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We all have a relationship with speakers, because we all have one - in our phone, headphones, etc. The speaker is a broad topic, but one of the essentials in the theory is how electric current is transformed into music in your eardrums. We will give you a basic understanding of the substance and delve further into the universe of the speaker.
Energy becomes sound waves
The speaker is an automated system in which electrical energy is converted into sound energy, also called kinetic energy. When this process culminates, the speaker creates vibrations in the air, after which sound waves are formed that the ear picks up. Sound is, in short, “invisible” waves that float through the air and into your eardrum.
Vibrations and frequency ranges
Sound is a term for acoustic vibrations that travel through air or water. Translated into the language of physics, we talk about frequencies measured in Hertz (vibrations per second, abbreviated Hz). A healthy newborn human can perceive the frequency range from 20-20,000 vibrations per second. At some point in your life, you have probably taken a hearing test where you found out how good or bad your ears are. It is natural for hearing to deteriorate with age; especially the highest treble tones in the 18,000-20,000 Hz range are weakened, but this is not necessarily due to age alone – your hearing can also get worse from listening to music at far too high a volume. So even if you are fit and young, you should still be careful, as otherwise it can result in hearing damage such as tinnitus or hyperacusis (sound sensitivity), and you do not get rid of that!
Infrasound, the audible range and ultrasound
Frequencies below 20 Hz are called infrasound, and above 20,000 Hz are called ultrasound. These are frequency ranges that can typically be heard by e.g. dogs and bats. Treble sounds with high frequencies lie roughly between 2,000-20,000 Hz (also abbreviated to 2 kHz - 20 kHz). Bass and low tones move in the frequency ranges from 20-250 Hz. Between the high and low tones are the midrange tones, also defined as the audible range. This can be compared to your conversations with others when you listen to another person’s voice.
The speaker and its function
If we take the typical dynamic speaker as a starting point, it essentially consists of the components
- a fixed magnet
- an incoming electrical signal
- a moving voice coil
- a chassis
- a cone
- a surround
As previously described, the speaker converts the electrical vibrations from the audio system into sound waves in the air.
When the speaker receives an electrical audio signal from e.g. a PC/mobile phone, it is carried into the voice coil, which is located inside a powerful magnet and attached to the speaker cone.
The cone is the component that is pushed back and forth by means of the voice coil, creating pressure waves in the air. The ear perceives this pressure as what we call sound, and it does this many times per second.
If you look at the frequency range, 40 Hz means in simple practical terms that the cone moves itself 40 times both forwards and backwards within one second, and when we talk about 2000 Hz or 2 kHz, then the cone moves 2000 times both forwards and backwards per second. That is also why you can typically see the fabric on the speaker (the cone) moving when the bass or the kick drum in, for example, a piece of music kicks in, because the wavelength in the low frequency range (20-400 Hz) is long and powerful.
… So you’re probably asking yourself how the cone is pushed back and forth? The answer is electromagnetism!
Inside behind the chassis (English term: the basket) there is a slot/channel at the bottom where the tube from the voice coil can be inserted. Here it is important that the voice coil does not hit the edges of the channel, as that will create friction and noise in the output. This is also called the magnet gap.
🕷 The spider is a kind of fabric that the voice coil is also fastened to. Together with the surround, the spider guides the driver to move perfectly in and out of the gap that sits down in the fixed magnet.
The voice coil is therefore pushed straight back and forth each time, and the spider helps keep the cone centered so the sound waves are emitted correctly.
🧵 The voice coil (in English: coil) consists of insulated copper wires wound as a very fine coil in several layers.
An amplifier can generate a magnetic field inside the voice coil, and because the amplifier from the system acts as alternating current, it causes + and - to become north and south in relation to the movement in the sound/music. In other words, changing polarity will occur inside the voice coil, just like with magnetism, which will alternate between north and south.
🧲 The fixed magnet (the speaker magnet) behind the chassis is oriented either north or south in a specific direction. If you take the voice coil, which has an alternating field in relation to the music, and place it down into the gap where the fixed magnet is located, movement is automatically created in relation to the music, because in the fixed magnet you have 2 north poles that will repel each other or 2 south poles that will repel each other, together with a north and south that will attract each other in the voice coil magnet, and the result is that the fixed magnet never moves, but the voice coil’s magnet does, as it has a changing polarity (north and south), and since it is also attached to a spider, a cone and a surround, it ensures movement that creates vibrations and thus sound waves.
