Marchand Electronics XM9 User manual

Marchand Electronics Inc.
Electronic Crossover Circuit Board
Model XM9
Users Manual
Assembly Manual
Marchand Electronics Inc. Rochester NY
c) 1990....2015 Marchand Electronics Incorporated
Last updated 5 March 2015
www.marchandelec.com

XM9 ELECTRONIC CROSSOVER NETWORK
Steep 24 dB/octave slope Crossover frequency 20 - 5000 Hz.
Outputs are always in phase Small 3.2" x 4.2" circuit board
Level controls on board Optional off board level controls
Subwoofer summing option On board RCA in/out connectors
No turn on/off transients Fourth order constant voltage design
Low noise circuit design Double sided cicuit board
The XM9 electronic crossover network module is a fourth order
constant voltage crossover design. The module provides both low-
pass and high-pass outputs. The slope of both outputs is 24
dB/octave. Because of the fourth order design the high-pass and
low-pass outputs of the crossover are always in phase with each
other. The crossover network is implemented as a fourth order
state variable filter. This filter provides both the high-pass and low-
pass function simultaneously, guaranteeing a near perfect match
of the high pass and low-pass responses.
One crossover network is needed for each channel of a bi-
amplified system. A tri-amplified system needs two networks per
channel, one to separate the high frequencies from the mid-low
frequencies and another one to separate the low and mid
frequencies. A quad system needs 3, and so on. The filter can also
be used to drive a subwoofer, where the subwoofer is shared by
the two channels of the stereo system.
The crossover frequency of the XM9 electronic crossover can
easily be changed by changing the value of four resistors. These
four resistors are mounted on an 8 pin DIP header plug for ease of
change.
Individual level controls for the high and low pass outputs are
provided with on board potentiometers. A damping control
potentiometer on the circuit board allows for adjustment of the
frequency response at the crossover frequency. A boost or cut of
up to 6 dB at the crossover frequency compensates for a dip or
bump in the response at the crossover frequency found in some
systems.
A time delay relay at the outputs of the XM9 eliminates the
transients that can happen when the unit is turned on or off. Off
board controls for the damping and the levels can also be used
with the XM9.
The XM9 electronic crossover is built on a 3.2" X 4.2" printed
circuit board of high quality glass-epoxy material. One side of the
double sided circuit board acts as a ground plane for the circuit.
This contibutes to the very high signal quality of the XM9. A silk
screen on the component side makes assembly very easy. The kit
uses only high grade components: 1% metal film resistors, 1%
matched polypropylene film capacitors for the filter capacitors,
three dual FET input and one bipolar operational amplifier.
Connectors for input, output and power make for easy assembly.
The XM9 is available as a bare board, with only the PC board and
the assembly manual; as a kit, with all needed components,
including a set of cable connectors; or completely assembled. The
frequency module consists of an 8 pin DIP header and 4 1% Metal
film resistors. The optional level/damping control potentiometer
and cable assembly can be used for mounting the level control on
a cabinet front panel. One of these XM9-PT is required for each
low-pass, high-pass and damping control.
INSTALLATION AND USE.
The typical application for the XM9 electronic cross-over filter is to
separate the high and low frequency bands in a multy-way audio
system. Figure 1 shows the application in a two-way amplifier
setup. The signal from the pre-amp is connected to the input of
the crossover. The high pass output from the cross-over is
connected to the input of the power amplfier driving the high
frequency loudspeaker tweeter), while the low pass output is
connected to the amplifier driving the low frequency speaker
woofer).
SPECIFICATIONS:
Frequency response: DC to 100 KHz, +/- 0.2 dB
Crossover frequency: 20 Hz - 5 KHz
Insertion gain: 6dB with level controls at maximum.
Filterslope: 24 dB/Octave
Harmonic distortion at 1KHz: less than 0.001%
Signal to Noise ratio: better than 110dB
Input impedance: 25 KOhm
Output load capability: 2 KOhm min.
Output impedance: 50 Ohm typ
Maximum input voltage 10 V peak-peak 4 V RMS)
Power supply requirement: dual regulated +15V and -15V @50 mA, typ
2

