help - speakers cutting off

[mcG]

yesterday i put my kenwood deck up all the way during a quiet song to see how loud it went, and its been acting funny since. i have a set of infinity components in the front, a set of midranges in the rear, and an amp/sub. so the problem is, if i turn on the unit, the 4 speakers will be fine for about 10 seconds then just go off, while the sub still plays.

any idea what is going on ?

ps i thought i should also add that the head unit (not the amp) powers the speakers.

 

[99MercNeer]

Not quite sure, but a few steps in troubleshooting:
-Try fading all fwd and all rear
-Try balance all left then right
-Try both at same time (ie all sound to right/front)
-While doing this adjust volumn through entire range
-These steps may isolate a failed speaker (a speaker that has blown and is "pulling down" the entire sound stage)

Well, post some more once you've tried this and let us know.

 

[izackary]

Naw. If the speakers start to play fine every time he turns his headunit on, it's most likely the internal amp, not the speakers. Only chance it's a speaker (and this is possible) is if the headunit was turned up so loud it clipped the audio signal. In a nutshell, clipping makes your speakers overwork themselves, and given enough time, WILL ruin them. If you fried a speaker's voice coil and shorted it, the headunit is likely going into a protection mode. If isolating one speaker doesn't work as the headunit shuts its amp down, you can measure resistance between each speaker's + and - wires. You could measure at the speaker, or what's probably easier is measuring each speaker at the headunit's harness. Make sure you check them all.

 

[Longjohn119]

Yup, sounds like a shorted voice coil/speaker wire or you blew an output and it's trying to send raw DC to the speakers and the protection is shutting down although I don't usually see that kind of protection except on home amps ... be careful because raw DC will toast a voice coil real fast

Like the gentleman said, measure the ohms of each speaker at the head and look for a short or abnormally low resistance in one speaker, if they look OK then put a voltmeter on the output wires of the head unit and look for dc voltage, any more than a couple of millivolts means you have a shorted output IC/transistor ... that's why you hear most home stereos go click a few seconds after you turn them on, they look for DC on the outputs and only click in the protection relay if everything is OK

I wouldn't run the unit with any speakers hooked up when testing because as I said if it's sending raw DC to the speakers you can toast a voice coil very easily before the protection shuts it down ... then you'll have a blown output amp AND blown speakers to deal with

 

[99MercNeer]

That's true... I was assuming (I know, I know an a_ _ out of me and you) that his unit would automatically self protect and shut down if his speakers clipped again. I had a similiar issue with my clarion head unit and the stock MACH audio door speakers... after I changed to the Memphis 5x7, I have not had an issue. Reading the DC resisitance of each speaker is the best option...... provided the guy has a multimeter (preferably a digital one since 4 ohms is quite hard to distinguish on an analog unit). Of course the Rat Shack has a $19.99 Digital Meter that would sufice for simple car audio applications. Well, keep us posted on your findings.

 

[Longjohn119]

You can usually find a digital multimeter for around 5 bucks that will work just fine for most people, I keep one 'cheapie' in my car, one in my boat and one in my house in addition to my 'good' multimeters ....