare-1.434583

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