The controls and jumpers on the circuit board have the following function:
LEVEL CONTROLS:
There are two level control potentiometers on the circuit board,
one for the low pass output and one for the high pass output. They
each have a range of off to +6dB. At the center position the
crossover network has unity gain 0 dB).
DAMPING CONTROL:
The damping control sets the frequency respose of the unit at the
crossover point. The range of the damping control is from -8 dB to
+6 dB, at the crossover point. This adjustment is usefull for
matching the frequency response of the high and low
loudspeakers at the crossover point. In the center position the
frequency response is totally flat, meaning that the sum of the
output voltage of the high pass and low pass channel is constant
for all audio frequencies.
--------------------------------------------------
| Table 1. |
| Connector pin assignments. |
| Connector Pin # Signal description |
|==================================================|
| - P1 | 1 | Low pass level control, signel |
| P1 | 2 | Low pass level control, wiper |
| P1 | | Low pass level control, ground |
| - P2 | 1 | -15 Volt power, 15 mA, typ. |
| P2 | 2 | Power ground |
| P2 | | +15 Volt power, 15 mA, typ. |
| - P | 1 | Damping control, ground |
| P | 2 | Damping control, wiper |
| P | | Damping control, signal |
| - P4 | 1 | High pass level control, signel |
| P4 | 2 | High pass level control, wiper |
| P4 | | High pass level control, ground |
| - P5 | 1 | Subwoofer output |
| P5 | 2 | Ground |
| P5 | | Subwoofer input |
| - P6 | | Signal input, RCA jack |
| - P7 | | High pass output, RCA jack |
| - P8 | | Low pass output, RCA jack |
--------------------------------------------------
FREQUENCY CONTROL AND FREQUENCY MODULE:
The crossover fequency of the XM9 can be set by installing the
apropriate frequency module. When using a subwoofer, with
standard full range loudspeakers, the crossover frequency will
normally be set at about 70-150 Hz. When using the crossover
network in a typical biamping setup the crossover frequency is
often set at 500-2000 Hz. These frequencies depend on the
loudpeakers used.
3

Fig 1. XM9 hookup.
Off board volume controls can be used to the high anw low pass
outputs and damping control of the XM9. Best results are
achieved when using 10 K potentiometers with linear taper. The
potentiometers should be connected with the wiper at pin 2 center
pin) and the outside leads to pins 1 and 3 of the connector. See
table 1. The jumpers should be moved according to table 2. The
low pass control is connected to P1, the high pass control to P4
and the damping control to P3.
4

--------------------------------------------------
| Table 2. |
| Jumpers for external controls |
| On Off Selected control |
|==================================================|
| J1 | J2 | Low pass level control, External |
| J2 | J1 | Low pass level control, On board |
| J | J4 | Damping control, External |
| J4 | J | Damping control, On board |
| J5 | J6 | High pass level control, External |
| J6 | J5 | High pass level control, On board |
--------------------------------------------------
Fig 10 shows some typical arrangements for 2-way, 3-way and 4-
way installations. For driving long lines a line driver buffer amplifier
may be needed. The XM9 outputs can drive shielded cable lines
of up to about fifty feet. The XM9 is implemented with a fourth
order state variable filter, see schematic diagram). The filter is
implemented with the Bi-Fet op-amp's IC1 and IC2. The virtue of
this type of filter is that it provides simultaneous high-pass and
low-pass functions at the two ends of the chain of four integrators.
This means that only 4 precision capacitors are needed in order to
implement both fourth order functions. Both high-pass and low-
pass functions will be perfectly matched, because they are derived
from the same network.
Fig 3. Example of subwoofer application.
COMMON SUBWOOFER
Two XM9 crossovers can be hooked up for driving a common
subwoofer. In this case the low pass outputs of the two
crossovers are summed together. Connector P5 is used for this
purpose. The two crossovers are connected together with a cable
from P5 on one crossover to P5 on the other. Table 3 showd the
wiring of the cable. Use a cable of not more than 30". Unshielded
wire can be used. The summed output can be taken from the low
pass output of either crossover board.
--------------------------------------------------
| Table . |
| Cable for common subwoofer |
| P5 board A P5 board B |
|==================================================|
| pin 1 connected to pin |
| pin 2 connected to pin 2 |
| pin connected to pin 1 |
--------------------------------------------------
POWER SUPPLY
5

The XM9 needs a dual +15V/-15V power supply for operation.
The best choice for power supply is a regulated one. A typical
power supply could be built as in fig 4. This supply can deliver 1
amp. of current; this will be sufficient for powering several
crossover networks. The Marchand PS10 power supply is of
similar design. It is a good choice for powering the XM9.
Fig 4. Simple regulated power supply for XM9.
CROSS-OVER FREQUENCY.
The cross-over frequency of the XM9 is easily changed by
replacing the frequency module. This 8-pin dip header holds the 4
resistors R11-14 that determine the frequency of the cross-over
point. The four resistors should have a tolerance of 1%, and be of
equal value. The value of the resistors is given by:
1
R = ------------- , F=cross-over frequency in Hz
6.28 x F x C R=resistance of R1..R4 in Ohm
C=capacitance of C1..C4 in Farad.
For a typical value of C1,C2,C3,C4 of 3300 pF, the value of R is given by
48.2
R = --------, F=cross-over frequency in KHz
F R=resistance of R1..R4 in K.
For example, a resistor value of 100K will give a cross-over
frequency of 482.3 Hz. Fig 8 shows the relationship between
cross-over frequency and R1 .. R4 for three different values of
C1 .. C4. The value of R should not exceed 10M and should not
be less than 10K. This gives a range of 4.8 Hz to 4.8 KHz for the
cross-over frequency with a value of C1-C4 of 3300pF. Outside
this range the value of C1-C4 should be adjusted. The minimum
value of C1-C4 is 300 pF. There is no maximum allowed value.
The components used for R and C should be audio grade.
Recommended are 1% Metal Film for R1-R4 and 1% matched
Polypropylene film for C1-C4. Polypropylene film capacitors
match Polypropylene in performance. Other types of film
capacitors are less perfect, because they have much higher
absorption coefficients. Never use electrolytic capacitors for C1-
C4!
On our website there is a handy calculator for finding the values of
R1...R4.
See www.marchandelec.com/programs.html
6

