Need Help Installing Subs in 05 Grand Prix

**2dee11** · 11-26-2011

hey guys, i just got a 2005 grand prix today (excited! its my first car, a hand-me-down from my mom) but i was also given a set of two 12" subs from a friend of mine a year or so ago. and im looking to install them in my Grand Prix. it does NOT have the monsoon system or the sterring controls. i was originally going to install and after-market head unit as well but found that the adapter was about $100 extra. so i want to just hook them up (with an amp) to the stock head unit. to do this i know you need to use a Line Output Converter. i also know you need to tap into the rear speaker wires. im not sure on how to do this though. you dont lose your rear spearkers do you? any pictures or videos would be excellent help! also where is a good place to put the power wire through the firewall? thanks in advance for all the help! stupid adapter through everything off. i knew how to set em up with an external head unit

**izup69** · 11-27-2011

Hey you can get a cheap harness for like $30 but you will loose your door chimes. I routed my 1/0 gauge wire though the firewall on the driver-side there is a rubber grommet plugging up a hole nothing is running through it. I just used a utility knife and cut a x into it ran it though there. Yes I know the car is very dirty. After it gets in the car it just runs along the floor under the back seat and into the trunk. I will eventually run it under the carpet all the way to the trunk.

This shows it running across the firewall it used to be tied up nice and neat but since the car is not running atm I uncliped to work on some stuff

Here is how I got it routed behind my fuel lines and down beside the break booster

The blue wire is my power for the amp it runs down underneath the brake booster I couldnt get a good pic of the grommit but it is right by there it is easy to find by feeling

Here is where it comes into the car right next to the steering collum

The peace pulled down is the carpet

I just cut a hole in the carpet to run the wire though so it would not interfere with the gas peddle

**ck115** · 11-27-2011

Hey, the line out convertor is quite simple, you just tap into the positive and negative of each rear speaker. I am not sure of the color codes for which is positive and negative off hand, but a quick search should find that for you. Also, there is a better grommet closer to the passenger side near the middle where all the engine bay wires come through. I was able to run three runs of 4 gauge through there, so there is plenty of room. then you can run it on the passenger side under the door sills so it is a shorter run.

**2dee11** · 01-07-2012

thanks guys. for now i dont have an amp and just used speaker wire from the subs to the wire going to the rear speakers. it seems to be working fine until i can get the money for the amp and everything else

**stealthee** · 01-07-2012

You can actually hurt the subs hooked up that way. Too little power is just as bad, if not worse, than too much.

**2dee11** · 01-08-2012

how bad? the subs are very cheap low end ones i got for free from my friend. 50-150 rms. 800 watts peak. and i had them hooked up to the radio in my room for probably a year or longer aswell.

**stealthee** · 01-08-2012

Its not something I would ever chance. You could smoke the subs and in turn cause it to short your headunit.

**SlowNA06** · 01-09-2012

I think most people run the power wire through the rubber grommet in the footwell of the front passenger seat. Just pop off the plastics and run it along the other wires there. No need to cut up your carpet.

**2dee11** · 01-09-2012

alright thanks for the advice

**tc300** · 01-09-2012

I wouldnt waste time installing a line converter.... Put that money towards a nice deck!!

**stealthee** · 01-09-2012

By the time you put the money towards the deck, and all the harnesses, its not worth it in my opinion. I have a nice Alpine unit just sitting in my closet because I am not about to spend as much as I did for harnesses as I did on the headunit just to be able to have pre outs. I'm going the line converter route myself once I replace my sub.

**tc300** · 01-09-2012

Geezz... Some of you ppl dont like sq of a stereo...

LC's most of the give clipped signals to you subs/speakers!! Fyi that mean you will fry something! :-)
Im not familiar with the newer Grand Prix, mite find a good local shop to have a deck installed...?

**csssaint12** · 01-09-2012

Wouldn't waste money? Around here they are only like 20-30 bucks not that much to put towards a headunit.

On another note like said previously don't run the subs without an amp. You will blow up your headunit.

**2dee11** · 01-10-2012

would that be why my old stereo i was using it on stopped working??

**stealthee** · 01-10-2012

Very well could be.

**2dee11** · 01-11-2012

never would have thought that. i just wont tell my mom that..

i uninstalled my subs for now, cant hardly tell the difference since they werent amplified, no need to risk tearing up my head unit too.
what all is lost on the 05 gp when you install an external hu?

**tc300** · 01-11-2012

Not sure what you will loose... Just google it.

Line converters are a huge waste of money take the better route buy a good head unit! :-)

**csssaint12** · 01-12-2012

The only thing you will lose will is the date and time but that is on the head unit most of the time.

**2dee11** · 01-12-2012

alright thanks guys

**06grandprix93** · 01-18-2012

Or instead of wiring through the firewall, you could do what I did. On the passenger side, there is a hole by the door jam that runs all the way up the inside of the fender and then there is another hole right next to the battery. The wire is slightly visible though where the door closes, but its not noticeable unless you are looking for it. Only thing is, this might not work if you're using 0 gauge or something cause the door might not be able to shut