[darkpuppet]

So what are you tuning for? SPL or Sound quality. for quality, it's a matter of getting an oscillascope (sp?) and a pink noise CD, and adjust your equalizer so your curve is flat.

I think it's pink noise.. man, it's been a while

SPL is just loudness, you can go to radioshack and get a Db meter, set it in the middle of the car, and get a CD that sweeps to take your readings. Simpler than going to a shop.