Precision Power PPI4240 - Manual (Page 8)

7
All PPI amplifiers are capable of being bridged into a 4-Ohm mono output
without switches or bridging modules. This in turn allows you to run Full
range or component speakers and a subwoofer off one PPI amplifier. (using
passive crossovers)
You can achieve this mono channel by using the Left positive (+) speaker
connection and Right negative (-) speaker connection. You can bridge
channels 3 and 4, on your PPI four channel amplifiers, in the same way.
(Refer to the end panel drawing on page 8.)
Your new PPI amplifier offers you the flexibility of mixed mono operation.
This means you can operate each pair of channels in both stereo and mono
mode at the same time. This is accomplished by using highpass filters
(capacitors) on the higher frequency stereo channels, and a lowpass filter
(coil) on the subwoofers. The frequencies of the chosen highpass and low-
pass filters must not overlap (allow the mids and highs to play the same
music as the subs) or the impedance the amplifier sees at those frequencies
will be cut in half possibly causing it to go into protection.