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each one octave interval, adjust the equalizer controls carefully. No large boost setting
should be used. Generally speaking, there should be at least as many cut settings as there
are boost settings. Working through the spectrum, each channel requiring it is adjusted
keeping in mind the comments above on rolling off the high frequency.
As the adjustment process nears completion, try moving the microphone around in the
listening area. Response dips may be discovered necessitating compromises on the best
setting. Keep in mind that perfect flatness is approximated only in the most specialized
rooms designed for monitor purposes, and small deviations will not be discoverable in
later listening tests.
After one channel has been equalized, the process is repeated for the other side.
Another common test method uses recorded noise on a standard record. The noise record
is played through the system and a sound level meter is used in the listening area to
measure the acoustic level. Usually, the C-Scale setting on the meter is used unless it is a
flat standard sound level meter. Again using only one channel at a time, the recorded
noise is followed through its program, and readings are noted as a preliminary to
adjustments. It may be that the only recordings available are in standard one-third octave
bands. Again an averaging of readings must be made. A first set of approximate
adjustment of the one octave controls is made and followed by another run to compute
smaller corrections to arrive at a desired house curve.
It is possible that a trained ear can attain some improvement by listening and adjusting. A
noise recording should at least be available to provide uniformity of signal level.
Adjustment while program material is being played will probably not lead to a
satisfactory result.
As a final adjustment ve should consider the low-cut controls. It is important that energy
at very low frequency should not enter the bass speakers to cause bottoming of cones
through unwanted excursions. The ear does not profit as much as might be imagined from
an attempt to reproduce the lowest frequencies. Above all, the octave controls should not
be used to boost a deficient bass capability more than a few dB. In the end, if the ear is
best pleased by setting the low-cut controls at a higher frequency than 20 Hz, then you
should not hesitate to do so.
After a satisfactory set of adjustments has been arrived at, all settings should be logged
for future reference on the label provided in the security cover. In this manner, later
experimental adjustments may be made but the original settings can then be recovered.
The security cover should be dropped into place when the work is finished. An equalizer
is a superlative challenge to the knob twiddler that lurks in all of us.
BI-AMPLIFICATION
Many of today's music reproduction systems utilize a technique called "bi-amping". This
is a means by which the high frequency and low frequency speakers are driven by
separate amplifiers. In a stereo system this means that there will be four amplifiers, two
for each channel. There are several aspects of bi-amped systems but this manual will not
discuss them with the exception of one: the crossover network.
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