Speaker
A dynamic loudspeaker converts an electrical audio signal into mechanical motion and sound. Current in the voice coil interacts with a magnetic field, moving the attached diaphragm. Only part of the electrical input becomes acoustic output; heating and other losses also matter.
The voice coil moves in the magnetic gap while the suspension helps keep it centred. Its force drives the diaphragm and surrounding air. Mass, compliance, electrical damping and the enclosure shape the response, so diaphragm motion is not a perfect copy of the input current at every frequency.
In plain terms
A lightweight paddle pushes and pulls on the air. The voice coil provides the changing force, while the suspension guides the diaphragm's motion.
Why designers use it
- Reproducing sound from an amplified electrical signal.
- Building loudspeaker systems with drivers chosen for different frequency bands.
- Providing speech, music or alerts where the complete speaker and amplifier meet the requirements.
Best for
- Music
- Voice
- Wide-band audio
Key specifications
- Nominal impedance: A rated description; actual impedance varies with frequency
- Sensitivity: Read the specified voltage/power, distance and measurement conditions
- Frequency response: Depends on the driver, enclosure and test conditions
- Power and excursion: Check thermal and mechanical limits separately
When not to use it
- Where ambient noise dominates — a haptic buzz may be a better cue.
Common mistakes
- Treating an externally driven sounder like a buzzer with its own oscillator.
- Connecting a speaker load directly to a logic output without checking the required driver and load limits.
- Assuming a microphone's output format, bias or pinout from its appearance.
Where you will find it
- A two-way loudspeaker combines low- and high-frequency drivers with a crossover that directs the relevant bands to them.
- An enclosure designer uses the driver's measured parameters to evaluate resonance, low-frequency response and excursion rather than choosing a box by diameter alone.
A short history
Chester W. Rice and Edward W. Kellogg's 1925 work helped establish the moving-coil cone loudspeaker. Early examples used an energized field coil rather than the permanent magnet common in later designs. Horn-loaded compression drivers followed a related but distinct development path; a patent for one must not be mislabeled as the other.
Good to know
- Nominal impedance is not DC resistance plus an average impedance.
- The enclosure and driver work as a system.
- Electrical input power is not the same as acoustic output power.