RTW SurroundMonitor 11900 Series, Manual, Page: 240 / 376

8 | Instruments (Display Modes) | 8.3 | The SSA Instrument EN-50 SurroundMonitor 11900 Series
8.3.1 | what is monitored in the ssA instrument?
With the Surround Sound Analyzer surround format signals
can be displayed as:
- Balance between front and surround channels
- Balance of the front L-C-R channels
- Display of front, side and rear phantom sound sources or
correlation of main channel pairs instead or in combination
- Display of dominant sound events, with memory
- Adjustable coordinate system (SPL or loudness)
- Total sound volume indicator for the surround programme
- Low pass filter for low frequencies
- Phase display between adjacent channels
The Surround Sound Analyzer gives you an accurately-scaled
visual representation of the relative volume relationships within
the overall surround sound. The interactions of sound levels
(loudness or sound pressure), phase correlation and level dif-
ferences between all five channels contributing to the overall
sound are converted into an immediately comprehensible visu-
al image. In addition to this, the visual display of the Surround
Sound Analyzer has been designed to ensure that the dynamic
behavior of the displays corresponds to the subjective acoustic
impression, making it possible to understand the balance of
your surround programme immediately, at a single glance. The
Surround Sound Analyzer display is based on the loudness like
ITU BS.1770 (k) or other weighting filters. It equates to the
listening sound pressure level, when the SurroundMonitor units
and the studio monitoring system are properly calibrated. The
axes of the 45° rotated coordinate system use dB SPL, LKFS,
LU, or LUFS scales, with a reference mark that is also shown
in the loudness and SPL displays in the Program Meter
Graphical display of overall loudness
Multi-channel display devices often show the relationships
between the individual sound levels that make up a surround
signal with circular or pie-slice graphics. Despite the great po-
pularity of round shapes we have chosen to use a combination
of a polygon and bar graphs in the Surround Sound Analyzer,
because this makes it possible to display more parameters si-
multaneously and with greater clarity. The polygon is generated
by combining the displayed level values on the scales of the
45° coordinate system. When all channels are set to the same
level with a white noise signal the result is a square, the area
of which is a measure of the total sound volume. The distri-
bution of the four quadrants shows the volume distribution in
the surround system. In addition to this the display also takes
into account the phase correlation and the position of possible
phantom sound sources.
The critical center channel
The balance between the center channel and the L and R
channels is a critical factor in all types of surround sound
productions. We have thus allocated a separate pair of display
bars to this parameter to show clearly the volume differences
between the center and the L and R channels. Another indica-
tor makes it possible to identify the base width of the center
sound source, which can be useful when there is crosstalk into
the L or R channels.
Phase meter for low frequencies
The „enveloping effect“ of the surround channels can be evalu-
ated with the help of a additional correlation display that shows
the phase correlation of the LS and RS surround channels at
low frequencies when the low pass filter is activated. Ideally,
the low-frequency signals (e. g. reverberation) should be de-
correlated as much as possible. The SurroundMonitor units al-
so feature an additional 10-fold phase correlation display that
enables you to check the correlation of all possible channel
pairs and a special LFE multi correlator that measures LF pha-
se of any available surround channel versus the LFE channel.
Loudness-based level control
Loudness-based level control has been recommended for so-
me time now for optimal adjustment of the volumes of several
individual programmes. The SurroundMonitor units support
loudness-based level control on the basis of a defined refe-
rence sound pressure level. To use this feature, the studio’s
monitoring system must first be calibrated against a reference
listening sound pressure level (e. g. 85 dB(A)) with a sound
level meter. Loudness-based level control provides much more
accurate and realistic monitoring of the balance between dia-
log, effects and music.