2002 pontiac trans am

According to information I have gathered at the other forums that you too have been visiting.  The speakers in question are subwoofers.  I would have to assume that each speaker has a left and right channel voice coil.  Thus meaning that each speaker will get a left channel signal and a right channel signal.  You cannot connect these 2 seperate outputs together.  It is a bit more complex than 2 batteries in a diesel truck. People have tried changing the speakers and using only one set of the wires.  The results are all the same, less volume.  If the left coil of the left speaker is paralelled with the left coil of the right speaker, the amp is seeing a 2 ohm load on each channel.  And the same for the right coils.  If this is the case the amp will put out half of the power into a 4 ohm load vs. the original 2 ohm load.  I know Infinity is now making some speakers that are 2 ohm.  I do not know if they are making woofers alone.  In order to verify my theory, first you need to remove the panels so you can see the speakers.  Balance to the left and see if both speakers still play.  Balance to the right and make sure they are both playing.  If they are both playing all the time, you will need to get an ohm meter, remove both speakers, remove one voice coil from one speaker, balance the system and see which channel is still playing (left or right) Go to the other speaker and remove one coil from it.  You need to unplug the same channel that was unplugged from the other speaker.  Balance to left or right and make sure that both speakers play when balanced either left or right and do not play when balanced to the other channel.  Once you do  this, you need to turn radio off       This is  a very important step.  Turn the radio off. 

Using the ohm meter set to the lowest ohm scale, check from one negative wire to the negative wire on the other side of the car. We are hoping for a dead short.  0 to 2 ohms depending on the quality of your meter and leads of the meter.  Now do the same for the positive wire   check from one wire to the other wire on the other side of the car.  We are Hoping for a dead short here too.  If both the positive and negative wires are shorted, you can try to find a  2 ohm driver (single voice coil) and connect only one set of wires to it.  You need to connect the left wire to the left speaker and the right wire to the right speaker.

If something is not exactly as I am assuming you really need to let me know before you connect anything.