The Symphony radio head unit for your A4 has the ability to set independent bass/mid bass/midrange/treble settings for the front and back speakers. This will allow non-bose users to achieve a much higher level and quality of audio without distortion and allow bose users to get some of that much-needed bass and, in theory, still move the sound stage forward at the same time.

If you somehow manage cook your speakers or your brain by playing your radio beyond the capability of your speakers I'm not responsible. Neither is Audiworld. You know the drill.

I'd like to thank all the people on the S4 forum who actually figured this out. I'm only writing the tech article because I don't want this info to disappear over time on the forum :)

So, on to actually making this work. To access the EQ all you have to do is turn off your car and remove the key. Then hold down the number '5' on your CD changer/Radio preset control and power on the head unit.

You will see '55555555' if your radio is in stock form. These numbers represent 4 EQ settings each for front and back. They are, in order from left to right (courtesy of LCP on the AudiWorld forums):

1. Front low bass
2. Front mid bass
3. Front midrange
4. Front treble
5. Rear low bass
6. Rear mid bass
7. Rear midrange
8. Rear treble

To adjust the settings, use your volume knob to change the flashing digit to a value from 1 to 9 (1 being the lowest level, 9 being the highest) and press P.SCAN to go to the next digit. When you get to the end it will wrap back to the first digit.

The most popular settings for bose seem to be 88698869, however after a bit of testing with my favorite music, I found that to sound boomy and hollow and have since gone with 76567656. My next task will be to increase the directional (midrange and treble) sound on the front speakers only to bring the Bose sound stage back towards the front without sacrificing bass out of my rear speakers.

The best setting that I have heard for the non-bose system is 38679657. It still doesn't sound like bose, and certainly not like a good after-market setup, but it's a major improvement for those that wish a simple change to improve their overall sound and reduce distortion.

As always, YMMV. Feel free to contact me with questions or comments, although your best resource may in fact be the AudiWorld A4/S4 forums to ask about people's favorite settings for whatever type of music they listen to.