The readout says 55555555 initially. Each digit is a band for either front OR rear speakers.
A= low bass front
B= upper bass front
C= lower treble front
D= upper treble front
E= low bass back
F= upper bass back
G= lower treble back
H= upper treble back
What this means is that the EQ bands are really wide, not quite narrow enough to fix some of the problems I hear. But the bands are narrower than the three tone controls in the dash.
How to do it:
First, access the settings... see this message
. Then, follow these steps:
1. Use well-recorded natural sounding CDs (preferably not synth or dance music).
2. Don't use FM stations because they all sound different.
3. Set the tone control ***** to flat. These you will use later only to adjust between sources (CDs, tape, FM).
4. Listen at a loud level so you can really tell what band sounds too loud or too soft.
5. Always experiment only with front OR rear speakers, using the fader at one extreme or the other.
- Adjust the fader so only the front are playing. Then adjust the first 4 digits until it sounds flat on several songs or CDs. Keep the settings near 5, and only change those bands that need a little more or a little less. In other words, 9999 is not a useful setting.
- When done, shift fader to rear, and adjust only the second 4 digits. Your goal is to make the front speakers sound like the back speakers, which should both sound like live unamplified music.
- When done, set the fader where you like it and check that it sounds good.
- In my 2001 A6 4.2L sedan, I thought that 6535 6474 sounded pretty flat, perhaps a bit bass-heavy if you play it loudly.
6. If the bass still sounds too bloated in the upper bass or too undamped (lags behind the music), then try either putting towels or other damping material next to and below the woofer in its compartment, or try also putting some taut electrical or duct tape across part of the port in the side of the woofer, as someone else here has recommended at this link
... the more of the port is blocked, the more effect it will have. I haven't tried the tape trick, so I can't comment. You can also try leaving the compartment door off.
Another option is to add a crossover to the woofer. I don't think Bose rolls off the highs, at least not by much because the highs still can be heard rather loudly out of the woofers. One could make a crossover and add it to the system. I'd try a 6 dB rolloff at around 100 Hz. Any more effort than this, the woofer doesn't deserve... just replace it.