Equalizers/Crossovers Basics



Equalizers enable you to fine tune your system. It is hard to get speakers to reproduce sound flawlessly. Multiple speaker system things are even more complex. With an equalizer you can boost or cut certain frequency ranges to tailor the overall sound to whatever you desire.

An electronic crossover divides a signal into separate frequency ranges. Usually crossovers come in 2-way or 3-way. You can get a single system with both an equalizer and a crossover. Electronic or active crossovers act on pre-amp level signals. They use the pre-amp level output of your head unit as input and their outputs go to your amp(s). By doing this you keep the amp from trying to amplify frequencies that you do not want (like high frequencies for a sub amp). A passive crossover acts on signals after they have been amplified, they are connected after the amp and before the speakers.

Things to look for:

Number of Bands in the EQ: The number of bands in an equalizer tells you how fine an adjustment you can make. A 10 band equalizer breaks up the audio range into 10 parts and you can adjust the levels of any of them. The Q of an equalizer tells you how wide a range each adjustment makes. Let us say a specific band is labeled as 100 Hz. A high Q high equalizer will only boost or cut frequencies right around 100 Hz and not really affect signals at say 70 Hz. . Typically, the more bands in the EQ the higher the Q so the different bands are not affected by each other. A tool called an RTA (real time analyzer) is used in configuring those equalizers. It gives the system a flat signal (pink noise) and displays to the user what the system returns. The user adjusts the equalizer until the RTA shows the wanted response. Working with an experienced installer is key here.

Slope of the Crossover: How fast the crossover transitions from one output with rising frequency to another is called the slope of the crossover. A 1st order crossovers transitions at 6dB/octave or 10dB/decade. A 2nd order one will transition twice as quickly. For tweeters a minimum of a 2nd order crossover should be use in order to prevent the tweeter from seeing any bass frequencies. 4th order crossovers are common and digital crossovers of any order are possible but costly. A 2nd order crossover is the safest choice. Analog crossovers change the phase response so try wiring your tweeter out of phase to see if it makes the sound quality improve or degrade and leave it the way it sounds better to you.

Crossovers can also be made to have a variety of responses near the crossover point. Butterworth filters have smooth but slow response. Chebychev filters are faster but have some overshoot.