no sound from front speakers

[gijoe 10+ year member]

First of all I would like to say that I'm an idiot! I was doing some sound deadening on my front doors when I decided to take the project a little further than originally planned. Long story short, I disconnected and reconnected both front woofers of my components (Boston Acoustic s60's) to get the dynamat onto the door skin. I didn't disconnect the battery. Now I don't have any sound from my speakers. My hu seems to work fine, all of the menus work as normal and my subs still play. I checked to see if I turned the internall amp off (since my components are running off of hu power), but it's on. What do you guys think I killed? Did I most likely blow something in the crossover or did I kill my hu's amp? I hope I didn't do something that can't be fixed without replacing my hu. It's an 880 and I've only had it a few months. Any suggestions on what I can do to check for problems would be appreciated.

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[TurdFergueson2 5,000+ posts]

have you checked the connections from the back of the HU? I work on my car without unplugging the battery all the time. Really I'm new to a lot of this as well. But i would start there. Especially when you say that the HU still comes on.

 

[gijoe 10+ year member]

That's not the problem, I unplugged the wiring on my hu and plugged it all back in and the problem is still there. I thought it might be the crossovers but, my back speakers aren't working either. I don't know what's going on. I only disconnected the 6.5's from my components. and now none of them work, except my subs. Is there a fuse for the internal amp that I may have blown? Is this something that can be replaced? Help please.

 

[gijoe 10+ year member]

Ok, problem solved! It turns out that the prongs that connect the wires to the right woofer were also touching some metal in the door. Never again will I risk frying anything, I will disconnect the battery every time from here on.

 

[dyohn 10+ year member]

Hi gijoe. While it's always a good idea to disconnect your battery when working on anything electrical in a car, I assume you realize your problem was not caused by the battery being connected? If you short out one of the speaker connections your amp (either external or the one in the HU) simply shut down in protection mode to keep it from being fried. If you cleared the short and the amp came back on, then you didn't damage anything. The battery being connected or disconnected would not have affected this...

 

[gijoe 10+ year member]

That's good to know, thanks dyohn. I'm learning a lot about audio and general electronics, but there is still a lot I have to figure out. I'm a do-it-yourself kinda guy, which is fun a teaches me a lot. I'm still not sure I understand what I was actually making happen when the speakers weren't working. Was it that everytime the metal was touch the inputs my hu's amp was shutting down for protection? From an electrical standpoint, what was happening?

 

[dyohn 10+ year member]

Was it that everytime the metal was touch the inputs my hu's amp was shutting down for protection? From an electrical standpoint, what was happening?

That's correct. From a (simplified) electrical standpoint, you were connecting the amp's output to the car's ground (anytime the speaker wire touched the door frame.) This would cause the output transistors in the amp to short out and too much current would be drawn, which would fry the transistor, but most modern amplifiers have a protection circuit built-in that will detect this condition and can shut off the transistor faster than it can be damaged.

A speaker wire or push-on connector touching ground is not that unusual and can cause problems ranging from uncontrollable alternator whine in the system to amplifier failure. The good thing is you found it and fixed it. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[gijoe 10+ year member]

Good info, so would this tie into ohms. My speakers create say 4 ohms of reseistance so they draw a certain amount of power. As you reduce ohms you get more wattage. So would the car body be equal to a really low ohms rating? With such little resistance, it tries to draw more power than the hu can produce so it shuts down?

 

[dyohn 10+ year member]

You can thnk of it that way, sure.