The frequency response for speakers illustrates the frequency range compared to the amplitude of the audio source. Speakers cannot play frequencies beyond their range. If a set of speakers has a frequency range of 50Hz to 20kHz, it cannot play sounds below 50Hz. Frequencies are measured in Hertz (Hz). The typical range of human hearing is between 20Hz and 20,000Hz (20kHz). High-end frequency sounds are referred to as treble while low-end frequencies produce bass. However, most loudspeakers cannot cover the lowest frequencies, which is why subwoofers exist. While frequency range is important, flat frequency response is more essential.
What Is Frequency Range?
The frequency range is the range of frequencies that a speaker can reproduce. If your speakers cannot reproduce sounds across the entire frequency range of human hearing, you may not hear some of the sounds from the source audio.
The range of normal human hearing is believed to be between 20Hz and 20,000Hz. However, as you age, your ears become less sensitive to high-frequency sounds. The upper limit of human hearing for the average adult may be closer to 15kHz to 17kHz.
The lowest pitch that your ears can hear is likely to be between 20Hz and 50Hz, which falls into the lower end of the bass frequencies. The frequency range is often divided into three main categories:
- Bass – 20Hz to 300Hz
- Midrange – 300Hz to 4kHz
- Treble – 4kHz to 20kHz
Speakers with a limited frequency range cannot play all sound. Speakers are also more likely to distort audio when playing frequencies that are close to the limits of the frequency range. For example, if a set of speakers has a frequency range of 100Hz to 15kHz, low and high pitches may become distorted at higher sound levels.
The typical frequency range for loudspeakers is 50Hz to 20kHz. The lower frequencies are more of a concern, as most speakers offer an adequate response for the upper frequencies.
With a frequency range of 50Hz to 20kHz, the speakers may miss most of the sub-bass frequency subset, which covers frequencies between 16Hz and 60Hz. Tubas and bass guitars fall into this category.
Even with a frequency range of 20Hz to 20kHz, a set of speakers may not faithfully reproduce bass sounds. If the pitch of the sound comes close to 20Hz, it may not sound the same as the original audio. The accuracy of the speakers at different frequency ranges depends on the frequency response.
Frequency Response for the Lower Range
Many loudspeakers offer a poor frequency response for bass frequencies. A typical tower speaker or bookshelf speaker includes two speaker drivers – a woofer and a tweeter. These speakers are called two-way speakers.
The woofer handles the low-end (bass) and midrange frequencies while the tweeter reproduces the high-end frequency sounds (treble). The frequency range of the speakers varies, but the average is 50Hz to 20kHz. Three-way speakers include a dedicated midrange driver that handles the midrange frequencies.
In a surround sound setup, surround speakers are added to create the 3D listening experience. Most surround speakers are two-way speakers with a midrange driver and a tweeter.
A center-channel speaker may be included in a surround sound setup to enhance the clarity of midrange frequencies. The center-channel speaker often includes a midrange woofer, which covers the frequencies produced during dialogue.
Many two-way speakers, three-way speakers, surround speakers, and center-channel speakers offer a limited frequency response for lower range frequencies. The bass may sound muted or missing entirely.
The easiest solution is to add a subwoofer. Subwoofers are designed to play bass frequencies up to about 300Hz. Adding a subwoofer ensures that you hear any bass sounds missing from your existing setup.
Why Frequency Response Is More Important
The frequency response of the speakers that you choose is more essential compared to the frequency range. Without a flat or smooth frequency response, the audio becomes less accurate.
The frequency response refers to the ability of the speakers to reproduce sounds across the frequency spectrum.
So, what is a good frequency response for speakers? The best speakers produce a flat response. This occurs when the speakers and amplifier output the audio signal without any changes.
A graph of the amplitude of the speakers compared to the frequency of the audio signal illustrates the frequency response. The most common way to visualize the frequency response is with an oscilloscope that produces sine waves.
The sine wave for the frequency response should be flat. Spikes indicate that the speakers are amplifying certain frequencies.
The overall effect of poor frequency response is less accurate compared to the audio source. For example, if a speaker has a low-frequency response for low-end sounds, the bass may sound more muted. If the speaker has a high-frequency response for high-end sounds, the treble may sound bright and inaccurate.
The ideal frequency response is flat across the frequency spectrum. However, achieving a totally flat response is difficult. The impedance of the speakers compared to the amplifier or the properties of your headphones or speakers causes variations in the frequency response.
Manufacturers typically list this variation in the product specifications for speakers. It is typically listed as (+/- dB) and appears after the frequency range, such as:
50Hz – 20kHz (+/-3dB)
A deviation of just one or two decibels is unlikely to impact your listening experience. However, variations of more than a few decibels cause spikes in the frequency response. A +/-6dB variation indicates that the frequency response is colored and inaccurate at the high and low ends of the frequency spectrum.
Reviewing the variation in the frequency response is a good starting point for finding speakers with a relatively smooth response. However, the listed variation does not describe the response of the speakers at different frequency ranges.
It is also difficult to analyze the frequency response of speakers without equipment or hearing the speakers in person. You should look at speaker reviews and buy from trusted manufacturers.
The frequency range is less essential, as most music does not include sounds below 50Hz. You can also add a subwoofer to handle the low-ends while your existing speakers handle the midrange and treble frequencies.