SAA7715 Datasheet, PDF (23/36 Pages) NXP Semiconductors – Digital Signal Processor

Philips Semiconductors
Digital Signal Processor
Preliminary specification
SAA7715H
10.3.3 CONTROLS
The equalizer module exposes three controls for each of
the five bands. These are referred to as gain, centre
frequency, and Q. The gain control sets the amount of
boost or cut applied to the particular band of frequencies.
Centre frequency controls the frequency at which the
boost or cut filter is centred, while the Q control determines
the bandwidth (the range of frequencies) over which the
filter operates.
10.3.4 CENTRE FREQUENCY
Centre frequency defines the frequency where boost or cut
will be centred. To set the centre frequency, select the
entry box and type in a number that is within the allowed
range.
10.3.5 GAIN
Use the gain control to adjust the amount or boost or cut.
Move the slider upward (above the 0 dB line) to add boost,
downward (below the 0 dB line) to cut.
10.3.6 Q
The Q parameter determines the sharpness of the filter.
As the value of Q increases, the filter becomes narrower,
thereby reducing the filters effective bandwidth. High Q
filters are useful for reducing speaker resonances, or for
eliminating resonance that may be caused by the acoustic
environment. Low Q filters, on the other hand, are useful
for operating on a broad range of frequencies.
10.3.7 HINTS AND TIPS
Avoid using the equalizer for volume control. This is not the
purpose of an equalizer. Remember, you are only trying to
correct frequency response deviations from some ‘ideal’
response that are due to loudspeaker deficiencies and
perhaps the surrounding environment. Therefore you
should strive to introduce the minimum amount of
equalization that causes the system output to reach your
desired response.
Avoid excessive boost or cut. This can introduce
noticeable coloration of the program material.
10.4 Stereo spatializer
10.4.1 OVERVIEW
In PC listening settings, the quality of the stereo image is
sometimes compromised by the short distance between
the loudspeakers, and also by the physical limitations of
the loudspeakers themselves. The spatializer effect
remedies these shortcomings by applying perceptually
tuned signal-processing to create the illusion of a wider
and more enveloping sound stage.
Users should be relieved to know that relative positioning
of instruments in the original material is preserved. In other
words, tracks that are centre mixed in the original material
remain centred; tracks panned left or right in the original
mix remain left and right panned. The main difference is in
the apparent width and depth of the sound stage, it is as
though the listener is hearing a larger and more distant pair
of speakers, spaced much farther apart than those actually
present.
10.4.2 CONTROLS
The spatializer effect uses only one control to change its
behaviour.
10.4.3 MIX
The mix control sets the intensity of the effect. Control is
straight-forward. Add more effect by pulling the slider
upward; move the slider downward to reduce the amount
of effect.
10.4.4 HINTS AND TIPS
Try a mix setting of about 0.7 as a starting point.
For best results, position yourself between the speakers
and a couple of feet back. Ideally, your ears should be at
about the same level as the speakers, but this is not so
critical.
2001 May 07
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