The loudspeaker as we know it today is available in many shapes, sizes, and configurations to fulfill various purposes. It has become a common device in such forms. We all own multiple speakers, technically speaking – from our personal headphones, earbuds, and handheld Bluetooth speakers we use daily to those we commonly tend to forget about, such as those on our television sets, in our vehicles, and on our cellphones.
What is a Loudspeaker? How Does it Work?
In short, a loudspeaker is what we – in the audio world – refer to as a transducer. The term transduction refers to the conversion of electrical energy into mechanical energy or vice versa. Some examples of audio transduction devices include our own ears. The human ear converts mechanical energy – vibrating sound waves – into complex electrical signals interpreted by our brain as sound. Microphones and loudspeakers are other examples of audio transducers.
A loudspeaker performs this transduction process by means of a series of components housed within what we refer to as a speaker cabinet or enclosure. Magnetic fields are generated inside this cabinet, and a speaker cone responds to these magnetic signals by vibrating in a back and forth motion, creating air pressure. This air pressure is converted back into an electrical signal by our ears, which, in turn, is processed by the brain to perceive the sounds – airwaves – we hear as ‘sound’.
The components of a working speaker are arranged linearly, from front to back as follows:
- The Speaker Cone and its Surround: This component is responsible for pushing air and creating sound.
- The Spider: This part is what holds the speaker cone in place in a suspended configuration, while also allowing for some movement.
- Magnet and Voice Coil: These elements convert electrical energy into mechanical energy (motion).
There are more parts of a loudspeaker that play a role in producing sound. However, these are the most important and basic and can be easily understood. To understand the workings of a speaker, it is important to understand what makes up an audio signal.
How Audio Signals Work
All sound is made from either a single or combination of frequencies. As humans, we can hear a set frequency range of 20 Hertz to 20 Kilohertz, which can vary from person to person and as we age. A sound’s frequency is determined by the number of cycles the waveform makes per second.
Therefore a lower frequency completes fewer cycles than higher frequencies. Because of this, lower frequencies cause the speaker to move slower, which requires a larger diameter speaker to accurately represent the audio signal. The waveform cycle of a frequency can be interpreted as positive and negative currents, which promotes the magnetic interaction between components.
The electrical current that carries the audio information is sent through a wire coil, stimulating a magnetic field. This magnetic field found in the coil interacts with the field of the magnet attached to the speaker. As the audio signal is transmitted through the coil and the waveform completes positive and negative cycles at different rates of speed, the coil is inherently repelled and attracted by the permanently fixed magnet in the speaker. This magnetic communication causes the coil’s speaker cone to move backward and forward, which creates the air pressure necessary to interpret sound.
Understanding Technical Specifications and Speaker Related Terminology
Lastly, before we get into some speaker specifications, we must understand the tech talk used to describe different speakers’ performances. Below is a glossary of some of the important terminology I’ll be using throughout this guide:
Active Speakers are also referred to as powered speakers, these loudspeakers feature onboard crossovers and separate power amplifiers for each speaker driver.
A Speaker driver consists of a speaker cone, surrounds, and other components that result in the movement of magnets and air to produce sound.
Passive speakers are loudspeakers that require an external power amplifier to perform.
Subwoofer speakers are responsible for reproducing low subsonic frequencies, often housed within a separate cabinet. Subwoofer speakers are typically found in diameters ranging from 15 to 20 inches.
Crossover is a component responsible for dividing frequency ranges to send each range to appropriate speaker drivers, respectively. Lower frequencies are sent to the woofer and subwoofer, while midrange and higher frequencies are introduced to the midrange drivers and tweeters. The crossover can be built into the speaker itself or as an external unit.
Frequency Response is represented as a figure or graph that displays a device’s ability to accurately represent the audio signal passed through it. As we know, our range of hearing is limited to the 20Hz to 20kHz region. Thus an ideal frequency response would be able to cover this entire spectrum, with as little exaggeration or forfeit of a certain area of this spectrum along the way as possible.
