MPC-X100 100 Hz Subwoofer Crossover
For JBL MPC and MPA amplifiers
Owner’s Manual and Installation Guide
I. Description
The MPC-X100 is a dual-channel 100 Hz crossover filter accessory for use with JBL MPC
and MPA power amplifiers.
The MPC-X100 is user configurable to fulfill these functions:
• active crossover—Channel 1: 100 Hz low-pass; Channel 2: 100 Hz high-pass or full-range.
• subsonic filter—programmable; preset @ 20 Hz to protect against damage from infrasonic signals.
• ultrasonic filter—programmable; preset @ 20 kHz to protect against damage from ultrasonic signals.
• CD horn EQ—for use in systems with uncompensated constant-directivity horns.
Each channel has an electronically balanced input and bypassable low-pass and high-pass
sections. Each filter circuit uses a 4-pole (24 dB/oct) Linkwitz-Riley alignment.
An alternative to the MPC-X100, the MPC-XU is a universal crossover with selectable
crossover frequency.
The MPC-X100 installs onto the amplifier’s input card, where its settings are not easily
accessible to the user. This makes the MPC-X100 ideal for installed or rental sound systems,
since it practically eliminates the danger of unauthorized tampering with crossover setting or
incorrect crossover output connections, as well as the loudspeaker damage that may result
from such user tampering.
Installing the MPC-X100 involves soldering a 10-pin and a 12-pin header into corresponding
holes on the input card, a process that only qualified technical persons should attempt. We
recommend that you enlist an authorized JBL service center to perform the task. See the
installation section of this manual for more information.
Figure 1 shows a block diagram of both channels of the MPC-X100:
Programmable
100 Hz
Linkwitz-Riley
Subwoofer
Linkwitz-Riley
Low-Pass Filter
High-Pass Filter
Output
(factory preset @ 20 Hz)
Channel 1
jumper block: 3-pin
header J101
jumper block: 3-pin
header J102
(subwoofer)
resistor network RN104
Programmable
Linkwitz-Riley
Low-Pass Filter
100 Hz
Linkwitz-Riley
High-Pass Filter
High-pass or
Full-range
Output
(factory preset @ 20 kHz)
Channel 2
jumper block: 3-pin
header J201
jumper block: 3-pin
header J203
jumper block: 3-pin
header J202
(high-pass or full-range)
resistor network RN202
& switch S201
*TD-000084-00*
Figure 1. Block diagram of the MPC-X100
TD-000084-00
Rev. A
1
NOISE SHIELD
#4-40 NUT
NOISE SHIELD
TAB
CH. 1 GAIN CONTROL
INPUT PANEL PCB
Figure 3
Figure 4
8 If you need to make any adjustments to the MPC-X100 settings or if you need to record
them, do so now, because the MPC-X100 will be inaccessible once the noise shield is
installed and the input panel is re-installed into the amplifier chassis. See Section III,
“Programming the MPC-X100,” below.
9 Using a ¼-inch (6.3 mm) nutdriver, remove the outer 4-40 nut from the stud in the panel
mounting bracket, next to Channel 1’s gain control potentiometer. Place the noise shield
over the circuit board of the MPC-X100 (Figure 3) and bend the grounding tab down so
its hole goes over the stud. Re-install the nut, and tighten it securely (Figure 4).
10 Reconnect the ribbon cable to the input board connector. Press the locking clamp wings
of the connector closed. You will feel them snap into place.
11 Carefully reposition the input board/MPC-X100 assembly into the amplifier chassis and
secure it by fastening the two mounting screws. Make sure the screws are tightened snugly,
but do not over-torque them. Re-install the upper blank panel.
Installation of the MPC-X100 is now complete, and the amplifier is now ready to be installed
into the system.
III. Programming the MPC-X100
The MPC-X100 is preset for a 100 Hz crossover point; this
frequency cannot be changed. The circuit board has four
switches, six 3-pin headers, and two SIP resistor network
sockets, all used for programming the module (see Figure 3).
The numerical designations identify which channel the
switch, header, or socket is part of: those designated by a 3-
digit number starting in a 1 (for example, headers J101) are
for Channel 1, while those starting in a 2 are for Channel 2.
Figure 3. The MPC-X100’s switches, jumpers, and resistor networks.
Setting input operating mode on amplifier or input card
The input board or accessory on which the MPC-X100 is installed has provisions—switches or
headers—for setting the operating mode of the amplifier. In the signal flow, the MPC-X100 is
located after these switches or headers, so its operation is affected by the mode setting.
Stereo or Parallel Mode Operation—With the amplifier in stereo or parallel mode, the
MPC-X100 operates normally: Channel 1 provides a 100 Hz low-pass subwoofer signal to
Channel 1 of the amplifier, while Channel 2 provides either a 100 Hz high-pass or a full-range
signal. Most 2-way applications will require operating in parallel mode.
3
Bridged Mode Operation—With the amplifier in bridged mono mode and driving a high-
power subwoofer system, the MPC-X100 can be used as a subwoofer filter, taking full-range
audio from Channel 1’s input and sending on a 100 Hz low-pass signal to the amplifier
circuitry. For correct operation, bypass Channel 2 on the MPC-X100 board and use only
Channel 1’s input and processing.
