Symetrix 601, Owner'S Manual

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2-3
Rev 2.2, 10/31/94
eight bass viols may be used. A total of 1000 bass viols in this case would only give an additional
21 dB of level, which is not an inordinate amount given a glance at Mr. Fletcher's equal loudness
curves. Pay attention to this range because the overall musical balance of your program can be
controlled by equalizing or attenuating the 100 Hz range.
2.4.3 Telephone Quality
The ear is reasonably sensitive in the midrange frequencies, and sound restricted to this range
has a telephone-like quality (which is generally why telephone-quality frequency response
covers the 300-3 kHz range).
If you make the 6th octave (500-1024 Hz) louder with respect to the other octaves, the
subjective result is a horn-like quality. If you emphasize the 7th octave (1000-2000 Hz), the effect is
one of tinniness.
The fundamental tones in most music lie equally above and below middle C (261 Hz), from 128 to
512 Hz. As most instruments are rich in the first overtones, the majority of sound energy is found up
to the 2.5 kHz range. Music editors and others engaged in listening to music over long periods
find that listening fatigue can be reduced by attenuating the 5th, 6th, and 7th octaves by about
5 dB.
2.4.4 Lisping Quality
The 3 kHz range delivers a generous stimulus to the ear. At very loud levels the region of greatest
ear sensitivity shifts downward from 5 kHz; this is why many "PA" speakers have broad peaks in this
region. A characteristic of low-level signals peaked at 3 kHz is a "lisping" quality, and the total
inability to distinguish labial sounds such as m, b, and v.
In wide-range lower level systems, a peak in the 3 kHz region has a masking effect on important
recognition sounds, and on others which lie above 4 kHz. Brilliance and clarity are lost and
without attenuation of this region, an unconscious strain with increasing fatigue is felt according
to the amount of 3 kHz boost.
2.4.5 Presence Range
The usual band affecting clarity in male speech is 3000 to 6000 Hz. In a woman's voice, the
fundamentals are roughly an octave higher than a man's, and a woman's range of consonant
clarity lies between 5000 and 8000 Hz (the high-end of this range approaches a region of
hearing insensitivity in humans). Furthermore, the total range of a woman's voice is about half
that of a mans, stimulating fewer hearing nerves, and for this reason, is consequently still weaker
upon reception.
Wide range sounds, especially those of singing voices, have fundamentals with harmonics in the
5 kHz region of good ear sensitivity. Voices that are powerful or rich with harmonics at 5 kHz
sound especially pleasing, clear and full. Male opera singers are particularly favored with 5 kHz
sounds, women less so. In popular music, this range shifts downward somewhat. It follows that
voices deficient in the 5 kHz range can be enhanced in listening value by a generous boost on
the order of 5 to 8 dB at 5 kHz. A secondary benefit of this boost is an apparent increase in level;
a 6 dB rise at 5 kHz frequently gives an apparent increase of 3 dB to the overall signal.
Attenuating the 5 kHz range on instruments gives a "transparent" quality to the sound, providing,
of course, that the remainder of the signal is otherwise wide range. Microphones having a dip in
this region lack the "punch" or "presence" to which we (Americans) are accustomed.
2.4.6 Brilliance
Unvoiced consonants attributed to tooth, tongue and lip sounds are high in frequency, and
reach the 10 kHz range. These frequencies account for some clarity and most brilliance, even
though they contain less than 2% of the total speech energy. This also holds true for musical
instruments; especially percussion. Boosting or cutting this range affects clarity and naturalness.