Audio Note AZ-Three Speaker - Manual (Page 5)

The AZ-THREE is a floor standing, rear loaded, folded quasi parabolic horn design
with a rear facing mouth, and uses two drive units per cabinet. It is very efficient and
offers the amplifier an easy ʻloadʼ, making it highly suitable for our range of superior
quality, low powered valve amplifiers.
As a company, our main aim is to design and manufacture equipment that provides
the maximum sonic performance for the price, and to achieve this we use many
unconventional solutions. In our quest to deliver an affordable, compact, high
sensitivity, wide frequency response loudspeaker to suit ʻreal worldʼ rooms, we
reinvestigated and re-evaluated the main principles of rear loaded horn cabinet
design. This research, coupled with our expertise in driver, cabinet and crossover
development, has resulted in a loudspeaker that not only redefines the quality / price
relationship, but more importantly offers an emotionally engaging performance that is
quite in a class of its own.
If you examine the vast majority of conventional loudspeaker designs, you will
discover that they have very poor acoustic impedance characteristics, resulting in low
efficiency. In contrast, a correctly designed horn loaded system allows the acoustic
impedance to be optimized for the driver across several octaves, resulting in higher
efficiency and better dynamic power transfer from the amplifier.
However, horn designs are not without their challenges, and one of the greatest
problems is physical size. For a simple horn the lower cut-off frequency is directly
proportional to the effective diameter of the mouth; a cut-off frequency at - 3dB of
50Hz, would require a horn with a mouth area of 3.8 square meters.
Clearly unsuitable for most domestic purposes!
So, we had to find a method of reducing the size requirement whilst maintaining the
low frequency response. By re-configuring the size and shape of the rear horn flare,
the (increasingly capacitive) throat impedance is off-set to a point below the cut-off
frequency. This, combined with positioning the loudspeaker in close proximity to a
corner further reduces the radiation impedance, and effectively increases the bass
horn moth area by a factor of around x16 (x8 when placed against a rear wall), which
provides a substantial boost at low frequencies.
As with all Audio Note (UK) loudspeakers, no corners have been cut in terms of
component and driver quality despite the modest price of the AZ-THREE. Both the
woofer and tweeter are the high quality units found in the AN-E, and are combined
with a heavy-duty crossover featuring air core inductors, Audio Note (UK) silver
plated speaker terminals and Audio Note (UK) AN-D internal wiring.
AZ-THREE LOUDSPEAKERS