I read about this a few years ago, and thought it was a cool concept. Now I can't remember what it's called or who makes it. It was a line level converter that plugged into your speaker harness, and internally equalized the input to produce a perfectly flat frequency response as the line level output. If memory serves, you played a supplied CD in your car stereo to 'train' the device to equalize according to what your stereo output. The idea was that you'd get a clean, flat signal to amplify. Anybody remember this?
umm never heard of anything like this. There are the standard line out converters but those are mainly for head units that dont have enough outputs or trying to hook up a sub on a stock HU. I dont get how that would work. The signal is already going to be flat unless you have a built in equalizer or crossover. I know my Alpine HU had a 'flat' mode you could turn it on if you were using an external equalizer. The main point of the equalizer is to maximize and even out the frequency response across the whole spectrum. Due to the placement of speakers you have to play around with boosting certain frequencies in order to get that even sound at your ear drums. Download some test tones and go play around with it manually. Sit in your car with your eyes closed and play.
I use a Navone LOC to get a signal to my amp, but what I really want is this: http://mobile.jlaudio.com/products_cleansweep_pages.php?page_id=79
It was a few years ago (probably 4-5) that I saw this. The main idea was that it would give an 'ideal' line level signal regardless of your stock head unit speaker line output. So yeah, it was for hooking up a nice amp/speaker system to a factory head unit that didn't have line level out to begin with. I know you still need to EQ according to your environment, of course. Not planning on getting one, but I was chatting with a co-worker about it and couldn't for the life of me remember where I saw it or who made it. If I can dig it up I'll post a link.
Any car audio place will have line out converters. You splice them into your speaker wires and can then run component audio cables to an amp. They make fancy ones where you can boost the signal a bit more than usual also, but overall LOCs are not that great for sound quality. Radon, that JL hardware looks pretty nice, but I'll stick to my Alpine with component outputs.
Thanks Radon! That is exactly the unit I was looking for. I knew I wasn't crazy. "To accomplish this complex feat, you simply load the supplied CleanSweep™ calibration CD into the factory-installed CD player, set its volume control between 1/2 and 3/4 volume, play the designated calibration track and then press the “Calibrate” button on the top of the CleanSweep™ processor."
That JL unit just came out a few months ago. Those of us with integrated stereos/climate control on the Legacy have little choice but to use LOC's unless we mount a 2nd radio in the upper cubby hole or shell out $400 for the cleansweep. http://www.autosound2000.com/ (Navone Engineering) has some of the best LOC's available.