Speaker Test System Configuration

A speaker test system needs a high-precision reference microphone to guarantee that the performance of a speaker rather than the reference microphone is measured. For better measurement results, you need to carefully consider how to set up the hardware and position the speaker and reference microphone.

Hardware Setup for a Speaker Test

The following figure shows a typical hardware setup for a speaker test.


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The following figure shows the hardware setup for a speaker impedance test.


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The following figure shows the hardware setup for a speaker crosstalk test.


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A speaker test system usually consists of the following components:

  • Sound and vibration module—Sends stimulus signals to the speaker, receives and analyzes the microphone signals.
  • Amplifier—Amplifies signals and matches impedances between the module and the speaker.
  • Chamber—Provides an environment for accurate and repetitive measurements. The chamber is covered by acoustic absorbent materials from the inside to prevent reflections and reduce the impacts of external noises.
  • Reference microphone—Captures acoustic signals from the speaker and converts them to analog or digital signals.
  • Resistance box (optional)—Provides a resistor to measure the speaker impedance.
  • Positioning of Speaker and Reference Microphone

    For research and development design tests, IEC 60268-5-7:2003 describes the distance between the reference microphone and speaker to be 0.5 m or an integral number of meters. IEC 60268-5-7:2003 describes 1 m as a standard distance in practice. Therefore, keep the distance between the reference microphone and speaker at 1 m or more to simulate the human ears’ experience in research and development design tests. Refer to IEC 60268-5-7:2003 for more distance recommendations and requirements.

    For manufacturing tests, use a shorter distance between the reference microphone and speaker for the following reasons:
    • Test results compare to relative limits in manufacturing tests. Relative limits are determined based on a batch of golden samples where a short distance is usually used.
    • In mass manufacturing tests, test costs increase when a longer distance between the reference microphone and speaker requires a larger acoustic chamber. To avoid this, the reference microphone is usually placed as close to the speaker as possible but without affecting the reproducibility of measurements at high frequencies.
    • A short distance achieves a high signal-to-noise ratio (SNR) and minimizes the impact of reflections.

    The distance between the reference microphone and speaker varies depending on the speaker size, frequency range, and the number of speaker drivers. For example, it may be a few millimeters for a smartphone type measurement and a few centimeters for bigger speakers with a closed cabinet and a single driver. More complicated distance solutions are required for bigger cabinets with multiple drivers.