30-07-2012, 04:09 PM
GRAPHIC EQUALIZER OWNER’S MANUAL
GRAPHIC EQUALIZER.pdf (Size: 207 KB / Downloads: 42)
Introduction
hank you for purchasing the TDM 15GE-2 graphic equalizer. These units are made from the
finest components and engineered to exacting standards. Precision components are used in
all critical circuitry for the finest sonic quality and performance. To get the most out of your new
equalizer, please take a few minutes to review this manual and familiarize yourself with the
proper operation of the unit.
Description
The 15GE-2 is a high-performance, 2/3 octave, constant-Q graphic equalizers. The 15GE-2
provides two channels of equalization in a two-rack-space package. Special circuitry is used to
limit adjacent band interaction making the TDM 15GE-2 equalizers easier to adjust than most.
About This Manual
This manual attempts to provide enough information for the novice user. Professionals should
skim through or skip the sections that provide technical background information while making
sure to read the sections that deal with the specifics of TDM 15GE- equalizers.
n equalizer is used to alter the balance of frequencies in an audio signal. In some cases this
is done to compensate for the poor acoustic characteristics of a room or the inaccurate
frequency response of a speaker system. In other cases it is done to change the characteristic
sound of a particular signal source such as a voice or a musical instrument. TDM 15GE-2
equalizers can be used for either purpose.
There are several different kinds of equalizers, but they all use filters to change the frequency
balance of an audio signal. Filters let the operator reduce or increase the levels of certain ranges
of frequencies in the signal. TDM 15GE-2 equalizers are graphic equalizers. Graphic equalizers
provide a series of sliders, one for each range of frequencies that the equalizer can influence.
They are called graphic equalizers because the sliders form a graph of the frequency response of
the equalizer.
Why Equalizers are Needed
Speaker systems and acoustic environments interact in complex ways. The result is that a
particular audio system in a particular room or environment will usually have less-than-ideal
frequency response characteristics. Speaker system designers do their best to manage the
tradeoffs involved and produce the best products they can for a particular purpose, but no
speaker system is ideal in all environments and situations. Many factors beyond the control of
speaker designers and audio engineers influence audio system performance. These factors can
include ambient temperature, air movement, and the number of people in an area. Additionally,
some rooms just have poor acoustics because of other practical considerations. Acoustics are
often not the first consideration when designing a space that will accommodate spectator events
(consider a high-school gymnasium for example). Because all of these factors beyond our
control can change the frequency characteristics of audio systems in undesirable ways, we use
equalizers to compensate—to try to adjust the signal electronically, to “equalize” its frequencies.
Equalizers are also used to adjust the frequency balance of a particular signal such as an
instrument or voice, either to compensate for some problem or to achieve a particular effect. For
example, an acoustic guitar with a pickup will produce a signal that is not generally an accurate
representation of how the guitar sounds acoustically. An equalizer might be used to make the
signal sound more natural. Perhaps an electric bass player likes a sound with a lot of presence
and attack. Many electric basses do not naturally have this kind of sound so an equalizer might
be used to achieve this effect.
There are a lot of applications for equalizers, but they all involve changing the balance of
frequencies in a signal so that it sounds better. It is important to remember when setting up
electronic audio equipment that the goal is to achieve good sound. Sometimes a good sanity
check is to bypass the equalizer at some point during the sound check (don’t do this during a live
event!) and compare the sound. If it doesn’t sound better with the equalizer in then you are not
getting any benefit from equalization. Be aware that if you bypass the equalizer where you have
a lot of frequencies cut, the sound will get a lot louder so be prepared for this.
• Filter: An electronic circuit that changes the levels of some frequencies without altering
the levels of others.
• Frequency Band: The range of frequencies that a particular filter operates on. Graphic
equalizers have one slider for each frequency band that they can control.
• Band Width: Specifies how broad a range of frequencies is encompassed by a frequency
band. Audio band widths are often given in octaves. TDM 15GE-2 graphic equalizers
operate on fixed bands that are 1/3 of an octave wide. That is why they are called 1/3
octave equalizers.
• Boost and Cut: Boosting a range of frequencies raises their level relative to the overall
level of the signal. Cutting a range of frequencies lowers their level relative to the overall
signal level. The amount of boost or cut is given in Decibels (dB). TDM 15GE-2 graphic
equalizers can provide up to 12 dB of boost or cut for each frequency band.
• Bypass: Bypassing a piece of signal processing equipment means electronically
removing it from the signal path. When you press the bypass switch, the unit internally
disables all signal processing. Thus it has the effect of simply routing the input to the
output as though the equipment were not there.
• Constant-Q: A design requirement for some equalizers that says that the band width and
characteristic shape or sound of filters remains constant as the center frequency varies. In
graphic equalizer design this means that each of the filters has the same effect on its
range of frequencies as all of the other filters have on theirs. TDM 15GE-2 graphic
equalizers are constant-Q designs.
• Interaction: Because of the way most equalizers work, adjacent bands interact. In other
words, changing the level of one band affects the levels of frequencies in adjacent bands.
This interaction makes it more difficult to adjust equalizers accurately because you need
to keep going back and readjusting the levels of some bands after changing the adjacent
levels.
15GE-2 Special Features
• Hard-Wire Bypass: When you engage the bypass switch on the TDM 15GE-2 graphic
equalizers, the inputs are electrically “hard wired” directly to the outputs with no
intermediate circuitry. This means that in a bypassed state the unit is truly, completely
removed from the signal path. Many equalizers have a bypass switch that simply
deactivates equalization. The signal still goes through the equalizer’s electronics. The
hard-wire bypass is very useful when diagnosing system problems, and it works even
when no power is applied to the unit.