Plane speaker

Flat-panel speakers which can be built directly into the walls, ceiling or floors, will work even if they are plastered, papered, carpeted or tiled over.

Hi-fi afficionados want the best sound possible, but that means finding space for a multitude of speakers of different shapes and sizes, all with their attendant cables. It might sound great, but it’s hardly streamlined.

A new system, developed by a group of German companies, may have the answer – flat-panel speakers which can be built directly into the walls, ceiling or floors, and will work even if they are plastered, papered, carpeted or tiled over.

The system, purSonic, was developed by polyurethanespecialist Puren Schaumstoff, along with Siemens, which worked on the electronics, and Bayer MaterialScience, which supplied the polyurethane raw materials.

Consisting of a series of tabletop-sized, 7mm thick rigid boards which are installed flush with the wall like panels of plasterboard, the panels work in a different way from conventional speakers. Rather than oscillating backwards and forwards to emit sound from a point, they are fitted with a series of vibrating coils on their reverse side which cause the whole panel to flex, emitting sound from the whole surface.

This, Puren claims, enhances the sound quality throughout the room. With conventional speakers, the soundwaves are emitted in a cone shape, and the best sound quality is only achieved where the cones from all the speakers intersect – this is typically a small area, known as the ‘sweet spot’.

Increasing the sound-emitting area eliminates the sweet spot and gives a 3D acoustic effect throughout the room, said Puren. Outputs ranging from 20W sine to 360W sine is said to be able to suit rooms of all shapes and sizes.

The development process proved to be tricky, said Hans Bommer, managing director of Puren. ‘You can’t predict which mechanical properties will make a plastic panel sound “good” using formulas, especially if other challenging requirements, such as lightness and resistance and air humidity have to be met,’ he said.

‘However, it was clear from the start that polyurethane was the material of choice for the project. Polyurethanes can be fine-tuned to optimally fit different applications using building blocks of isocyanates and tailor-made polyols.’

Bayer MaterialScience worked with Puren on this, eventually developing a blend of two polyurethane precursors from the Desmophen and Desmodur ranges, creating a strong but lightweight cellular structure which is highly efficient at transmitting oscillations.

Siemens’ contribution was a digital processor that controlsthe oscillating coils behind the panels. This can be programmed to allow for the properties of the materials behind which the panels are fitted.

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