I have just finished my audio upgrade on my 89 560SEL.

I read ALL the threads here on a W126 and asked a lot of questions. This solved my speaker selection and then I went and looked at a lot of headunits.

I wanted something that wasn't garish at all and pretty low key and fitting with the interior. I ended up getting the black stealth front JVC head unit which is 4x50w, mp3 etc. This really fits and looks great. When not in use you would be hard pressed to pick it out as being a stereo.

I ran new wiring to the front and rear speakers directly from the head unit to the factory locations in the front dash and rear parcel shelf.

I ran the wiring for the rear along under the plastic door sill plates and under the carpet, up through the seat base and through a grommet into the rear deck area. I used the original cabling that ran across to the drivers side speaker as a draw wire to draw my new cable through in the stock location. Make sure your join is very tight :-)

I used the Eclipse 6.5in rear and the 6x4in front. Both are reasonably well priced and slot in with little modification. The 6x4 front requires an ear to be cut off and a couple of holes drilled to allow the speaker to screw in with three screws.

The rear requires the factory speaker with integrated raised mount to be removed from the rear deck and the speaker "separated" from the mount. The mount must be used as the deck opening is really shallow.

Both rear speaker covers had disintegrated foam so I removed that completely. Both covers also have a broken lug at the front, they still secure fine with no issues though. One broke on removal and the other on replacement. These are $199 from the dealer each so I reused them.

Thanks to Scott at La Jolle audio as his speaker recommendations and fitting guides here were invaluable. Search here on Scott's username and you will find a lot of valuable info.

This link is the best with pics. I unfortunately didn't get any pics of my install :-(

W126 question for Scott

The sound difference is amazing, both in quality and volume. The fader and stock cabling certainly won't be helping and judging by the foam in the rear speaker covers these things get baked.

I am going to replace the fader switch with a lock switch from a W140 which will activate my central locking.

Matt.

You might not need to rewire the speaker wires if you had just connected your new hu directly to the 2 rear oem amps' speaker connectors. That way you could still use the factory speaker wires (saves both time and possible damage to upholstery due to opening and closing all those panels).

The factory speaker wire is pretty poor. Removing the trim panels isn't really an issue if you are careful and know what you are doing.

Matt.

I have a 1991 300SE and am looking to replace the head unit and speakers also. My question is I have 2 door speakers in addition to the 2 fronts and the rear parcel shelf ones and I am not sure about wiring in the head unit to the factory harness. Any ideas how best to do it?

If you are just looking to wire in the new head unit correctly without replacing all the oem speakers and speaker wires, then your best bet is wiring the 8 speaker leads from the new unit to the 2 oem amps behind the rear seat cusions.

You'll see 1 amp on either side behind the cusions and you'll want to connect your speaker leads to the connector that connects to the factory amp. Connect 4 wires onto each connectors and you'll get perfect sound.

You'll be bypassing the oem amp and powering the oem speakers with your head unit.

The factory speaker wires might not be the best, but connecting this way gives you the optimal sound quality short of changing the whole setup.

I did my 90 560sel this way with an old JVC mp3 unit (paltry 23 watt rms per channel ) and the sound is just great. No hissing noise and no alternator noise. Just great audio.