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Contact Information
Phone:
765-649-8111
Toll Free: 1-800-428-6306
FAX : 765-641-7261
Postal address
3273 N. State Rd. 9
Anderson, IN 46012
Email- Click here
Hours
11:00 am to 5:00 pm Monday - Thursday
(Fridays & Saturdays by appointment only)
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Basic Equalization
The purpose of basic equalization is to provide a flat response from
the speakers that matches the output of the console as closely as
possible.
If your system was installed by a competent sound contractor; it was
tested and the equalization was set for maximum performance and should
not need to be changed. Any changing you may need to do should be
accomplished using the equalizer on your mixing console.
Before equalizing a sound system the gain structure must be optimized.
Start with the input and output gains on all electronics in the signal
path all the way down. If the signal path has an equalizer, it should be
set to 0 dB. Also compression/limiting must not be operating during gain
optimization.
Once the measurement microphone has been positioned for each passband of
interest, the level of the appropriate amplifier is to be turned up
until it matches the adjacent lower passband with a pink-noise source.
Whenever possible use filters to cut rather than boost to flatten the
response. If an adjustment requires more than 3 to 6 dB of cut or boost
at one filter as compared to the adjacent filter, you need to look for
problems outside of equalization. Start by checking for structural
vibrations and transmission paths, or electrical oscillations in the
system's wiring as the source of the problem.
For subwoofer-to-low frequency equalization, the slotted grille of the
microphone should be placed directly on a hard, smooth surface like a
concrete floor or finished plywood. Walls, ceilings, or stage-fronts
should be more than double the distance between the speaker and the
microphone to keep interference at a minimum.
When checking the low frequency-to-mid frequency equalization, place the
microphone half way between the speaker system and any large flat
surfaces (i.e. walls, ceilings, stage-fronts) and centered between the
drivers to be tested. This combination works together to minimize the
acoustic reflection. Also use this position to check the crossover's
smoothness.
For the mid frequency-to-high frequency equalization, adjust the
microphone vertically to be centered between the drivers being tested.
The process of program equalization creates a pleasing tonal balance
much like the contouring done in a recording studio, on the mixing
console via the input EQ and levels at the sources rather than at the
main front-of-house equalizer.
The final step is known as restoring unity gain. To do this, a pink
noise is run through the system with the equalizer bypassed and the
overall broadband level noted. The ambient noise level should not be
significant. Next, reinsert the equalizer into the signal chain and note
any change in the broadband level. Make adjustments until it matches the
bypassed level. To go down, adjust the equalizer's input gain, to go up
adjust the equalizer's output level. If you only have one gain control,
use it in either case. Unity gain has been restored.
The process is now complete and the sound system's performance should
exhibit the best frequency response and dynamic range.
EQ (equalizer) A class of electronic filters designed to augment or
adjust electronic or acoustic systems. Equalizers can be fixed or
adjustable. Indeed, in the early years of telephony and cinema, the
first equalizers were fixed units designed to correct for losses in the
transmission and recording of audio signals. Hence, the term equalizer
described electronic circuits that corrected for these losses and made
the output equal to the input. Equalizers commonly modify the frequency
response of the signal passing through the; that is, they modify the
amplitude versus frequency characteristics. There are also fixed
equalizers that modify the phase response of the transmitted signals
without disturbing the frequency content.
Gain The amount of amplification (voltage, current or power) of an audio
signal, usually express in unites of dB (i.e., the ratio of the output
level to the input level). For example, amplifying a voltage signal by a
factor of two is stated as a voltage gain increase of 6 dB.
Compressor A signal processing device used to reduce the dynamic range
of the signal passing through it. For instance, an input dynamic range
of 110 dB might pass through a compressor and exit with a new dynamic
range of 70 dB.
Passband The range of frequencies passed by an audio low-pass, high-pass
or bandpass filter. Normally measured at the -3 dB point: the frequency
point where the amplitude response is attenuated 3 dB (decibels)
relative to the level of the main passband. For a bandpass filter two
points are referenced: the upper and lower -3 dB points. The -3 dB point
represents the frequency where the output power has been reduced by
one-half.
Pink Noise A random noise source characterized by a flat amplitude
response per octave band of frequency (or any constant percentage
bandwidth), i.e., it has equal energy, or constant power, per octave.
Passing white noise through a filter having a 3 dB/octave roll-off rate
creates pink noise. Since pink noise has the same energy in each
1/3-octave band, it is the preferred sound source for many acoustical
measurements due to the critical band concept of human hearing.
Frequency Response It connotes amplitude-frequency response and
quantifies a device's maximum and minimum frequency for full-output
response. The electrical passband of an audio device. It is used to
express variation of gain, loss, amplification, or attenuation as a
function of frequency, normally referred to a standard 1kHz reference
point.
Dynamic Range The ratio of the loudest (undistorted) signal to that of
the quietest (discernible) signal in a unit or system as expressed in
decibels (dB).
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