A crossover is a necessary element in any quality car audio set up. EA crossover’s basic function is to take a single signal and split it up into multiple signals of specific frequency bands, low range, mid-range and high range frequencies. These devices ensure that no individual speaker is working to reproduce frequencies it’s not designed to make. 

A speaker is comprised of a driver which moves the cone back and forth to create sound waves. The smaller the speaker the higher the frequencies it’s able to replicate and vice-versa. 

Without a crossover your system would waste a significant amount of energy trying to play frequencies it isn’t designed for, your subwoofer will be trying to play notes intended for your tweeters and vice-versa. This results in poor overall sound quality and can also be potentially hazardous to your system. 

There are three types of crossovers that can be installed: Passive, In-Line, or Active.

Crossover in the NVX VSP525KIT

Passive Crossovers

Passive Crossovers are non adjustable, preset, unpowered units. They use capacitors and inductor coils (that store energy from the amplifier) to passively send frequencies to their desired drivers.

 For example, in component speakers, the crossover will passively send the high frequencies to the tweeters and the mid and lower frequencies to the mid bass drivers. 

A good example of a passive crossover is the crossovers that come with a component speaker system. Passive crossovers are wired in-line between the speakers in your system and the amplifier (or source). 

The passive crossovers that come with your component system come tuned and ready to be installed. One drawback of these crossovers is because they are located after the amplifier and can waste power filtering a signal that has already been amplified.

In-Line crossover

Another form of a passive crossover is the in-line crossover. An in-line crossover can come in a few different forms. They look similar to a AA battery with an RCA connection on either side for your amplifier’s RCA inputs. Other in-line crossovers will protect your speakers from unwanted frequencies when used after the amplifier by separating the frequencies before they reach the driver.

The biggest tradeoff with a passive crossover is ease of installation while sacrificing some flexibility in your system with the loss of sound customization.

Active Crossovers

Active Crossovers use the input side of the amplifier rather than the output like a passive crossover does. It is a common conception in the audio world that active crossovers are more accurate and flexible than passive crossovers. 

Active crossovers are adjustable and have variable filters such as low-pass, high-pass, and gain. They also have deeper crossover slopes. This allows for a more customized and desirable sound for the user. Another advantage to active crossovers is their ability to allow bi-amping – allowing for two amplifiers to power multiple drivers.

Unlike passive crossovers, an active crossover requires a direct power source. Active crossovers are installed between your receiver and amplifier. As a result of this, active crossovers filter your frequencies before they reach your amplifier – which means no wasted energy from filtering amplified signals. 


Active crossovers also usually feature a variety of adjustments, including gain controls, low pass and high pass filters while select active crossovers feature built-in equalizers to give you the ultimate control over your system.

Low-Pass Filter- This allows the low frequencies to pass or be allowed to play. This feature is used mainly for subwoofers. The low frequency spectrum will contain any frequency of about 100 Hz or lower.

High-Pass Filter- This allows the high frequencies to pass or be allowed to play. Mainly used for Mid-bass drivers and tweeters. The high pass will usually be for frequencies of 100 HZ and up.

Subsonic Filter- This filter prevents any frequencies that are not audible to be blocked. This filter is usually set around 20 Hz. It is essentially a safe guard to keep you from damaging your subwoofer.

Phase- This feature ensures that the sound from your subwoofer reaches you at the same time as your speakers. For example, if you are hearing an echo, your should set your phase to 0. This feature is adjustable from 0-180 degrees.

Bass EQ- Also known as a bass boost, this feature is designed to boost select frequencies, usually around 40 or 45 Hz.

Gain or Level- This function is used to match the voltage that is coming from your headunit in order to prevent clipping.

Rolloff or Slope- This concept is the most difficult to comprehend. This describes the rate in which the audio level will increase or decrease per octave as the frequency rises or falls. Most commonly, amplifiers will have a 12dB octave slope. Basically what this means is that once you have changed the frequency of the signal by a factor of 2 or 1 octave, the signal will change by 12 dB.

The only disadvantage to an active crossover is installation. Since an active crossover has to have a power, ground and turn-on connection it has the potential to complicate your install more than a passive crossover. If you’re interested in making your system really sing, an active crossover is a must-add piece.