Why do some old speakers have an electromagnet instead of a permanent magnet? - Quora
How a Speaker Works - dummies
The function of permanent magnets in some industrial devices – European Training Network for the Design and Recycling of Rare-Earth Permanent Magnet Motors and Generators in Hybrid and Full Electric Vehicles (DEMETER)
Magnets in Speakers | Stanford Magnets
How Permanent Magnets are Used for Making Loudspeakers? | Stanford Magnets
Types of Speaker Magnets That Are Makes The Speaker Sound Better! - Dragon Matrix
Speaker Magnets: What Do Magnets In Speakers Do? | Nucoustics
Neodymium Speaker Magnets Explained - Official Fluance® Blog