Crossover Frequency is the frequency at which sound transitions from one speaker to another, and each one is set in the AV receiver by a processor. This filters frequencies away from speaker channels and redirects them to others.
It is basically the point at which low, mid and high frequencies are reduced between each frequency. All sound frequencies after the Crossover Frequency are increasingly cut the further they pass it, to the point where they are completely blocked.
In a loudspeaker, these are determined by a Crossover, which is designed to split the sounds and send them to the right frequencies. And it’s this that makes lows, mids and high frequencies stand out better in a driver.
Crossovers In A Speaker
The most common speakers are 2-way and 3-way speakers which indicates how many drivers a speaker has. A 2-way speaker has a woofer and tweeter, and a 3-way speaker has a woofer, tweeter and a midrange driver. A subwoofer typically only has one driver.
The reason speakers have multiple drivers is because each one performs optimally within a certain range of frequencies, and the more drivers, the more speaker crossover it has.
The more components the better each driver can work within that frequency, but just because a 3-way speaker has more drivers than a 2-way doesn’t always mean it’s a better sounding speaker. I will discuss this later.
The crossovers can either be built into the speaker, as is the case with coaxial speakers, or they can be a separate component, as you get with component speakers and subwoofers. And the crossovers take the sound frequencies and deliver them to the right speaker.
What Is A Sound Frequency?
A Sound Frequency is a measurement of soundwaves, which are alternating waves that happen many times per second. Each sound frequency is assigned a number by the amount of times they occur per second, and is measure in Hertz (Hz).
The generally accepted standard hearing range for humans is 20 to 20k Hz. In air at atmospheric pressure, these represent sound waves with wavelengths of 56ft to 0.67″.
Frequencies below 20 Hz can’t be heard by humans, instead these low frequencies can be felt, hence when your car seat shakes when the bass is pumping.
Frequency Ranges are roughly:
- Low: 20 Hz – 100Hz
- Midrange: 100 Hz – 3k Hz
- High: 3k Hz – 20k Hz
What Is A Speaker Crossover?
A speaker crossover is a combination of resistors, inductors and capacitors in a specific array that are frequency specific. The job of a speaker crossover is to takes a single input signal and create two or three output signals consisting of separated bands of high-, mid-, and low-range frequencies.
The frequencies are divided at the Crossover Frequency which starts the cut-off point for crossover filters. It’s the frequency point at which signals are reduced by 3 decibels (dB).
A loudspeaker without a crossover wouldn’t sound right, because every speaker of every size is designed to reproduce frequencies within a certain range. And a speaker without a crossover means it will be working hard to reproduce all frequencies, and the result would be a terrible sound and it would most likely damage your driver.
Using a speaker crossover, therefore, gives us control over which frequencies go to which driver, so that when all the drivers work together, they produce the best possible sound.
For example, if you have a 2-way speaker of a woofer and a tweeter and want to set the crossover, you would use a Low Pass Filter to the woofer allowing only low frequencies to pass. You would use a High Pass Filter to allow only high frequencies to the tweeter.
Crossovers have three filters: a Low Pass Filter, High Pass Filter and a Band Pass Filter, all of which have 2 settings: Cut-Off Frequency and Slope.
The Cut-off Frequency determines where the frequency reaches -3 dB of reduction from each filter.
Slopes are determined according to a level in decibels (dB), which is shown as a representation of the attenuation (reduction) of a signal. The steepness of the slope determines the strength of filtering past the Crossover Frequency point.
Slopes can be gradual (6dB / Octave) or steep (24dB / Octave), but the most common slopes used in speaker crossover settings range from 12dB – 18dB / Octave.
Crossover Slopes aren’t necessarily better the higher they go, because you lose out on certain things while gaining on others the higher or lower you go with the crossover slope.
Therefore, a -12dB crossover slope is usually considered a good compromise and works well for most speaker system, as it’s easier to design with fewer complications and still possesses good ability.
Your High, Low and Band Pass Filters will slope and meet at the Crossover Frequency between the frequencies. The ideal crossover point -3dB of attenuation from each filter, and depending on how steep the slope is will determine the absolute cut off for that frequency in that driver.
Types of Crossovers
There are 2 types of crossovers: Passive and Active, and each one is best suited for specific set ups.
A Passive Crossover is usually placed between the amplifier and the speaker, which means they’re dealing with Speaker Level Signal, and their job is to filter out unwanted frequencies.
Some speakers have built-in Passive Crossovers, and these are relatively easy to install. However, Passive Crossovers are limited and there’s a certain amount of inefficiency that is inherent in them, especially the cheaper ones.
Active Crossovers are placed before the amplifier, so these are dealing with Line Level Signal, and they are both more complex and more expensive than Passive Crossovers.
Active Crossovers require power sources, but because they’re installed before the amplifier, they don’t waste power by filtering out amplified signals the way Passive Crossovers do. This also makes them more effective.
Passive Crossovers are the most popular, because of their simplicity, and if you have a standard speaker set up with a single amplifier, you will probably be using Passive Crossovers anyway.
However, if you have a more complex set up such as a Subwoofer, it will benefit from an Active Crossover, but it must be set up correctly, as the fidelity will be wasted and blurred if not.
Setting The Right Crossover Frequency
If your car stereo has an EQ feature, it should set the Crossover Frequency automatically, so it’s better to leave them settings. However, if you don’t have that or you prefer to set your own Crossover Frequency, it just needs a bit of knowledge and patience.
The main ingredients needed for manually setting the Crossover Frequency for your car audio stereo system is a lot of listening and tweaking.
- First you need to determine the driver’s frequency range. Play some music, listen to it for a bit, and determine in what range sounds the best.
- Set the Crossover Frequency around 10 Hz below the lowest frequency your driver can produce without issue.
- Then play some more music, and gradually turn up the volume until you start to hear some distortion. At this point turn the music back down until the music sounds clean, noting the head unit’s volume at the clean point (threshold).
- Then set the gain for the amplifier to the lowest possible value, and switch on the Low or High Pass Filter and set it as high as possible.
- Play some music and wait for a smooth transition between the drivers. At this point you shouldn’t be able to distinguish the different frequencies and the music should sound like its all blending.
- If you hear a bump in the highs or lows when you set a Crossover Frequency, adjust the volume control until it matches your main speakers’ output. To do this, you need to turn up the volume to the threshold, and steadily turn up the gain on the driver’s amp until the frequency sounds balanced.
Recommended Crossover Frequencies
There’s no exact Crossover Frequency between low-, mid- and high-frequencies as each speaker is designed differently, and crossovers need to be matched with the impedance of the speaker they’re working with.
Crossover Frequencies’ roundabout ranges are as follows:
- Subwoofers: 70-80 Hz – (low pass ) will block midrange sounds
- Car main speakers: 50-60 Hz – will block low-end bass frequencies
- 2-way speakers: 3-3.5k Hz (high pass)
- Midrange: 1-3.5k Hz
- 3-way speakers: 500 Hz and 3.5 kHz
What Is The Best Crossover Frequency Settings?
As you now know, setting the Crossover Frequency takes a bit of patience and knowledge, and there’s no universal crossover point for all speakers. Crossovers help filter out unwanted frequencies and in doing so promote optimal sound output from loudspeakers.
Use your EQ if your car stereo has one, but if not, just follow the directions above and set it to your liking, and as long as you set it correctly, it will enhance the soundscape in your vehicle.