Loudspeaker Diaphragm Displacement Measurement Using a Laser
A test sequence to measure the peak (max and min) displacement of a loudspeaker diaphragm using a laser
Introduction
Loudspeaker diaphragm displacement measurement with a laser is easy in SoundCheck. This pre-written test sequence demonstrates how to measure the peak (max and min) displacement of a loudspeaker diaphragm using a laser.
The user is first prompted to input several parameters: Test Level, Start Frequency, Stop Frequency and Stimulus Frequency Resolution. The sequence then plays the Start Frequency through the DUT and records the resulting diaphragm motion with the laser. The recorded waveform is then post processed to determine its maximum and minimum values across a search range. These two values are combined with the stimulus frequency to create maximum and minimum x-y pairs and these values are then converted into maximum and minimum curves. The stimulus frequency is then incremented according to the selected resolution and the process is repeated until the Stop Frequency is achieved. The resulting maximum and minimum curves are displayed on an x-y graph and on a table.
Required Software
- SoundCheck 21 Basic or higher
Required Hardware
- Displacement Laser: Keyence IL-065 or similar
- Amplifier: Listen SCAmp or similar – part number 4060
- Audio Interface: Listen Audio Connect 2 or similar – part number 4047
Setup Diagram for Loudspeaker Diaphragm Displacement Measurement
Hardware Setup and Calibration
Laser: When first loading the sequence, you may be prompted to add the Signal Path named Laser to your calibration. You may choose to add it or to select an existing calibrated Signal Path. If you choose to add the Signal Path to your calibration, you will then be prompted to add the corresponding Calibrated Device file to your calibration to which you should respond Yes. Go to Setup > Calibration > Input and enter the sensitivity of your displacement laser into the Sensitivity field and assign an available Hardware Channel to the Laser signal Path. Click OK to save your Calibration.
Amplifier: Calibrate your amplifier per the instructions in the SoundCheck user manual
Connections: Connect the output of the laser to Input 1 of the audio interface and connect Output 1 of the audio interface to the input of your amplifier per the diagram below.
Further Development of the Loudspeaker Diaphragm Displacement Measurement Test Sequence
This sequence has been designed for simplicity, to be accessible to 100% of SoundCheck customers. Ways in which you could modify or further develop the sequence include:
- Adding separate stimulus, acquisition and analysis steps using Reference Microphone and/or Impedance Box to add acoustic or electrical measurements to the sequence
- Add an Autosave step
- Add a loop to create multiple displacement curves and then perform an Average Curve function on them
Get Sequence
Download Laser Displacement Measurement Test Sequence (zip file)
Download Laser Displacement Measurement Sequence documentation (PDF)