Fig 8. Relationship of crossover frequency and R1..R4.
DESCRIPTION
The XM9 implements a fourth order constant voltage low-pas
and high-pass filter. The filter has a fourth order transfer function.
The sum of the high-pass and low-pass output signal of the filter
is thus equal to the input signal. Also, the two output signals are
always in phase. This means that the output soundwaves of the
loudspeakers at the crossover frequency add up in phase.
In some cases the total sound pressure at the crossover
frequency may show a dip, because the sum of the output power
of the loudspeakers is not unity. The XM9 has an damping factor
control that allows adjustment of the frequency response at the
cross-over point. The range of the damping at the crossover point
is from -4dB to +6dB. Figure 9 shows the frequency response for
3 different settings of the damping control. The high-pass
function, low-pass function and sum of high and low pass are
shown. The phase function is the same for all three transfer
functions.
Fig 9. XM9 High-pass, Low-pass, and sum functions, with correction.
7

PARTS LIST
The XM9 electronic crossover kit should include the parts listed
below. Please check the contents of your kit to make sure no parts
are missing. All parts are available separately consult factory).
-------------------------------------------------------------------
| Table 4. |
| XM9, Electronic Crossover Network, parts list |
| part # Description |
| ==================================================================|
| R6,10,11,12| | | |
| 15,16,20,22| | | |
| 2 ,24,25,28| | | |
| 29 | 1 | 24.9K,1% Metal Film | |
| R7 | 1 | 15.8K, 1% Metal Film | |
| R18 | 1 | 17.4K, 1% Metal Film | |
| R8,17 | 2 | 49.9K, 1% Metal Film | |
| R1 ,14 | 0 | not used | |
| R19 | 0 | not used | |
| R26 | 1 | 5.2 K, 1% Metal Film | |
| R27 | 1 | 1M00, 1% Metal Film | |
| R 0, 1 | 2 | 49.9 Ohm, 1% Metal Film | |
| C1,2, ,4 | 4 | 00pF, 260 WVDC, 1% Polypropylene | |
| C5,C6 | 2 | 0 uF, 25 WVDC, Alum. Electrolytic | |
| C7,8,9,10 | | | |
| 11,12,1 ,14| 8 | 0.1 uF, ceramic axial capacitor | |
| C17 | 1 | 1 uF, yellow box film capacitor | |
| C15,16 | 2 | 100 pF, Polypropylene | |
| IC1,2, ,4 | 4 | OPA21 4 Dual Bi-Fet Op Amp | |
| D1,2 | 2 | 1N49 7 1A diode | |
| D | 1 | 1N4148 signal diode | |
| D4 | 1 | 1N52 2 5.6V zener diode | |
| Q1 | 1 | 2N5087 or MPSA92 PNP transistor | |
| Q2 | 1 | PN2222 NPN transistor | |
| RLY1 | 1 | Relay DPDT 24V | |
| P1...8 | 8 | -pos terminal block | |
| M1,2, ,4,5 | 5 | 8 pin DIP sockets | |
| M14 | 1 | Circuit board, XM9-B | |
| R1,2, ,4 | 4 | 10K-10M, 1% Metal Film (in frequency)| |
| M15 | 1 | 8 pin DIP header ( module )| |
-------------------------------------------------------------------
MODIFICATIONS FOR BALANCED INPUT.
The XM9 can be operated with a balanced differential) input. This
is normally used with the XLR connectors. The circuit board needs
to be modified by cutting the trace at point F near the input
terminal block). The differential inputs are the terminals marked +
and - at the 3-position terminal block marked INPUT. The ground
is the third terminal marked G)
MODIFICATIONS FOR FIRST, SECOND AND THIRD ORDER OPERATION
With some changes in component values the XM9 can be used as
a first, second or third order filter. The changes are shown in table
5. In these modes the trimmer resistor R9 is unused and the
vaiable damping is not functional any more. Some of the
polypropylene filter capacitors are replaced with jumper wires. A
jumper wire has to be installed and a trace has to be cut. The
locations for the jumpers and cuts are marked on the solder side of
the circuit board. The cut has to be made at point A, near R5. Use
insulated hookup wire to make a connection between point E near
R5) and point B,C or D near C3, C2, C1). See table below. For
the second and third order filter a standard Butterwoth slope was
chosen; for most applications this will be a good choice.
8

