Specifications

Truck installations / Center channel
speakers
The main differences between a sedan car for perso-
nal use and a truck are:
- 1 the wideness of the car and
- 2 the high noise level in a truck in motion.
This makes it hard for the driver to listen to the right
speaker ( if the steering wheel is on the left ) and for the
passenger to hear the speaker on the drivers side.
Although a single driver can adjust the balance left right
to compensate for this, a better solution is to add a
center channel speaker / speakers.
Often you use a 4 or preferably a 5.25 inch speaker
positioned at the center of the dashboard. Very often
you use two speakers of reasons we will show later.
One center speaker connects to the left channel, but
often at a lower level compared to the main speaker.
The other center speaker connects likewise to the right
channel. The two speakers together will thus play the
sound of Left + Right.
This will fill in what you can call the gap in the
soundstage of the earlier installation.
Your side system will hopefully be good 6,5 inch coaxes
or two-way systems or even better. A small center
channel speaker of smaller size will have to be feed at
a lower level of volume and if possible through a band
pass filter to limit the frequency response to say 500 -
6000 Hz.
You can also use one speaker only, but connect it to
the CAT31 amplifier in the bridge mode way. Thus the
speaker will receive the Left + Right channel.
As this voltage is twice as high as what we feed to the
left or the right speaker, we now must use a voltage
divider or attenuator to bring down the power to what is
suitable for the speaker.
Connecting two center channel speakers
with bandpass filter
Connecting one center channel speaker
in bridge mode with bandpass filter
It is not necessary to use a bandpass filter, only if you
want to limit the frequency range. The bandpass filter
limits the frequency range from 500 to 6000 Hz.
On next page is a drawing if you want to build your own
bandpass filter.
7
0-20 Ω
15 Watt
+ A-CH - - B-CH +
+
+
-
-
-
+
R = 50 ohm
15 Watt
Center channel
Left + right
Right
Front speaker
Left
Front speaker
Bandpass filter
Left
Center channel
Right
Center channel
Bandpass filter
+ A-CH - - B-CH +
Left
Front speaker
Right
Front speaker
+
-
R = 20 ohm
15 Watt
0-20 Ω
15 Watt
+
+
-
-
-
+
R = 20 ohm
15 Watt
0-20 Ω
15 Watt
The drawing below show how to connect two center
channel speakers to the CAT 31, through a voltage
dividing circuit. Using a potentiometer you can adjust
the volume from the speaker.
If you want to connect a bandpass filter, do so by
using the filter design suggested on next page.
The drawing below show how to connect one center
channel speakers to the CAT 31, through a voltage
dividing circuit. Using a potentiometer you can adjust
the volume from the speaker.
If you want to connect a bandpass filter, do so by
using the filter design suggested on next page.