ESSENTIAL HABITECH
THE ULTIMATE COVER STORY Promising the performance of visible speakers, the Sonance Motion Flex Invisible range changes everything, says Habitech’s Gio Scatola. In 1983 Scott Struthers and Geoff Spencer put a speaker in a wall and, arguably, catalysed an entire industry. Since then, the company they founded has been leading the charge to make audio disappear, ultimately with the completely invisible speaker. But as any engineer will tell you, the big design challenge to the wider deployment of invisibles of every stripe has always been sound quality. How do you make a speaker that’s buried in plaster sound like one that isn’t? For Sonance it’s a philosophical challenge as much as a commercial one, as Chief Engineer Todd Ryan explains: “if an invisible speaker could reproduce sound with the quality level of a visible speaker, then that would be the ultimate promise of the brand”. Today, with the arrival of the Motion Flex Invisible range, that promise has been kept.
THE GREATEST WOW OF ALL
It’s taken two years of research into the physics of flat diaphragms to refine the ideal marriage of aesthetics and acoustics. Traditionally the drivers inside all invisible speakers, including Sonance
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models, are mounted to a metal frame and drive the diaphragm directly and simultaneously. But there’s nothing to stop the waves from the mid driver rippling outwards to interfere with those from the bass driver on the same radiating surface, boosting distortion and colouration. It’s a recipe for acoustic disaster and, as it turns out, completely avoidable. Because in a breakthrough for invisible speaker design, Sonance has found a way to isolate discrete wave patterns on a single diaphragm for optimum fidelity. First the team recalibrated its Klippel laser scanning tools (designed to study the micro behaviour of cone diaphragms) to map the movement of flat surfaces, revealing that different drivers produce very distinct responses in the diaphragm: mid/hf drivers create a bending wave motion (imagine a pebble being dropped into a pond and the ripples that it would create) while woofers generate a totally different pistonic movement (back and forth like a piston). Armed with this proprietary knowledge, the team devised a blend of four innovations to ensure that the two waveforms can successfully co-exist on the same panel. They called it Motion Flex technology.
THE FRONT DIAPHRAGM
The new diaphragm is made from FibreReinforced Polymer (FRP), selected for its exceptional temperature/dimensional
stability and leading acoustic and vibrational performance. Covering the diaphragm is a paper, matching the properties of gypsum wall board to allow the topping compound to dry evenly without cracking.
Klippel analysis of flat surfaces reveals that mid/hf drivers create a bending wave motion (top) while woofers generate a totally different pistonic movement
THE TRANSDUCERS
Custom designed for the project, the allnew ‘Wave Flex’ mid/hf driver has a wide response from 30kHz down to lower midrange frequencies where it crosses over with the proprietary ‘Air Flex’ carbon-fibre woofer. As part of the Motion Flex approach, the woofer couples to a chamber of air behind the diaphragm, and it’s the air rather than the woofer itself that drives the panel, producing a uniformly pistonic surface motion.
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