how to test speakers for short to ground?

[bhawk]

Installed a new alpine head unit in my son's 94 Ranger. It seemed to operate the 4 stock speakers okay after the install, but we couldn't get the subwoofer to deliver the kind of sound he had with the old head unit. Seemed there was no power going to the amp from the head unit using the RCA cable. Since the old head unit was set up to provide speaker level inputs to the amp, we plugged those into the amp. Got better bass out of the sub with that input, but still nowhere near what he had with old head unit. After trying the unit out for an hour or so, the sound out of the 4 stock speakers diminished, and eventually stopped altogether. Now there is no sound out of any speakers, even tho we disconnected the amp and subwoofer setup. I am thinking maybe the head went into safe mode after it detected a short to ground in one of the speakers. My question---how do I test each speaker or the wires to each speaker for a short? Right now I have all 4 speakers out of the panels sitting on the bench. Can I test the wires without speakers attached? Or do I need all speakers plugged in, and then remove each speaker one at a time to test?

 

[AgPete139]

If you have a multimeter, you can test the amperage & voltage coming from each hot wire to the speakers. You can get one for about $10-$15, from Walmart to RadioShack to Autozone.

You are basically saying that the 8 wires to the 4 speakers from the headunit are not working?

Also, the red+black RCA from the headunit to the amp, and then the 12 gauge/or whatever wire to the sub is not working?

Play with the settings again with the new head unit. You could have switched something off accidently. Put the gain and the bass boost on the amp to about 50% and go from there. May sure that the connections in the sub box are secure and everything is hooked up correctly. I've seen installations where the owners did poor quality connections, or where wires crossed at the amp. There needs to be a good power, solid ground (no more than 3 feet long), and the REM cable (usually the "skinny blue wire") is a must back to the head unit. In the head, have the polarity to stock +/- and make sure the sub option is on. Also, a good 12 gauge (or whatever size) power wire that has an inline fuse (say 35 amps) from the battery to the amp is also needed. **Check to make sure the fuse in the amp has not blown.

As far as your individual speakers go, there isn't much else to say but the run the wires correctly back to the head. If there are kinks or breaks, that could be a reason why they are not working (in which case, you could just run all new wire underneath the carpet to the dash and forget about all the old stock wiring). If you are going crazy with varying multimeter readings at each wire end, new spools of wire can be had for relatively cheap.

This is basically it. You are not running an outrageous system with 1200 RMS or anything. Good luck.

Pete

 

[bhawk]

thanks pete. I found one of our problems. When I tested each speaker off the car on the bench with my multimeter, I found one was basically a short directly to ground. No resistance on the meter. So we put the other 3 speakers back in place and tried the unit again after disconnecting the battery cable and hitting the reset button. Now we have sound at the 3 speakers, decent enough. Then we hooked up the amp and sub and find that it works if we use the speaker wire inputs that we jumped off the 2 rear speakers. But we have no sound at the subwoofer if we hook up the RCA cable coming from the head unit as an input to the amplifier.
Is there a way to test for voltage coming out of the head unit at the subwoofer RCA out plugs? This head unit, Alpine 9886, claims to output 4 volts on the RCA out plugs? If I test the rca cable for voltage out, how do I do that with a multimeter?

 

[Snowboarder7710]

you need to turn the subwoofer setting to "on" i believe on the 9886 i installed in my g/fs car i had to turn the sub output on. also on the "imprint" button on the right of the face, press that and change it to "sub sys 2" it pumps the output up for the sub quite a bit.

 

[bhawk]

thanks snowboarder for the info on the alpine 9886.
My son says that the sub output is automatically on by default according to what he reads in the electronic owners manual. The head does display a SW setting screen that allows us to dial in higher settings, but in our case no sound comes out to our amp no matter what the subwoofer setting. I will try and find that "imprint" screen button to see if that helps. I have this nagging feeling we just haven't got the head unit set right to output to the sub RCA's. Why do they make these head units so complicated.

 

[Slim]

RCA cables are an over-glorified regular speaker wire. They have a positive and negative all the same, they're just shaped different. If you want to test for Voltage on an RCA you stick one of the probes on your MM to the outer and the other to the inner. Biggest differences with RCA are ease of connection and better shielding.


Head units are only as complicated as you purchase. (sorry, cheap shot)

 

[4x4fun]

RCA cables are an over-glorified regular speaker wire. They have a positive and negative all the same, they're just shaped different. If you want to test for Voltage on an RCA you stick one of the probes on your MM to the outer and the other to the inner. Biggest differences with RCA are ease of connection and better shielding.


Head units are only as complicated as you purchase. (sorry, cheap shot)

rca' if i recall, dont have set +/- and depending if your using dc or ac, aand were the vol noob is alot can change. but its not a DC circuit. and you should never really have to check them any way,

 

[Slim]

rca' if i recall, dont have set +/- and depending if your using dc or ac, aand were the vol noob is alot can change. but its not a DC circuit. and you should never really have to check them any way,

Well, neither RCA nor speaker wiring alike necessarily have a set + /- and we're obviously specifically talking about an auto application, so ..... I don't know where you're really going with that anyway.

 

[Snowboarder7710]

im pretty positive you need to go into the menu and turn the subwoofer on. the sub level adjustment is still visible but it needs to be turned on. and the imprint button is on the right side of the face. it looks like this: ((())) sorta....with imprint written on it too. theres 2 different menus....theres a setting when you hold it down for a few seconds....or just push it once theres a diff. menu

 

[AgPete139]

BHawk...updates?

 

[bhawk]

Well, I tested the RCA cables and get no voltage readings, so I am pretty convinced the head unit is bad. We can get the sub going by using the old speaker wire\splices as input to the amp. Will work for now. The 4 stock speakers sound okay but we were hoping that the subwoofer system on the head unit would allow good loud bass with an ability to dial the remaining 4 stock speakers to where we like them without much bass. I will advise what Alpine says after we yank it out and deliver it to their service place. Thanks for all your input boys.

 

[4x4fun]

Well, neither RCA nor speaker wiring alike necessarily have a set + /- and we're obviously specifically talking about an auto application, so ..... I don't know where you're really going with that anyway.

sorry it was a long day for me, i dont remember how rca work. on of thoes things i never really needed to remember, but i just didnt want him to hook it up, and not see 12v and freak out or ect. its based of the vol noob if the sound is not up you can get a "0" reading, and they really work fine, there kinda crazy and its 2 am, and im trying to knock out cobwebs......google it first