The prior owner (or someone) must have fiddled with the stock sound system in my 1991 560 SEC. Maybe there was an after market CD player installed or removed during the transfer of ownership. Anyway, the system is extremely bass heavy with most of the bass coming from the door speakers. Adjusting the tone controls on the stock Becker barely make it listenable and that's with full treble, no bass. I think they got some wiring screwed up somewhere. Radio/Casette (no CD) work fine otherwise. Any thoughts on what to check?

Thanks,
J.Chip

The 1991 560SEC (10 speakers from the factory) routs signal from the front end Becker unit pre-amplifier to power amplifiers located behind the rear set back (that's how it is in my 1990 560SEL, and I suspect your 1991 SEC s/b the same). The output from the power amps powers the speakers.

You may want to check that the power amps have not been by-passed. Is there a separate power amp installed somewhere? It may also be possible that your mid-range speakers and tweeters are blown from excessive current, though this is more likely if after-market power amplification was used.

I suggest you inspect the tweeters (in the dash under the windscreen) and the mid-range speakers (in the door panels) for damage first, then check if the OEM power amps are in circuit - you will have to remove the rear seat back to get at them.

My problem is too much bass so I doubt that the amps are being bypassed. I am assuming the door speakers are for midrange while the rears should handle most of the bass output. If this is true, I'm guessing they may have mixed up the amp outputs sending the door signals to the rear and the bass to the door speakers. Sound logical or are the connectors tabbed to prevent such a screwup? Anyone know?

J.Chip

....the connectors to the power amps are keyed, so they would have to be cut and recrimped to do what you are suggesting.

i have some diagrams for the becker system on a 91 560sel. let me know if this would help. i can send it to you. basically, the head units feeds into an amp installed inside the trunk. The then feeds into the front and rear speakers via the fader wheel. The front consists of front door speakers and dash speakers. For the rear, there are 2 amps installed behind the backseat that powers the rear speakers( one for each channel).

Thanks. If they can be e-mailed, I'd appreciate it.
J.Chip