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I was listening to a podcast the other day, and the discussion revolved around the PA systems. One subtopic, however, that piqued my interest the most was about the value of crossovers in a PA system. As a singer in a live band, I have been very fascinated and fond of crossovers. The PA system uses the crossovers to separate the audio signal into various frequency ranges. This splitting up of audio signal allows the sound engineer to channel signals of different frequencies to loudspeakers designed for various frequency ranges.
The crossover receives the signal from the mixer. It splits this signal and sends the resulting split signals to individual loudspeakers with the appropriate frequencies.
Manufacturers did not design the loudspeaker drivers to cover the whole audio spectrum range because the audio spectrum ranges from the low to high frequencies. Thus, the audio signals must be split when it passes the crossover before the split signals are routed to the designated speakers.
Recommended Crossover Frequencies
There is a frequency range wherein the crossover can perfectly filter the unwanted sounds. Although there is no unified crossover frequency for all speakers, there is, however, a standard frequency range in which the crossover can effectively filter unwanted sounds:
1) Recommended Frequency for Subwoofers
The most recommended crossover frequency for subwoofers is 80Hz (low pass). At this range, the subwoofer bass is given priority without incorporating midrange sounds. Thus, this range is perfect for low-end bass.
2) Recommended Frequency for Main Speakers
The recommended crossover frequency for the main speakers is 80 Hz (low pass). At this range of frequency, the crossover filters the low-end bass that can create distortion. This crossover frequency is the ideal middle ground between the full-range and the midrange bass.
Tweeters and two-way Speakers
For tweeters and two-way speakers, the best crossover frequency is 3.5kHz for a high pass or low pass. Below this range, these speakers will exhibit below-par performance.
Woofers and Midrange Speakers
The ideal crossover frequency for the midrange speakers and woofers is 1-3.5 kHz (low pass). Most midrange speakers and woofers fail to deliver quality audio signals beyond this range. Hence, it will help to augment them with the tweeters to have a good treble.
For three-way speakers, the best crossover frequency range is 500Hz to 3.5 kHz. Below 500 Hz, the midrange drivers will fail to deliver great sounds in a 3-way system.
How To Set Up the Crossover
To set up the crossover frequency for your speakers, you need to engage in critical listening. Moreover, you can experiment to attain the ideal sound results for each loudspeaker. If you fail to set right the crossover frequency, chances are, the subwoofer will not correctly perform, failing to deliver the low-frequency deep bass and notes.
On using, for the first time, your integrated system equipped with the EQ feature, you may find the crossover automatically set on the right crossover frequencies. You will not have a problem setting up the crossover frequencies for each speaker in such a case.
However, if it is not automatically set, you need to set the crossover manually. Here are some straightforward guidelines on how to set the crossover:
- You need to check the user manual to figure out the subwoofer’s low-end frequency range at the onset.
- Once you’ve found the recommended crossover frequency range, set the crossover 10 Hz above the low-end for optimal result.
- Listen critically to achieve the smooth transition between the subwoofer and the other speakers. You will hear a crisp sound if you got it right.
- However, if you notice a bass bump or distortion at that given frequency, you can tinker with the subwoofer volume and match its sound with the other speakers.
Your speakers will begin to roll-off, and the bass notes and LFEs will start to kick if they reach the recommended crossover frequency limits. If you have a modern AV receiver with Auto EQ Program, you will find that this program will assign the right crossover frequency automatically to each loudspeaker based on each loudspeaker’s capability. So, you don’t need to tinker with these settings to achieve the loudspeakers’ optimal sound results.
To properly set a crossover frequency, you first need to know the speaker type. Once you’ve learned the speaker type, you can then tinker with its recommended crossover range.
Crossovers are grouped into active (electronic) and passive (speaker). Active crossovers require power and ground along with ground connections. They are also more flexible than the passive crossovers and provide better control for finer details in your sound output. Passive crossovers don’t necessitate the power to filter or block sounds.
As mentioned above, you should engage in experimentation and critical listening to attain the best audio output results. Moreover, if you are cognizant of the speaker’s frequency range, it will help to set the crossover point 10 Hz over the lowest frequency that the speaker can handle without distorting. Below are guidelines for the crossover frequencies of speakers and subwoofers:
- 150-200 Hz—Small Satellite Speakers
- 100-120 Hz— Small center, surround, and bookshelf
- 80-100 Hz— Mid-size center, surround, and bookshelf
- 60-80 Hz— Large center, surround and bookshelf
- 40-60 Hz— Very large center, surround, and bookshelf
- 60 Hz— Tower speakers (4”-6” woofers)
- 40 Hz— Tower speakers (8”-10” woofers)
As a sound engineer, you would surely aim for a smooth transition between the subwoofer and speakers. The ideal blend would be seamless and smooth, with no localize bass. Besides, everything should be playing in synchrony and unison.
If you’re shopping around for the best audio crossover, you can quickly zero in on the one that could best address your PA system needs once you know the speaker’s frequency range. Equipped with such knowledge, you can set the crossover point properly. Moreover, with the crossover, the range of sound you want to filter out is prevented from reaching a speaker.
As a sound engineer, I often get fascinated by the crossovers’ function simply because it can split signals into various frequencies. This function counts for audiophiles like me because it can enhance the overall sound of the speakers.