I was searching for a guide on how to properly tune a cars stereo (lo's, mids and highs) and eventually found a very helpful page, figured some of you might find it useful too.
Amplifier Tuning (Tutorial) - Nissan 350Z & 370Z Wiki

 

good read

 

I gave it a shot. The mid was extremely easy to adjust. The high was much harder to get right but I got it. And my low can't be adjusted because I can't get distortion at the required sound level (infinity 6X9's, no external amplifier), but that's ok because I like the bass tunred down anyways. Highs and lows are now adjusted as close as possible to reproducing the music as it was recorded, according to the article. And it sounds really good, so it was worth the time IMO.

Distortion at volume level 32 / 50, so adjustments were made at volume level 30.

High is at 7 (-10 to 10)
Mid is at -8

 

Horrible way to tune. Even with a O-scope it has been proven that this method is still very inaccurate.

 

so what would you recomend?

 

Play music and use your ear... I mean o-scope is going to be the best method with tones, but you have to use several tones for each speaker. I watched a video a while back showing that method with an o-scope... what wasn't clipping at 60hz, was still clipping at 30hz.

 

Tuning is the hardest part of stereo installation, in my opinion. I've always been one to use a DMM to get stuff within the right level, then use my ears to 'spot' out any distortion. Tone CDs are great for sub tuning, but when it comes to tuning your mids and highs, get familiar with a song that has alot of different instruments and/or tone ranges. I listen to alot of jazz, and there are several songs I am familiar with that I've listened to for years on my Sennheiser HD600s(HiFi headphones). These are the songs I use to tune stereos. When tuning, try to use an audio CD(not an MP3 CD) that has been burned with high quality files or preferably an original CD.

 

I go by ear. Your setup never stays the same because of gradual improvements.

 

The problem with this method as 727kid said above is that it only includes 60hz and 1000hz. 60hz is too high. On many high end SQ systems the crossover points are going to be below that anyhow. But even if they're not, if your sub happens to not distort at 60hz but distorts severely at 35hz what good did it do for you?
1000hz is the same issue. That's very low on the midrange scale, so what about 1001hz through 20,000hz? Do we just not care how it sounds through that huge range?

You do not tune a stereo that is expected to play 20hz-20,000hz with only 2 poorly chosen tones.

 

correcto, lol. do not use any external devices like aux. cables going to your ipod either...idk y but my freind learned that the hard way. lol good quality cd's will bring you your true sound