Magnetic gel creates light, flat eco-speakers

AUTHOR: Inavate

A substance derived from wood pulp has been used to develop flat, high quality loudspeakers by researchers at KTH Royal Institute of Technology in Sweden. Using magnetic cellulose gel the team were able to remove the need for a large permanent magnet and create speakers where the magnetic particles were part of the membrane itself.

Richard Olsson, a KTH researcher in chemical science, supervised the doctoral research behind the magnetic cellulose gel and worked with fellow KTH researcher Lars Berglund and Valter Ström, a scientist in engineering physics of materials.

The group recently demonstrated the speakers for the first time and published their findings in the journal of the Royal Society of Chemistry.

Olsson believes this is the first reported magnetic speaker membrane and, along with his colleagues, has patented the magnetic cellulose gel, which was created by attaching magnetic nanoparticles to cellulose nanofibrils.

 The cellulose comes from renewable wood pulp. 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.