Solidyne AUDIMAX 362, Руководство пользователя, Страница: 11 / 19

SOLIDYNE
AUDIMAX 362
Pág. 11
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.
Stage 6 – Energy Bands
Band Energy controls increase the peak density of
the audio bands, obtaining signals with very high
loudness. Knobs act on the recovery times of the
compressors. Each band have a different
recovery time, of variable range.
"Energy Bands" adjusts according to the music’s
style that the radio manages. Turning the controls
to the left you will have a smooth sound (long
recovery times); whereas turning them to the right
you increases the energy for the bands, which will
produce a more “hard" sound with great "punch"
and "sharp" highs (fast recovery times). As
example we say that for melodic music, classic
(academic), etc., in which there is no noticeable
rhythmical support, agrees not to emphasize too
much the Energy Band controls, that is to say, to
use long recovery times. For Rock & Pop is
advisable to increase the energy bands so that the
sound has more "punch".
Stage 7 – Stereo Coder
The sum of the signals is sent to the
stereo
coder
. It uses digital technology to generate the
MPX signal. This technique, created by Solidyne,
allows to obtain a perfect coder with distortion 10
times below the audibility threshold and channel
separation better than 75 dB.
It’s based on the oversampling concept, that
divides the audio signal in 16 samples that are
processed separately at 38 x 16 = 608 KHz. Due
to this elevated sampling rate, the anti-alias filters
works over 500 KHz, eliminating the “phase
rotation” effect at 53 KHz. With this new solution
and the use of advanced technology in each part
of the circuit, residual components of distortion
below -90 dB are obtained.
It is described separately in this manual, the way
to do measurements and reception tests of the
stereo coder (see Chapter 4).