What are Voice Coils?
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Promos
Voice coils are relatively simple structures, but have the power to make your speakers and hard drives work! How do they do this? Freshbooks message: Head over to freshbooks.com and don’t forget to enter Tech Quickie in the “How Did You Hear About Us” section when signing up for your free trial. Techquickie Merch Store: designbyhumans.com Techquickie Movie Poster: shop.crowdmade.com Leave a comment with your requests for future episodes, or tweet them here: twitter.com Follow: twitter.com Join the community: linustechtips.com
Voice coils are small, seemingly simple coils of wire that sit behind moving diaphragms in speakers and behind read/write heads in hard drives. The video explains that the core advantage of voice coils is their extreme accuracy and high movement speed, made possible by the Lorentz force: when current passes through the coil in a fixed magnetic field, it becomes an electromagnet and experiences a force that pushes or pulls the coil. This force allows rapid acceleration and deceleration, with speakers capable of about 800 m/s^2, which translates to tens of Gs in practical terms and enables fast on demand changes in sound output. The narrator also describes how the same principle is used in microphones, where electrical signals cause a coil and diaphragm to move in a magnetic field, converting audio into an electrical signal, and then how the reverse process creates sound from a signal in speakers. The discussion expands to hard drives, where a voice coil and a movable arm position the read/write head with remarkable precision, decelerating and stopping within a fraction of a micron. Finally, the video covers downsides of voice coils, including magnetic field management and heating, and touches on novel uses such as voice coil actuated camera stabilizers that can reposition a camera between frames to create the illusion of multiple cameras. The host closes by noting future potential and inviting ideas for future episodes or demonstrations, while also plugging related tools and merchandise.
Topics · electronics · audio_technology · data_storage · mechanical_engineering · physics
Questions answered
- What is a voice coil and what are its two main uses in everyday tech?
- A voice coil is a coil of wire placed in a fixed magnetic field that, when current flows, becomes an electromagnet and experiences a Lorentz force. This enables movement in two common applications: driving the cone of a speaker and positioning the read/write head in a hard drive.
- Why can voice coils achieve rapid acceleration and deceleration?
- Because the coil in a fixed magnetic field experiences a strong Lorentz force when current is applied, allowing fast and precise movement of the attached structure, such as a speaker diaphragm or a hard drive head.
- What limits voice coils from replacing motors in every application?
- Excessive magnetic force and heat buildup can be problematic; making magnets too large can cause control and safety issues, and high current can heat the coil, reducing performance or causing damage.