Speakers are divided into several different musical instruments, one is a wind instrument, which is thin on the top and thick on the bottom, mostly made of copper. The other is a modern electro-acoustic element, which converts electrical signals into sound, also called a speaker. It can also be used to describe someone who advocates and publicizes for others.
As early as 1877, Ernst werner of Siemens obtained the patent of the moving-coil horn according to Fleming's left-hand law. 1898, Sir Oliver Lodge of England further invented the conical horn according to the principle of telephone megaphone, which is very similar to the modern horn we are familiar with. Sir Lodge called it a "roaring phone".
But this invention can't be used, because Lee De Forest didn't invent the triode vacuum tube until 1906, and it was several years later that it was made into a usable amplifier, so the cone-basin horn didn't gradually become popular until 1930. Another reason is that 192 1 year produced a new record recorded by electricity, which has a better dynamic range (up to 30dB) than the traditional mechanical record, so people have to try to improve the speaker characteristics to match it.
1923, Bell Laboratories decided to develop a complete music reproduction system, including new record player and speaker, stereo recording and MC head, stereo carving, etc. It was in this wave of action that it was invented. The important task of developing speakers falls on two engineers, CW Rice and EW Kellogg.
The equipment they used was unprecedented at that time, including a 200-watt vacuum tube expander, many recordings made by Bell Laboratories, and various speakers developed by Bell Laboratories over the years, such as Rocky's cone-basin speaker prototype, compressed air speaker controlled by diaphragm flap, corona discharge speaker (today called ionization driver) and electrostatic speaker.