Assuming your amplifier is capable of being bridged and you have decided it will work with your equipment, the actual process of bridging your amp is fairly simple. Turn off the power to your amplifier and disconnect your speakers. Most amplifiers will use the left input as the bridged mode input. Check the back of your amp for this information - the input to use for bridged operation should be marked in some fashion. Connect a single RCA cable from your pre-amp to this input. Run a strand of speaker wire from the positive (red in almost all cases) input on your speaker to the positive speaker-level output on your amplifier corresponding to the bridged input you just connected. Connect the negative (black in almost all cases) input on your speaker to the second POSITIVE (red in almost all cases) output on your amplifier. In most cases the wiring will work like this: a speaker wire connection will run from the positive (red) output on your amplifier''s left channel to the positive (red) input on your speaker and a speaker wire will connect the positive (red) output on your amplifier''s right channel to the negative (black) input on your speaker. Once you have made your connections, flip the bridging switch from stereo mode to bridged or mono mode and power the amplifier back up.
The important points to remember in bridging an amplifier are to switch the amp to bridged mode, use ONLY the amp''s positive speaker outputs, and be sure your amplifier and speaker will work well in bridged mode based on the speaker''s nominal and minimum impedance (halved) and your amp''s capability to operate into low ohm loads.
the reason im asking is because someone told me this isn't how you do it