Live Sound Crossover: Yes You Need One. Here’s Why


You don’t have to spend long around sound equipment before you hear the word “crossover”. It’s a term that is not familiar to most beginners, but it is one of the most important pieces of equipment you will learn how to use in live sound… or any type of sound, really.

What is a system crossover? A system crossover is a piece of hardware that divides an audio signal’s frequency content into 2 or more parts. It then sends these divided signals to the appropriate speakers/drivers based upon the frequency range they are designed to handle.

Crossovers are one of the most important pieces of equipment to be familiar with in live sound. But maybe you don’t understand them yet. You may have a lot of questions about how they work and at what point in the sound system they fit in. Well, that’s why I’ve written this article… just for you! Hopefully, I can answer your questions about them. Read on to learn more!

Why Do You Need a Crossover?

There are 3 main reasons you need a crossover for your system.

  1. To protect your system

Using a crossover protects your system from being damaged by too much frequency content going to the wrong drivers.

For example – The tweeters in your main speakers are meant to handle the highest frequencies – normally about 2.5kHz and above. If we try to send the lower frequencies to this tweeter, it’ll probably last about 2 seconds (if that) before it blows – not good. So, we use the crossover to send only the high frequencies to the tweeter to protect it.

The same goes for all driver types in the entire sound sytem.

  1. For efficiency

The next reason you need a crossover is for efficiency. Dividing your system into dedicated parts helps spread the work load across multiple driver types, instead of forcing 1 type to do it all.

Imagine this – A family of 3 is moving into a new house and they back up a truck to the front door. They open the back of the truck and it’s completely full – everything must go inside. Let’s say the dad is 6’4″ and 250lbs (1.9m and 113 kilos) of pure muscle. The mom is 5’4″ and 120lbs (1.6m and 54 kilos). And the kid is 4’10” and 90lbs (1.47m and 41 kilos).

Could the dad do all the work himself? Technically, yes he could. But is that efficient? Not at all. It makes more sense to divide the work between the three of them, with each carrying what they can. The work will get done much quicker and with less strain on a single person.

That’s another reason we use a crossover in a sound system. Could we make a speaker that can handle the lowest of lows and the highest of highs? Yes… in fact, we have that and it’s called a subwoofer. But we don’t use it in that way because it’s so inefficient.

  1. Sound Quality

The last reason is for sound quality. This goes hand-in-hand with efficiency. The less efficient your system is, in terms of frequency distribution, the worse the sound quality will be. (at least to a certain point)

Take what I said about the subwoofer, for example – could we make do everything? Yes. But because of the extreme inefficiency of it bearing the whole burden and what it’s designed for, it will not sound very good. In fact, it will probably sound pretty bad.

Active vs Passive Crossovers

Every sound system has a crossover, no matter how big or small. And you should know that there are two different types of crossovers: Active and passive.

So, what’s the difference?

Active Crossover

Active crossovers are external pieces of hard hardware. These typically have several parameters which you can adjust in order to have the appropriate settings for the speakers you have. The recommended settings are normally supplied by the manufacturer of the speaker.

Active crossovers are needed for most (but not all) passive loudspeakers in live sound. (passive loudspeakers are those in which must be supplied with power from an external power amp)

Most professional sound systems you see, such as concerts, will utilize active crossovers, with a few exceptions.

Passive Crossovers

Passive crossovers are built into a speaker’s wiring/circuitry. These are designed by the manufacturers of speakers for one main reason – simplicity for the end user.

Passive crossovers limit the amount of knowledge required to use an active crossover, in turn eliminating the possibility of damaging the speaker due to improper crossover settings.

These are typically found in active speakers (active speakers are those in which have power amps built into the speaker cabinet), and in budget passive speakers.

This is not a hard-and-fast rule, but just a broad generalization.

What Kind of Crossover Should You Get?

There are many manufactures who make system crossovers. Some of them are very basic stand-alone units and others are very complex built into a system processing unit, which has many other features apart from the crossover itself.

That said, when considering the crossover feature, whether stand-alone or in a system processor, you will want to know how many divisions of frequency ranges you need.

But determining how many divisions you need can sometimes be a little confusing. For example – you can have a 3-way system, but only need to use a 2-way crossover. Let me explain –

Let’s say you’re using a subwoofer and a main speaker. Sounds easy enough, right? Well… not exactly.

You must first determine if your main speaker requires more active divisions for separating the horns from the woofers. Your main speaker may have a passive crossover built into it to separate the horn from the woofer. If this is the case, then you will need a 2-way crossover to separate the subwoofers from the mains.

So even though you may be using a 2-way active crossover, you actually have a 3-way system – Subwoofers, main-woofers, and horns.

But what if your main speakers don’t have any passive crossovers built in? Well, then you will need a division for each component of the speaker.

In the example above, you would need a 3-way crossover to isolate the subwoofers, main-woofers, and horns.

Check out this chart to see what kind you need!

Choosing a Crossover Type
Mains with Built-In Crossovers – 2-way mains 3-way mains
With Subwoofers – 2-way x-over 2-way x-over
No Subwoofers – no x-over no x-over
Mains without Built-In Crossovers – 2-way mains 3-way mains
With Subwoofers – 3-way x-over 4-way x-over
No Subwoofers – 2-way x-over 3-way x-over

How to Set Up Your Crossover

For a more in-depth explanation of how to set up your crossover and adjust it’s settings, click HERE.

Setting up a crossover can be difficult when first learning about them. But once you understand the signal flow and put it into practice a few times, it’s actually pretty simple.

Since passive crossovers are pre-installed, we’ll just talk about active crossovers in this section.

Essentially, you come from the output of your mixer into the crossover. The crossover works its magic and then has a number of outputs for your different frequency ranges, depending on how many divisions you need.

Then each output of the crossover goes into separate power amps that you’ve specified beforehand to handle each frequency range.

The outputs of those power amps then connect to the corresponding speakers/drivers.

I’ve made a simple diagram here to help you understand.

Note: The two inputs you see on the main speaker were drawn for simplicity and understanding. In the real world, this would be a single cable with several connectors on the amp side and a single connector on the speaker side, which would then break-out on the inside of the speaker and connect to the appropriate drivers.

Conclusion

As you can see, crossovers are an essential piece of equipment in any sound system, whether they be passive or active. They make the system more efficient as well as protect it from being damaged.

I hope I’ve helped you in understanding what they are and why you should know about them. If it hasn’t sunk in quite yet, please come back and re-read!

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