What Is a Crossover?

Crossover is often mentioned in loudspeakers but what exactly is it and why do we need it? Here's a simple and quick guide.

What Is a Crossover?

One of the questions we hear frequently is what is a crossover? This may be just a quick refresher if you're familiar with loudspeaker design, electronics, or audio in general. We're not going to go into a ton of science or engineering detail on these things, just basically: what is it, what does it do, and why it exists. 

Crossover: What is it? 

I had a comment from somebody saying, "I hear this term crossover talked about in terms of loudspeakers and receivers and things, and I don't really understand. What's a crossover, why do we need it, what does it do? Can you explain that very, very simply?" 

Crossovers can be called many, many different things. You may hear it called a dividing network, something like a filter network, crossover, or crossover network. 

In a frequency graph, you'll see where the two sections of the filter come in, one for the woofer, one for the mid-range, one for the tweeter, that they cross over. 

The actual frequency where those two meet is the crossover point or the crossover frequency. And that's how we got the name crossover. In electronics, you would call it a filter network. 

Passive vs. Active Crossover: What's the Difference? 

Passive Crossover

A passive crossover doesn't require electricity from the wall or the circuitry. The signal from a power amplifier or a receiver connected to your speaker will go through this crossover network and all of these components to the woofer, tweeter, or the woofer's mid-range tweeter, all the drive units that are in the speaker.

Active Crossover 

On the other hand, an active crossover needs an additional power source. You don't have all these components sitting between your amplifier or receiver output and those drive units. You have to divide them first and then have a separate amplifier for each driver or each group of drivers.

Why Do Loudspeakers Need A Crossover? 

Why do we need a crossover? If you look at a speaker, we have a woofer and a tweeter. We have to send the right content from the amplifier to those two drive units. For instance, if we send a lot of bass frequencies to the tweeter, we will burn it out.

It's small and doesn't move very much. So, we only have to send frequencies or a part of the music you're playing to the tweeter. And the rest of it goes to the woofer.

What Is the Crossover Setting in My AVR? 

You have also probably seen crossover settings or frequency settings in your AVR or audio-video receiver. That's another crossover. 

You have a crossover between where a subwoofer stops working and where the main speakers come in. There's nothing complicated about crossover networks, at least at a very basic level. 

Just think of them as dividers to ensure that the right parts of the music get to the right components in the speaker, between your amplifier or subwoofer and the other speakers in your system. 

What Crossovers Can Do? 

Many people who DIY their loudspeakers sometimes don't fully understand that a crossover network doesn't just roll off the frequencies. Passive crossover networks and other active crossovers, for instance, can do and usually do many other things.

We can change the level with them. So, if your tweeter naturally has a higher output level and is louder than the woofer, we have to bring it down in the crossover network so the two line up. Otherwise, your tweeter would be screaming, and the mid-range and bass would be down in level. 

We can also do some tailoring to the frequency response. What I mean by that is if the output of a tweeter is flat, maybe we want to tilt it a little bit. 

We can also add bumps or dips in the frequency response by adding more components, filters, really, to the crossover network.

Final Thoughts 

Hope that clears that up. It's, like I said, a simple concept to grasp. Keep those questions coming as usual. I'll try to cover as many of these basic refresher topics as possible. 

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