Bypassing the filters
To completely bypass the filter circuitry of a channel, set the jumpers on both Jx01 and Jx02
across pins 1 and 2, which are the upper two pins on their headers (see Figure 4). Note: If
you neglect to place jumpers on either header, no signal will pass on that channel. To
bypass Channel 2 for bridged mode operation, set the jumpers on headers J201 and J202
across pins 1 and 2.
Figure 4
Channel 1 (subwoofer): Programming the subsonic (high-pass) filter
Bypass/enable header—To use the subwoofer channel’s high-pass subsonic filter, set the
jumper on header J102 across pins 2 and 3, which are the lower two pins. If you do not want
any subsonic filtering, bypass the filter by setting the jumper across pins 1 and 2. Note:
Subwoofers tend to sound best when used with suitable filtering, which prevents the
amplifier and speaker from wasting power trying to reproduce frequencies that are too
low. For best performance it is recommended that you bypass the high-pass filter only
if there is suitable filtering elsewhere in the audio signal path.
Switch S102 in
"×1" position
Resistor network
in RN104
20 Hz
30 Hz
40 Hz
50 Hz
120K
82K
56K
47K
Subsonic (high-pass) filter
frequency table
Setting frequency—To set the corner frequency (at which the output is 6 dB down) of the
high-pass filter, set switch S102 to ×1 (down) and choose the appropriate resistor network
value for RN104. Use the high-pass table to select the right combination. See the appendix of
this manual for keys to identifying the correct resistor network. Note: Switch S101 should
also be set to ×1 (down).
Inserting the resistor network—The factory preset frequency is 20 Hz. If there is a resistor
network already installed in the socket, carefully pull it straight out. Insert the pins of the new
resistor network into the socket holes and carefully press the network into the socket. Be
careful to avoid bending the pins of the resistor network. Orientation of the resistor network
is unimportant, as long as all 8 pins are well seated in the socket.
Channel 2: Programming the ultrasonic (low-pass) filter and CD horn EQ
Bypass/enable header—To use the low-pass ultrasonic filter, set the
Switch S201 in
"×1" position
Switch S201 in
"×10" position
Resistor network
jumper on J201 across pins 2 and 3, which are the lower two pins. But if you
do not wish to use the low-pass filter and want to bypass it instead, set the
in RN202
•
800 Hz
120K
jumper across pins 1 and 2. Note: Ultrasonic filtering is recommended to
reduce susceptibility to RF and other types of interference.
•
1000 Hz
1200 Hz
1600 Hz
2000 Hz
2500 Hz
5000 Hz
8000 Hz
16000 Hz
20000 Hz
82K
•
68K
To engage the 100 Hz high-pass filter, place a jumper across pins 2 and 3 of
header J202. To bypass the filter for full-range audio, place the jumper across
pins 1 and 2. Note: if you need CD horn equalization, you must engage
the 100 Hz high-pass filter also.
•
56K
•
47K
250 Hz
500 Hz
800 Hz
1600 Hz
2000 Hz
33K
Setting frequency—To set the corner frequency (at which the output is
6 dB down) of the low-pass ultrasonic filter section, choose the appropriate
resistor network value and switch setting for RN202 and S201, respectively.
(Sx01 is a ×10 range switch. In its upper position, the frequency range is ×10;
18K
12K
5.6K
4.7K
in the lower it is ×1.) Use the low-pass table at left to select the right combi-
nation. See the appendix of this manual for keys to identifying the correct
resistor network. Note: Switch S202 should always be set to ×1 (down).
Ultrasonic (low-pass) filter
frequency table
The high-pass frequency is fixed at 100 Hz and cannot be changed.
4
Inserting the resistor network—The factory preset frequency is 20 kHz. If there is a
resistor network already installed in the socket, carefully pull it straight out. Insert the pins of
the new resistor network into the socket holes and carefully press the network into the socket.
Be careful to avoid bending the pins of the resistor network. Orientation of the resistor
network is unimportant, as long as all 8 pins are well seated in the socket.
CD Horn Equalization (Boost)—In addition to enabling the 100 Hz high-pass filter at
J202, if you opt for CD horn equalization you must place a jumper at J203 as well. The MPC-
X100 offers two equalization curves for CD horn correction:
• For +6 dB of boost at 20 kHz, place the jumper across pins 1 and 2 of J203.
• For +10 dB of boost at 20 kHz, place the jumper across pins 2 and 3 of J203.
• To bypass the CD horn equalization, do not place a jumper across any pins on J203.
Pins 1 & 2 Pins 2 & 3
None
The table at left is a summary of the jumper
settings for the MPC-X100.
