Upgrading your car's factory stereo system can take your music listening experience from dull and lifeless to vibrant and immersive. However, rewiring the system usually requires splicing into the original harness which can be complicated and risky for your car's delicate electrical system. Thankfully, there are methods to dramatically improve sound quality by tapping into the rear speaker wires alone, leaving the rest of the wiring untouched.

Assessing Your Factory System

The first step is understanding what you're working with. Pop off the factory stereo and look at the rear of the unit. Note the wire colors and where they connect to the harness. The key ones we care about are:

We will tap into the rear speaker wires to insert our own amplifier, leaving everything else untouched.

Shopping for New Gear

To make this work, we need two new components - an amplifier and a line output converter (LOC).


This will provide amplified signal to our new speakers. Look for an amp between 50-100 watts per channel to sufficiently power most aftermarket speakers. Ensure it has low-level RCA inputs. Major brands like Alpine, Rockford Fosgate and JL audio make excellent amplifiers in this range.

Line Output Converter

The LOC will convert the rear speaker output from the factory stereo into an RCA line-level signal we can feed into the amplifier. There are two types:

Active LOCs are higher quality and recommended if you want the best performance. Brands like AudioControl and PAC make great active LOCs.

Running New Wires

We'll need to run power and signal wires for our new amp.

Connecting the Gear

With all the gear and new wiring in place, we can now make our connections:

Once everything is securely connected, test it out! You should now have a loud, clean signal going to your new speakers without ever touching the factory wiring.

Tuning Tips

To get the most out of your new sound system:

With a little wiring know-how, you can dramatically enhance your car's audio system while keeping the factory setup intact. Follow these steps and you'll be enjoying supreme sound quality in no time.