A new 20cm polypropylene mid/bass driver was developed for the re-engineered 770, mimicking the extended response and low coloration of the original, while upgrading the motor system to take account of modern power handling and dynamic requirements.
Like the original, the driver is built onto a die-cast chassis with large rear ‘windows’ to reduce early reflections back through the cone. Special care has been taken to marry a low-density nitrile surround to the cone, to match its impedance and reduce reflections from the cone edge.
The new polypropylene cone is loaded with minerals to make it stiffer than the original, yielding fast, tight bass that enables the listener to hear exactly how bass instruments are being played. This is balanced by tuning the cabinet and reflex port to a very low frequency, avoiding the ‘one note bass’ that is typical of a lot of bass reflex systems. In addition, the port is strongly flared at both inlet and outlet to smooth airflow and eradicate distortion. Bass extends powerfully and cleanly to below 30Hz in room, which is remarkable for this size of speaker.
The Woven textile soft dome treble unit – true to form, with a high ﬂux ferrite magnet, is engineered for smooth, detailed HF extension. This new treble unit uses a lightweight, damped microfibre dome with an ultra-smooth response, backed by a damped rear chamber that pushes the fundamental resonance well below the crossover region. The quality of this 28mm dome marries perfectly with the mid/bass driver to ensure evenness of character throughout the range of the whole speaker.