Speaker Technical Specifications and Connection Methods

Loudspeaker Technical Specifications

Impedance

The nominal impedance presented by a speaker at its input provides information about the type of load the speaker offers to the amplifier at a certain frequency. This depends on the ohmic resistance of the coil wire, the inductive reactance of the coil, and the speaker's design and construction.

Resonant Frequency

This is the characteristic vibration frequency of the mechanical elements, including the diaphragm, the moving coil, and the suspension elements. This frequency is crucial as it marks the point where the speaker is inoperable for frequencies below this resonance.

Frequency Response

This reports the sound intensity provided by the speaker for each frequency across the audio spectrum. It is desirable that the response curve is as flat as possible, but a single speaker cannot cover the entire range, necessitating various types of speakers for different frequencies.

Sensitivity (SPL)

Sensitivity is the Sound Pressure Level (SPL) that a loudspeaker produces at 1 meter distance on its axis when fed with 1W of power into an 8-ohm impedance.

Power Considerations

Power handling is divided into two main categories:

• Continuous Power: The maximum power that can be applied to a speaker continuously without causing damage.
• Minimum Power (Low): The minimum power required from the amplifier to achieve a listening level capable of exciting the loudspeaker.

Performance (Efficiency)

This is the ratio of acoustic power delivered at the speaker output to the electrical power supplied at the input (for each Volt applied). It is expressed as a percentage (%).

Angle of Coverage and Directivity

This defines the angle at which the Sound Pressure Level is reduced by 6dB compared to the level provided by the speaker on its principal axis.

Distortion

The speaker is the element that introduces the most distortion into the audio chain. Typical distortion levels are around 5% at low frequencies and between 0.5% and 2% at high and medium frequencies.

Types of Loudspeakers by Frequency Range

• Woofer (Bass)

  Features a very low resonance frequency, typically between 20 Hz and 50 Hz. The effective frequency range is usually between 20 Hz and 3 kHz.

• Midrange (Squawker)

  Designed for medium frequencies, with a resonance frequency below 300 Hz.

• Tweeter (Treble)

  Designed for high frequencies, with a resonance frequency typically between 3 kHz and 4 kHz.

Loudspeaker Connection Methods

When connecting speakers, two factors must be considered: their rated power and impedance. The amplifier output impedance must match the total impedance of the connected speakers. There are three main types of connections:

1. Series Connection

   The total impedance is the sum of the individual impedances. This method is used when the goal is to increase the total impedance presented to the amplifier.

2. Parallel Connection

   This method is used when the goal is to reduce the total impedance presented to the amplifier.

3. Mixed Connection

   An association combining both series and parallel wiring. It is typically used when the power delivered by the amplifier is higher than the power the individual speakers can dissipate, requiring complex load matching.

Speaker Testing and Troubleshooting

Coil Resistance Test

The coil resistance should be checked with a multimeter; the reading must match the value provided by the manufacturer. If the reading is infinite, the coil is broken.

Troubleshooting Distortion

Distortion often occurs because the coil may have become unfocused (misaligned). We can check this by gently applying surface pressure to the cone, moving it inward and outward to feel for resistance or scraping.