What does the bullet horn do?

The pronunciation principle of bullet horn is the same as that of ordinary horn. The bullet in the bullet horn is called a phase cone, which is used to improve the directivity of the middle and high notes at the bottom of the cone basin. However, under the dynamic condition of the cone basin, the airflow ejected from the gap between the phase cone and the diaphragm will also interfere with the sound quality of the horn. However, it is good for alto, so the bullet horn has been popular for more than ten years and has not been seen much.

As for why bullet horns are so common in car horns, one of the main reasons is that it is convenient to install tweeters on them and flexibly change them into split or coaxial ones.

The commonly used material of "bullet" is aluminum. It is structurally independent of the sound cone and will not move with the vibration of the diaphragm. Therefore, when the speaker outputs sound, the sound wave inside the cone can be reflected more quickly by contacting the bullet. In other words, "bullet" changes the reflection angle of sound waves, that is, the phase expression of sound, which is why "bullet" is called phase cone.

Extended data:

Advantages of phase cone:

The dust cover on the traditional unit improves the quality of the diaphragm. Diaphragm must have the characteristics of light weight, high rigidity and high internal damping in order to approach perfect piston motion. Therefore, this will reduce the sensitivity of the unit, and the unit with phase plug has higher sensitivity.

At the same time, an air cavity will be formed behind the dust cover. When the diaphragm moves like a piston, the cavity will be compressed or stretched in the opposite direction, which will lead to the decrease of efficiency.

In addition, when the current passes through the voice coil, it will generate a lot of heat, and the increase of temperature will increase the impedance of the speaker unit, thus requiring more current to drive, resulting in lower efficiency. However, the voice coil and the driving magnet are sealed inside the unit and cannot directly contact the outside air, so the heat dissipation is very slow. The phase plug has two characteristics that contribute to heat dissipation:

1. Due to its own characteristics, aluminum metal will serve as a huge heat capacity body;

2. When the phase plug is directly exposed to the air, it can dissipate heat quickly.

References:

Baidu encyclopedia-phase cone

Baidu encyclopedia-trumpet