Very few loudspeaker companies can claim to have created a unique technology, but the Swiss manufacturer Piega owns that distinction with its coaxial ribbon driver. Since 1986 Piega has built, from scratch, the ribbon drivers found in all the company’s upper-end speakers. In fact, in 2014 Piega sold its 100,000th pair of ribbon-based speakers, with every single ribbon made in-house. That’s quite an achievement.
Indeed, the company was founded on the ribbon driver; “piega” means “fold” in Italian, a reference to the pleats in the diaphragms of its first drivers. Note that although Piega calls its drivers “ribbons” they are technically planar-magnetic designs. Nonetheless, I’ll brave the inevitable deluge of emails from the audio pedants and refer to the drivers as ribbons in this review. (See the sidebar for a discussion of the distinction between a ribbon driver and a planar-magnetic.)
Although Piega is far from the only company building ribbon drivers, what is unique to Piega is the company’s concentric ribbon midrange/tweeter module. This amazing piece of audio technology positions a ribbon tweeter inside a larger ribbon midrange. Also called a coaxial driver, a concentric design is a true point source, with none of the nodal cancellation that results when the midrange and tweeter are physically separated on the baffle. The midrange and tweeter outputs combine perfectly no matter what the listening height, listening distance, or listening axis. The Piega coincident ribbon measures about 8" x 7.5", with the tweeter occupying a 1" x 2" rectangle in the center.
Piega has been making a series of speakers with this concentric ribbon for many years, but recently updated and improved its technology for the new Coaxial line reviewed here. This line consists of three models, the stand-mount C311 along with the floorstanding C511 and C711. All three feature the same coincident midrange/tweeter; the difference is in the cabinet size and the number of woofers and their dimensions. Upgrades to this new version of the coincident driver include stronger neodymium magnets and pole plates made of high-strength steel, both of which increase the driver’s sensitivity. The layout of the conductors that are bonded to the diaphragm has been revised, and the diaphragm has a new damping system. On the woofer side, the bass driver is entirely new, with titanium voice-coil formers, a new suspension, and a coated-aluminum diaphragm that is reportedly stiffer than its predecessors. In the three-way C711 two of the 220mm woofers are active, and two are passive radiators. Sensitivity is a highish 92dB, making the C711 a fairly easy load for an amplifier.
Another distinctive Piega technology is the extruded aluminum enclosure, which Piega was using long before it became de rigueur. In addition to internal horizontal braces, the enclosure is lined with a viscoelastic damping material to suppress resonances. Finally, the cabinet is put under “controlled tension” to further reduce vibration.
The C711 is a moderately sized speaker with a slim profile. The enclosure curves toward a rounded point at the back, forming a parabola when viewed from the top. The speaker is supplied with an optional bottom plate larger than the speaker. This plate has four corner protrusions for attaching rubber feet or spikes (I used the supplied spikes). Two pairs of binding posts are provided for bi-wire connection. My review samples were finished in black anodized aluminum, although polished aluminum and white lacquer are available. Piega also offers a full range of RAL colors at an extra charge. The magnetically attached grilles are slightly inset in the cabinet, giving the speaker a sleek and streamlined appearance. Build-quality and fit ’n’ finish are very high, just as you’d expect from a premium Swiss-made product.