What Is a Speaker to Line Level Converter?

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Upgrading car audio systems was a pretty straightforward process for decades, but the complexity goes through the roof when you have an integrated infotainment system or a non-standard radio that just isn't shaped like most aftermarket units.

The main problem is that if you want to get the best possible sound out of a car audio system, you need an external amp, and most external amplifiers just don't play nice with factory car stereos.

There are two real solutions to this problem. One is to find an amplifier that has line-level inputs, and the other is to use a speaker to line level converter along with the amp of your choice. The first option may be easier because there are fewer components involved, but the second is less restrictive.

Who Needs a Line Level Converter?

Line level converters are mostly useful whenever you want to upgrade your factory car audio system without touching the radio that came with the car. This is most often applicable when upgrading a car audio system that is integrated into a factory infotainment system, but it really comes into play any time you have a factory car radio that you want to leave in place for any reason.

The issue is that upgrading to premium speakers can help a lot, in terms of sound quality, but there's a hard limit on what you can accomplish without adding an amplifier to the mix. This is especially true when you upgrade the speakers and install a new amp at the same time since that allows you to choose components that work great together.

Before you buy anything, though, it's important to look at what you're working with first. While most factory car audio systems don't come with an amplifier, there are some exceptions. If you're lucky, and your car did come from the factory with an amplifier, then you can just replace it with a better unit with no need for a line level converter.

Even if your factory system didn't come with an amp, there’s still a chance that the factory head unit came with preamp outputs. This isn’t an extremely common thing, but it is worth checking out to potentially save time, effort, and money.

If your factory car radio didn't come with preamp outputs, then you'll need some type of speaker to line level converter.

What Do the Terms Line Level and Speaker Level Mean?

In very basic terms, a line level signal is just an audio signal that hasn't been amplified. This type of signal can't be used to drive speakers, so it has to be passed through an amplifier before it can be of any use. Once the signal has gone through an amplifier, it becomes a speaker level signal that can then be used to drive speakers.

In most cases, factory car stereos don’t have external amps, and factory head units don’t include preamp outputs. The most common situation for a factory car stereo system involves a head unit with a built-in power amp and speaker level outputs. This is also the most common design for aftermarket head units, but a lot of those also include preamp outputs.

In order to better understand the difference between speaker level and line level signals, it’s important to remember the fact that car radios come with built-in power amps. If they didn’t, they wouldn’t be able to drive the speakers at all, because the unamplified audio signal is simply too weak.

That unamplified, analog audio signal is known as a “line level” signal. After it passes through an amplifier, whether it’s an internal or external amp, it becomes a more powerful signal known as a “speaker level” signal.

Most amplifiers only have line level inputs, so they can only be used with head units that provide line-level outputs. However, some amps have speaker level inputs. If you want to add an amp to a car audio system without replacing the head unit, and you haven’t already bought the amp, then that’s the easiest solution.

Installing an amp that has line level inputs is a simple matter of connecting your head units speaker outputs to the speaker level inputs on the amp, and then connecting the amp itself to your speakers.

Using a Speaker to Line Level Converter

The other option is to use a speaker to line level converter. In simple terms, these devices lower the power of the speaker outputs to a point where it is similar to the power level of an actual line level output. That allows you to essentially connect the speaker level signal.

This isn’t the same thing as having actual preamp outputs, and it can result in lower sound quality, but it does allow you to use a factory head unit with virtually any power amplifier.

If you want a lot of flexibility with the amp you buy, or you want to retain the option to upgrade your head unit, without buying a new amp, then a speaker to line level converter is a better idea than an amp that has speaker level inputs.