Have you ever bought a speaker system on a great deal to take it home and be underwhelmed by the sound? The bass may be lackluster, or the highs may sound tinny, leaving you wondering what you missed about this system that would have informed you about its true quality. Speakers are complicated, so that several factors could cause low-quality sound, but it is often the result of poor speaker frequency response.
Speakers can cost a lot, so it is crucial to understand what goes into a high-quality speaker before you shell out any cash for them. Arming yourself with knowledge about how speakers work and the importance of speaker response frequency makes your choice easier and saves you money in the long run.
How Speakers Work
Speakers have been around for ages, but that doesn’t make the way they work any less fascinating. To generate sound, speakers take electrical energy from an outlet or battery and convert it to mechanical energy. How? An electrical current is sent through a voice coil, which interacts with a magnet permanently placed inside the speaker.
As the voice coil receives different charges, it either repels the magnet or attracts it. Attached to a cone, the voice coil creates pressure waves as it is forced back and forth. This motion is what we perceive as sound.
Distortion, directionality, and frequency response determine the quality of sound coming from the speaker. The closer the speaker cone’s pressure wave is to the sound recording’s electrical speaker, the better the quality of sound.
What is Speaker Frequency Response?
Speaker frequency response is a measure of the range of sounds a speaker produces. To understand the frequency response measurements, you have to have a decent understanding of the terminology used. For example, sounds are measured in Hertz (Hz).
The human ear hears sounds ranging between 20 Hz, which are low bass tones, and 20,000 Hz, which are very high-pitched. Most people can’t hear all of those frequencies, especially if they have ever had any kind of ear damage.
Most speakers produce sounds as low as 45 Hz and as high as 20,000 Hz, but we may not be able to hear them all. Audiophiles still drool over a speaker that can produce all of those frequencies. However, just because a speaker produces those frequencies doesn’t mean that it sounds good when it does. High-quality speakers will have a flat sound across the entire audio spectrum, whereas low-quality speakers change volume as they produce high or low tones.
If you want to understand frequency response and how it affects the sound you perceive, you should know the different bands that comprise the audio spectrum. These include:
Sub-bass frequencies range between 20 and 60 Hz. They are responsible for the lowest tones you can hear. It can be hard hearing the lowest of these notes, but the strong vibrations they produce are usually still felt.
Some instruments that produce these low notes include the tuba, bass guitar, and trombone, but no human voice can make notes this low. It is the section of the audio spectrum referred to as deep and low bass.
Bass falls between 60 and 250 Hz on the audio spectrum. Audio experts may refer to these tones as mid and upper bass. Some people with a low singing voice produce notes this low and instruments like the saxophone, trumpet, bass guitar, and clarinet. These tones still carry a vibration, though it is less pronounced than those in the sub-bass category, and you will likely find that these are easier to hear.
Low Midrange Bands
While this range is a few steps up on the audio spectrum, the average person considers these tones to be pretty low. Low midrange tones fall between 250 Hz and 500 Hz. You should hear these sounds easily, and many male and female voices produce them. A wide range of instruments makes these notes, including guitars, cellos, trumpets, and flutes.
You may be tempted to boost this range to get that ever-popular shaking bass effect from your speaker, but you need to be careful when doing this. Increasing this range could muffle the bass sounds and cause the overall sound output to seem muddy.
Midrange frequencies sit between 500 Hz and roughly 2,000 Hz. It’s the range where most of your melodies live. Most vocal sounds belong to this frequency range and are the sound produced by nearly all popular instruments. By far, it’s the most critical frequency range, and speakers should always make a crisp, clean sound with tones in this range.
If you boost this frequency, most instruments take on a horn-like quality. It could make the output seem tinny, especially human voices.
Upper Midrange Bands
Upper midrange tones live between 2,000 Hz and 4,000 Hz. The essential sounds produced in this range are vocals, and voices in this range are considered pretty high. Poor quality speakers will distort vocals in this range, so speakers must pass this part of the frequency response test. Instruments that produce sounds in this range include piano, violin, pipe organ, and piccolo.
If you boost the sounds in this range even a little bit, it makes a huge difference. If you get the setting just right, the speaker’s sound is rich and full. However, too much of this frequency and you’ll be risking listening fatigue.
Lower Treble or “Presence” Bands
This range is an important one for a good quality speaker. Sounds in this category sit between 4,000 Hz and 6,000 Hz and is the range that most home stereo systems base their treble control. This frequency determines the definition and clarity of sounds produced by the speaker.
Over-boosted sounds on this frequency result in a harsh and irritating output. Having these tones set too low will make all the sounds produced by the speaker seem distant.
Highs or “Brilliance” Bands
This sound range is the highest of all, falling between 6,000 Hz and 20,000 Hz on the audio spectrum. It is the widest band of the entire spectrum, but most instruments don’t produce sounds this high anyway. Many people can’t hear tones that are at the highest end of this frequency spectrum.
An excellent example of a sound that lives on the higher end of this spectrum would be the high-pitched noise made by old tube TVs of the 80s and 90s. Most adults have lost enough hearing that they can’t even hear that sound anymore. You should still hear much of the sounds that live in this range, and speakers that fail to produce them accurately will be pretty apparent to you.
If you boost this frequency, you can make the overall sound seem more high fidelity. However, boosting them too much produces an irritating hiss that will have you reaching for the power butting fast.
How to Measure Speaker Frequency Response
Now that you understand what frequency response is and the different sections of the audio spectrum, you are probably wondering how to recognize speakers with good frequency response. As I mentioned above, high-quality speakers can not only play a wide range of frequencies, but they can also play them all at the same volume. Ideally, a speaker should produce the same consistent, well-orchestrated sound that you would hear if the sound were live.
