Have you ever been listening to music and wondered, “How do speakers work?” The problem is that while there are plenty of articles out there, they’re just not very good.
To help, I’ve decided to do something about it! In this detailed article, using clear explanations and diagrams, I’ll explain how they work along with:
- The parts inside a speaker
- Single cone vs coaxial speakers
- 2 way and 3-way speakers explained
- Speaker crossovers
- What speaker impedance, sensitivity, and frequency response mean
First things first: What is inside a speaker?
While there are some unique and unusual speakers out there, nearly all speakers, regardless of their size or sound function, use the same basic design and parts.
What is inside a speaker?
Most speakers are made of the following parts that work together to create sound:
- Permanent magnet: A magnet is used to provide a fixed magnetic field surrounding the voice coil to make movement possible.
- Voice coil and bobbin: The bobbin is a round tube attached to the bottom of the speaker cone. A very long and tightly wound coil of wire, called the voice coil, creates a magnetic field as electricity flows through it from the musical signal from an amplifier.
- Spider: the spider is a wavy-shaped thin woven material that supports the voice coil bobbin assembly and helps push the cone back in place as it moves.
- Speaker cone & dust cap: the speaker cone is a cone-shaped stiff material that’s moved by the magnet & voice coil together to move air & create sound. The dust cap is a thin material (like a “cap”) that covers the opening in the speaker cone to keep out dust & dirt.
- Speaker basket: the basket is a cast metal or stamped metal frame that the speaker parts attach to an keeps everything aligned. It also provides a way to mount the speaker assembly to a box.
- Speaker terminals & braided wire: speaker terminals are metal tabs or connectors that connect speaker wire to the speaker. These connect to the voice coil using a flexible braided wire that moves with the speaker cone.
- Surround: this is a flexible and durable circular material (usually rubber or some type of foam) that attaches the top edge of the speaker cone to the basket.
What does a speaker cone do?
A speaker cone is the main speaker component responsible for creating sound by moving air back and forth rapidly. These are typically made of a lightweight but stiff material such as pressed paper, plastics, carbon fiber, or even thin metal.
The speaker “cone” name refers to its shape: an inverted cone shape with a central opening where the bobbin & voice coil assembly is attached. A dust cap is attached to the cone over this opening at the bottom to prevent contaminants from getting inside.
Speaker cone types vary by the type of speaker. For example, subwoofers produce very large bass sound waves and substantial air movement and need a thicker, more rigid design.
By contrast, tweeters use a very small, dome-shaped, and lightweight design for higher-frequency performance because this sound range uses smaller sound waves.
As electric current flows through the voice coil, a magnetic field is created that moves the cone away from or towards the permanent magnet. This creates sound from the movement of air as the speaker cone moves.
What does a speaker magnet do?
Speaker magnets are usually a permanent magnet with a thin circular gap in which the voice coil is suspended. The magnet provides fixed magnetic fields the voice coil can move towards or away from to move the speaker cone.
The purpose of a speaker magnet is to provide a fixed magnetic field area that the voice coil can move towards and away from (alternating) to move the cone and create sound.
A permanent magnet (usually ceramic or neodymium) is most commonly used. Neodymium magnets are are stronger for their size (denser magnetic fields) but ceramic magnets, while larger, are more cost-effective. That’s one reason why ceramic magnets are more popular for speaker use.
The magnet is designed to provide a small circular gap in which the voice coil is suspended to keep it close to the magnet’s polarized fields. Some, but not all, speaker magnets have a hole in the center to help keep the voice coil cool during high power handling.
What is a dual voice coil speaker?
Dual voice coil speakers offer a second voice coil winding in the same speaker and on the same voice coil bobbin assembly. These types of speakers allow some additional options that single voice coil speakers do not:
- Flexibility in how they’re wired (2 ohms, 4 ohms, 8 ohms, etc) for better compatibility with amplifiers and stereo receivers.
- For subwoofers or other larger speakers, you can power them with more wiring configurations or even 2 amplifiers each which you can’t do with single voice coil models.
- These can be driven with 2 channels from amplifiers that can’t be bridged for more power.
You’ll most often find subwoofers that are available in a dual voice coil version for a little bit more money.
While they offer more wiring configuration options, dual voice coil (DVC) speakers don’t offer better performance than their single voice coil (SVC) counterparts.
Additionally, speakers like tweeters for treble sound and midrange speakers for instrument & vocals aren’t normally made in a dual voice coil version.
Examples of two speaker bobbins with dual voice coils. Left: the two coils are not together while (right) on this example woofer they’re layered one on top of the other.
