Why does both of the front door speakers sound so low? I have a 2000 jeep grand cherokee with a infinity gold soung system with a amp under the rear seats.

A bad connection at the speaker or the unit could be a problem. Burned out amp section as well.
This may help.

Make sure the speakers are matched to the system

1997 Jeep Grand Cherokee Car Stereo Radio Wiring Diagram.
Car Radio Constant 12V+ Wire: Red/White
Car Radio Switched 12V+ Wire: Red/Gray
Car Radio Ground Wire: Black
Car Radio Illumination Wire: Blue/Red
Car Radio Dimmer Wire: Orange
Car Radio Antenna Trigger Wire: Green/Red
Car Radio Amp Trigger Wire: N/A
Front Speakers Size: 5 1/4′
Front Speakers Location: Doors
Left Front Speaker Wire (+): Green
Left Front Speaker Wire (-): Brown/Red
Right Front Speaker Wire (+): Purple/Yellow
Right Front Speaker Wire (-): Blue
Rear Speakers Size: 5 1/4′
Rear Speakers Location: Rear Doors
Left Rear Speaker Wire (+): Brown/Yellow
Left Rear Speaker Wire (-): Brown/Light Blue
Right Rear Speaker Wire (+): Blue/White
Right Rear Speaker Wire (-): Blue/Pink

pls rate
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Yes, the Infinity Gold series audio systems have a separate amplifier. In my '97 the amplifier is located under the drivers side rear seat.
Note that the amplifier is set to have speaker level inputs as opposed to regular level inputs. Both the amplifier and the speakers are NOT easily mixed and matched with after market components.

no, you have to ck each wire where it goes.

The speakers are available online and at the dealer. The amp is under the rear passenger seat. I suspect you are right that the speaker is blown. Make him pay!
Rudy

no you dont have to take the dash out, all you have to do is take the defrost part of the dash off and it just lifts up and it uses plastic clips that if you are carefull it wont break, this will allow you to access the speakers with a small screw driver, if you have the ( Infinity sound system ) in your jeep make sure you replace the speakers with the infinity speakers or your sound system will not sound good, youcan purchase these speaker at your local jeep dealership how ever they are expensive I suggest looking in a salvage yard for some, to keep from blowing them turn your volume down.

Check here, this guide might have what you need.

http://www.installdr.com/InstallDocs/Jeep/PDF/533013.pdf

I have the file on my other computer - search other bulletin boards. Check with Crutchfield help desk.

Input wires are the speaker wires from the Amp head/receiver (so you can go to a BestBuy and ask them for the speaker wire colors). Black is ground. Yellow/black is main power. Blue/white is turn on wire. If in doubt take off the door panels and look at what color wires go to the speakers.