Infinity RS-4.5 Owners manual

The Electronic Crossover/Equalizer Unit

The active Crossover/Equalizer control unit,which is part of the Reference Standard 4.5 system and
optional with the RS 2.5, makes it possible for the user to compensate for room acoustics and
speaker placement.

The unit is connected into the signal path between the preamplifier(s) and power amplifier(s). In the
case of a receiver without an externally accessible link between its pre-amp output and its power amp
input, the connections are made through the tape monitor circuit for equalizer use only.

When active bi-amplification of an RS 4.5 or RS 2.5 speaker system is desired, the
Crossover/Equalizer must be used.

Brief Theory of Operation

Each signal channel of the unit consists of a 6-dB-per-octave low- and high-pass filter. Each of these
filters has its own variable cutoff frequency (3 dB down point) and output level controls. The high-pass

portion of the circuit has a high-frequency

MODE switch in the EQ position, the output of the high and low filters is summed electrically. By

the
varying LOW PASS GAIN, LOW PASS and/or HIGH PASS frequency controls, it is possible to
generate a wide variety of frequency response contours in the 2OHz- 1 kHz range. Use of the high­frequency contour control (HF) affects the response in the 2-20 kHz region. The EQ position of the
MODE switch permits frequency response variations in modes 2 and 4 that are essentially like those
possible in mode 5. (See RS 4.5 and 2.5 speaker instruction manuals.)

With the MODE switch in Bi-Channel (BI-CH), the low- and high-pass filter outputs appear at their
respective output jacks and will feed separate low- and high-range power amps as outlined in mode 5.
The effect of the controls is similar to the EQ position, except the "summing" is taking place
acoustically.

Description of Front Panel Controls

A summary of the controls and their functions on the Crossover/Equalizer from left to right on the
front panel listed below:

Figure A. (EQ unit, front)

contour control giving 5 dB of boost or cut at 15 kHz. With

1. LOW PASS Frequency: Sets the - 3dB point of the low-pass filters from 110 to 440 Hz in 1/2-

octave steps.

2. LOW PASS Gain: Adjusts the output level of the low-pass filters. Low-pass output appears at
low-pass output jacks regardless of the position of the MODE switch. With the MODE switch in EQ,
LOW PASS GAIN sets the amount of low-frequency signal in wide-band sum appearing at high-pass
outputs. Absolute gain from input to low-pass outputs is unity (x 1 or 0 dB) with LOW PASS GAIN
control at 0 mark.

3.

HIGH PASS Frequency: Sets the - 3dB point of the high pass filters from 110 to 440 Hz in

1/2-octave intervals.

4.

HIGH PASS Gain: With the MODE switch in Bi-Channel setting (BI-CH), the HIGH PASS

GAIN adjusts the output in the high-pass frequency range independent of the LOW PASS GAIN

settings. When the MODE switch is set to EQ, the HIGH PASS GAIN controls the output level of the
wideband output at the high-pass jacks on the rear panel. In this mode, bass is adjusted relative to mid
and high frequencies with the LOW PASS GAIN. Absolute gain from input to High Pass outputs is
unity in either mode when the HIGH PASS GAIN is set to the 0 mark. This control should be set to
unity (0) for most installations. The Crossover/Equalizer has 6 dB of excess gain with the HIGH PASS
GAIN rotated fully clockwise. This can be put to advantage if the overall system gain is low because of
the use of some lower-gain preamps or power amps (such as the Infinity Hybrid Class A Power Amp).

It is not recommended that the HIGH PASS GAIN be used as an overall system volume control in the

EQ mode and further should not be set at less than unity (0).

5. HF (High Frequency Contour): Adjusts high-frequency response of system in a boost/cut
fashion with a range of ± 5 dB @ 15 kHz.

6. MODE sets the unit for functioning as a low-level active electronic crossover in the BiChannel
(BI-CH) position or as an active equalizer in the EQ position.

7. POWER turns unit power on and off. Power on is indicated by a red LED indicator to the right
of the POWER switch. Power can be switched on or off with system preamp power, switched
independently, or left on continuously.

Figure B (EQ unit back)

BACK PANEL FUNCTIONS

Viewed from rear of panel from left to right:

AC Voltage Selector. Allows the unit to be externally set to operate in different countries. Insert

pointed object, such as a small screwdriver, into depression of switch and set position of switch so that
white line lines up with correct voltage range.

AC line cord: Connect to suitable source of power (50/60 Hz frequency 105-125 V AC).

Fuse: Replace with AGC 1/8A fuse only. If fuse blows, most likely cause is voltage selector switch set

in wrong position.

BYPASS Switch:
Permits the unit to be signal-bypassed in the EQ mode. Normal operation as described herein is with

the BYPASS switch placed at IN. With the BYPASS switch placed at OUT, the input signal will
appear at the High Pass/EQ outputs.

Inputs:

Connect the signal source from the preamp, or preamp outputs of receiver or integrated amplifier, to

these jacks.

HIGH PASS / EQ:

Connect these jacks to system power amplifier inputs in operational modes 2 and 4. Connect them to
system midhigh power amplifier inputs in mode 5. The signals at these jacks are phase inverted in
respect to the inputs with the bypass switch in.

LOWPASS: