Calibrating the SPL Input

Calibrating the SPL input has two stages: the first is to adjust the soundcard's input volume control so that there is sufficient headroom to properly capture peaks in the response whilst having sufficient signal level to get clean measurements - the target is for the RMS reading on the input to be around -18dB when a speaker calibration signal is played. The second is to give the Wizard an absolute SPL reference by entering a reading from your SPL meter while a speaker or subwoofer calibration signal is playing. Note that the Measurement Level must be set before setting the input volume.

Setting the Input Volume

  1. The selected soundcard input must be connected to the meter's analogue output, see Getting Started for leads/adaptors that may be required
  2. Set your SPL meter to C weighting and set the range to suit the Measurement Level (the 80dB range is recommended for the Radio Shack meter)
  3. Press the Set Input Volume button
    Set Input Volume button
  4. Follow the on-screen instructions and wait for the volume setting to complete

    Setting input volume

Setting Input Volume Notes

Trouble-shooting Setting Input Volume

Calibrating the SPL Reading

Once the input volume has been set the Wizard's SPL Meter reading needs to be calibrated against your SPL meter.

  1. Turn off the Signal Generator if it is running
  2. Press the Calibrate button below the SPL reading and follow the on-screen instructions
    SPL calibration button
  3. Enter the reading from your SPL meter and press Done

    Calibrating the SPL Reading

The wizard remembers the SPL calibration for the next startup, so it will usually not be necessary to repeat this process, but check the Wizard SPL reading against your SPL meter before starting a new set of measurements

Having set the measurement level, the Wizard is ready to calibrate the soundcard.

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