The speaker made for precision
Speakers come in many versions and sizes, with different characteristics. They may have an extra boost in the bass or a sharper treble than normal (2 kHz – 20 kHz). As a manufacturer, you always aim to produce speakers that reproduce the input signal as accurately as possible, regardless of the volume level. The most traditional speaker is based on a moving voice coil. It typically consists of two or more drivers (bass, midrange, treble) to deliver the most accurate sound of what was created by the producers in the studio. Speakers such as table radios, earpods, TVs and other similar product categories are often built around a small full-range driver.
Low, mid and high tones have different vibrations and therefore spread differently. The higher the tones, the more vibrations are created and the more directional the sound becomes. That is why different speaker drivers are used, each specifically suited to a particular frequency range. High-frequency sounds have great difficulty passing through walls, but low-frequency sounds can pass through walls, floors and ceilings—this is one reason you hear your neighbour’s deep sub frequencies (30 - 80 Hz) and kick drum (85 – 350 Hz) pumping out of his speakers on a Friday night.
The speaker drivers
As described earlier, a typical speaker consists of three drivers: bass, midrange and treble. A 2-way speaker does not have a dedicated midrange driver. This means the midrange is handled together with the bass driver and pushes the sound out. With a 3-way speaker, on the other hand, you get a separate midrange driver to play only in that frequency range, which will likely deliver a clearer, more defined sound from the input signal. Some speakers consist of only one full-range driver, where all frequency ranges are produced by the same driver.
The effect of sound insulation and correct placement
We all know the feeling of the bass pumping and the door making small movements because the room is resonating. Speaker placement has a massive effect on how you hear the output from your speakers or your monitors. If they are set up close to a wall without bass traps or other sound insulation on the walls and ceiling, the sound waves are reflected, creating either constructive or destructive interference.
Most often, you want to avoid reflections in the room, especially if you work with music and production. That is why we have recording studios and cinemas that are well isolated with sound-absorbing materials, such as fibreglass wool. In this way, you avoid degrading the sound from the speakers.
Sound waves from the midrange and treble, which travel in a specific direction, are also especially reflected by hard surfaces such as wooden floors, tiles, or empty walls.
⏰ All these reflections of sound affect the consumer’s experience of the product. Timing, depth, and the quality of sound choices when, for example, producing, get ruined. You want to avoid all of this so you can get the most accurate sound from the input signal. That is why many professional audio engineers recommend placing the speakers a good distance away from the back and side walls, and acoustically treating surfaces so you can control reflections and thereby achieve as even a frequency response as possible.
🪤 Bass traps are also key to controlling and absorbing low frequencies. A rug as well as soundproof curtains—yes, even a fabric sofa—could make a difference. All rooms have different acoustics, which is why a tailored solution is most often needed to build a sound-isolated room. As for the placement of speakers or monitors, the typical 45° rule applies, especially if they are wall-mounted or placed on a shelf. This provides the best possible stereo effect from two speakers.
It is also recommended that you position the speakers so that the tweeter is at ear level when you are seated and listening. These rules also apply to the general consumer. If you want good sound, it is recommended that you follow the manufacturer’s procedure for setting up and positioning the speaker.
Which speakers should you choose?
Choosing a speaker depends on what type of person you are and what you need it for. If you are an ambitious musician who works with sound every day, it is extremely important to have a pair of speakers that do not colour the sound from the input signal. These types of speakers are also called studio monitors. They are available in many different brands, price ranges and levels of quality. There is also a huge range of different types of speakers for the general consumer. They might be for the bathroom, the living room, your bedroom, for your TV, or the ultimate speaker for the party!
👬🏼 If you want a speaker for everyday use and for a smaller pre-party with friends, it is recommended to buy one of our wireless speakers, which can be connected via Wi‑Fi or Bluetooth and are also portable. If you are the ultimate host of private parties, it is optimal to invest in something bigger that can get the party going and raise the pulse to a higher level. For that, we also offer a selection of party speakers, which are tailor-made for this purpose.
🎙 If you love belting out the biggest classics, we also have karaoke systems. If you are a nightclub owner or run a mobile disco, it is clearly recommended to invest in some of our PA systems, which is a term for large sound systems that deliver sound to many people. You can, among other things, read our articles “buy your first PA system” or “how to start a mobile disco”, which shed light on the topic of PA systems. It will give you a clear picture of what you are missing and why.
