Before measuring

When you are measuring using external signal you must use exactly the same measurement settings as when the signal was generated. Therefore it is strongly recommended that you use the same setup for your measurements. If you need a special post-processing, you can load post-processing settings from Window->Load Post-processing....

At the bottom of the Measurement->Settings... dialog, you can limit the length of the impulse response to be measured to reduce the file size, below it is limited to 2 seconds.

Now click the Imp/Freq Res tag shown below

The calculation part should be set as shown in the figure below

Now click the  button. If you are using an external source and have no connection, it is impossible to measure the delay (time of flight) between the loudspeaker and microphone. Therefore it is very important that you select No, remove system delay as shown below.

If you have not selected this setting, the impulse response may not be positioned at the beginning as shown in the figure below where the impulse response starts at 9000 milliseconds. This is wrong and may cause problems for the calculation.

When using an external source the impulse response should always start at the beginning as shown in the figure below.