Editor's note: originally posted in 2022, this blog has been updated to include the latest resources from MISCO on loudspeaker components.
A loudspeaker is an electromechanical acoustic transducer that converts an electrical audio signal into the sound people hear. Whenever a signal is put into a sound system, there is the possibility that differences will arise between the input and output that comes from the loudspeaker.
Each part of a loudspeaker works together to contribute to its audio quality—or lack thereof. The materials used, engineering standards, and arrangement of components all influence the final output.
Resource: Video series on designing and building an OEM speaker
Let’s take a closer look at the key parts of a loudspeaker:
Magnets
Every moving coil loudspeaker must incorporate a permanent magnet. The magnetic field generated by the magnet differs based on the materials used, but it always has the same purpose: To interact with the voice coil. By generating attraction and repulsion, the magnet creates the motion of the loudspeaker.
Several different materials can be used alone or in alloys to make the loudspeaker magnet. Advances in audio engineering and materials science have improved the design of magnetic motors for speakers. Musicians may have strong opinions about the sound qualities provided by different magnet types.
The most common magnets are:
- Ferrite: Today’s standard low-cost magnet material, especially for larger speakers.
- Neodymium: Premium rare earth metal that can be as powerful as a 10x larger ferrite magnet while weighing a lot less.
- Alnico: Once a common choice, this is an alloy of aluminum, nickel, and cobalt. It can be more costly, but is still preferred for some guitar speakers.
Cost, engineering, and performance qualities all bear on the choice of magnet material. For example, the warmer sound produced by an alnico magnet may be essential to some performances. Neodymium offers the greatest magnetic strength, but is vulnerable to rust and sensitive to external conditions.
Voice Coil
The voice coil can be called the heart of the speaker. It is the component that causes the diaphragm, or speaker cone, to move and produce sound. The flow of electricity through the coil wire turns the voice coil itself into an electromagnet, interacting dynamically with the permanent magnet described above.
As alternating current enters the voice coil, its magnetic field polarity is changed. Interaction with the permanent magnet’s field drives the conversion of electrical energy into mechanical energy. The motion produced “pushes or pulls” the cone, creating the sound you hear.
A typical voice coil features copper or aluminum wiring wrapped around a form material like paper, aluminum, Kapton (a polyimide film invented by DuPont in the 60s), or fiberglass. Voice coils generate massive amounts of heat: With about 95 watts of every hundred becoming heat, voice coil heat dissipation capability is crucial.
Cone
Also called the diaphragm, the speaker cone may be the most important element of a top-performing loudspeaker. As the component that directly produces sound, it delivers the results that all the other parts contribute to. It takes the form of a relatively thin, semi-rigid membrane, vibrating to generate sound.
As the voice coil moves, variable air pressures are created around the cone. The cone converts those vibrations into a signal and emits acoustic energy. Physically, the cone’s operations mimic those of the human eardrum. It must be held securely, yet still be able to freely move.
Effective speaker cones have low mass but retain rigidity during operation. Throughout much of modern history, speaker cones have been made from specially designed paper or polypropylene plastic. Carbon fiber, kevlar, mylar, PEI cones, and others are also available.
Suspension
The suspension holds everything in the right place as a speaker is in action. It includes the spider and the surround. The spider connects the voice coil to the speaker basket. It’s made with specially treated cloth and attached with special adhesives (the glue impacts how a speaker performs). The spider makes sure the voice coil stays aligned and returns to the right position with each vibration.
The surround is typically made of either poly-foam, foam, paper, cloth, or butyl rubber. It holds the cone and basket together, working in conjunction with the spider to keep all the components aligned and moving in the right way.
The properties of the suspension (materials, weight, thickness, stiffness, etc.) will impact the speaker’s resonant frequency. Typically the more flexible the suspension the lower the resonant frequency will be.
Baskets
The basket, frame, or chassis is responsible for holding all the active parts of the loudspeaker together. The magnet assembly, suspension, and cone assembly are all secured to it. In addition to supporting the key parts, the basket provides an attachment flange that enables the speaker to be mounted.
The basket is arguably the simplest part of the entire speaker, yet one on which everything else relies and sometimes the most expensive. It provides much of the branding opportunity for the system. The basket’s material, finish, and even paint color are all visual indicators of quality that may influence the perception of the product.
Enclosure
The enclosure isn’t just to protect the speaker from its environment and give it an aesthetic appeal. It can have a big impact on the sound produced. Depending upon how it is designed it can amplify or diminish various frequencies. Because of this, it’s important to consider the enclosure early in the design process and figure out how it will contribute to the sound the speaker creates.
Today’s enclosures are often made from specialized plastics that can be formed into virtually any shape.
Grilles
To protect a speaker from physical damage, especially to the cone, it generally is mounted behind a protective grille. The role of a speaker’s grille is to provide this basic protection while minimizing the reduction in sound quality.
Sometimes the lack of acoustic transparency of a durable grille can lead to acoustical compromises that should be accounted for elsewhere in the system or system tuning.
In each audio system, grilles must be designed for the right balance of audio quality, durability, and aesthetics. The appropriate balance depends on the specific details of each application. A system that will be outdoors may need more robust protection from water and direct sunlight, for instance.
Shop MISCO’s catalog of waterproof/outdoor speakers
To meet your goals, each element of a speaker must be calibrated to your exact needs. Contact MISCO to find out more or discuss your project.
