Sonus Faber Extrema: Why Audiophiles Still Chase This Legend

Some loudspeakers are built to a price. The Sonus Faber Extrema was built to prove a point. Launched in 1991 as the Italian company's flagship, it was founder Franco Serblin's statement of everything he believed a loudspeaker should be: handcrafted from solid wood, built around a radically simple crossover, and able to deliver full-range, room-filling sound from a speaker that sits on a stand.

More than three decades later, the Extrema is still one of the most collectible vintage high-end speakers ever made, and in Chinese-speaking hi-fi circles it's known simply as "火车头", the Locomotive. In our video above we take a close look at a pair here at Audio Image in Malaysia. This is the full story of the speaker, its engineering and why audiophiles still chase it today.

 

Sonus Faber's No-Compromise Flagship

The Extrema is a two-way, stand-mounted loudspeaker with an auxiliary bass radiator. It sat at the top of the Sonus Faber range in the early 1990s, above well-loved compact monitors such as the Minima and the Electa Amator. At launch it cost US$12,500 a pair, plus US$1,500 for its matching stands. For a stand-mount at the time, that was an extraordinary price, and it put the Extrema in direct competition with floorstanding speakers several times its size. Stereophile summed up the thinking behind it: with the Extrema, "performance rules absolutely, price only being a minor consideration."

Calling it a bookshelf speaker would badly undersell it. Each cabinet weighs about 40kg, sits on a dedicated iron stand and reaches down to 35Hz, which is deeper than many floorstanders. It is a full-range loudspeaker that just happens to sit on a stand.

 

火车头: Why the Extrema Is Called "the Locomotive" in China

Among Chinese audiophiles in China, Hong Kong, Taiwan and here in Malaysia, the Extrema is almost never called by its Italian name. It's the 火车头 (huǒ chē tóu), which literally means "train head" or locomotive. The nickname comes from its unconventional shape. Viewed from the side, the cabinet is far deeper than it is tall, and its sloping, sculpted front curves back into a long, heavy body. Sitting on its massive iron stand, it looks remarkably like the front of an old steam locomotive, and the name stuck.

The nickname fits more than the looks. At around 40kg per cabinet, on stands that weigh even more, the Extrema is built like a piece of heavy machinery. It also has the momentum to match: the deep, powerful bass and sheer drive of a much larger speaker. The name has lasted so long that when Sonus Faber released a sharper, modern tribute to the Extrema decades later, Chinese hi-fi media joked that the "Locomotive" had been upgraded to a high-speed train. You'll also see the brand written in Chinese as 世霸 (or 势霸), so a search for "世霸 火车头" or "Sonus Faber 火车头" will lead straight to this speaker.

 

Franco Serblin's Masterpiece

Franco Serblin founded Sonus Faber in Vicenza, northern Italy, in 1983. His approach was unusual in the hi-fi world: he treated loudspeakers as musical instruments rather than boxes of drivers, and he borrowed heavily from Italian violin-making in his choice of woods, shapes and finishes. The Extrema was his first no-compromise flagship. It took everything he had learned from his compact monitors and pushed it further in engineering, materials and scale. For many collectors, it is the purest expression of the "Serblin sound" before the company's later floorstanding designs.

 

Design & Engineering

Up front, the Extrema pairs a 28mm soft-dome tweeter with a 190mm mineral-loaded polypropylene mid/bass driver. Both were premium units of their era, sourced from specialist Scandinavian driver makers and tailored for Sonus Faber. The tweeter is widely reported to be a custom Dynaudio Esotar, and the mid/bass comes from Scan-Speak. Together they cover everything from the upper bass to the highest treble, so voices and instruments come from one coherent source.

The Extrema's secret weapon is its auxiliary bass radiator (ABR), a large bass unit (a KEF B139 in early production) that isn't connected to the amplifier. Instead it moves in response to air pressure inside the 20-litre enclosure, reinforcing the lowest octaves. The result is bass extension down to 35Hz, remarkable for a stand-mounted speaker. It also avoids the port noise ("chuffing") and timing smear that a conventional bass reflex port can add. It's a big reason the Extrema sounds like a much larger speaker than it is.

Serblin believed that every component in the signal path takes something away from the music, so the Extrema's crossover is famously simple. It uses gentle first-order slopes of 6dB/octave at 2kHz and very few parts, so the signal passes through as little circuitry as possible. That keeps phase and timing coherent between the two drivers. It's one reason the Extrema is renowned for its imaging and its natural, unforced presentation.

The cabinet is Sonus Faber at its most sculptural: solid walnut shaped into curves and slopes, finished to fine-furniture standard and paired with black satin lacquer. The deep, non-parallel shape helps break up internal standing waves, and the sheer mass of the build keeps cabinet colouration to a minimum. The matching stands are an integral part of the design, not an accessory. They are massive six-pillar iron platforms that anchor the speaker so the cabinet stays still and the bass stays tight and controlled.

 

The Sound of the Extrema

A well-driven pair of Extremas combines the intimacy and focus of a great monitor with the scale and weight of a floorstander. The midrange has the warmth, texture and tonal richness Sonus Faber built its name on, which is ideal for vocals, strings, piano and small jazz groups. The minimal crossover and compact front baffle help the speakers disappear into a wide, deep soundstage. The ABR-loaded bass has the extension and authority to carry orchestral crescendos, double bass and rock recordings without losing their foundation.

 

Technical Specifications

The Sonus Faber Extrema is a two-way, ABR-loaded, stand-mounted loudspeaker designed by Franco Serblin and introduced in 1991. It uses a 28mm (1.2") soft-dome tweeter, a 190mm (7.5") mineral-loaded polypropylene mid/bass driver and an auxiliary bass radiator, with a first-order 6dB/octave crossover at 2kHz. Frequency response is 35Hz–18kHz (±3dB), sensitivity is 88dB (2.83V/1m) and nominal impedance is 4 ohms, with amplifiers of up to 200W recommended. Each speaker measures 460 x 270 x 550mm (H x W x D), has a 20-litre enclosure and weighs 40kg. The finish is solid walnut with black satin lacquer. The original 1991 price was US$12,500 a pair, with stands at US$1,500 a pair.

 

Amplification & Setup

With a 4-ohm nominal load and 88dB sensitivity, the Extrema rewards an amplifier with genuine current delivery. A high-quality solid-state integrated or power amplifier, or a powerful valve amplifier, will bring out its full bass extension, dynamics and control. Low-powered single-ended triode amps are best avoided. For placement, give the speakers room to breathe. Pulling them well out from the rear wall and toeing them in slightly lets the bass radiator load the room evenly and brings the soundstage into sharp focus.

 

The Extrema's Legacy

The Extrema set the template for Sonus Faber flagships that followed: sculpted wood, obsessive attention to materials and a musical rather than clinical sound. Its influence was so lasting that Sonus Faber later honoured it with the Ex3ma, a modern tribute to mark the Extrema's 30th anniversary, limited to just 30 pairs worldwide.

 

Owning a Sonus Faber Extrema

The Extrema was made in limited numbers, and complete pairs in good condition, with their original stands, rarely come up for sale anywhere in the world. If you're considering one, check the condition of the walnut and lacquer, make sure the drivers and bass radiator surrounds are original and healthy, and confirm the original iron stands are included. The stands are part of the design and very hard to replace.

If you've always wanted to hear what made Franco Serblin's flagship a legend, now's your chance. Watch our video above, then get in touch with Audio Image to arrange a private audition of the Locomotive at our store, or browse our pre-owned hi-fi collection for other classic speakers, amplifiers and turntables.