Function
Header
J101
J102
J102
J103
J201
J201
J202
J202
J203
J203
J203
J201, J202
J203
All operation
X
Bypass subsonic
X
Channel 1:
(subwoofer)
Enable subsonic
X
All operation
X
Bypass ultrasonic
X
X
X
X
Enable ultrasonic
Bypass 100 Hz high-pass
Enable 100 Hz high-pass
Disable CD horn boost
CD horn boost, +6 dB @ 20 kHz
CD horn boost, +10 dB @ 20 kHz
Bridged mono
Channel 2:
X
X
X
X
X
IV. Typical configurations
Subsonic Filter (Infrasonic Filter)
Applications: Subsonic filters are commonly used in sound installations to filter out rumbles
and other inaudible or unwanted low frequency signals and to protect speaker tuned vented
speakers from damage due to excessive energy below the tuning frequency.
For a subsonic filter, determine the lowest useable frequency that the speaker can safely
handle and set the high-pass filter to that frequency. Typical subsonic filters are set at 50 Hz,
40 Hz, 30 Hz or 20 Hz.
Program settings:
1 Set J102 to enable the high-pass filter by placing jumper across pins 2 and 3.
2 No jumper on J103.
3 Insert proper resistor network in RN104 socket.
5
Ultrasonic Filter
Applications: An ultrasonic filter is useful for minimizing RF interference, oscillations,
leakage or aliasing from digital devices, or other signals that are too high in pitch to hear but
may wreak havoc in an amplifier system.
Typical ultrasonic filters are set at 16 kHz or 20 kHz.
Program settings:
1 Set J201 to enable the low-pass filter by placing jumper across pins 2 and 3.
2 No jumper on J203 unless you need CD horn equalization.
3 Insert proper resistor network in RN202 socket.
CD Horn Equalization Filter
Applications: A constant directivity horn requires a 6 dB per octave boost at high frequen-
cies to provide a flat frequency response. On the MPC-X100 you must use the CD horn
equalization in conjunction with the 100 Hz high-pass filter.
Program settings:
1 Set J202 to enable the 100 Hz high-pass filter by placing jumper across pins 2 and 3.
2 Set J203 to select the EQ curve you desire: across pins 1 and 2 to +6 dB at 20 kHz, or
across pins 2 and 3 for +10 dB at 20 kHz.
Full-range
speaker system
F =
C
100 Hz
MPC-X100
Subwoofer
2-Way Active Crossover
This configuration routes the frequencies below 100 Hz to amplifier Channel 1, which will
driver the subwoofer(s), and the frequencies above to Channel 2, which will drive the full-
range (typically, woofer + high frequency as passive 2-way, or woofer + midrange + high
frequency as passive 3-way) speaker(s). Using the MPC-X100 as a crossover requires that you
drive both amplifier inputs with the same full-band signal.
Program settings:
1 On the input module, set the amplifer mode to parallel. Alternately, you could use a Y-
cable to provide the same signal to both channel inputs.
Channel 1:
2 Subsonic (infrasonic) filter—If you need subsonic (infrasonic) filtering, set J102 to enable the
high-pass filter by placing jumper across pins 2 and 3, and insert a resistor network into RN104
corresponding to the roll-off frequency you desire. If you do not want subsonic (infra-
sonic) filtering, set J102 to disable the high-pass filter by placing jumper across pins 1 and 2.
6
Channel 2:
3 Set J202 to enable the Channel 2’s 100 Hz high-pass filter by placing jumper across pins 2
and 3.
4 CD horn EQ—If you need equalization for a constant-directivity horn, set a jumper on
J203 for the amount of boost you need. If you do not want CD horn equalization, do not
place any jumper on J203.
5 Ultrasonic filtering—If you need ultrasonic filtering, set a jumper on J201 across pins 2 and 3
to enable Channel 2’s Low-pass filter and insert a resistor network into RN202 that
corresponds to the desired roll-off frequency. If you do not want any ultrasonic filtering,
set the jumper on J201 across pins 1 and 2 to bypass the low-pass filter.
V. Warranty & Contacting JBL
These products are designed and backed by JBL Professional, the world leader in sound
reinforcement. For complete JBL warranty information, to order replacement parts or to ask
for clarifications to this manual, contact JBL Professional:
Within the United States: Contact the Applications Dept, JBL Professional, PO Box 2200, 8500
Balboa Blvd, Northridge CA 91329 USA. In the USA you may call Monday through Friday
8:00 a.m. to 5:00 p.m. Pacific Coast Time: (818) 894-8850.
In other areas throughout the world: Contact the JBL Professional Distributor in you country.
A list of JBL Professional Distributors and U.S. Service Centers can be attained from the JBL
7
Appendix
Identifying resistor networks
Use this chart to identify the values of the resistor networks. See the tables on page 4 to find
the correct values for the desired filter frequencies.
RESISTANCE CODE
2.7K 272
3.9K 392
4.7K 472
5.6K 562
6.8K 682
8.2K 822
10K 103
12K 123
15K 153
18K 183
20K 203
22K 223
27K 273
33K 333
39K 393
47K 473
56K 563
68K 683
Use only these three digits to
determine resistance code.
Disregard the other
numerals and letters.
JBL Professional 8500 Balboa Boulevard, P.O. Box 2200 Northridge, California 91329 U.S.A.
A Harman International Company
MPC-X100 MANUAL 3/99
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