Audio Note AZ-One Speaker - Manual (Page 2)

redefines not only the quality-price relationship at any level which is important
when making basic comparisons to the competition, but more importantly the AZ
Series speakers offer an emotional quotient of reproduced acoustic performances
that is quite in a class of its own.
The vast majority of directly radiating diaphragm designs have very poorly
matched acoustic impedance resulting in the characteristically low efficiency, in
contrast a horn loaded system where a suitable geometric design of the horn
mouth and internal expansion rate allows the acoustic impedance to be optimised
to match that of the driver across several octaves, resulting not just in higher
efficiency but also in better dynamic power transfer from the amplifier..
This better matching achieves two important benefits, firstly the efficiency is
greatly increased and secondly, the resistive termination presented to the
diaphragm reduces the amplitude of any response anomalies.
The greatest problem of horn loaded systems is physical size. For a simple horn
the lower cut-off frequency is directly proportional to the effective diameter of the
mouth when radiating into free space, for example a cut-off frequency at - 3dB of
50Hz would require a horn mouth area of 3.8 square meter!!
Clearly unsuitable for most domestic purposes.
The most important consideration must therefore be to first reduce the size
requirement whilst maintaining the low frequency response. To do this the rear
of the diaphragm needs to be loaded by an inductive impedance component. This
can be designed by re-configuring the parameters of the horn flare to off-set the
increasingly capacitive throat impedance below the cut-off frequency. This, in
combination with a speaker position that takes advantage of close proximity to
room boundaries (wall or corner) reduces the radiation impedance further. With
corner positioning the bass horn mouth area is effectively increased by a factor of
x16 or x8 when placed against a wall, providing a substantial boost at low
frequencies.
In the Audio Note™ AZ-One Quasi horn, rear diaphragm radiation is controlled by
critically positioned acoustic impedance matched foam, further aiding low
frequency performance by levelling out the amplitude of standing waves.
ROOM PLACEMENT.
In common with our more conventional ported speakers, the Zero AZ Series
speakers are designed to be placed very close and at an angle to a rear wall or
preferably with the rear horn mouth firing assymetrically into a corner close to