How do speakers work? Step by step explanation + animated diagram
In this animated diagram, you can see how a speaker works. A stereo or amplifier drives the speaker with an electrical signal that alternates from positive to negative in the shape of the musical signal.
As it does so, electric current flows through the speaker’s voice coil, creating a magnetic field that causes it to move toward or away from the magnet as it changes from positive to negative. This moves the speaker cone that creates sound waves as the air moves rapidly. Speakers use alternating current (AC).
How does a speaker work? A step by step explanation diagram
Speakers (also referred to as loudspeakers, a name from the older days) use an alternating current (AC) electrical power signal and are driven by a stereo or amplifier.
The electrical signal to the speaker is an amplified voltage that’s a duplicate of the original musical signal from an audio source but with enough power to drive the speakers with a good volume.
Here’s a step-by-step detail of how speakers work:
- (Starting from the zero output point) An output voltage representing the musical waveform starts and begins to rise. The electrical current starts flowing through the speaker’s voice coil from the positive side to the negative side.
- A magnetic field is created around the voice coil and is the same polarity as the permanent magnet attached to the speaker basket (frame). (Remember that identical magnetic fields repel and opposites attract)
- The cone begins moving forward and pushes air, creating sound.
- As the electrical signal voltage rises towards the top of the sine wave in the musical signal, the current increases, and the voice coil increases its magnetic field strength.
- This pushes the speaker cone out even further.
- The signal passes the highest output point and begins to fall. The current starts to fall also and the cone will begin to return closer to its off (zero voltage) position.
- The signal reaches zero (also called the “zero voltage crossover threshold”) and the cone is back where it started.
- The electrical signal begins to reverse as it changes to a negative voltage. When this happens, current flows from the negative voice coil side to the positive, creating a reversed polarity magnetic field.
- The voice coil magnetic field is now the opposite of the permanent magnet which attracts it and the cone begins to move from front to rear (instead of the original rear to front).
- As the signal continues the speaker cone moves in reverse, creating the other half of the sound waves created by the movement of air.
- The amp or stereo output returns to zero and the next audio signal begins as the new signal output voltage starts to rise, with the cycle starting over again.
In a matter of speaking, speakers are just an electric motor of sorts: they do work (moving air using a cone) which duplicates an electrical signal and changes it into a mechanical output in the form of sound you can hear.
Sometimes speakers are referred to, in scientific terms, as transducers. This just means they’re an electrical device that converts electrical signals to sound.
What does speaker impedance mean? (Speaker Ohm ratings explained)
Speaker impedance, measured in Ohms, is the total resistance to the flow of electric current through a speaker voice coil.
Unlike standard conductors, as the voice coil is tightly wound in a coil the makes this complicates things because it adds inductance. Inductance is different from resistance as it changes as the frequency changes and this is called inductive reactance.
In other words, when the magnetic fields of the voice coil are created they oppose the flow of electrical current a bit.
Because of the property of physics and how inductance works, the speaker “impedance” (total resistance) isn’t the sum of the resistance and the inductive reactance – it’s a bit more complicated than that.
Instead, it’s the algebraic sum (the square root of the sum of the squares) of each. Inductive reactance is commonly written as “Xl” and is measured in Ohms just like standard resistance.
Speaker impedance formula
If you like fancy math, you can see here how speaker impedance is calculated. It is the geometric sum of the resistance in the voice copper wire winding and the resistance caused by its inductance at a given frequency.
The most important thing to understand about speaker impedance is:
- The speaker impedance is always equal to or greater than the voice coil wire resistance. You can measure this with an Ohm meter.
- The impedance number on a speaker is a general guideline for compatibility, not exactly what the speaker measures.
- The impedance changes slightly (goes up) as the frequency being played increases.
In fact, if you were to use a test meter to measure the Ohms (impedance) of the voice coil on a speaker, you’d find a reading of about 3.2-3.6 ohms or so for a 4 ohm speaker and 6 ohms or higher for an 8 ohm speaker.
Image showing how to measure speaker impedance with an Ohm meter. This measures only the direct current (DC) resistance of the wire in the voice coil, not the total impedance of it with music playing due to inductance. however, it will be very close in most cases and you can tell the speaker Ohm category (4 ohms, 8 ohms, etc).
Where did 4 ohm and 8 ohm speakers come from?
4 ohm speakers (and sometimes 2 ohm) are most commonly used for car stereo systems. The practice began long ago when radios and speakers were first installed from the factory when cars were built. Because only a lower voltage (12V) is available to power them in cars, it’s more difficult to produce power for the speaker than it is for home stereos where plenty of voltage is available.
