Volvo 850 Made from 1993 to 1997, this Volvo line was available in both a wagon and a sedan, both with were graced with several trim levels.

Rear Speakers Donít Work

  #1  
Old 02-01-2019, 11:55 PM
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Join Date: Feb 2019
Location: San Diego, California
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Default Rear Speakers Donít Work

Hey there! First post in the forums but long time lurker. Iíve had my 850 NA for almost three years now and am looking for some advice for the sound system.

When I got the car, the rear shelf speakers didnít work great. One seemed to work, while one seemed like it was blown. I ended up disconnecting both of them and had good sound for a week before suddenly the rear door speakers stopped working...

As of now, all of my front 4 speakers work fine. The rear door speakers donít work at all, and one of the rear shelf speakers works intermittently. It has the SC-815 in it with no external amp. Iíve been wanting to install a new head unit.

TLDR - Basically all of my rear speakers have stopped working. Rear shelf works intermittently but sounds blown or extremely underpowered/tinny. Will a new radio fix this? What do you think is the solution?

Thanks for any input in advance folks!
 
  #2  
Old 02-07-2019, 02:24 PM
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Location: Ridgefield, CT
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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 :-)
 

Last edited by mt6127; 02-07-2019 at 02:29 PM.
  #3  
Old 02-09-2019, 10:26 PM
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Default Update

So I pulled the rear deck speakers and rear door speakers today. Hooked them up to my home stereo, as they are 8 ohm outputs. Did the same thing- super tinny and the large cones didnít move.

My working theory is as follows- itís not the head unit at fault. When I bought the car one of the rear shelf speakers sounded blown/cut out. Found out today that one of the contacts had become desoldered. At the time I decided to unplug the rear speakers, effectively making the rear speaker output an impedance of 8 ohms. When wired in parallel, these 8 ohm speakers result in a 4 ohm impedance. Having disconnected the rear shelf speakers, my rear door speakers sounded great for a week before they cut out. I replaced the rear shelf speakers in hopes of solving this, but I probably replaced them too late and put them under the 4 ohm load and fried those as well.

As of now, it looks that my options primarily involve replacing these speakers or attempting to rebuild. Iím not sure of the possibility of rebuilding these speakers, despite the cones being in good shape.

Will update as this project continues...
 
  #4  
Old 02-12-2019, 11:35 AM
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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.
 
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