Can Any Speaker Be Used As A Subwoofer?

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At its core, every subwoofer is a speaker, but not every speaker can be a subwoofer. If you asked a question about using a speaker as a subwoofer, then it is worth understanding what makes a subwoofer and why an ordinary speaker cannot cope with this role. Also, this information will be you will choose and compare subwoofers.

What is a subwoofer?

If the high or medium frequencies need small speakers, the diaphragm of which has a small stroke, the low and sub-bass frequencies set completely different tasks for the equipment. To reproduce the first and second octaves, it is necessary to resort to a driver of large diameter, which can operate with a large amount of air, and equipped with a membrane that can withstand heavy loads. Because to produce bass, the speaker has to move a large volume of air. The lower the frequencies, the more distance the sound wave requires to develop.


There are two key characteristics of low-frequency reproduction:

  • a large diameter speaker
  • a speaker that can handle heavy loads at high speed.

The diameter of a speaker

The larger speaker is, the better the ability of the subwoofer to produce low frequencies. Common diameters for subwoofers vary from 6 to 11 inches for home use, and often 14 to 18 inches for studio systems.


It is to expand this frequency band that a subwoofer is added to the audio system. The subwoofer is capable of producing frequencies from 25 to 120 Hz.


Sound pressure

A subwoofer produces slow, wide sound waves that are felt more by the listener’s body than heard. This is about sound pressure, expressed in decibels (dB). For a Hi-Fi system, a subwoofer capable of producing 120 dB of its useful bandwidth is generally sufficient.

Cutoff frequency

To obtain a harmonious marriage with the low frequencies produced by the main speakers, the passband of the subwoofer must be able to be adjusted by an active filter (of the low pass type). Low-pass filters are traditionally used to improve the signal-to-noise ratio of the signal path by suppressing interference with frequencies higher than the upper limit of the information signal frequency band. Low-pass filters are also widely used to suppress high-frequency noise in power supply and signal circuits to ensure the electromagnetic compatibility of equipment.

However, it is not necessary to set the subwoofer cut-off frequency to 30 Hz or about this, as have other speakers in the Hi-Fi system. It is an adjustment to be made by ear and according to individual tastes.