See-Through Speakers

I'm always casting about for interesting high-end products to feature in this blog, so I suppose it was inevitable that I would eventually find the FH001 speaker from a British company called Ferguson Hill. As soon as I saw a photo of this intriguing design, I knew I had to profile it here.

As you can plainly see, the FH001 is a horn speaker made of clear acrylic. Horns are among the oldest speaker designs because they are incredibly efficient, and they also extend the low-frequency range of the driver. As a result, the FH001 boasts an efficiency of 100dB/W/m and needs only 3 to 50 watts of amp power, making it ideal for tube-based power amps so beloved by many audiophiles. And its frequency range is an astounding 150Hz-20kHz (±5dB) with no crossover.

The shape of the FH001's horn was designed to maintain a uniform expansion of the sound wavefront from the circular driver to the oval mouth while minimizing vibrational modes and making the low-frequency rolloff less steep than it would be with a circular mouth. But why acrylic? According to the company, this material exhibits great damping and toughness for its strength-to-weight ratio, and it can be readily formed into complex shapes with compound curves. And the fact that it's clear is way cool!

The driver is a modified Lowther DX3 fitted with a precision-machined aluminum-alloy phase plug designed to produce the best frequency response with the shape of the horn. Lowther's claim to fame is its rare-earth magnet technology that is said to dramatically increase acceleration and damping factors, resulting in exceptional transient response. In this case, the driver is open at the back, preventing the backwave interactions that occur in a cabinet.

Because the FH001's lower limit is 150Hz, a separate bass speaker is required for full-range sound. Enter the FH002, an acrylic sphere 24 inches in diameter with a 12-inch cone driver. The enclosure has six small holes behind the driver, which provide a resistive element to improve power handling without the resonant frequency of a normal port. The in-room measured response is -3dB at 40Hz and -6dB at 35Hz. (Obviously, this still doesn't provide "full-range" sound, which requires another octave below 40Hz.)

To power a pair of FH002s, Ferguson Hill offers a dedicated bass amp dubbed—you guessed it—the FH003. This 2-channel, Class B, solid-state amp provides 100 watts per channel into 4Ω. Normally, the FH003 would be fed from a full-range preamp, and its active crossover rolls off above 150Hz at 12dB/octave.

A complete 2-channel system with two FH001s, two FH002s, and one FH003 carries a price tag of just over $26,000 at the exchange rate from British pounds to US dollars as of this writing. But the coolness factor alone is easily worth that much!