Speaker setup and options in my 928s4 MY 1988

  Size Depth Type Mounting Remarks
Front Door speaker 4" 1,5" Generic speaker   Boston Acoustix RX47, Blaupunkt PCXT402, MB214.03, Rockford-Fosgate (FRC2204), JBL40
Front Door tweeter     Dome hightone speaker   The originals seem to hold fine.
Rear Seat speaker 6,5"   Dual speaker or dual cone May need some Dremel work to fit in. QWC160s, JBL60, MB328.03, Infinity 6.5"
Rear Hatch speaker 4" 2,5" Coaxial    
Door Speaker Grill Some unscrew anti-clockwise, but  the 1988 S4 (and GT) just pop off. They become very brittle over time
Stock Amplifier 1988 928s4     Blaupunkt BQA107 4x25 watt In mounting space next to pass. seat


The large speakers on the '90 GT are two-Ohm units, while the rest of the speakers are the more common four-Ohm units.

This means that if you use the stock Blaupunkt amp, you have to use the stock speakers.

If you use different amps, you have to change the large speakers, which means finding suitable units, cutting the speakers out of the housings (they are part of the housing, not separate units) and gluing the new speakers into the housings.

There is more info in this thread...

Wally Plumley
928 Specialists


Ever seen the new flat Blaupunkt car speakers.
They use a push/pull magnet assembly so the speakers are much flatter than regular.

You might be able to gut the door panel and place in the shallow mount 6.5" all range speakers.