[niral622]

oooh, another western ny'er :P

it depends on how you hook the tweeters up...if you put then in parallel with the 4x6 plates, then it will reduce the impedance (which can be bad if your HU doesnt support it)...if you hook them up in series, then it will add up the impedances..

1/Rp = 1/R1 + 1/R2
Rs = R1 + R2

Rs = Impedance when hooked up in series
Rp = Impedance when hooked up in parallel

If you got those 4x6 plates for bass, then I think you might be better off getting a 5" or larger speaker in the door (kick panels?)...

Btw, if the tweeters are 8 ohms and your plates are 8 ohms, then you can put them in parallel to get a 4 ohm total impedance to the HU.