Tower Speaker Reviews

Like three-button suits, ribbon drivers seem to go in and out of fashion arbitrarily. But there's a pattern. First, they're all the rage for their airy, transparent, detailed sound. Then they're shunned because of inherent technical limitations or their low impedances (which present a difficult load for an amplifier to drive). Or because of the complexities involved in getting them to mate with the traditional cone drivers typically used to produce low frequencies. Or because new materials and technologies have improved the performance of cone and dome drivers, which, being easier to manufacture and use, make ribbons' theoretical advantages not worth the hassle. Then there's a breakthrough in ribbon design and the cycle repeats.

There's another issue: When is a ribbon driver not a ribbon driver? Ribbon purists claim that in a true ribbon driver, the entire moving element (usually made of aluminum) is conductive. The ribbon, often pleated for extra stiffness, is suspended between two electric terminals, almost like the filament of an incandescent light bulb. But instead of being encased in a vacuum, the ribbon is immersed in an external magnetic field that interacts with the field produced when an alternating current (the audio signal) runs through the ribbon, causing it to vibrate.

In theory, a ribbon's movement should be truly coherent (that is, the entire ribbon should move uniformly), which is the ideal. In reality, unless the magnetic field's energy and the ribbon's thickness and stiffness are absolutely uniform, the material will bend or flex, causing nonlinearities in the driver's response. But linearity is possible, at least in theory; with proper design and implementation, a true ribbon tweeter can behave in a nearly ideal fashion. A disadvantage of this design is its inherently low impedance, which requires a transformer.

Compare that to cone and dome drivers, in which alternating current in a coil of wire (the so-called voice coil) creates a magnetic field that interacts with an external magnetic field, causing the coil to vibrate. The coil is attached to the cone or dome, which vibrates as well. Unfortunately, this results in an inherently nonlinear response as the vibration propagates through the driver material from the point at which the voice coil is attached to it. As materials have improved in stiffness and weight, from paper to (for example) sandwiches of aluminum and ceramic, linearity has improved. Today there are some superbly designed, very linear cones and domes.

A pseudo-ribbon driver uses a nonconductive film (such as Mylar or Kapton), on which a thin line of conductive material (such as copper) is etched or deposited to form a sort of flat voice coil that snakes back and forth along the substrate. Like cones and domes, these pseudo-ribbons tend to behave in a nonlinear fashion as the current traverses each leg of the conductor and interacts with the external magnetic field; due to the snaking nature of the conductor, it is virtually impossible for the material to behave linearly. A large proportion of drivers claimed to be ribbons really aren't, in the strictest definition of the term, because they use this type of architecture. Nonetheless, these designs have a particular sound that many audiophiles find attractive and describe as sounding "fast."

Piega's Swiss Ribbons
Founded in 1986 by Kurt Scheuch and Leo Greiner, Piega SA has staked its reputation on its proprietary, "breath-thin" (0.02mm) ribbon tweeter and midrange driver of aluminum foil and neodymium magnets, handmade in its factory in Horgen, Switzerland, which is idyllically located on the picturesque Lake Zurich.

Piega's tweeters and midrange drivers use conductive aluminum-foil ribbons into which, on close inspection, ultraminiature copper elements appear to have been etched or embedded. Whether or not these are true purist ribbons, pseudo-ribbons, or a hybrid closer in nature to a true ribbon but using the coil as an impedance matcher, really isn't important. (Perhaps Piega will tell us in their "Manufacturer's Comment.") What's important is the sound.

I first became acquainted with the striking-looking and -sounding Piega speaker line at a European hi-fi show a few years ago, before they had an American importer. I was impressed by the sleek, aluminum-skinned speakers' appearance, as well as by their extraordinarily airy, open sound. American importer Steve Davis of Sanibel Sound then asked if I'd like to review a system based on four of the magnificent-looking, limited-edition P5 LTD towers. This was around the time I proposed a piece on SACD and DVD-Audio (SGHT, January 2003), so the timing was ideal. I apologize to Sanibel and Piega for the time it took to get this review in print. This was a system I took my sweet time to review and return!

Sleek and Expensive
As the Piega speakers were unloaded and unboxed, I looked forward to listening to a room full of ribbons and to having four essentially full-range speakers instead of the usual wimpy satellites in the back. But four P5 LTD towers at $9269/pair, a P4 C Mk.II center at $1515, and a P Sub 1 powered subwoofer at $3099 add up to $23,152. This had better sound really good, I told myself.

The P5 LTD is a 3-way design featuring one Piega LDR/II ribbon tweeter and one P-1 ribbon midrange, both located about midway in the column and flanked by a pair of 6.5-inch ported woofers made by Vifa to Piega's specifications. The crossovers are at 3.5kHz and 450Hz, and both woofers operate in the same frequency range. Because the ribbon drivers are extremely efficient (97dB/W/m for the tweeter, 100dB/W/m for the midrange), the P5's overall efficiency is a high 89dB/W/m, though the 4? impedance might be hard for some receivers to drive. Then again, if you're spending $23k on speakers, you're probably not using a receiver, though I used the exceptional Denon AVR-5803 and Integra DTR 9.1 receivers for my audition. The P5's claimed response is an astonishing 30Hz–50kHz, ±2dB.

The approximately 8-inch-wide towers are over 5 feet tall and weight about 100 pounds each. A cautionary note: The compact steel base plate doesn't provide a lot of stability; the P5 is not that difficult to knock over, especially when placed on a carpet. Spikes are available as an option for $125/set.