I've been toying with the head unit in my car for the past week to try and squeeze as many decibles out of my current speakers as I can. Strangely enough, I've had that deck for eight years now and I haven't stopped finding settings that would allow me to make better use out of my hardware.
My change yesterday trumped all so far. My deck has a mode called SF-EQ that pushes different frequencies out of the front and rear interior speakers. Essentially, this will let you push lower midrange and bass out of the rear speakers and upper midrange and treble out of the front speakers and/or tweeters.
Before I continue, this is what I'm dealing with right now. I have a Pioneer DEH-5500MP head unit (4x50W peak, 4x22W RMS) with a P-bus auxiliary adapter installed. My car uses 6" speakers all around. I'm not sure what the models for my speakers are (and I don't feel like popping the door panels and rear shelf off, thank you), but I have a set of 6" 2-way Rockford-Fosgates in the rear and a set of 4-way Pioneers in the front. The Fosgates deliver reasonable bass and excellent midrange with poor treble while the Pioneers deliver decent bass, good midrange, and fantastic treble (it has two little tweeters on it, so if you push the 10-12k range up, hihats and cymbals are ear-piercing).
As anyone would guess, the problem that I always ran into was that too much bass would cause the front speakers to distort and too much treble would cause the rear speakers to distort. I'd tried to use SF-EQ in the past to mitigate that, but while it seems like a no-brainer, the configuration options are lacking, to say the least. There is no real way to adjust the cutoff. It's pretty much just "somewhere in the middle of what you might consider to be 'midrange.'" So, obviously, it takes quite a bit of dicking around to be able to figure out how in the hell you're supposed to make it sound decent. I've figured out the secret to taming it a bit, and it's a very subtle one -- the fader. Setting it to the rear increases the perception of bass and setting it to the front increases the treble. It seems obvious, but when you consider that there are three other ways to adjust the bass and treble it's easy to neglect.
I threw a bunch of different music at it from every genre that I have on my iPod and found that I have to go back to Ex-EQ for songs with heavy midrange, as the EQ behaves strangely when you reduce the midrange (probably due to the fact that there are so many seemingly unrelated settings for it) and pushing more bass on the front speakers helps that. In some other cases, the bass frequencies creep a bit too high and move into midrange territory and cause the rear speakers to distort, so I have to play with the midrange band to exclude that (which, in turn, negatively affects other songs...sigh).
In other songs, most notably anything on Celldweller's first CD (haven't tried anything past that), it sounds incredible. With Ex-EQ I'd have to cut the volume back to get reasonable bass or cut back on the bass to get louder overall volume. With SF-EQ I drove the speakers hard and they didn't distort. The bass wasn't as loud as it would be with a subwoofer, but it was at least there, which is more than I could say about my previous settings.
Unfortunately, now I'm running into limitations of what the amplifier can handle. Oh well...
