Audio Systems: Installing speakers, impedance mismatch, 6x9 speaker

Question
I just installed 2 6X9 speaker in my truck and when I turn the head unit up the speaker cut out. Is there something else I need to install

Answer
Possible causes are:

ONE:  Incorrect wiring which has placed a short on the line and causing the amplifier to shut down.

TWO:  Incorrect impedance match of the speakers to the amplifier inside the unit.

If the speakers cut out quickly upon turning up the volume that points to incorrect wiring.  If it takes some time before the speakers cutout it is more likely an impedance mismatch.

Wiring is easy to correct; especially if you have a VOM or meter to check the wiring for shorts or wrong connections.  You did not give the head unit particulars so I don't know what goes with that, but most in dash units have 4 ohm output quality; some are 8ohms.  If the ovals you put in are low impedance it could part of the problem.

Good Luck,
C