5234 ELECTRONIC FREQUENCY DIVIDING NETWORK
Operation
Verification Of System Wiring
It is imperative that each output of the electronic frequency
dividing network be properly connected. Inadvertent
exchange of low and high frequency output connections—
at the network, power amplifiers or transducers—may
result in severe damage to midrange or high frequency
loudspeaker system components.
The following procedure should be followed for each
program channel prior to operation.
1.
With all power off, set the High Frequency Level control at
"2"
and adjust the program source level to minimum. (The
source material may be wideband noise or music.) If the
power amplifiers are equipped with level controls, adjust
them to approximately one-quarter power.
2.
Turn on the program source, network and amplifiers for the
channel under test.
3. Gradually increase the program source volume level until
audible.
If the sound comes predominately from the midrange or
high frequency drivers, immediately shut power off and
check all wiring.
4.
If the low frequency loudspeaker produces bass, gradually
advance the High Frequency Level control.
Correct system wiring will be verified if the treble com-
ponent of the program material simultaneously increases in
level while coming from the midrange and high frequency
drivers.
Transducer Phasing
One important factor contributing to the natural sound
character of a loudspeaker system is the phase relationship of
the transducers for an octave below and above each cross-
over frequency. Two suitable methods for establishing proper
phase of the components in a two-way loudspeaker system
are described in the following paragraphs. Either one may be
used,
depending on the availability of test equipment. A three-
or four-way system should be treated in a similar manner by
first establishing the proper phase for the transducers of the
low frequency transition and then progressing to the mid-
range, high frequency or ultra-high frequency transducers,
as applicable.
Objective
Method-A real time third octave analyzer,
con-
denser microphone and a pink noise source can be used to
establish proper phase of the loudspeaker system com-
ponents as follows:
1.
Using pink noise as program material, adjust system
volume for comfortable listening and set the levels of the
individual transducers to display flattest overall frequency
response on the real time analyzer.
2.
Reverse polarity of the high frequency driver and observe
the effect on frequency response through the crossover
region
Proper phasing of the transducers will have been achieved
when the flattest frequency response has been obtained
through the crossover region, as shown on the real time
analyzer.
5
5234
PROGRAM SOURCE
(UNBALANCED)
PROGRAM SOURCE
(BALANCED)
AMPLIFIER
AMPLIFIER
AMPLIFIER
LOUDSPEAKER SYSTEM
HIGH
MID
LOW
Figure 4. Wiring Diagram For Tri-Amplification
Shielded cable is necessary for all input and output connections, as
shown.
Make certain that the shield is properly connected to the
ground terminal.
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