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SOLIDYNE

ORION 462 MKII

4.4.6.1 SRS TruBass

IMPORTANT NOTE

•

SRS WOW

is placed

before

the

multi-band

compressors; therefore SRS WOW

settings interact

with the LF Band compressor and Density EQ settings.
Coordination between the three processing stages
should be achieved for a natural sounding sound.

SRS Labs TruBass

technology is based on the

fundamentals  of  the  human  hearing  system  and
the  psychoacoustics  of  sound.  In  order  to
understand  how  SRS  TruBass

is able to create

the perception of deep bass from smaller
speakers, it is helpful to understand the
psychoacoustic

principle

upon

which

SRS

TruBass

is based.

The  human  hearing  system  exhibits  non-linearity,
which  produces  intermodulation  distortion  in  the
form  of  additional  overtones  and  harmonics  that
do not exist in the actual audio received at the ear
canal.  These  non-linear  effects  are  most
pronounced  at  low  frequencies.  SRS  TruBass

takes advantage of this phenomenon in its
operation.

When  the  human  ear  is  presented  with  specific
harmonic  frequencies  relative  to  a  missing
fundamental  tone  it  will  fill  in  the  fundamental
frequency based on the higher harmonics that are
present.  By  accentuating  the  second  and  higher
frequency  harmonics  of  a  fundamental  tone
present  in  the  audio  signal,  yet  outside  the  range
of  reproduction  by  a  certain  speaker  size,  SRS
TruBass

gives the perception of greatly improved

bass response. For example, if two tones are
generated from a speaker at 100Hz and 150Hz,
the

hearing

system

will

produce

intermodulation component at 50Hz, which is the
difference of the two actual frequencies.

SRS TruBass

generates the perception of greatly

improved bass by taking the difference between the
two actual frequencies.

The  process  of  sound  reproduction  does  not
simply stop  with the acoustic energy produced by
the loudspeakers. The shape of the outer ear, the
auditory  nerves,  the  brain,  and  the  recognition
process  used  to  extract  useful  information  from
those  cues  are  also  part  of  the  listening
experience.  All  of  these  elements  are  used  to
translate acoustical vibrations in the outer ear into
nerve  impulses,  and  finally  into  a  "sensation",  or
perception  of  sound.  SRS  TruBass

creates the

perception  that low-frequency  sounds  are  emitted
from  a  loudspeaker  by  selectively  processing
higher  frequency  bands,  depending  on  the
frequency and amplitude of the fundamental input
signal.

The  brain  extrapolates  this  set  of  boosted
harmonics  to  restore  a  bass  signal  in  the  audio
source that is significantly attenuated or lost by the
physical  limitations  of  the  speaker.  None  of  the
original  audio  is  removed  or  altered.  The  bass
enhancement  is  added  in  such  a  way  that  the
audio  quality  is  not  compromised.  SRS  TruBass

enhancement  is  dynamically  processed,  with  little
or  no  harmonic  boost  when  there  is  no  low
frequency  content,  and  increased  as  strong  bass
is  detected  in  the  audio  source.  After  harmonic
processing a proprietary compression algorithm is
applied  to  control  driver  excursion  and  create
additional bass impact.

In summary, SRS TruBass

selectively enhances

frequencies that the speaker can easily reproduce
to stimulate the ear/brain system to perceive
intermodulation

components.

The

brain

extrapolates these tones back to the much lower
bass frequency that the speaker is unable to
generate.

562dsp  TruBass  control  sets  the  level  of
processed  signal  added  to  the  direct  signal.  This
value  is  strongly  interrelated  with  the  Density  EQ
level. For  high  levels  of  SRS TruBass

, you must

use low levels for the LF band on Density EQ to
avoid an excessive bass processing.

The  CutOFF  control  defines  the  frequency  range
to  be  processed.  The  options  are  40  Hz;  50  Hz
and 60 Hz. At 60 Hz frequencies up to 180 Hz are
processed,  so  you  must  use  moderate  levels  of
SRS  TruBass

at 60 Hz to avoid an excessive

boost in low-mid frequencies. 40 Hz brings a
boosting at very low frequencies, very nice to
obtain deep basses on medium sized speakers.

Take  in  mind  that  SRS  TruBass®  processes  the
signal  previous  to  multi-band  compression.  For
that reason, attack and recovery times of LF Band
compressor  have  great  influence  over  the