6/17/2017
XKITZ XAMP-M2
8
Initial Power-up and Calibration
Before applying power for the first time, it’s a good idea to make sure the bass, treble and BSC are fully
disabled. The trim-pots are high precision, 20 turn pots, so in order to ensure the bass, treble and BSC are fully
OFF you need to turn all three trim-pots 20 full revolutions counter-clockwise.
There are a number of different methods to calibrate a 2-way active crossover. Below is the method we generally
prefer. We like to first set the bass level using a voltmeter or an oscilloscope, then gradually raise the level of the
high channel and set the ideal level exclusively by ear or with a spectrum analyzer.
In a stereo system, you’ll want to try and calibrate both L and R at the same time to maintain a close balance of
the L and R volume levels.
For steps 1-4, you should disconnect your speakers from the amplifiers because it’ll be very loud.
1.
Use a signal generator of some kind to inject a sine wave into the XAMP. Free signal generator apps are
widely available for any smart phone or on the PC.
2.
Set the level of the signal generator to 0.5V RMS. On a voltmeter set to AC, it will read 0.5V. On an
oscilloscope you’ll see a signal with a swing of 1.41V peak-to-peak.
3.
Set the frequency of the signal generator to around 50Hz.
4.
Set your voltmeter to AC and connect it to the Woofer speaker outputs. Raise the Bass level pot until
the output voltage is equal the ‘Volts RMS’ listed in Table 4 below for your power supply voltage and
woofer impedance. The table also shows the max RMS watts per channel power you can expect for each
setting.
5.
Now that you have your bass level set, it’s time to set the crossover Treble levels. Connect your
speakers to the amplifier and your normal audio signal source to the input and set the volumes to a
comfortable listening level. Either use a spectrum analyzer (free smart phone or PC apps are available)
or just use your ears to monitor the audio from your speakers. Since the Treble levels are set to zero,
the sound will start out dull and lacking in any high frequencies. Slowly raise the Treble level control
pot until your treble levels are flat on the spectrum analyzer, or until they sound natural by ear. You
may want to adjust the L and R in isolation so that you can make sure both are dialed in perfectly,
without the other channel interfering.
6.
Now slowly raise the BSC pot(s) until your bass response sounds natural, or the lows below the baffle
step frequency look flat on the spectrum analyzer (see table 3).
Table 4.
Max Woofer Output Voltage vs. Power Supply Voltage and Driver Impedance
4 Ohm Speaker
8 Ohm Speaker
Power Supply
Volts DC
Volts RMS
RMS Watts
Volts RMS
RMS Watts
22V
5.9V
9W
6.2V
5W
24V
6.4V
10W
6.8V
6W
26V
6.9V
12W
7.5V
7W
28V
7.5V
14W
8.3V
9W
30V
8.1V
16W
9.0V
10W
32V
8.6V
19W
9.4V
11W
>34
9.2V
21W
10.0
12W