distortion, head unit 3/4 volume?

So, was installing a deck in yet another customer's car and got to thinking bout some stuff past installers would say. The one that I'm wondering about today is the whole 3/4 volume rule. Is it really true all cd players will exhibit after 3/4 volume? I ask this because I was tuning a deck in a 04 Tahoe, using a Pioneer Deh80mp with a Alpine 4ch amplifier going to 6.5" Type R components. With the amp all the way down, crossover bout 100hz (I know, kinda high, but I was experimenting) with the deck all the way up, sounded like hell. Even when I took the crossover to 150hz, it helped, but didn't solve the problem. If'n I take the volume down round the magic 3/4 volume, distortion goes away. Any thoughts?

No... It's not a magic number, merely a suggestion. Ideally, you look at the signal with an oscilloscope, and set your volume control to wherever it needs to be, not necessarily at 75%. Pretty much ANY deck will have BADLY clipped outputs if you crank it up like that. You didn't say whether the deck was aftermarket as well, but if you are using an LOC on speaker leads, you are only sending it over the clipping edge faster. It is possible that on that PARTICULAR source unit, 75% might still have as much as 10% clipping happening, or conversely, that one MIGHT be able to go as high as 85% before radical clipping is happening. As I said, you cannot tell easily by ear, and should be using instrumentation to ACCURATELY set all of your levels.It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

As far as what deck, the one I was tuning at the time was a Pioneer Deh80mp. I've noticed it with other brands as well. Factory decks with LOCs would obviously do it. What I was hoping to do is find out if you fellas with oscilloscopes might do a head to head with a few decks (real world decks, not just the exotics) and let the rest of us po' boys in on the info. Any takers?

Yup, try a Eclipse cd player and see what you get. Many of them use a non-clipping high voltage low impedence preout. Now of course that is all fine and dandy but the second you start using eq's, bass settings turned up too high, crappy recordings etc., that lowers the threshold yet again. Careful experimentation and years of experience are the installers best friend here. Sadly, there is not much that can be done for those that do not have it yet, save for asking questions.Top Secret, I can tell you but then my wife will kill me.