Impedance Measurement – Dual Channel Method Using Transfer Function

Impedance measurement - dual channel using transfer functionThis sequence demonstrates an alternative to the traditional SoundCheck single channel impedance measurement method. A white noise stimulus (10 Hz – 10 kHz) is played through the speaker while the signal across the amplifier terminals is recorded by Direct In 1 and the signal across the impedance box is recorded by Direct In 2. A transfer function analysis step is then applied to the recorded time waveforms to calculate the impedance curve. Subsequent post processing steps apply a frequency window, 1/24th octave smoothing and 1/24th octave resolution to the impedance curve. The curve is then post-processed to calculate resonance frequency, maximum impedance and Q of the resonance peak. A set of arbitrary limits steps are also provided to generate pass/fail results. The final display shows the post processed impedance curves and results window.

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Loudspeaker Splice Test Sequence

Loudspeaker Splice Sequence ScreenshotThe purpose of this sequence is to measure the anechoic response of a loudspeaker in an ordinary room using both a near field and time-windowed, far field measurement “spliced” together to cover the full bandwidth of the loudspeaker’s response from 20 to 40 kHz.
First, the near field frequency response is measured using a 1/12th octave stepped sine sweep by placing the microphone very close to the low frequency driver (less than an inch from the woofer). Then the far field frequency response is measured using a continuous log sweep with the Time Selective Response analysis algorithm.

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Ported Loudspeaker Splice Test Sequence

Ported Splice Sequence Screenshot

Ported Splice Sequence Screenshot

This loudspeaker splice sequence measures the anechoic response of a loudspeaker in an ordinary room using both a near field and time-windowed, far field measurement “spliced” together to cover the full bandwidth of the loudspeaker’s response from 20 to 40 kHz. It can accommodate ported as well as sealed loudspeakers.
First, the near field frequency response is measured using a 1/12th octave stepped sine sweep by placing the microphone very close to the low frequency driver and the port(s) if any. Then the far field frequency response is measured using a continuous log sweep with the Time Selective Response analysis algorithm.

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