Car Stereos: Head Unit/ New speakers, sony head unit, factory speakers

Question
This is somewhat of a follow up question to this particular one: http://en.allexperts.com/q/Car-Stereos-3638/2009/3/Car-Audio-Amp-Head-1.htm

The story goes, I just bought a new Sony head unit with the normal rating 52 x 4, and I installed it with my factory speakers.  I also bought Kicker 4 x 10s that are rated at 70 watts peak, and 35 RMS.  I had just installed 1 of my speakers and tested it out, and sure enough, my head unit shut itself down, I knew it couldn't have been a problem with the speakers because they are rated higher than the unit, and when you answered that other gentleman's question, you mention faulty power connections, what can I do to fix this problem?

PS. I did install it myself, but it has worked fine with the factory speakers at full blast.

Answer
Hi Luke,

Sorry about the delay in answering this question.

A mismatch in power ratings, no matter how great, won't cause a head unit to shut down.  The fact is, your Sony head unit has no way of knowing what the power rating is on your speaker; and in your case, it's really not a mismatch--the RMS power output of the head unit is around 20 watts, so you won't find many after-market speakers that come closer than the 35-watt rating on your speaker.

What can shut down the head unit is a mismatch in impedance, or a speaker wiring problem such as a shorted or grounded speaker wire.  As long as you're using a speaker rated at 4 ohms or higher, and the speaker wire isn't grounded or shorted, the head unit should be able to produce sound through it even if it's a 100-watt speaker.  

Given that the head unit shut down as soon as you connected the speaker, I'm wondering if there may be a problem with the speaker itself.  It's not completely unknown to have a speaker that's defective out of the box.  Did you try the connecting the second speaker of the pair instead?

I've seen speakers that had an internal short, so that the terminal or tinsel lead was touching the speaker basket--they'd work fine, until you screwed the speaker into place.  Then the speaker wire would be grounded through the speaker basket to the chassis metal, and the deck would shut down.

In the other question, I mentioned a possible power wiring fault because there was some question about whether the deck was shutting off entirely, or whether the deck stayed on but the sound shut off.  If the deck shuts off altogether, with no lights or display, it's probably a power wiring issue rather than a speaker problem; but if it's just the sound that cuts out, then the problem's likely in the speaker or speaker wiring.

Hope this helps!

Brian