LOWTHER - THE COMMANDING VOICE OF QUALITY

The type of loudspeaker drive unit upon which Lowther's reputation has held pride of place for many decades, grew from the twin-cone units invented by P.A.G.H. Voigt. At the same time two sound- engineers, Rice and Kellog, were designing single cone drive units, a pattern which has served for a very long time in meeting listening requirements. However, when the very best possible standards of reproduction were wanted, it was to the twin-cone unit that the experts invariably turned. Oddly enough, patents for both these types of units were lodged within two weeks of each other.

In the mid-1930's , moving-coil loudspeakers, which were rapidly growing in popularity, used a mains energized coil to produce the required magnetic field. To ensure optimum quality from the unit he had designed, Voigt coupled it to a horn loaded system embodying a tractrix formation - again both examples of Voigt's inventive approach to new loudspeaker designing.

Today such loudspeakers are very much sought after, not only on account of their undoubted historical value, but even more so for the excellent sound quality they offer to this very day.

Just prior to 1939, Donald Maynard Chave joined forces with Voigt on what today we would call R & D (Research and Development). Chave, whose name was eventually to become a by-word the world over, for the very best in sound reproduction, became responsible for the design of permanent magnets to replace the old wound-coil methods previously used.

Our original horn loaded designs were created in the main by Voight. He firmly believed that the audio spectrum should be covered by a single speech coil source. Lowther has never deviated from that principle, believing that reproduced sound lacks a degree of life when electronic filters are used.

Donald Chave, the founder member of Lowther, continued the design philosophy, modifying and improving our systems wherever new techniques and materials allowed. Mr. Chave remained with us until his demise in 1985.

Our present Logic Series and Fidelio Series ranges are completely original, based on the balancing of two finely tuned air columns (the Bicor system). A problem in the past has been the necessity to have large cabinets in order to create the smooth bass response that only a horn can give.

H.F. Olson, and many other Acoustic engineers, have shown in their writings that when the mouth area and length of horn is reduced, sound waves reflect back towards the throat and create standing waves. The Bicor systems eliminate this completely by allowing such reflected sound waves to pass through the first air column, and to pass out of the cabinet through the second column. By finely tuning the opposed internal pressures, we are able to add to the control of the speech coil, over and above that created by the magnetic damping provided by the very powerful magnet systems we use. By this method, we keep the generation of back electromotive force to a minimum. Back EMF is a problem inherent in long throw drive units which is normally overcome by using more power and often relying upon the amplifier to assist in the damping control. A further advantage of keeping the speech coil within the gap area is that heat dissipation is allowed through the ironwork of the magnet system allowing adequate power handling, which in conventional systems is carried out within the cross over circuitry.

The cones are made of a cartridge paper especially produced for us. These cones are treated with a compound in order to eliminate uncontrolled cone breakup. During the initial 50 or 60 hours listening time, this unit will continue to improve to a level that makes the midrange response unparalleled by any other unit. During this 'running' in time, the cone surfaces will break up, in a controlled manner, into millions of separate areas. As the frequency response climbs these breakup areas increase in quantity but progressively reduce in size.

Each model in the latest range, (the ‘EX' Series), incorporates an acoustic chamber precisely tuned for optimum performance. Cone assemblies are pressure balanced between the acoustic chamber at the rear and a phasing equalizer fitted to the front. No unwanted oscillations of the speech coil occur. Only bass frequencies will pass through the acoustic chamber, so avoiding bass/mid-range confusion, often a cause of coloration.

At the top end of the frequency range, the inner speech coil itself breaks up into individual areas producing the high frequencies of this unit. In order to allow this to happen we have designed our own adhesive that remains flexible throughout their life, yet firmly hold the speech coil, which is of aluminum wire to the former. A further complication we had overcome was to produce an adhesive that would withstand temperatures of 180 centigrade. In all, three separate adhesives are used on the coil.

Our back centering device is not the conventional fabric type as this would allow air to pass between the weave of the fabric. The horn would then transfer this into very audible sound at its mouth. Both the centre and surround are of the lightest possible material but treated with a compound to give maximum control. The complete diaphragm assembly with suspensions weigh a mere 11 grams including air load. (Incidentally, each piece is weighed on assembly, in order that variation between units is kept to an absolute minimum).

We guarantee our drive units for 1 years. It is however, unusual to see them back in our factory in under 10 years of use, except where Lowther enthusiasts have upgraded using our exchange scheme to take advantage of the new developments in sound reproduction that we constantly strive to achieve.