Stock Audio System Mods

[jrobsea]

I'm just about done with adding on a sub and mono amp to the stock system. I wasted too much time figuring out if it was possible, if I could do the work myself, how to do it, etc. I figured I'd post what worked for me and what didn't.

Power cable routing:

I purchased an 8AWG power cable kit. It came with 22' of power cable, terminals, fuse block, etc. I think I could have gotten by with a 17' kit - which seems to be more common, but 17' would be too short if you route through the driver's side since the battery is on the passenger side.

I first removed the battery from the car. There is a clip on the side supporting the main power cables. I had to open the clip - which was difficult due to how accessible it is, but doable.

Behind the battery, there is a rubber grommet in the firewall where a bundle of cables passes through to the front passenger side. There was an extra little 'nub' on it that I opened to pass the power cable through. Pulling the 8AWG cable through the nub was tight, so it might be tough to get anything bigger through.

Routing the cable through the door sill was pretty simple. There is already a big cable bundle running along the passenger side, and you can tuck it under trim all the way to the trunk.

I removed some clips holding the carpet on the roof of the trunk, and pulled the carpet down. I think there were 5 clips to remove, and another 4 hidden clips keeping the carpet tight against the rubber strip around the trunk. Once I got the carpet loose, I had to disconnect a power cable running to the trunk light.

Ground cable:

On the left and right side of the trunk, there is already a chassis ground bolt. I used an existing ground. I did take some sandpaper and rub the paint off a small area where the existing ground connected since it's not intended to handle the current from an amplifier. This seems to be a decent ground point.

Remote/turn on Signal:

The stock amp is under a removable panel on the right side of the trunk. I used a volt meter to find which wire was the signal for the amp to turn on. I found it on an orange cable in the connector with the smallest wires (thanks to Justin Pammer in another thread). There is almost no space to work here for making connections. I think there is a way to splice a cable in without cutting, but I used a little plastic terminal instead. I cut the wire, then reconnected it through the terminal - and tied in another wire to send to the new mono amp.

Audio signal:

This was the hardest part. I used the speaker level signal from the factory sub to send to a speaker level input on my amp. If you can figure out how to get at the factory sub, that would be the best place to wire it. I removed the entire back seat of the car and couldn't figure out how to get at it. I abandoned that idea and took another approach to figure out which 2 of the ~20 speaker wires I needed to use.

There were two connectors for speakers (about 10 wires each), so I tried running the system with one at a time to figure out which one the factory sub is on.

Each speaker has two wires, so you can use an ohm meter to figure out how the wires are paired up.

Once I had it narrowed to 5 pairs, I used my home stereo receiver to power one speaker at a time. I did this very carefully (to avoid shorting the receiver), at low volume level, and with small gauge wire. It was pretty easy to hear which wires are powering the speakers behind the back seat - but there seems to be a sub and a mid/high - and I couldn't tell which was which from sound or from feeling the sub.

At this point, I had a 50/50 shot at getting the right pair. I cut one wire and realized I ended up with the losing 50%. I had to put in an extra terminal to reconnect the mid/high signal behind the rear seat. But at least I had narrowed it down to the right pair of wires. After some excruciating work with the tiny wires/terminals in an area you can barely see or reach, I had a wire spliced in to the speaker wire going to the factory sub.

Finally, the easy part:

Making the final connections to the amp and subwoofer is simple. All the connections are to accessible wires that I put in. I recommend that the very last thing you do is to install a fuse into your power cable fuse block. That way you're less likely to short something out.

The end result:

The amp and sub sound great. The stock audio is very good except it's a little weak on low bass. A 10" Alpine Type R sub in a sealed box and a 200W Alpine class D amp add plenty of bass.

Overall I spent about $400 on the amp, speaker, wiring kit and wood for the speaker box. Part of the advantage of DIY is that you can buy the amp from one place, wiring kit from another, etc to get the best deal. Unless you're extremely cheap like me - and if you don't have the patience to spend about 8 hours doing all this, it's probably worth having a professional install. Just make sure you get someone who will be as careful about doing it right and not butchering your wiring as you would be.

[DArustik]

That was long, but Thanks!!!

[Rocco B.]

Thanks for the info, I'm looking to do this myself and I've had no idea where to start until reading your post. Is there any other way of figuring out which wires go to the subwoofer? Hooking up an AC powered amp is a good idea but I just feel like there has to be a better way of doing this...

[LEX-SV]

I've always thought the factory sub was pretty good...

[Rocco B.]

I've always thought the factory sub was pretty good...

I actually have too but I have these two 10's just lying around, bought them for the old car and then it died on me. 200k miles so I can't complain there but I currently have the subs hooked up to a computer power supply (essentially an AC/DC converter) in my house and the small little power supply doesn't do them any justice. So, needless to say, I want to get them back in a car.

[LEX-SV]

R.B. - Got your subs installed in your IS250 yet?

[Rocco B.]

R.B. - Got your subs installed in your IS250 yet?

I have not yet. A mechanic friend of mine did hook me up with the wiring diagram, though (I could not figure out how to attach it to this). Hopefully it comes in handy when I get around to doing it. I'll keep you posted and maybe even make a play-by-play for those who are also trying to do the same.

[LEX-SV]

Thanks for checking in Rocco B. Best of luck with the sub upgrade.