April 2003

While Genelec's new LSE™ (Laminar Spiral Enclosure) subwoofer technology has been winning much praise, little has been said about the background to this revolutionary approach to low frequency speaker design.

The 'secret' behind the Genelec-developed Laminar Spiral Enclosure technology is the way that a long vent with large cross sectional area has been fitted into a small enclosure. Such a vent allows the movement of large amounts of air at low speed which is necessary to maintain a constant frequency response over the full range of low frequencies but it must be smooth with no acute angles or performance will deteriorate. Like all the best ideas it is clever but basically simple.

It began in Genelec's R&D lab during an evening discussion where different ideas were being talked through. Ilpo Martikainen, Genelec's co-founder, himself an engineer, said that "Suddenly something flashed in my head, I took a piece of paper and drew a spiral. If we could make it from sheet metal, it would make a very long and smooth tube."

Thinking it too difficult to manufacture, the 'spiral' concept was put on hold but a little later Ilpo decided to build some prototypes in his garage.. They measured well in the R&D Lab and so further development work followed. This included a fresh look at how that metal spiral might be manufactured. That problem was solved by Genelec’s own mechanical engineers who designed and made an unique metal bending machine that uses two rollers to draw the metal in where it is bent by a third. That machine is now at the heart of LSE™ production, precision bending metal with all parameters under digital control.

 

The metal spiral is then held rigid by grooved side panels. Following the addition of a bass management system and power amplifier positioned to gain cooling effect from the vent air flow, the LSE™ subwoofer is complete.