Of course, without a live performance to compare it to, it isn’t easy to know if the speaker is precisely outputting as it should. That is where measuring speaker frequency response comes into play.
What You Will Need
Generally, speaker frequency response is measured using a measurement microphone. Depending on your level of involvement, these can range from relatively affordable to pretty expensive. The more costly and higher quality microphones have higher bandwidth and will give you the most accurate results.
The other important thing you will want to invest in is a good audio interface. Again, it is best to avoid the cheapest options as they will not give you accurate results. Most experts recommend using an interface with two inputs and outputs.
The last thing you will need before moving onto testing strategies is software. Plenty of software options exist, ranging from free to several thousand dollars. If you are new to this, then playing around with the free software is a great place to start while you get yourself acclimated. Once you are a little more seasoned, you can move onto the more expensive software.
There are four key strategies used to take measurements. These include:
Taking free-field measurements means nothing around the speaker impedes the sound for a full 360-degrees, including upward and downward. How far away the first obstacle (such as the microphone) is, depends on the frequency you want to measure. For example, low tones have a much longer wavelength, so you will have to put it far out to measure those.
Usually, this measurement method occurs in an anechoic chamber, which is neither common nor cheap to use. This method is not the most practical means of determining speaker quality and is used mostly by manufacturers and sound professionals.
Gated measurement is a little more accessible to the average person than free-field measurement. This method limits the testing time, so any sound that comes after the “gate” is ignored. Gated measurement is useful for measuring frequencies down to 200 Hz, but the lowest notes will still need the microphone to be at least 27-feet away, which is not exactly practical. Nevertheless, this method will be more useful for sound professionals than anyone else.
The half-space measurement method uses essentially the same space requirements as free-field measurement, except for the floor. If you use this method to measure speaker frequency response, then you will have to go outdoors.
To get started, you will place the speaker on a baffle (if it doesn’t already have one) on the ground. The baffle is the speaker’s front face that keeps sounds in the speaker’s front and rear from colliding. After it is placed securely on the ground, you will dig a hole around it so that the baffle is entirely flush with the ground. Using this method eliminates the need to care about vertical space and measures sounds emitted in a 180-degree half-circle around the speaker.
Ground Plane Measurement
Ground plane measurement is a more simple method of measuring frequency response. To do it, you place the speaker on a hard reflective surface and put the microphone on the ground. You will want to do this in a parking lot or similar place, which will ensure you have the right surface and a large amount of space surrounding you.
You should place the microphone around six feet away from the speaker and point tall speakers towards the ground. When you measure from the ground like this, you measure both the speaker’s sound and sound reflecting from the ground.
How to Read a Speaker Frequency Response Chart
So you have set yourself up and taken your speaker’s measurements, but now you have to understand how to read the results. Speaker frequency response tests plot their results on a chart. You may find the chart intimidating at first, but it is pretty simple to read.
The chart lists sound frequencies horizontally from low to high. Generally, the chart will list frequencies between 20 Hz and 20,000 Hz, but ultimately that depends on your microphone, interface, and software. Vertically, the chart displays sound pressure levels, or how loud it is, in Decibels (dB). The graph itself shows a horizontal line that rises and falls depending on the dB the speaker produces at each frequency. The flatter the line is, the better quality of sound the speaker makes.
The Importance of Speaker Frequency Response
Considering there are other specifications that determine a speaker’s quality, you may wonder why the speaker frequency response is so critical. A good speaker frequency response, which is a very flat one, ensures that you hear the sound the way the recorder intended.
Many speakers do not have a flat speaker frequency response. Instead, they may not produce adequate volume for the bass or treble frequencies or may have peaks and valleys through the whole audio spectrum. Speakers with these issues can sound muddy, hollow, tinny, distorted, or flat. No matter the specific deficit, the speaker’s frequency response is that you won’t enjoy what comes out of it if one exists.
Choosing the Best Speaker
Once you have an understanding of how speaker frequency response affects overall sound quality, you can make a more informed speaker purchase. Choosing the best speaker depends on what you will use it for and where you will install it. For example, you wouldn’t use the same kind of speaker for a home theater that you would in a car.
Types of Speakers
Understanding the types of speakers that exist and their limitations makes it easier to shop for the best quality speaker. Using what you now know about frequency response, you can adjust your needs based on where the speaker lives. Below are some examples of popular speakers and what you should look for in terms of speaker frequency response.
Car Speakers: Coaxial Vs. Component
Car speakers generally come in two varieties, which are component and coaxial. If you are looking for the best sound possible, most experts recommend going with component car speakers. Unlike coaxial speakers, component car speakers come with the speakers, tweeters, and subwoofers separated. The separation allows for the car speaker’s frequency response to be more specialized, giving you customization control and a more accurate and rich listening experience.
Tower or Floor-Standing Speakers
Floor-standing or tower speakers usually sit on a room floor, such as a living room or home theater. These speakers feature larger cones than other types, which means they have an easier time projecting low frequencies accurately. Since these speakers are loud and have a high-quality bass projection, you will find them an excellent option for a large room.
If you listen closely to the average speaker system, you’ll notice that the speakers have the hardest time projecting low frequencies accurately. If you hope to enjoy rich, deep bass, then a subwoofer is a must-have. These specialized low-frequency speakers blend seamlessly with the rest of the sound system to create an overall rich sound quality.
You are probably aware of the low sound quality in most TV’s built-in speakers. The easiest way to improve this is with a soundbar. Soundbars are a simple unit, and often you need only to plug them in and they’re and ready to go. It is essential to look out for low-quality bass frequencies with soundbars.
The Bottom Line
Speaker frequency response may sound like a professional term reserved for the most knowledgeable audiophile, but it is a fundamental metric for you to understand. By demystifying speaker frequency response, you can make the most informed decision about what speaker to buy for any space.