Getting the right sound and long operational life from a speaker system requires expert knowledge of material sciences.
MISCO’s video series on “Designing & Building a Loudspeaker” explores the component choices made in constructing one specific 5.25” subwoofer, but the principles apply broadly to almost any speaker project.
Designing and Building a Loudspeaker Video Series
To help our customers better understand the process and what goes into designing and building a speaker, MISCO has created a unique, five-part video series that gives a behind-the-scenes view of designing, building, and testing a speaker. If you missed video #1, watch it here.
Each component part selected for the construction of a speaker will affect how the final system operates. Watch the video or continue reading for a breakdown of each part of the speaker, what it’s made with, and why that material was selected.
Selecting Materials for Speakers Parts
The frame (or basket) is what every other part of the speaker attaches to. It must be sturdy because it’s going to hold the magnet assembly, the cone, the spider, and more.
The frame is commonly made from stamped steel with a powder coat finish. The coating further strengthens the steel, protects it from corrosion, and deadens the acoustical properties of the metal. A more expensive, lighter-weight option is a powder-coated cast aluminum.
The speaker terminal is how a speaker is connected to an audio source. The speaker terminal in this subwoofer example consists of a quick connect lug and insulator board.
The T-yoke is part of the magnet assembly. It’s made out of low-carbon steel with zinc plating. The hole in the middle acts as a vent to help in thermal management within the speaker.
A speaker’s magnet is often made of a ferrite material (it may also be called a ceramic magnet). The magnet used in this subwoofer is a Y30-grade ferrite magnet. The magnet isn’t charged until the very end of the speaker’s assembly.
Another option for a speaker magnet is neodymium. Neodymium has stronger magnetic properties to create a smaller, lighter assembly. However, as a rare earth material, it is much more expensive than ferrite.
The front plate (or top plate) is made from stamped, low-carbon steel. The one in this speaker is about 6mm thick. The four nubs on the front plate are used to securely attach the entire magnet assembly to the basket.
The voice coil is the heart of the speaker. When the audio signal is applied, it becomes an electromagnet that causes the motion within a loudspeaker which creates the soundwaves. To create a voice coil, copper or aluminum wire is wound around a form. This example speaker has four layers of 31-gauge copper wound around an aluminum form with a DC (direct current) resistance of about 6.5 ohms. Aluminum is used for the form because it helps dissipate heat and is part of the thermal management within the speaker.
The spider helps keep the voice coil stable and moving in a linear fashion. Spiders may be made out of specially treated cloth so that it is compliant, yet fairly stiff. A stiffer spider is beneficial to provide stability in a speaker that will experience greater excursion, like a subwoofer.
A speaker cone can be made from a number of different materials, including specially designed paper, polypropylene, aluminum, carbon fiber, or acrylic-coated cloth. Each has unique acoustical and durability properties.
There are two parts to the cone for this speaker–the body and the surround. The body in this example is made from a kraft paper that incorporates abacá fibers. Abacá is a banana leaf fiber recognized for its great mechanical strength, resistance to saltwater damage, and long fiber length. The cone’s surround is made of a polyether foam, a very compliant and lightweight material, which is preferable to balance out the moving mass of the driver. The goal is to keep more of the mass in the body of the speaker and less in the surround.
There are two eyelets in the cone where the voice coil wires and tinsel leads will attach to it. The tinsel wire must be extremely flexible and durable because it will bend as many times per second as the frequency of the input signal. The tinsel wire in this speaker is made of four strands of thin copper wound around a Kevlar core. This makes the wire both flexible and conductive.
A gasket is often incorporated into the design on top of the cone and/or behind the basket. It is often made of plastic and/or foam. Gaskets are instrumental in how a speaker is mounted providing a seal to the speaker enclosure. Communicating with your manufacturer on where a speaker will be installed helps them recommend the best gaskets.
The dust cap is part of the diaphragm and adds to the moving mass of the cone. It needs to protect a speaker but also be extremely light. The dust cap for this speaker is a kraft material with glass fiber mixed into it. It weighs less than a gram but is surprisingly stiff.
The next video in this series explores how all of these individual parts are actually assembled together in the building of the speaker driver. If you have any questions about how a speaker can be designed with the best material to fit your specific application and budget, please reach out to our team.