(1) Permanent magnets are made by mixing iron oxide with strontium, then grinding the compound into a very fine powder. The powder is mixed with a ceramic binder and then sealed in a metal mold. The mold is then placed in a furnace and sintered to bind the mixture together.
(2) The frame is made of aluminum or steel. The sheet arrives at the intended factory, where it is then placed on a conveyor belt and conveyed to a cutting machine. The cutter uses a hydraulic press to cut holes in the sheet to allow air to move freely from the cone. The sheet is then formed by a hydraulic press, which forces the sheet into a mold of the desired shape and then drills the mounting holes in the appropriate locations.
(3) Cones: The surround and the star wheel are each made of laminated paper and are then glued together as components.
(4) Voice coil: The voice coil is made by winding many very thin insulated copper wires on a plastic spool. The spool and voice coil assembly are glued to the dust cap of the cone assembly.
(5) Frame: The soft iron core and permanent magnet are bolted together.
(6) Then, first manually glue the star wheel to the bottom of the frame, then glue the surrounding sections to the top of the frame, attaching the cone assembly to the frame assembly.
Inspectors monitor all steps of the manufacturing process. Check the permanent magnet for chips or cracks. Check the paper cone for defects or holes in the material, and check whether the paper cone components are properly bonded. Check whether the overall quality of the entire assembly meets specifications.
The final assembly of amplified speakers is connected to an audio generator that tests the speaker's frequency response and power function to ensure that it produces sound within the desired specifications before the amplifier speaker for sale.
Scrap metal in the frame and wastepaper in the cone are sent to a recycling plant for recycling. Foreign materials such as strontium must be disposed of according to government regulations.
The industry has been experimenting with raw materials to improve the sound quality, frequency response and power output of amplified speakers. New technologies are being developed in the form of direct drive amplified speakers that do not use cones.