MaxAP1

Hey all,

Recently my driver side lower speaker stopped working. I figured it could be either a loose wire, a bad speaker, or a bad amp. I pulled my door panel off this morning and messed around with my multimeter. I don't know much about car audio (proper voltages, ohms, etc) so I was hoping you guys could help me diagnose the issue.

Here was a resistance test of the speaker. 2K ohms x .002 = 4ohms Does this mean the speaker is ok?


I tested the speaker wires at 20V with the radio playing and got no readable signal even after maxing out volume


When I tested the speaker wires at 2V I got a readable signal that would change with the volume


Is that voltage way too low to run a car speaker? Is the headunit amp the problem here?

windhund116

Disconnect the speaker from the amp. Measure the static (DC) resistance across the two speaker terminals. See what you get. For 8-ohm nominal OEM impedance, should be around 2-3 ohms DC resistance.

kwakhead

Those are 4 ohm speakers. Unhook all wires from them. Set your meter to its lowest setting. Looking at your pics that would be 200 ohms. Unhooked the speaker should read 4 ohms or very close to it.

windhund116

IME, 4-ohm rated impedance speakers --- measure around 1.5-3 ohms DCR. In any event, if the speakers read 100-ohms or higher, you prolly have a shot voice coil (need to replace speaker).

dwight

When using a multimeter, the number you select is the maximum value it will measure, so when you selected "2k", it was 2 kiloohms or 2,000 ohms maximum. The 0.002 it displays is showing you 0.002 kiloohm, or 2 ohms. You should not multiply the value by the range. The reason the range maximums start with a "2" is because the meter's left most number that it can display is is only a "1", so when you select 2 kiloohms, it can really only show up to 1.999 kohms. When selecting the range for what you're trying to measure, you should keep turning the range down until the meter maxes out, often showing "OL" and then go back a step. By setting the lowest range that is just over the value you're measuring you'll have a more accurate measurement.

As windhund116 alluded to, even though the speakers are "4 ohm" speakers, that's impedance, not DC resistance that you're measuring. Impedance is about AC and it's slightly more complicated that plain DC resistance.

i just replaced a pair of defective DB6501s with MM6501s. The MM manual lists the MM651/MM6501 impedance as 2.7 ohms even though it's considered a 4 ohm speaker. I have no idea what the resistance is, but it would be lower than the impedance. The DB manual might specify for your speakers, but as windhund116 mentioned, if it's shot it might be drastically higher.

My defective right channel was heavily distorted. It still reads 2.8-3 ohms. My left channel reads 3.0-3.1. It was nearly silent. The cone was frozen in place which prevented it from making sound.

Good luck with your trouble shooting,

MaxAP1

So I hooked up the "bad" left speaker to the other side and it worked fine (ruled out the speaker). Then I tried hooking the speaker up directly to the harness behind the head unit and it worked fine (ruled out the amp). I tested continuity in the speaker wires from behind the harness to the wire in the door and that pointed to the problem. There were some bad solder connections when the previous installer cut the factory speaker harness and soldered in the universal connectors. I cut all that out and spliced in the new speaker wire that goes to the crossover. Now everything works beautifully Figured I'd update in case it helps anyone else.

Next up, add in a bridged KTP-445U for some real power!

Chuck S

Thanks for posting your solution. Too many guys don't.

-- Chuck

windhund116

Yes!