Crystal Cable Arabesque Loudspeaker (HiFi-Plus 67)

Glass speakers are not new, and many previous designs have placed emphasis on aesthetics over sound quality. As you can see inside a transparent cabinet, the use of internal acoustic damping largely defeats the object. It’s not impossible to build good sounding speakers without internal wadding – but it makes the job much harder. Consequently, glass speakers got pigeonholed as ‘lifestyle’ products.

That started to change with the arrival of Waterfall loudspeakers from France. With striking, clear cabinets and neat internal construction these sounded way better than anybody expected, proving that glass might well have its uses in loudspeaker construction. But if Waterfall put the material back on the map, Crystal Cable’s dramatic debut Arabesque loudspeaker is tilting directly for a place at the audiophile top-table. With a price-tag of €45K, this needs to do a lot more than simply look pretty; glass needs to become an essential part of the design and construction, not just an aesthetic gimmick.

Having said that, just standing in front of this speaker it is hard not to be impressed by its material content and clean, flawless execution. It’s weight will impress too; despite its insubstantial appearance, the Arabesque weighs 103kg.

Almost more so than any other product, this is one where the input from your eyes is in danger of overriding the evidence of your ears. After all, it can’t be serious – can it? Well, like I said, the price alone adds up to 40,000 reasons why it better had be. Then there are the electrical specs: 95dB sensitivity and a -3dB point of 27Hz from what is, in volume terms, a pretty small cabinet.

Built from carefully cut and mitred sheets of 19mm plate glass, the intricate shape of the enclosure is far from an accident. Each panel enjoys a different width so that no two elements support the same resonant behaviour. But the really clever part of the structural design derives from the use of advanced Comsol FEA software to model both the mechanical behaviour of the cabinet and the gas dynamics of the enclosed volume. Employed by the likes of NASA for product development, it allows a designer to work with incredibly complex shapes in real time, allowing the shape itself to become a critical factor in the resonant behaviour of the system – and resulting in the Arabesque’s complicated but precisely calculated, tapered footprint. Shaped rather like a Comma, the curved tail section is left open to vent the internal volume. Referred to as a friction port due to its tapered form and narrow mouth, the precise dimensions of the neck allow equally precise control of the air mass. This, combined with Comsol’s deep insights into the cabinet’s mechanical behaviour allows the speaker to virtually dispense with internal damping without compromising performance, arguably actually realizing the potential of glass as a structural material for the first time.

In theory of course, you could take things further, with different thickness panels and mitred construction, the joints would introduce steps into the internal or external faces, as well as ruining the appearance. Likewise, parallel top and bottom panels (the only parallel surfaces in the cabinet) are pretty much mandatory. As it is, even using 19mm glass throughout, each pair of cabinets take nearly a month to complete.

But it takes more than a great cabinet to make a great speaker. The Comsol software allows precise tuning of the speaker’s vent, its mouth being partially closed by a slotted 316 grade, stainless steel plate. This is damped to prevent it resonating, while the only other internal damping is an unobtrusive, domed cushion in the base of the cabinet to help control the vertical standing wave.

For once the drivers, that normally get all the attention in a loudspeaker, are in danger of being overshadowed by the striking, clear cabinet, but again it would be wrong to overlook them. The high-frequency driver employed is a specially modified version (employing an amorphous magnet and silver/gold alloy wiring) of the highly respected RAAL ribbon tweeter from Serbia, with an aluminium diaphragm that’s claimed to be lighter than the air it drives up to an upper limit of around 100kHz. To match its polar dispersion, the Arabesque uses three of the latest Scan Speak Illuminator bass/mid drivers, specially modified and arranged in a vertical line. These employ a double skin paper cone with offset lobular reinforcements – the retro version of composite, if you like. These are driven by a powerful motor whose neodymium magnets and contoured housing ensure a small reflecting area in the face of the driver’s rear wave, current hot topic amongst cone speaker designers. The benefit is extended to the minimal but carefully profiled legs of the driver basket, whose elegant curves also serve to minimize reflections as well as offering a pleasing aesthetic touch to the drivers’ exposed backsides.