2.1.6 Null Fill
Phase Nulling... NULL FILL is a new and useful tuning adjustment introduced for the first
time with the Aural Exdter Type III. The addition of NULL FILL to the
PEAKING and TUNE controls gives the Type III more power and flexibility
to enhance all types of audio sources. To understand how it works, it is nec
essary to understand a physical phenomenon called "Phase Nulling" which
occurs with all Aural Exciters when the MIX control is adjusted to obtain
high frequency enhancement.
There is a time delay associated with the sidechain signal which is an impor
tant part of the operating theory of the Aural Exciter. This time delay causes
transient waveforms to be slightly "stretched" as the sidechain signal is
added to the main audio path. The "stretched" transients are then perceived
by the ear as more pronounced or "louder". The side effect of the time delay
is a "dip" or "null" in the output equalization curve. The null can be a
desirable characteristic because it compensates for the slight additional
power added to the signal by the high frequency shelving boost. The null
de-emphasizes the frequency range around the TUNE control setting, thus
giving even greater emphasis to the higher frequencies.
There are times, however, when the Phase Null is unwanted. The NULL
FILL control allows the user to "fill-in" the phase null to any desired amount,
thus further improving presence.
2.2 Typical Applications
Operational Characteristics
2-3
The Aural Exciter may be used in many ways for audio enhancement.
Depending upon the requirements, either pre- or post-processing may be
selected. Either source or system optimization, or a combination of both, is
possible.
2 .2.2 Sound Reinforcement
Increase intelligibility For example, a P.A. system may be greatly enhanced by using the Aural
Exciter to increase the intelligibility of the loudspeakers, thus improving
penetration of the sound around comers and in areas usually difficult to fill.
In another case, the source may sound dull and hard to understand. The
Aural Exciter will compensate for this deficiency by adding brightness and
clarity to the sound more effectively than use of equalization alone.
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