The loudspeaker is the transducer that converts electrical energy into acoustic energy. The electrical energy causes the membrane to vibrate, which sets the surrounding air in motion, creating a pressure wave.
In a loudspeaker's characteristics table, the most relevant data are:
| Sensitivity | Sound pressure at 1 m when 1 W of power is applied. Typically at 1 kHz. |
| Frequency response | Sensitivity for each frequency. |
| Directionality | Speaker behavior depending on the direction of sound emission. |
| Power | Power Indicates the maximum electrical power applicable to the speaker without causing damage. |
| Impedance | Between 8 and 16 Ω. The 100 V line transformer raises the impedance of the assembly. |
A loudspeaker is composed of a cone or diaphragm, a magnet, and a coil. The movement of the diaphragm moves the air, producing the sound wave. It's important to note that in public address systems, as in other audio disciplines, the speaker and enclosure combination is also referred to as a loudspeaker. Even acoustic columns, composed of many speakers, or three-way speakers with three speakers, are colloquially referred to as loudspeakers, although it would be more appropriate to call them by their correct name, or, more generally, "sound point."
As with microphones, loudspeaker classification is based on several criteria. The most common are:
According to their mechanics
- Direct radiation: The diaphragm radiates directly into the air. These are the most common.
- Indirect radiation: A horn adapts the high impedance of the diaphragm to the lower impedance of the air. They are more efficient and capture more acoustic energy, for example exponential speakers.
According to their frequency range
- Broadband: They cover a wide band of the audio frequency range.
- For low frequencies: They cover the band below 700 Hz (woofer) and 80 Hz (subwoofer).
- For mid frequencies: They cover the frequency band from 400 ~ 700 Hz to 3 ~ 8 kHz.
- For high frequencies: They cover the band above 3 ~ 8 kHz (tweeter) up to 20 kHz.
According to their electrical design
- Electrodynamic: The electrical signal acts on a moving coil, creating an electromagnetic field that interacts with the field created by a magnet attached to the speaker, causing the cone or diaphragm to move.
- Electrostatic: An electrically charged plate acts as a diaphragm. It moves when the charge of the two plates (the capacitor) between which it sits changes.
- Piezoelectric: Based on the property of piezoelectric materials to contract in response to electrical impulses. High performance and small size, for high frequencies.
En megafonía se atiende a una clasificación en función de la forma y tipo de recinto utilizado. Las clases de altavoces utilizados normalmente son:
- Horn speakers
- Sound projectors
- Ceiling or wall speakers
- Acoustic columns
- Acoustic spheres
- Two-way speakers
- Low, medium, and high power
- Compact array
- Line array
- Specialty speakers
- Garden speakers
- Moisture-proof or underwater speakers
- Dust-proof speakers
