The Lowther Academy
by Jean Giguére
Son & Image Magazine, Volume 8 Number 6, July/August 2007

What Is Progress?
To a beginner, it is an obvious truth that "More" equals "Better". In a loudspeaker, that means innovative design, exotic materials, superior power handling and several drivers are all associated incontestably with more realistic reproduction. What is the point, then, of building a one-way speaker with no crossover and a driver with a paper diaphragm, using a technology dating from the 1930s? What possible interest could such a product have in the fullness of the digital age? Still, if you look at the myriad of makers of new turntables and tube amplifiers, it is clear the phenomenon goes beyond nostalgia. Why such a stubborn determination to deny progress, or even reverse it? In the face of this fervour, I actually begin to wonder if progress has really occurred. Things look very bad.

The Story
In the beginning of electronics, during the 1930s, combining the terms "power" and "amplifier" was almost absurd. It was in this technological context that Paul Voigt created his first loudspeaker. It was meant to make up for power limitations with its high efficiency. The Voigt corner horn speaker, with its considerable sensitivity, made it possible to install an effective sound system in a relatively large room. Its full-range 6-inch driver used a very powerful electromagnet. Later on a second cone was added to extend the frequency range beyond 13 kHz. Shortly afterwards, Paul Voigt entered a partnership with Peter Lowther, a gramophone maker, and the basic concept of the Lowther speaker has changed little since then. After the Second World War, Paul Voigt settled in Canada and left his driver and enclosure ideas in Lowther's hands. The range of horn speakers evolved further during the Fifties; Lowther's research made it possible to replace the electromagnet of the famous Voigt driver with a permanent magnet without diminishing its performance.

The Speaker
The "Academy" Lowther enclosures which this test is about are a little unusual: there are two drivers, both full-range. One of them is located in the top panel and points back and up at 25 degrees from horizontal. The cabinet design can thus be considered a bipolar radiator. On our test examples, the veneered finish was in natural maple and in my opinion the cabinetwork was beautifully done. With a relatively narrow facade and a parallelogram-shaped grill to hide the front driver, the Academy cabinets offer aesthetics that are both classic and contemporary. The front driver is loaded by a quarter-wave horn whose mouth is placed at the bottom of the rear panel. It is folded many times within the enclosure, for a total length of about 1.7 metres. This horn is partially shared with the top driver. The top driver's compression chamber in fact has two openings, the first being connected to the one for the front driver, the second opening into a tuned chamber with a laminar vent. This vent is 36 cm. (about 14 in.) long and is placed on the rear panel just above the horn mouth. No absorbent material whatever is used because the design, dubbed a "Bicor system", prevents the formation of the standing waves that are typical of labyrinth enclosures. Two sets of terminals connect to each driver directly, making it possible to bi-amplify the Academy. Since the drivers are full-range, I don't believe that bi-wiring would offer any benefit.

The Academy enclosures are specifically intended for Lowther's EX driver, their best unit. Normally the Academy is supplied with the EX2 model, but our test units were equipped with the EX3, which at 2.1 Teslas has a magnetic field 0.35 Tesla stronger than the ES2. This translates to one decibel more sensitivity, or 98 dB (at the standard parameters of 1 watt at 1 kHz at 1 metre). One of the EX series' attractive features when coupled with a rear horn has to do with the fact that the driver's chassis includes an acoustic chamber. Working together with the centrally-placed phase plug (or "phase equalizer"), this chamber is tuned and damped specifically to balance pressures on the two sides of the diaphragm, so that only the low frequencies escape through the openings in the back of the driver. This further explains why there is no absorbent material (which would affect sensitivity) in the cabinet. Faithful to tradition, the double-coned diaphragm is made of paper. A half roll of foam glued around the circumference suspends this thin and fragile piece of origami. The phase equalizer is in the centre, a piece of black plastic in the form of a trumpet mute. Fixed in place, it is an evolved version of the "phase stabilizer", the centrally placed nose cone typical of Lowther drivers for over a half-century. Of course this device helped to minimize the frequency cancellations caused by interference between sound waves from opposite sides of the cone. Today's perfected version, joined with the inner surface of the central cone, forms a horn that noticeably improves the reproduction of high frequencies. Finally, the form of this phase equalizer together with the tubes which traverse it make up, along with the rear chamber, the system which maintains equal air pressure on both sides of the diaphragm. Without these parts, the lower the frequency, the more this pressure would become unbalanced, causing forward over-excursion of the diaphragm. These nonlinearities created low-frequency distortion. All in all, this evolved design provides the advantage of front horn loading without the colourations usually associated with it.

