What does the column in the center of the horn do and what is it for?

The horn is divided into several different musical instruments, a wind instrument, thin on the bottom of the thick, mostly made of copper. Another is a modern electro-acoustic components, the role is to convert electrical signals into sound, also known as loudspeakers. Can also be used to describe people who advocate, publicity. Horn is divided into several different instruments, one is a wind instrument, the upper thin bottom thick, mostly made of copper, commonly known as the horn. The trumpet is also commonly known as the oboe wind instrument wind instrument, thin on the bottom of the thick, the lowest part of the mouth to the surrounding open, can amplify the sound. There are many ways to categorize them, generally according to the way of articulation, they are divided into blowhole pneumatic instruments, single-reed pneumatic instruments, double-reed pneumatic instruments and lip-reed pneumatic instruments, and the tone lacks a sense of metal, so they are collectively referred to as woodwind instruments, even though many of these instruments have been made of metal, rubber and even synthetic materials. In orchestras and marching bands, this group of instruments is known as the woodwinds, while the lip-reed aerophones are known as the brass (and are indeed made of brass). The horns we often refer to are generally the horns in electro-acoustic components, and this entry focuses on the horns in electro-acoustic components. For wind instrument horns, look up the common names, oboe, trumpet, and bugle. The basic principle comes from Fleming's left-handed law, put a current wire and the magnetic line perpendicular to the magnet between the north and south poles, the wire will be subject to the magnetic line of force and the current and the interaction of the two and move, in the piece of the diaphragm attached to the line, with the current changes in the diaphragm to produce the front and back of the movement. Currently more than ninety percent of the cone monobloc is moving coil design. Electromagnetic in the middle of a U-shaped magnet set up a movable chopper (armature), when the current flows through the coil, the armature will be magnetized and the magnet produces suction-repulsion phenomenon, and at the same time drive the diaphragm movement. This design is inexpensive but ineffective, so it is mostly used in telephone handsets and small headphones. Inductive and electromagnetic principle is similar, but the armature is doubled, and the magnet on the two voice coil is not symmetrical, when the signal current through the two armature in order to different flux will push each other and movement. With electromagnetic is different is inductive is can regenerate lower frequency, but the efficiency is very low. The basic principle of electrostatic is Coulomb (Coulomb) law, usually plastic diaphragm plus aluminum and other inductive materials vacuum vaporization process, two diaphragms placed face to face, when one of them plus a positive current high voltage when the other will sense a small current, by mutual attraction and exclusion of each other to promote the role of the air will be able to emit sound. Electrostatic monomer due to the light weight and vibration dispersion is small, so it is easy to get clear and transparent midrange and treble, the bass power has not caught, and its efficiency is not high, the use of direct current electrodynamic and easy to gather dust. At present, such as Martin-Logan and other manufacturers have successfully developed a hybrid electrostatic and moving-coil speakers, to solve the problem of electrostatic body bass is insufficient, the use of electrostatic headphones is also very extensive.