Car Stereos: 2004 Pontiac Rear Speakers, monsoon sound system, monsoon system

Question
QUESTION: I recently bought Pioneer 6 x 9 rear speakers but I cant
manage to figure out how to install them. Can you give me a
step by step process on how to install them and tell me if any
extra parts or wire adapters are needed. Thank you

ANSWER: Hi,

I'd be glad to help you with this, but first I need to know what model of 2004 Pontiac you have.  Also, is the vehicle equipped with an upgraded factory sound system, like Bose or Monsoon?  How many wires are in the plug at each rear speaker?

If you can submit a follow-up with more information, I'll help you as much as I can.

Thanks

Brian

---------- FOLLOW-UP ----------

QUESTION: 2004 Pontiac Grand AM GT and it does have a Monsoon sound
system. There are 4 wires in each rear speaker.  

Answer
Hi Joshua,

I apologize for the extended delay in answering your follow-up question.  

Assuming that you're keeping the factory head unit and just replacing the rear speakers, the Monsoon system is going to cause a problem.  The trouble is that the stock speakers are a two-in-one design; they have separate connections for a high frequency input and a low frequency input.  The Monsoon amplifier has separate outputs for the rear channel bass and treble.  Of the four wires in the stock speaker plug, two of them are carrying only bass frequencies and two are carrying only high frequencies.  There's no wire pair in the rear that carries the full audio range.  Unfortunately, your Pioneer speakers are designed to work with a full-range signal; they don't give you the option of connecting separate bass and treble inputs like the stock speakers.  You can't combine the two outputs together on a single speaker terminal; this will result in poor sound, and may damage the Monsoon amp.

You can install the speakers, and connect just one pair of wires.  The bass frequencies are carried by the dark blue/white and light green/black wires on each side.  This is a mono, deep bass output.  If you connect these wires to your new speakers, they'll only play deep bass and no vocal range.  This might be acceptable if your stock speakers are blown and rattling, and you're satisfied with the full-range output from the front speakers, and just want to get a clean bass output.  

If you use the high frequency wires--dark brown and yellow on the left, and dark blue and light blue on the right--you'll hear the high frequencies and vocal frequencies, but no deep bass.  This might be acceptable if you're planning to add an amplifier and subwoofer to pick up the low end frequencies.

To replace the speakers, you'll need to fold down the seats, then unclip the plastic panels on each side of the rear window.  Then you should be able to remove the panel that rests on top of the rear deck.  The speakers are mounted in factory spacers, on top of the rear deck metal and under the top panel.  You'll need to keep the spacers and use them with the new speakers.  To the best of my knowledge, there's no wire harness adapter for the 4-pin speaker plugs, so to connect your new speakers, you'll need to splice into the existing wires.

Hope this helps!

Brian