The voice coil also benefits from an innovation, this one developed by Hi-Ferric Technology Ltd., a company in the Lowther family. Hi-Ferric's technology aims to apply the benefits of the ferrofluid, which is used in many tweeters, to low-frequency transducers as well. It controls the coil by lowering its temperature and thus reducing the associated rise in impedance and decrease in sensitivity. The Hi-Ferric process adds ferrous metals, mainly cobalt, iron and nickel, to the voice coil composition. When current circulates in the coil, the amalgam generates an electromagnetic field in phase with the coil. Working in opposition to the fixed field of the pole piece, the coil's field raises the velocity of the diaphragm. The effect is to improve transient response. As well, when current stops circulating in the coil the ferrous composite becomes neutral again. It is then attracted to the centre of the magnetic field of the pole piece, so that damping is improved and the oscillations due to resonance and inertia are diminished. I have to mention that the Hi-Ferric coil control system is sometimes contested by Lowther purists. Nevertheless, even though its benefits may be cast in doubt, the process seems to have no negative impact on the speaker's sound. Really, though, who would have expected this driver type to contain so much technology!

Acoustics
The Lowther driver, like a pair of jeans, is reputed to need a lot of breaking-in before it's comfortable. The low mass of its moving portion is only 11.5 grams and the initial stiffness of its suspension mean that the speaker must be run for a while before the desired linear response is obtained. Fortunately I didn't have to start from scratch, since the Academies I tested had already played throughout the Sound and Image Festival. The included graph shows that I was able to measure a very satisfactory frequency response.

These measurements were obtained using an NTI 3382 acoustic pressure probe and the program WinMLS, properly calibrated for the probe. As one would expect for a full-range driver, performance at the frequency extremes is poor. However it must be noted that response from 70 Hz to 10 kHz is situated just about within +/- 3dB. This is a remarkable result considering that it was obtained in my listening room from a high-efficiency loudspeaker without a crossover. The measurements also reveal a tendency to emphasize the midrange from 350 Hz to 2.5 kHz.

Finding the best position for the speakers turned out to require several tries, as did finding the ideal listening position. In my situation the best distance between the wall and the rear of the cabinets, at 35 centimetres, was about equivalent to the height of the horn mouth. This position, a convenient one, was made possible by the ingenious placement of the second driver. I obtained an acoustic focus at one metre from the floor, which corresponds to the height of the cabinet. The significant other for a pair of high-efficiency speakers is of course a class A single-ended triode amplifier, so it was a Connoisseur SE-2 using 300B tubes which applied itself to driving the Lowther Academy for the purposes of this listening test.

Listening
The first time I heard the Lowther Academy, at the 2007 Montreal Sound and Image Festival, I was struck right away by the depth and width of the soundstage. This characteristic accompanied the speakers all the way to my listening room. Their bipolar radiation means that no matter where you are in the room, you perceive a three-dimensional stereo image. However the Academy creates this effect with naturalness and especially a precision that is surprising. On Francine Kay's interpretation of Debussy's Preludes, her instrument's sound was located behind the speakers and the hall reverberation was present. What surprised me was that the illusion persisted even when I was seated in an armchair at right angles to the speakers. The piano remained whole and well proportioned under these conditions. Of course this recording, made with a Sony C48 microphone pair, has a sonic perspective that suits this kind of speaker well. The Lowthers' dynamics also contributed to the realism. The attack of the piano notes was lively, well defined and reproduced without compression. This very subtle recording also set off the Academy's ability to reproduce very fine details. The thin diaphragms seemed to vibrate like the skin of a snare drum at the slightest electronic impulse. The pianissimo passages, instead of creating the impression of repose, communicated the complex emotions of anticipation and exaltation.

