Complete End-of-Line Speaker Test (includes ePRB)
Template for an end-of-line test sequence including the new ePRB. Customize it as needed!
This sequence is an example of the many types of tests that can be performed quickly and simultaneously on a loudspeaker production line. A stepped sine sweep (StweepTM) from 20 kHz to 50 Hz is played through the speaker and measured via two channels of the audio interface. A calibrated reference microphone is connected to one of the channels and an impedance reference built into the SC Amp or AmpConnect is connected to the other. A HarmonicTrak™ Analysis step analyzes the recorded waveform from the reference microphone, and outputs Frequency Response, THD, Normalized Rub & Buzz, Perceptual Rub & Buzz, Loose Particle Envelope and Polarity. A Post-Processing step calculates the Ave. Sensitivity from 100 – 10kHz.
A second Analysis step analyzes the waveform from the impedance reference and outputs a curve of impedance versus frequency. Another Post-Processing step performs a curve fit of the impedance curve and calculates the max impedance (Zmax), precise resonance frequency (f0), and the quality factor (Q) of the resonance peak. All measurements and parameter are tested against limits in Limit steps. All these test parameters can be adjusted accordingly.
The sequence begins with a prompt that gives the user the option to Recall an example Sound Check recorded waveforms from disk or make a new measurement. If the user chooses to Recall a waveform, the recorded waveform is both analyzed and independently played out of another loudspeaker or headphone so that the user can hear it as well as analyze the original waveform.
If the user chooses to make a new measurement, a Stweep from 20 kHz to 50 Hz at a user defined level is played out of a connected loudspeaker, and all the measurements and results of the device under test are displayed.
A good starting point for setting an ePRB limit for the threshold of audibility, based on our listening tests, is about 10 phons. In practical application, this value should be adjusted depending on the device under test. Varying amounts of distortion may be acceptable in a product depending on its characteristics, price point and target application.
The example data in the sequence shows the perceptual distortion curves for a good, borderline, and bad speaker of the same model.
- SoundCheck 20 or later
- Reference Microphone – Listen SCM-4 or similar
- Audio Interface – Listen AudioConnect or similar (note: AudioConnect provides bias voltage for Listen’s SCM microphones. If you use a different microphone or interface, you will likely need to add a microphone power supply such as the Listen SoundConnect to your hardware setup.)
- Power Amplifier – Listen SC Amp, AmpConnect or similar
Hardware Setup & Calibration
- Calibrate the amplifier as instructed in the SoundCheck manual.
- Calibrate the reference microphone as instructed in the SoundCheck manual.
- Connect output 1 of your audio interface to the input of the amplifier.
- Connect the output of the amplifier to your loudspeaker.
- Position your reference microphone in the nearfield of the loudspeaker under test and connect it to the microphone power supply.
- Connect the mic to input 1 of your audio interface
- Connect the impedance sense out from the SC amplifier to input 2 or use AmpConnect or measure across a reference resistor between the power amplifier and loudspeaker.
You are ready to start the sequence.