4 or 2 ohms allows more power to be delivered to speakers with simple & basic electronics as you’ll find in car stereos.
In this way, 4 ohm speakers became the unofficial standard for car speakers as cars came from the factory with them. Over the years, aftermarket manufacturers followed the same practice too and it became common.
Likewise, 8 ohms is most commonly used for home stereo system speakers. Home stereos are powered by a higher voltage source (110V like in the USA) so they’re easier to design and can power higher impedance (8 ohm) speakers easily.
Similar to car stereo radios back in the day, 8 ohm speakers became common and sort of became an unofficial standard for home stereo systems as well.
What is speaker frequency response and speaker sensitivity?
What is speaker frequency response?
An example of a typical speaker frequency response graph is shown here. Speakers aren’t perfect and don’t produce a perfectly even volume over the range of sound we can hear. Because of that, it’s helpful to know their frequency response – or how they perform over the range of music frequencies – to pick the right speaker or correct problems in the sound performance.
Speaker frequency response is the measured performance of a speaker, in decibels (dB) of volume, over a range of sound frequencies. This is usually the 20 Hertz (Hz) to 20 kiloHertz (KHz) range used as the standard for audio speakers.
The 20-20kHz range is used because it’s the range of sound a human with good hearing can perceive and music is often recorded within.
Speaker frequency response is helpful for several reasons:
- Matching speakers together for 2 or 3-way systems
- Choosing the best performing speakers for an audio design
- Designing speaker systems and speaker crossovers
- Using audio equipment such as an equalizer or digital signal processor (DSP) to correct areas where the speaker produces too much (a peak) or not enough (a dip)
While some speakers include a graph or other specifications to help you understand how they perform, not all do. It’s something you’ll usually find from retailers who stock bare speakers for more advanced speaker design.
Most off-the-shelf car or home speakers don’t include the actual response graph but instead an approximate range instead. More expensive speakers may do so, however.
If you have the right equipment you can also measure it yourself at home using a real-time analyzer (RTA) program and a high-quality microphone for this purpose.
What is speaker sensitivity?
A speaker’s sensitivity is a measurement made by the manufacturer. It’s a measurement of the volume produced at a fixed sound frequency and (usually) with 1 watt of power is delivered to the speaker at 1 meter (3.28 feet) from the test microphone.
Speaker sensitivity is a manufacturer-provided specification useful for comparing or matching speakers. It’s a measurement of the volume produced, in decibels (dB), from a speaker at 1 meter (3.28 feet) from a test microphone for a single frequency.
The sensitivity parameter is usually expressed as “89dB @ 1W/1M” for example.
In most cases, the standard measurement is the dB volume at one watt of power at 1 meter distance and often a sound frequency like 1KHz (depending on the type of speaker) may be used.
Sensitivity measurement differences
Sensitivity is sometimes measured slightly differently. That’s because a different voltage is needed for 4 ohm vs 8 ohm speakers to produce the same amount of power as the resistance in Ohms (speaker impedance) is different.
Therefore less current flows through an 8 ohm speaker, causing it to receive less power for the same voltage as a 4 ohm speaker.
In that case, a sensitivity of dB at 2.83V/1M may be used for 8 ohm speakers. At 2.83V an 8 ohm speaker develops 1 watt of power. Similarly, for 4 ohm speakers, a dB of 2V/1M may be used.
These measurements aren’t really standardized in the speaker industry, so the measurements provided by a manufacturer may be “1W/M” or “xV/M”, depending on what they happen to provide. When using this measurement to compare or match speakers it’s important to pay attention to this.
What are coaxial speakers?
Coaxial speakers are type of 2-way speaker designed to take up less space and to replace single-cone speakers. They usually include a separate tweeter and one or more crossovers built-in. Coaxial speakers provide improved sound over a single cone speaker and allow more pricing choices and installation options.
Coaxial speakers are 2-way speakers mounted on the same “axis” or in the same speaker assembly. Most coaxial speakers provide a woofer cone and add a separate tweeter with crossover for improved sound quality & frequency response versus a standard single cone speaker.
Think of coaxial speakers as a middle point between single cone speakers (the most basic speakers, with mediocre or poor sound quality) and component speakers (separate speakers with an external speaker crossover). They offer good sound quality at an affordable price in most cases.
Coaxial speakers offer several advantages:
- Easy sound upgrade: they’re a drop-in replacement for existing poor-sounding single cone speakers.
- More speaker manufacturing options and price ranges for buyers (different levels of tweeter quality, crossover design, cone materials, etc).