The subwoofer you can feel
You have probably heard the term subwoofer a billion times. In short, it is a separate speaker that delivers sound in the deepest frequency range. Its function is to lift the missing frequencies from 30-120 Hz. In general, you can say that a subwoofer frees up a lot of headroom in full-range speakers, which, with a subwoofer, do not have to deliver anything below 100-120 Hz. As mentioned, the subwoofer reproduces a small part of the frequency spectrum, which means that, cosmetically speaking, it has a simple design with only a single driver. There are both active and passive subwoofers. An active subwoofer is built in such a way that it has its own built-in amplifier, power supply and equalizer. All of this helps reproduce the deepest frequencies. In a PA context, a subwoofer is also called a bass bin.
Bass unit
The bass driver is the part of the speaker that, depending on size and type, pumps out sound waves from the frequency range 30-600 Hz. It is typically sub, Bass and kick drum that are prominent in this sound image, although there is also much more than Bass up to 600 Hz. However, the bass driver is not designed exclusively to deliver sub frequencies, which is why a so-called subwoofer is used. The subwoofer adds an extra contribution to the bass driver in this range.
In a three-way speaker, the bass driver has the function of handling the lower frequencies from the speaker’s input signal, but if it is a two-way speaker, the bass driver is also used for the midrange. This can be done by blending some frequencies from the tweeter into the bass driver, giving you a clearer and more precise midrange.
You are probably also wondering why the bass driver typically has a larger cone than, for example, the midrange and tweeter. This is because low frequencies have a longer wavelength and fewer oscillations per second, which requires more energy. It also requires a larger cone area, as more air needs to be moved at a time.
The midrange driver
The midrange reproduces sound from the frequency range 300-5000 Hz. Typical instruments that sit within these frequencies are piano, guitar, violin, cello, trumpet, as well as snare and kick drum and many other synthesizers. This is where they have their timbre (in English: timbre), meaning the character and quality of the fundamental tone.
The kick drum in the midrange
It was also mentioned earlier that the kick drum sits in the bass driver. The reason for this is that you can hear the kick drum across the entire spectrum, as it also emits frequencies in the midrange and treble. However, the kick drum is dominant in the low end, where from a mixing perspective, in some genres, you typically sidechain (English term) the low frequencies to the kick drum—that is, mute them every time the kick hits. Especially sub and Bass must work in harmony with the kick drum (in English: kick-drum). This makes the kick drum stand out, and you can feel its pumping effect!
It is also in the midrange that the ear is most sensitive. This is where, as humans, we find it easiest to detect faults and distortion as well as deviations from natural sound. That is why many speakers have an extra driver for this range.
The tweeter
Treble is fairly straightforward. It typically consists of high frequencies such as s and t sounds, which dominate the frequency range from 2 kHz to 20 kHz. This is where the ear picks up the crisp tones that can become too sharp. From a production perspective, you often use a plugin called a de-esser. It can turn down the sharpest tones in your audio, so you get balanced treble without it piercing your ears.
The full-range driver
The term full-range driver refers to a driver that covers the entire frequency spectrum. They are typically used in small radios, TV speakers and other smaller speakers. These drivers operate without a crossover. The reason full-range speakers are small is because they also need to reproduce the treble, and for that reason alone the speaker has a harder time delivering deep low frequencies from the Bass and playing loudly, since, as described earlier, you need a larger diaphragm and more power to reproduce deep frequencies such as sub and Bass.
When there is only one driver to consider and you also avoid a crossover, you can achieve a more dynamic and consistent sound. There are also the so-called phase and timing problems, which are easier to control with a full-range driver, as there are not multiple drivers integrated into one chassis. People also talk about coaxial speakers, used for example in car stereos and scene monitors, where you have two speaker drivers, a Bass and a tweeter, in one chassis. You can also have three speaker drivers, where the midrange is also built into the chassis.
The crossover and its function
A crossover consists of three electrical components: a coil, a capacitor and a resistor. The coil (L) blocks the high frequencies but lets the low frequencies pass through. The opposite effect is seen in the capacitor (C). It blocks the low frequencies but lets the high frequencies pass through. The resistor (R), also known as the resistance, is used to control the AC resistance and also attenuates the signal.
