Tone Controls; Treble; Bass; Advanced Controls - Bang & Olufsen BeoLab 90 Technical Sound Manual

Figure 5.34: The Volume control (the ex-
terior circle) and the Mute control (the
icon in the centre of the circle).
In order to unmute the sound, either
press the mute button again, or adjust
the volume.
Note that, if the volume setting of the
BeoLab 90 was higher than the startup
volume when muted, then the volume
setting after unmuting will be the same
as the startup volume.

5.9 Tone Controls

The Tone Controls on the BeoLab 90
consist of traditional Treble and Bass
controls. These are global adjustments
that are applied to all Presets and to
both loudspeakers simultaneously.

5.9.1 Treble

The Treble adjustment allows you to
change the relative amount of
high-frequency sound globally using a
high shelving filter with a fixed
turnover frequency of 8 kHz and a Q of
0.707. Note that the gain at the
turnover frequency is one half the
maximum gain applied by the filter in
decibels. For example, when the gain
of the controller is -4 dB, the gain at 8
kHz is -2 dB.
The Treble control is applied to a global
filter and therefore is applied to all
Presets. It is also is independent of the
settings of other equalisation
controllers in the system such as the
Frequency Tilt, Sound Enhance and
Parametric Equaliser controls. The
range of the controller is from -6.0 dB
to +6.0 dB in steps of 0.5 dB.
6
4
2
0
−2
−4
−6
10 100 1,000
Frequency (Hz)
Figure 5.35: Magnitude Responses, Tre-
ble controller. Note that this filter is ap-
plied to both loudspeakers simultane-
ously.

5.9.2 Bass

The Bass adjustment allows you to
change the relative amount of
low-frequency sound globally using a
low shelving filter with a fixed turnover
frequency of 120 Hz and a Q of 0.707.
The gain at the turnover frequency is
one half the maximum change in gain
applied by the filter in decibels. For
example, when the gain of the
controller is +6 dB, the gain at 120 Hz
is +3 dB.
The Bass control is a global filter and
therefore is applied to all Presets. It is
also is independent of the settings of
other equalisation controllers in the
system such as the Frequency Tilt,
Sound Enhance and Parametric
Equaliser controls. The range of the
controller is from -6.0 dB to +6.0 dB in
steps of 0.5 dB.
6
4
2
0
−2
−4
−6
10 100 1,000
Frequency (Hz)
Figure 5.36: Magnitude Responses:
Bass controller. Note that this filter is
applied to both loudspeakers simultane-
ously.

5.10 Advanced Controls

The Advanced Controls section gives
the user an almost-surgical control
22
over the timbral characteristics of the
BeoLab 90 using a combination of
legacy Bang & Olufsen audio
processing, standard equalisation tools
found in professional studio
equipment, and proprietary processing
available only in this loudspeaker.
10,000
The Advanced Controls of the BeoLab
90 are

Latency Mode

Loudness
Frequency Tilt
Sound Enhance
Sound Design
Parametric Equaliser
5.10.1 Latency Mode
In order to control the Beam Width of
the sound radiating from the BeoLab
90, a customised Finite Impulse
Response (FIR) audio filter is selected
for each woofer, midrange and tweeter.
These filters are applied to each of the
DSP's 18 audio output channels.
However, in order to control the very
low frequency bands, it is necessary
for the woofers' FIR filters to be very
long. One implication of this is that it
takes some time between the moment
an audio signal enters the input of the
loudspeaker and the moment it exits
the loudspeaker as sound. The lower in
frequency the Beam Width Control is
extended, the longer the latency (or
delay) of the loudspeaker.
This ultimately means that there is a
direct relationship between the overall
latency of the loudspeaker and its
sound characteristics – especially in
the low frequency bands. One example
10,000
of this e ect is: the longer the latency,
the "tighter" the bass.
However, this may mean that, for
some sources and program materials,
there is a loss of synchronisation. For
example, in its longest latency setting,
the loudspeaker may be too late to
maintain lip synch with some
televisions or some multiroom
systems. This is why the latency of the