------------------------------------------------------------------------
| Table 5. |
| |
| Changes for lower order filter applications. |
| |
| Component Fourth order First order Second order Third order |
| Constant V. Butterworth Butterworth |
|======================================================================|
| R6 24.9K, 1% MF deleted deleted deleted |
| R7 17.4K, 1% MF deleted 49.9K, 1% MF 24.9K, 1%MF |
| R8 49.9K, 1% MF deleted deleted deleted |
| R10 24.9K, 1% MF 24.9K, 1%MF 17.4K, 1%MF 24.9K, 1%MF |
| R11 24.9K, 1% MF deleted deleted 49.9K, 1%MF |
| R18 17.4K, 1% MF 49.9K, 1%MF 49.9K, 1%MF 49.9K, 1%MF |
| R26 5.2 K, 1% MF 24.9K, 1%MF 16.5K, 1%MF 12.4K, 1%MF |
| C2 00 pF Jumper wire 00 pF 00 pF |
| C 00 pF Jumper wire Jumper wire 00 pF |
| C4 00 pF Jumper wire Jumper wire Jumper wire |
| Jumper D to E C to E B to E |
| Cut at E at E at E |
------------------------------------------------------------------------
MODIFICATIONS FOR FOR HIGH INPUT IMPEDANCE
The standard imput impedance of the XM9 is 25 Kohm. A higher
impedance can be achieved by replacing some resistors according
to Table 6 below. The penalty for increasing the impedance is a
decrease in signal to noise ratio. The added noise depends on the
op-amps used. For 100K impedance and OPA2134GP op-amps
the noise will increase by about 2dB.
------------------------------------------------------------------------
| Table 6. |
| |
| Changes for high imput impedance. |
| |
| Component Standard Value |
| 25K impedance 100K impedance |
|======================================================================|
| R6 24.9K, 1% MF 100K, 1% MF |
| R7 17.4K, 1% MF 69.8K, 1% MF |
| R8 49.9K, 1% MF 205K, 1% MF |
| R17 49.9K, 1% MF 205K, 1% MF |
| R18 17.4K, 1% MF 69.8K, 1%MF |
| R24 24.9K, 1% MF 100K, 1%MF |
| R25 24.9K, 1% MF 100K, 1%MF |
| R26 5.2 K, 1% MF 20.5K, 1%MF |
------------------------------------------------------------------------
9

MODIFICATIONS FOR FOR BAFFLE STEP COMPENSATION
The baffle step effect causes a driver mounted in a cabinet to
radiate more to the front of the speaker at higher frequencies. This
results in a increase in frequency response at the higher
frequencies. For a cabinet with a baffle size of 12" the effect starts
at a frequency of about 400Hz. The total increase of intensity is 4-
6dB at the higher frequencies. A baffle step compensation circuit
can be installed on the XM9 circuit board. This circuit has the
effect of reducing the high frequency response. The circuit can be
installed on the high-pass output or on the low-pass output.
------------------------------------------------------------------------
| Table 7. |
| |
| Baffle step compensation for 1000Hz (4.8" baffle). |
| |
| Component 4dB compensation 6 dB compensation |
|======================================================================|
| Rb 4 .2K, 1% MF 24.9K, 1% MF |
| Cb 000pF 4500pF |
------------------------------------------------------------------------
The table shows the values for Rb and Cb for 1000Hz 4.8"
baffle). For a wider baffle the frequency is less. The frequency is
given by Fc= 4800/Wb, where Wb is the width of the baffle. For
frequency other than 1000 Hz the value of Cb is chosen as
Cb=1000*Cbt /Fc, with Fc in Hz, Cbt is the Cb shown in the table.
In other words, choose Cb=Cbt * Wb/4.8. Use nearest standard
value available.
Usually a 4 dB correction is best.
XM9 Baffle step compensation
Rb
Cb
R22 or
R23
XM9 circuit
board
Select R22 for hi-pass channel
Select R23 for lo-pass channel
Solder parts to
bottom of board
10

Fig 10. Typical uses of XM9 crossover network.
11

Fig 11. Top view of crossover network.
Fig 12. Potentiometer cable assembly for level and damping control.
12

Fig 13. Typical installation in cabinet.
13

14