How to Line Output Converter Installation: A Step-by-Step Guide

4 sections 6 min read

1 Understanding Why You Need a Line Output Converter
1.1 Key Takeaways: Quick Installation Overview
2 Choosing the Right Line Output Converter for Your System
2.1 Passive vs. Active Line Output Converters
2.2 Key Features and Comparison
2.3 How Many Channels Do You Need?
3 Essential Tools and Materials for LOC Installation
3.1 Required Tools
3.2 Required Materials
4 Step-by-Step: How to Connect Line Output Converter to Rear Speakers
4.1 Step 1: Safety First – Disconnect the Battery

Understanding Why You Need a Line Output Converter

Staring at the back of your factory car stereo, you’ve probably noticed a frustrating lack of RCA outputs. This is a common roadblock for anyone wanting to add an amplifier for a powerful subwoofer or upgraded speakers. You’re stuck with a great head unit but no simple way to get the audio signal to your new amp. This guide provides the definitive solution.

We will walk you through exactly how to connect a line output converter to rear speakers, a simple device that solves this exact problem. By tapping into your existing speaker wires, a Line Output Converter (LOC) creates the low-level RCA connections your amplifier needs. In my years of professional car audio installation, I’ve found this to be the most reliable and cost-effective way to dramatically upgrade a factory sound system without replacing the head unit.

Key Takeaways: Quick Installation Overview

Purpose: A Line Output Converter (LOC) converts high-level speaker signals from a factory stereo into low-level RCA signals that an amplifier can use.
Connection Point: The easiest and most common connection point is tapping into your vehicle’s rear speaker wires.
Safety First: Always disconnect the negative terminal of your car battery before starting any electrical work.
Wire Identification: Use a vehicle-specific wiring diagram or a multimeter to correctly identify the positive and negative rear speaker wires.
Connection Method: Use high-quality connectors like Posi-Taps or solder the connections for the most reliable signal transfer.
Active vs. Passive: Choose an active LOC (like the AudioControl LC2i Pro) for better signal strength, bass restoration, and a remote turn-on signal, especially for modern cars.

Choosing the Right Line Output Converter for Your System

Before you start cutting wires, it’s crucial to select the correct LOC. Not all converters are created equal, and the right choice depends on your specific audio goals and your vehicle’s factory system. Making the wrong choice can lead to poor sound quality, noise, and installation headaches.

Passive vs. Active Line Output Converters

The most significant distinction is between passive and active LOCs. I’ve installed hundreds of both, and the choice really boils down to your budget and performance expectations.

Passive LOCs: These are simple transformers that reduce the voltage of the speaker signal. They don’t require a separate power source, making them very easy to install. They are a great, budget-friendly option if you’re just adding a basic subwoofer. A popular example is the Scosche LOC2SL.
Active LOCs: These are more sophisticated electronic devices that require a 12V power and ground connection. They don’t just reduce the signal; they actively process and condition it. This results in a cleaner, stronger, and more adjustable output signal for your amplifier. Most active LOCs also feature a signal-sensing turn-on, which creates a remote turn-on signal for your amp, a feature modern cars often lack.

From my experience, if your budget allows, an active LOC like the AudioControl LC2i Pro or Kicker KEYLOC is always the superior choice. The improvement in bass response and overall clarity is immediately noticeable, especially in factory systems that roll off bass at higher volumes (a common feature to protect cheap factory speakers).

Key Features and Comparison

Here’s a breakdown of the key differences to help you decide.

Feature	Passive LOC (e.g., Scosche LOC2SL)	Active LOC (e.g., AudioControl LC2i Pro)	Expert Recommendation
Power Required	No	Yes (12V Power & Ground)	Active LOCs are worth the extra wiring for the performance gain.
Signal Quality	Good (Basic signal conversion)	Excellent (Clean, strong, conditioned signal)	For sound quality enthusiasts, Active is the only way to go.
Gain Control	Yes, basic level adjustment	Yes, advanced gain and level matching	Active LOCs provide more precise control to prevent distortion.
Remote Turn-On	No	Yes (Signal-sensing circuit)	A lifesaver in modern cars without a traditional remote wire.
Bass Restoration	No	Yes (e.g., AudioControl’s AccuBASS)	Essential for overcoming factory bass roll-off at high volumes.
Cost	$15 – $30	$100 – $200+	An investment in an active LOC pays dividends in sound quality.

How Many Channels Do You Need?

2-Channel LOC: This is the most common type and is perfect if you are adding a single amplifier for a subwoofer. You’ll tap into the left and right rear speakers to create one pair of RCA outputs.
4-Channel LOC (or more): If you plan to amplify your front and rear speakers with a 4-channel amplifier, you will need a 4-channel LOC. This requires tapping into both the front and rear speaker wires to create two pairs of RCA outputs.

Essential Tools and Materials for LOC Installation

Having the right tools and materials ready before you start makes the job infinitely smoother. There’s nothing worse than having to stop midway through to run to the store. Here’s the checklist I use for every installation.

Required Tools

Wire Strippers/Cutters: A good, sharp pair is non-negotiable for clean cuts and strips.
Wire Crimpers: For securely attaching terminals if you’re not soldering.
Automotive Panel Removal Tool Kit: These plastic pry tools are essential for removing interior panels without scratching or breaking them.
Multimeter: Absolutely critical for verifying you have the correct speaker wires before you make any connections.
Socket Wrench Set or Screwdrivers: For removing panels, seats, or bolts as needed.
Flashlight or Headlamp: Car interiors can be dark, especially under the dash or in the trunk.
Soldering Iron (Optional but Recommended): For the most secure and reliable connections.

Required Materials

Your Line Output Converter: The star of the show.
Wire Connectors: I highly recommend Posi-Taps over the classic blue T-Taps. They make a much more secure, vibration-proof connection. If you’re aiming for a professional-grade install, soldering and heat shrink tubing is the gold standard.
Electrical Tape: For tidying up and insulating connections. I prefer Tesa cloth tape for a factory-look finish that prevents rattles.
Zip Ties: For securing the LOC and all your new wiring.
Speaker Wire (16-18 gauge): A small amount to run from the factory speaker wires to your LOC’s inputs.
RCA Cables: A quality, shielded pair long enough to run from your LOC to the amplifier.
Remote Turn-On Wire (18 gauge): Needed if your LOC creates a remote output for your amp.

Step-by-Step: How to Connect Line Output Converter to Rear Speakers

Now we get to the hands-on part. Follow these steps carefully, and you’ll have your LOC installed professionally and safely. We’ll focus on the most common scenario: installing a 2-channel active LOC for a subwoofer amplifier.