AUDIMAX 362 HD, Owner'S Manual, Page: 16 / 19

sensation (and even the coverage area of the radio
transmitter) is related to the average energy, which
depends of the compression of the energy level.
You can see that they are two concepts different.
With audio processors of conventional design, the
expander and the compression were antagonistic
concepts. This does not happen in the field of the
psychoacoustics processors.
Stage 3: Level Input Control
The Audimax 362HDHD has an automatic control
for the input gain. Manual adjustments are not
necessary. The
AGC (Automatic Gain Control)
guarantee that the audio signal enters to the
delicate multiband compressors always with the
same level, avoiding variations on the transmitted
signal.
The AGC is designed to work with input levels from
–10 dBu to +15 dBu, which qualifies to the AudiMax
to work with all types of audio consoles, from DJ’s
mixers to professional broadcasting consoles!
Stage 4: Multiband Compressors
The purpose of the multiband compressors is to
increase the perceived loudness sensation. The
human voice and music will sound more solid, with
better dynamic balance. Still more, the increase of
the average energy of the audio signal is very
considerable, increasing the coverage area of the
radio for A.M. and FM transmissions (for more info
visit www.solidynepro.com).
Multiband technology bases on the studies of
Stevens (ref 1.2.3) about the loudness of each band
frequency and the studies of Zwicker (ref 4) about
its relation with the Critics Bands of the human ear.
The integration time of the ear to reach the
maximum loudness is of the order of 200
milliseconds (ref 5). This time must carefully be
incorporated to the controls of the loudness
compressors, to obtain the desired effect. The ear
will perceive a greater loudness when the band
compressors increase the relative loudness level.
The processor Orion 462 has frequency splitters
with Butterworth filters of 18 dB/octave that divides
the program signal in four frequency bands: low,
low-middle, high-middle, high. In this form, the
multiband compressor in independent form
processes each bank of frequencies. This way is
possible:
1. To increase the total energy , by the use of fast
compressors for bass and ultra-fast for treble. If the
bands were not divided, the compressors with so fast
recovery time would produce a disagreeable sound
effect; the percussion of low frequencies would
modulate the high notes. And the high notes of an
instrument would as well modulate the low tones, of
violoncello, for example.
2. To increase the perceived loudness . This is
because most of the modulation capacity of a
transmitter is generally devoted to low frequency
signals, of less than 160 Hertz. Nevertheless this
information contributes very little to the loudness
sensation, due to the reduced sensitivity of the ear
for those frequencies. Therefore is desirable to
increase the level of the medium and high
frequencies. But this cannot be obtained by simple
equalizing, because the sound balance would be
destroyed. On the other hand, the peaks of high
frequency would saturate the transmitter. The
compression in separated bands allows increasing
between 6 and 12 dB the energy for high
frequencies without altering the tone balance; in
fact, the frequency response continues being totally
flat.
3. To improve the audio quality . Processing
completely eliminate the "flat sound" sensation,
perceived when a sonorous material is
compressed, by means of fast compressors. This
is obtained, additionally to the division in bands,
using attack times appreciably elevated. This
allows that very short peaks of the audio signal
arrive freely to the following processor (peak
clipper), that eliminates them, but maintaining the
psychoacoustic sensation of power associated with
the audio peaks.
Stage 5: Dynamic Equalizer
The Dynamic EQ is a 3 bands audio equalizer that
acts over the threshold of the multiband
compressor.
This technology operates in 3 bands (low, middle
and high) modifying the density of energy (instead
the level) of each band. Is formed by
complementary filters of 18dB/octave carefully
designed to obtain flat response. This built-in
equalizer offers an enormous flexibility. In example:
is well-known that the use of EQ at the console
output has an adverse effect in the sound quality,
since the more a frequency band is emphasized,
grater is the action of the audio compressor
(previous to the transmitter) for that band. Equalize
a band implies to unbalance the entire audio
spectrum. It doesn’t happen with DENSITY EQ,
since its action is coordinated with the following
stages. The boosting of a frequency band is
translated then in a correlative modification of the
multiband compressor threshold, to carry out the
new equalization.
In this form, its action extends to the range of
sounds of very high intensity, where the
conventional EQ’s are inefficient, due the excessive
compression.
Page 16 Audimax 362HD SOLIDYNE