you can do a few different things - first is to test the wiring to the rear speakers and drive with some external source (like a portable radio with speaker out jack). You should be able to find the pin out for the factory connector online along with the wire color codes. Next would be to connect directly to the speakers. Third would be to use an external power source and pull the head unit from the car to see if it drives an external speaker.

Usually speakers can fail one of two ways - the coil or spider wires can open up - which means cone action or the foam surrounds tear limited bass and adding distortion. So your testing needs to consider the head unit, wiring and the speakers. I doubt both rears would fail at the same time due to the speakers so I'd look at the wiring and head unit.

In terms of replacing, Any Volvo "double DIN' should be plug and play and can be found cheap on eBay - if you buy a replacement for your head unit just make sure that 1) the seller provides the code (you can't get the code from the radio unit serial number, only the original car's VIN). 2) choose the proper face color (radios came in black or gray) and whether you want a CD player or just cassette.

Note that RobertDIY also has a vid on Youtube for modifying the head unit to accept an MP3 player input. I have not tested that out yet but may do so shortly on an old SC-813 I have in the basement :-)

 

Thanks for the reply!

I'm going to give this a go tomorrow after I replace my spring seats. I think I'm going to open up the rear shelf speakers and see if I can't find any problems in those. I tried it out again tonight and with the fader completely to the rear I hear just the shelf speakers (no rear doors) and they are almost inaudible and tinny. I had the same thought about the rears failing all at once- seems suspect and doesn't seem like they were blown or there is a wiring issue.

I looked at the Volvo double DIN and I would prefer to keep the complete stock look, but I want a bluetooth connection (new iphones...). I was hoping to find an aftermarket double DIN that has a clean, minimal look without a ton of unnecessary features.

I'll be back with any discoveries!

 

 

I wouldn't worry about matching speaker impedance when testing. That only comes into play when you are driving speakers under full load. Most car systems use either 4 or 8 ohm speakers. As you noted if you wire 8 ohm speakers in parallel (ie rear doors and rear deck on the same wires to the amp), the amp sees a 4 ohm load. The problems start when you wire 4 ohm speakers in parallel and create a 2 ohm load where the amp will now be asked to produce double the current at a given volume. If the amp is designed for a minimum 4 ohm load and you turn up the volume you can overdrive the output of the amp (which will either distort the sound or overheat the output transistors risking damage to the amp). For testing purposes its not a problem to put 4 ohm speakers on your home stereo (most home stereos can tolerate 4 ohm loads - in fact higher end stuff can go to 2 ohms by design to show their ability to handle high output current).

When you inspected your speakers, did you notice if the cone's foam surround was torn? That will keep the cones from springing back and make the tinny sound (time to fix or replace). Note a speaker outside of a box or casing will sound tinny but if you have a good surround and the cone has proper excursion it should be good. if the speaker is a "coax" then you need to inspect wires for any solder cracks or broken leads as the speakers have a crossover circuit (effectively its a high pass filter that sends the signal's high frequencies to the tweeter and the low frequencies to the woofer. Its possible for the wires or circuit components to fail so one of the speakers gets no energy. If that's the case then you'll hear the highs but the woofer speaker won't even get a buzz.