The crossover can split the signals from the amplifier and send them to the different drivers. Put simply, the low tones are sent to the Bass driver and the high tones are sent to the tweeter. The different drivers are designed so that each one plays within its specific frequency range. The crossover ensures, for example, that the tweeter only receives tones from the 2 kHz – 20 kHz frequency range. Frequencies that do not fit within this range are filtered out. This is how the speaker and its drivers are able to perform optimally.
The crossovers can vary, and each of them can have different values. These values, together with the speaker drivers, have a major influence on how the filter performs. Even speaker cables have an effect on it.
The Cabinet
Yes, you might be surprised, but even the cabinet around the drivers has an influence on the speaker and the sound that comes out of it. The cabinet’s function is to retain some of the emitted frequencies coming from the rear of the speaker drivers. Those frequencies must not mix with the sound being projected forward. This creates phase cancellation, which means that some sounds drop to zero. The sound waves simply cancel each other out, and that has a negative effect on the sound quality and volume of the speaker.
Reflections and distortion
The pressure the sound creates is just as high inside the cabinet as what we hear outside the speaker. Many of the sound waves inside are reflected back, which can distort the output for those listening. The reflection of the sound can also be sent back and through the speaker diaphragm, which particularly results in poor sound.
Just like in recording studios, you can reduce this distortion by adding some foam or sound-absorbing material on the inside of the cabinet. The cabinet can also be designed so that many of these reflections will not occur in the first place.
Today, there is a vast range of different types of speaker cabinets. The most commonly used in hi-fi speakers are sealed cabinets and cabinets with bass reflex. The advantage of the sealed cabinet is that it is easier to build and has the inverse curve in the Bass range compared to most rooms, which provides a lift in this frequency range. Therefore, a speaker with a sealed cabinet works well in these rooms, especially if you place them close to the wall. You can even get small speakers to play Bass, even with a smaller cabinet. In this type of cabinet, the impulse response is also efficient. However, it requires more power from the amplifier, as the downside is low efficiency.
In a bass reflex cabinet, a kind of port tube is built into the enclosure together with the drivers. This port is designed to resonate at a specific frequency—in other words, it is tuned. In this way, you can either boost the Bass, attenuate it, or help the speaker achieve a better Bass response. The port can also support and help the drivers to be tuned to the cabinet. This method is far more efficient and is used for most enclosures. The downside of bass reflex is that if the port’s resonance is close to the room’s, it can trigger an uncontrolled resonance, resulting in a poor listening experience. Another drawback of bass reflex is that high sound pressure levels can create noise from the port and the airflow passing through the bass reflex port. It’s like blowing across the neck of a bottle. It’s not very pleasant for the ears!
Active Speakers
Active Speakers are designed with a built-in amplifier, which means they do not require a separate amplifier to drive them, as is the case with Passive Speakers. They can receive and amplify direct audio signals from sources such as computers, phones, or mixers. In general, Active Speakers are economical for users because they provide a compact all-in-one solution for sound amplification, eliminating the need for external amplification while also saving space and heavy lifting. Active Speakers are often used for home theatre systems, computer speakers, and portable PA systems.
Amplification of audio signals
The most notable feature of Active Speakers is the built-in amplifier. In short, its function is to boost the incoming audio signal to a level that can drive the speaker and produce sound. Having a built-in amplifier is especially an advantage if space is limited or the setup is challenging.
Tone controls
Many Active Speakers with digital displays have built-in tone controls (e.g., bass, treble), allowing the consumer to adjust the sound in, for example, bass or treble to their preference. You may know this, for instance, from when you’re sitting in the car, where on the multimedia player you can adjust how much you want to turn up or down, for example, the treble, midrange, or bass.
Power management
Active Speakers typically have a protection circuit to prevent damage to the speaker and amplifier in the event of overload, clipping, or overheating.
Inputs
Active Speakers often have multiple inputs, allowing connection to various audio sources.
DSP and signal processing
Active Speakers also have a built-in Digital Signal Processor (DSP), which is a microprocessor developed for signal processing. With a DSP, you can, among other things, create a high-pass filter so that the tops only play everything above 120 Hz, and you can then add a subwoofer that delivers the rest of the sound image from 120 Hz and down.
Disadvantages of Active Speakers can be that the built-in amplifiers are not as powerful or as high-quality as separate amplifiers, and the signal-processing options may be limited compared to an advanced Passive Speakers system.
Passive Speakers
Passive Speakers are in direct contrast to active speakers. These speakers do not have a built-in amplifier and therefore depend on an external amplifier to drive them. Passive Speakers can be combined with additional components (e.g. crossover networks, equalisers) to create a customised sound system.