The fundamental interest of a full-range driver is that it is a single point source for all the sounds it reproduces. Since the Academy has two sound sources, I was afraid the coherence so typical of the full-range driver might be lost. From the listening position, the top speaker seemed to have the effect of raising the image centre, but the unit itself never made its presence felt as a source. On voices, especially female ones, the timbres were unified and consistent. On Imogen Heap's album Speak for Yourself, the intimate voice of the artist was reproduced with naturalness and finesse. The speakers did a good job of supplying the synthetic textures of the accompaniment, demonstrating the quality of the studio work. I continued with Holly Cole, whose all-acoustic instrumental accompaniment was a complete contrast. The voice on the Temptation album, big and rich, dominated the centre of the image in front of the instruments. The double bass furnished only just enough foundation, but the play of its strings was clear and articulate. Given the Lowthers' affection for the midrange, I had expected a more forward sound, but the image never really came further than the speakers' front panel. Perhaps it is this perspective that makes those generous mids never turn aggressive. The speakers' construction means that the highs won't be crystalline, since they are limited in dispersion and extension. Honestly though, this doesn't really cause any problem in practice, especially since the highs don't drop off dramatically as one leaves the listening zone. At the other end of the range, the lows are pure and genuinely present but definitely retiring. As the volume goes up the bass seems be independently limited, not following the overall level. The maximum excursion of the EX3 driver's voice coil is +/- 1 mm and this speaks to the unit's ability to move a large volume of air.

Because the Lowther was king in the Fifties, I thought I'd get lucky with a Dizzy Gillespie album recorded in New York in 1957. This particular one was a disappointment, though, because the recording had no ambiance and was compressed and limited at the frequency extremes, exaggerating the mid band. In no way did it show off the transparency and the dynamic and spatial performance of the Academy. Fortunately Oscar Lopez' Flashback CD brought out all these qualities. The guitar, front and centre, had a neutral and coherent tone. The attack of the strings, lively and smooth, showed the speed of the drivers' transients. The speakers had a certain sonic fullness without any unfortunate colouration. The percussion of the second piece, Bailando Rumba, floated above the harmonies. The stereo image, big and deep, went beyond the speakers on both sides, and it was easy to forget they were there.

Epilogue
The combination of a Class A triode amplifier and a full-range transducer represents the smallest possible number of elements in the reproducing chain. The goal is to reach a divine level of purity and transparency. The detail and precision obtained depend entirely on the design quality of these few elements. Electronic corrections are not permitted and everything hangs on the physical properties of the components. The Lowther EX3 drivers are a fine example of a mature design, the fruit of constant improvement in conception and material. The passionate audiophile can count on the sure and established value of this legendary make. This type of speaker is certainly not for everyone, because its remarkable rendition of tiny detail, its limpid smoothness, its dynamics and the coherence of its midrange are obtained at the expense of the overall balance of the performance. The Academy is not a speaker that does everything, and it needs a specific kind of amplification for its qualities to outweigh its limitations. As a general rule, acoustic recordings come across very well, but on studio productions of popular artists the results are not flattering. The bipolar concept of these Lowthers adds to their setup possibilities by enlarging the zone in which listeners can perceive an interesting sonic image. The Academy therefore lends itself to the ear of the well-informed music-lover and the audiophile whose daily life turns around music. For the Lowther speaker, progress lies in continuity. Even now in the digital age, the results show that its technological approach and ideology of musical reproduction have a real place among today's offerings. Bend your ear to the Lowther horns and see if these speakers enliven your music.