We refer to this as a flat frequency response as no regions of the frequency spectrum are inaccurately displayed – e.g., a system that emphasizes lower frequencies or lacks midrange. This is defined as the amount of unwanted noise that becomes audible as the volume is increased. Think of an old HiFi system that produces a humming or crackling sound as the volume increases and no signal passes through it. This sound is still there when your music starts to play. It’s just not as easy to hear. This is, therefore, an important specification to note.
Impedance is the measurement of resistance in alternating current (AC) electrical circuits, measured in Ohms. Typically, loudspeakers are rated at an impedance of 8 Ohms. It is very important to match the impedance of a speaker to the correct power amplifier impedance. This can become slightly more complicated when running large systems, as impedance can either be divided or multiplied depending on the configuration.
Now that we’ve gained a basic understanding of some audio terminology and the fundamental workings of a loudspeaker, we can examine some speaker types available on the market.
Types of Speakers
Speakers come in many styles, shapes, sizes, and designs to suit different applications and uses. Some of the most common types are as follows.
PA speakers form part of what is known as a PA system, used to bring sound to large-scale events, and are generally very powerful speaker systems. PA speakers usually work in collaboration with one another to form an overall satisfying sound experience. This includes subwoofers, midrange drivers, tweeters, etc., all of which are in separate cabinets or enclosures and strategically placed to provide a pleasing listening experience.
PA speakers are situated in different configurations depending on the scale and nature of an event. This can be anywhere between a simple pair of full-range drivers found on independent stands to a large series of subwoofers placed at ground level and midrange and tweeter drivers stacked in an array-like vertical fashion high above the ground angled downwards.
The calibration, setup, and routing of a PA system requires intense technical knowledge, so if you’re looking to hire speakers for a party at home, be sure to double-check specifications such as power ratings, impedance, and other factors.
Headphones and Earbuds:
These are based on very small speaker drivers housed within compact cabinets designed to fit into or onto our ears. These can feature a series of speaker drivers or also operate off a single speaker. Many different styles of headphones and earbuds are available on the market, so be sure to match the specifications to your specific needs. There is a model for any and all applications.
Studio monitors, also referred to as audio engineers, use reference monitors to record, mix and master music, film, radio, and other recorded media. Studio monitors are designed to reproduce sound as accurately or flat as possible to allow the engineer to interpret the recorded material objectively and make necessary edits and adjustments.
Of course, not all speakers are entirely flat, so an in-depth knowledge of sound and speakers is necessary to work with such equipment to adapt to the qualities of the monitors to make informed decisions on a mix or master. These speakers are not recommended for casual listening but rather for professional work or audiophiles and critical listeners.
Amplifiers for Guitar or Bass:
Guitar and bass amplifiers are designed to ‘color’ the instrument’s sound and anything else in the signal path before it to provide a unique tonality. Guitar speakers are commonly found with 10- or 12-inch speaker drivers, while bass cabinets house speakers around 10, 12- and 15-inch speakers. Different speaker and cabinet or enclosure materials produce different tonal qualities and are favored by musicians for such characteristics.
Most Bluetooth speakers make use of a single full-range driver that replicates the entire frequency range in a single speaker, while some include woofers and midrange or tweeter drivers. The quality of portable Bluetooth speakers is quickly improving, and some impressive models are available on the market. Some specifications to consider here are weight, output volume, power handling, frequency response, battery life, and water-resistance features.
The Speaker Cabinet
The cabinet or enclosure of a loudspeaker is vitally essential to the sound quality and characteristics it produces. The shape, size, weight, and materials used all impact the speaker’s response to the audio signal. First, we’ll take a look at the materials used and the influence this has on the overall sound characteristics of the speaker and the sound it reproduces.
Most speaker cabinets are constructed from hardwood or medium-density fiberboard. These materials’ weight, absorption qualities, and density play a massive part in the final sound quality. Many different wood types and shapes are used to construct speaker enclosures. However, nowadays, plastics are often used to build speakers of all types and sizes for various reasons.