Speech Coil Choices
Silver or Aluminium?
If the chosen drive units are to be used in a 'live' environment: i.e. wood flooring, minimalist furnishing and colour washed walls etc. silver coils may be the best choice; they will slightly attenuate the top response. Silver coils are also recommended if the speakers are not used regularly, i.e. in a holiday residence or if needed to be stored for periods longer than three months.
For rooms that are carpeted, have soft furnishings, papered walls and curtains (drapes), then aluminium coils will provide the 'attack' that such rooms can absorb.
For aluminium coils, it is recommended that prior to playing music through your speakers, a minute or so warming-up period is given. This is achieved by switching on the amplifier without volume gain, thus permitting the aluminium coil to warm through, allowing the wire to become more malleable. This is particularly important when using your Hi-Fi equipment for the first time after a lengthy period of non-use.
8 Ohm or 15 Ohm?
8 ohm speech coils are favoured by transistorised amplification owners.
15 ohm speech coils are favoured by valve (tube) amplification owners.
15 ohm speech coils should be used where two units are required in one enclosure.
Lowther developed their unique 'HI-FERRIC' coil control system in order to overcome the problem of keeping colloidal ferromagnetic fluids within the magnet's air gap throughout the frequency range of our full-range drive units.
We realised ferromagnetic fluids offered advantages, but except for the higher frequencies we were unable to keep the fluids in place. This was disappointing as we, like many other loudspeaker manufacturers, realised magnetic fluids could offer improved performance. Determined not to lose the advantages ferromagnetic fluids provided we developed our own coil control system.
The Lowther 'HI-FERRIC' coil control system incorporates all the benefits of ferromagnetic fluids with some additional advantages. Lowther's latest 'HI-FERRIC' Coil Control System is based on a compound of ferrous oxides securely encased in a high temperature resistant plastic cocoon which is attached to the voice coil. It remains securely in position throughout the entire frequency range of our full-range drive units.
The 'HI-FERRIC' coil control system, as with ferromagnetic fluids, can assist in maintaining better temperature control. Sensitivity can fall approaching 1.0 percent for every 2 degrees C increase in temperature of the coil. In addition unwanted voice coil oscillations are greatly reduced. The improved damping factor allows for a faster transient response.
The 'HI-FERRIC' coil control system has another advantage. It is actually an energised magnet system in it's own right. As current passes through the voice coil, the ferrous material of the 'Hi-Ferric' system is magnetically energised. As like poles repel and unlike poles attract, the 'Hi-Ferric' system attached to the voice coil is either attracted to or repelled from the host magnet's air-gap, depending on the polarity of the applied signal. As the velocity of the voice coil is substantially increased the transient response time is reduced. Between signals the 'Hi-Ferric' system is immediately attracted to the central position within the air-gap, thus increasing the rate of damping. Unwanted Coil oscillations are therefore reduced to a minimum.
Using the latest method of construction, the inner cone is now isolated from the outer. This is not readily visible, but what is noticeable is that the rim of the inner cone is terminated with a reverse roll. Where once sound frequencies cancelled each other and information was lost, now all that information is retrieved and can be enjoyed. Where once sound frequencies were reinforced by the two cones working in unison at certain frequencies, now there is no over-forward sound reproduced. The frequency range is so smooth, and so much more detail from the recorded source is reproduced, that an entirely new level of listening experience will be enjoyed.