- Somewhat similar performance to separate 2-way component speakers without the need for a bulky separate crossover box.
- They’re very common – in fact, they’re the most popular car speaker upgrade and they’re easy to find when shopping.
- Very affordable: good coaxial speakers can be found for around $25 and up per pair depending on the size & quality.
- Coaxial speakers can fix the poor frequency response (missing sound frequencies) you find with single-cone speakers.
Coaxial vs standard/single cone speakers
Coaxial speakers offer better sound performance than standard single-cone speakers, even those with a “whizzer” cone added to improve the treble sound. Coaxial speakers can provide better frequency response and sound quality because they add one or more speaker cones (usually a tweeter) to produce the sound that a single cone woofer speaker is poor at.
Standard (single cone) speakers are notorious for mediocre – or bad – sound quality. But why? As you can see from the image above, they’re poor performers because having only a woofer cone isn’t good enough.
Single cone speakers can’t produce a great-sounding full-range sound as 2-way coaxial speakers can. Coaxial speakers are designed to improve upon standard low-fidelity speakers by filling in the missing range of sound and providing a much more enjoyable listening experience.
Coaxial speakers sound better
While some cheaper standard speakers may have a “whizzer” cone added, which is a small 2nd cone attached to the dust cap, for improved treble, they’re still disappointing. I’ve yet to hear one that sounded very good.
Coaxial speakers, on the other hand, use at least one additional speaker cone (usually a tweeter) to make up the difference and produce crisper & better-sounding higher frequencies.
In fact, in all my years of car speaker installation work I can’t recall a single standard speaker that wasn’t good enough to keep vs replacing it with a coaxial model.
While factory-installed speakers are often very low cost, coaxial speakers – even for a nice sounding pair – aren’t expensive. You can get a great-sounding pair for $25-$30 or more these days and around $20 if you’re on an extreme budget.
What is a 2 way speaker? What is a 3 way speaker?
What is a 2 way speaker?
2 way speakers use a tweeter and separate woofer, working together, to the full range of music reproduction with better sound quality. In this type of speaker system, tweeters are supplied only a high frequency sound from a high-pass crossover while the woofer is fed midrange and bass from the low-pass crossover. The result is a very clear & enjoyable sound.
2-way speakers are the most common low-cost speaker design in use today both for home and car stereos.
2-way speakers use a tweeter, receiving only higher frequencies from a high-pass crossover, and a woofer, receiving only bass & midrange sounds from a low-pass crossover, to produce the full range of sound with better clarity & performance.
In other words, 2-way speakers separate the sound you hear between two speakers for better results than a single speaker alone.
This is done because woofers can’t produce higher frequency sounds well and should be prevented from producing treble frequencies. Similarly, tweeters become distorted when attempting to produce bass or lower-frequency sounds.
The use of a 2-way speaker crossover system limits the range of sound each receives, allowing for lower distortion and better sound quality at higher volumes, too.
How does a 2 way speaker crossover work?
2-way speakers sound great thanks to the crossovers they use to split the audio signals between the tweeter and the woofer. The end result is good full-range sound.
2-way crossovers use electrical components to filter and split the electrical music signal from an amplifier or stereo and divide it between the tweeter and woofer.
The high-pass crossover blocks distortion-causing bass & midrange the tweeter can’t handle. Likewise, the low-pass filter blocks higher frequencies that a woofer cannot reproduce well and that would cause a poor sound quality if produced by it.
As the speakers play, the divided crossover output results in a complete full-range audio output that’s much better than what a single speaker could produce.
What is a 3-way speaker?
3-way speakers are an extension of 2-way speakers with the addition of a 3rd speaker using a bandpass crossover. The 3rd speaker allows improved midrange and even better sound production, lowered distortion, and clarity by offloading midrange sound to a dedicated midrange speaker.
However, the crossover design (depending on the crossover order, or the steepness of the cutoff) is more complicated for those with a sharper cutoff to block unwanted frequencies.
3-way speakers are less common due to the added cost & complexity but are a good choice for speaker builders and audiophiles who want more advanced performance. They also offer the option to get improved sound by using high-performance midrange speakers that are better suited to it than a woofer with its larger cone.
More great speaker info, articles, & diagrams
There’s lots more to learn! Check out these great articles also on my site:
- Connecting your speakers? Check out this article with great speaker wiring diagrams here.
- Find out here what tweeters are and what they do (and much more!).
- Does speaker wire affect the sound quality? Read more and find out.
- Find out more details about what speaker crossovers do and how they work here.
Got comments or questions?
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