Customisation
Since Passive Speakers do not have built-in amplifiers, they can be used with a range of different amplifiers. If, for example, you are not completely satisfied with the amplifier, you can optimise it, which you cannot do with active PA speakers. This provides more options for customisation and sound quality.
Scalability
Passive speaker systems can easily be expanded by adding more speakers and amplifiers, so they can accommodate larger rooms or more demanding events.
In general, Passive Speakers provide more flexibility and customisation options compared to Active Speakers, but they also require more setup and more components (e.g. amplifiers, cables, etc.). It is recommended to invest in Passive Speakers if you need stationary installations in, for example, a hall or a nightclub. It is also more practical at a festival if there are technical issues, because you can see and analyse everything on stage via the amplifier and the other connected components that sit in racks. This is also where you can switch off the speaker without having to walk behind each individual speaker, as with the active ones, and turn off the power switch. Passive Speakers are often used in professional sound reinforcement systems and advanced home audio systems.
What is Watt?
Watt is the unit of measurement for electrical power. Watt on a speaker is the specification that states the power the speaker can tolerate under certain conditions. As a result, it is also important to separate myth from fact and remember that
- Watt does not say anything about how loud a speaker can play. Here you need to know the operating power and the speaker’s power handling, in order to then convert it to sound pressure measured in decibels (dB).
- Watt does not indicate whether the amplifier can damage the connected speakers. They are more often damaged by distortion than by electrical power from an amplifier.
- Watt does not determine sound quality. Sound quality is difficult to measure, and power handling—i.e. how many Watts a speaker can handle—has nothing to do with quality at all.
- Watt does not say anything about durability, i.e. its actual lifespan.
- Last but not least, Watt also does not say anything about whether the speaker matches the rest of the system.
What is operating power?
The operating power, efficiency, or sensitivity indicates how many watts must be supplied to the speaker for it to produce a sound pressure of 96 dB measured at a distance of 1 meter. A high operating power means that a speaker will require a more powerful amplifier to be able to play just as loud as a speaker with a lower operating power. If you know the speaker’s operating power and its power handling, you can calculate how loud your system can play in decibels (dB).
When the power to a speaker is doubled, i.e. from e.g. 10 to 20 Watt, the sound pressure also doubles. When the sound pressure doubles, this corresponds to an increase of 3 decibels (dB). Therefore, you can calculate how loud a speaker can play if you also know its power handling. If we take an example as a starting point, we have a speaker with
- An operating power of 10 watt
- And can handle a 320 Watt load
This means that 10 Watt provides 96 dB SPL at a distance of 1 meter from the speaker. When the power and sound pressure double, we therefore get that
10 Watt → 96 dB
20 Watt → 99 dB
40 Watt → 102 dB
80 Watt → 105 dB
160 Watt → 108 dB
320 Watt → 111 dB
What does the frequency range mean for the speaker?
As explained earlier, the human ear can perceive tones as low as 20 Hz up to 20,000 Hz without damage. 20 Hz is well known from the sound you hear during a thunderstorm. These tones can not only be heard, but also felt in the body. Music as we know it and listen to every day contains frequencies from 30 Hz to approx. 15,000 Hz. It is therefore crucial that the speaker covers this tonal range. If the speaker covers a wider range, the quality will improve. If it covers a narrower frequency range, the quality will deteriorate.
What is impedance?
Impedance is measured in ohms, but it is important to understand what the term means in the relationship between an amplifier and a speaker. When an amplifier sends an audio signal to the speaker, the amplifier senses the impedance from the speaker—i.e., the resistance coming from the speaker that the audio signal must be driven through. Impedance typically varies between 4 and 16 ohm speakers, and the vast majority of newer amplifiers are built to work well under these conditions. In other words, impedance is the information that, as a sound engineer, you can best use to assess whether an amplifier matches a given speaker. The less the impedance varies, the better the amplifier sounds—not because the impedance is lower, but because it varies less. Here are two examples showing the impedance curve from a speaker at 8 ohms and 4 ohms.
Example 1
This example shows an impedance curve of an 8-ohm speaker, where the impedance is at least 8 ohms. The curve has large dips and therefore has a negative effect on the amplifier’s current and voltage. This degrades the sound quality of the speaker.
Example 2
In this example, we have an impedance curve showing a 4-ohm speaker. Here, the amplifier has an easier time driving the speaker tha
