Manual-14
Constant Directivity Horn
Equalization Modification
Constant Directivity (or CD) horns need additional
equalization to help cover the same area a long throw horn
can cover. Additional circuitry has been added to the AC 22B
layout for the additional equalization of the High Frequency
outputs for CD horns. This modification should only be
attempted by an experienced technician who is adept at
soldering.
It is important to know the 3 dB down point of the CD
driver's frequency response. The manufacturer of your driver
should be able to supply you with a chart showing a fre-
quency response curve. Find the point where the high end
starts to roll off, and look for the point on the chart that is 3
dB down from that point (toward the right, as the higher
frequencies roll off). Find the frequency at the bottom of the
chart of this point — an approximate is fine, you don't have to
be exact. Find the closest frequency in Figure 6 to determine
the correct value capacitor to install in the AC 22B to correct
for this high frequency roll off.
STEP BY STEP PROCEDURE
The following procedure is for Stereo 2-Way. For a Mono
3-Way system with a CD horn on the high output, only place
C212 in Channel 2.
1. Remove the top and bottom covers of the AC 22B.
2. Locate the positions for C112 and C212 on the following
page and on the circuit board. C112 (for Channel 1) is
located near the middle of the board. C212 (for Channel 2)
is located near the middle and right edge of the board.
3. Clean the solder pad on the underside of the board so that
the appropriate capacitor can be inserted. Install the
capacitor, and solder the leads from the underside using
fresh solder. Clip the excess leads.
All features & specifications subject to change without notice. 520-438 SEP96
©Rane Corporation 10802 47th Ave. W., Mukilteo WA 98275-5098 TEL (425)-355-6000 FAX (425)-347-7757 WEB http://www.rane.com
IMPORTANT NOTE
CHASSIS GROUNDING
If after hooking up your system it exhibits excessive
hum or buzzing, there is an incompatibility in the
grounding configuration between units somewhere. Your
mission, should you accept it, is to discover how your
particular system wants to be grounded. Here are some
things to try:
1. If your equipment is in a rack, verify that all chassis
are tied to a good earth ground, either through the line
cord grounding pin or the rack screws to another
grounded chassis.
2. Units with outboard power supplies do not ground the
chassis through the line cord. Make sure that these
units are grounded either to another chassis which is
earth grounded such as an amplifer, or directly to the
grounding screw on an AC outlet cover by means of a
wire connected to the grounding screw on the chassis.
3. Try moving the device away from high magnetic field
sources, such as large transformers used in power
amplifiers.
4. Be sure of properly balanced inputs and outputs.
Connect balanced devices with balanced connectors
and cables. Runs longer than 10 feet require balanced
interconnect.
Please refer to RaneNote “Sound System
Interconection” for more information on system ground-
ing and balanced/unbalanced connections.
3 dB Down
Frequency
Capacitor
2.2 kHz
.0027 µf
2.5 kHz
.0024 µf
2.7 kHz
.0022 µf
3.3 kHz
.0018 µf
4.0 kHz
.0015 µf
5.0 kHz
.0012 µf
6.0 kHz
.001 µf
