DRC123: Room measurement

Measure room response

Prerequisites

First of all you need a measurement microphone.
Secondly you microphone needs a microphone amplifier. While most PC sound devices have such an amplifier they are often of rather poor quality and not suitable for measurement purposes. So I recommend to use an external one.

Setup

Be sure to have configured DRC123 properly.
Optionally select a a sound card calibration file made before.
Select a calibration file for your microphone if possible.
Set all sound controls of your amplifier (like bass, treble, balance) to zero or push direct sound button.
Disable any effect processors, equalizers (like RealEQ) and so on.
It might be required to do some adjustments in the extended measurement options page.

Measure with external loopback reference and external microphone amplifier

Check the option reference input and use the setup shown in the image.

If you have the option, use a special cable that returns a mix of line out left and right line input. This will compensate for almost any properties of your sound device. The mix can be done with two 10 kΩ metal film resistors as shown at the right. This will only work if you use an external microphone amplifier, because the microphone input has a too high sensitivity and is often only mono.

Measure without loopback reference and external microphone amplifier

Uncheck the option reference input and use the setup shown in the image.

If you do not have the option for the loopback above DRC123 can also use an internal loopback. In this case it is recommended to measure only in stereo mode because otherwise the delay between the left and the right channel is unknown and cannot be compensated. Furthermore you should work with a calibration in this case.

Do the measurements

Place the microphone at a location where you intend to listen music. Remember to use approximately the same altitude than your ears.
Select mode Noise (default).
Select the channels to measure.
Press Run button.
Adjust the volume to get a reasonable recording level.
Avoid any noise in the room during the measurement. Neither move items nor your body.
Wait until the results are reasonable smooth and stable. The indeterminate phase rate below the graph is a good indicator for the quality of the measurement. Good values are at 40 and less.
Press Abort/Stop button.
Enter a description to identify your measurement (optional).
Enter a file name - without extension.
Press Save button to save the result.
Repeat the procedure for different locations of the microphone and save the result to different file names.

It is not required that the response is approximately at 0 dB.

It is not required that all measurements are done with exactly the same parameters. But if you measure the left and right channel separately you must not change anything between this measurements.

Verification

If you want to verify the results from DRC123 you may check the Verification mode box. This will apply the currently selected deconvolution filter to the reference signal before output. This is how your music is played with DRC123. Ideally the response should be flat in this mode, but usually there are some residuals because the correction is not exact and the response depends highly on the microphone position.