Guenter Villnow
Guenter Villnow

In this app note, we will demonstrate subwoofer integration for miniDSP's stereo Dirac Live processors using only the Dirac Live app for measurement. This app note applies to:

For more advanced subwoofer integration using Room EQ Wizard, see the app note 2.1 Subwoofer Integration with miniDSP and REW.

1. Getting set up[Top]

We will assume that you have already set up your system containing the miniDSP processor and installed the miniDSP and Dirac Live software as per the user manuals.

For measurement, you will need to connect the UMIK-1 or UMIK-2 to your computer. This diagram shows a typical system connection for measurement, using the miniDSP SHD as an example:

SHD subwoofer integration - system connections

2. Configure routing and crossovers[Top]

Start your plugin and click the Connect button. Use the Outputs tab to change the displayed labels on the output channels. In the example below, we have used "Left Sp", "Right Sp" and "Sub". Then set up the Routing matrix like this:

SHD subwoofer integration - routing matrix

Note: if your subwoofer has a built-in low pass filter, set it to the highest possible frequency. This is because we will be doing the crossover in the miniDSP processor.

Click on the Xover button for output channel 1. Link it to output channel 2:

miniDSP SHD: linking Xover or PEQ

Set a high pass filter to remove low frequencies from the left speaker. For example:

SHD subwoofer integration - high pass filter

Click on the Xover button for output channel 3. Set a low pass filter to remove high frequencies from the subwoofer. For example:

SHD subwoofer integration - low pass filter

3. Set time delay (optional)[Top]

If you wish, set the time delay between the speakers and the sub. As a starting point, use the difference in the distance of the speakers and the sub to the listening position. For example, if the sub is 1 meter further away from the listening position than the speakers, set the delay on the speakers to 2.9 ms:

SHD subwoofer integration - delay on speakers

If the sub is 1 meter closer to the listening position than the speakers, set the delay on the sub to 2.9 ms:

SHD subwoofer integration - delay on sub

Note: setting the time delay this way does not guarantee good integration. After running a measurement, you may need to adjust this time delay again.

4. Run a single-point measurement with Dirac Live[Top]

Click on the Start Dirac Live Software button in your plugin. The plugin will disconnect and the Dirac Live app will start. Proceed through the steps described in the miniDSP Dirac Live User Manual.

When you get to the Volume Calibration tab, note there will be only two channels shown. This is because the miniDSP SHD Series/Flex/DDRC-24 are stereo Dirac Live processors. They treat each speaker combined with the subwoofer as a single channel. There is no separate Dirac Live channel for the subwoofer.

Volume calibration for stereo Dirac Live

When you get to the Measure tab, run just a single measurement, with the microphone located in the center of the listening area. Here is an example of that measurement:

Single measurement for stereo Dirac Live

5. Analyze your result[Top]

Proceed to the Filter tab (and click through the warning).

Analyze your result. The first thing to check is the level of the subwoofer relative to the speakers. This diagram below shows the subwoofer level too high on the left, and the subwoofer level too low on the right:

Subwoofer levels check with stereo Dirac Live

A level imbalance can be corrected by adjusting the volume control on your subwoofer if it has one, or by changing the output level of the subwoofer output channel in the plugin. (To do this, you will need to quit the Dirac Live app, then start the plugin and click Connect.)

(Additional information: While Dirac Live will work to correct the response if the subwoofer level is too high or too low, other issues can arise. For example, in the graph on the left, the response at 80 Hz is about 10 dB too high due to the subwoofer, causing the effective crossover frequency to be higher than expected (about 110 Hz in this example). If the subwoofer level is too low as shown on the right, Dirac Live will need to apply additional boost to the subwoofer. This will reduce boost available for correcting for room modes and tend to increase the low-frequency roll-off of the system.)

A second thing to check for is a large dip at the crossover frequency caused by cancellation between the subwoofer and the speakers. This diagram below shows such a dip on the left, and corrected by inverting the subwoofer output on the right:

Subwoofer cancellation and phase inversion with stereo Dirac Live

To invert the subwoofer, quit the Dirac Live app. Start the plugin and click Connect. On the Outputs tab, click the Invert button for output channel 3:

Invert button for subwoofer integration

(Additional information: There is usually no need to worry about dips in the measured response, as these move around with different measurement positions and Dirac Live will make the most sensible correction possible. However, a deep wide "hole" near the crossover frequency is probably caused by cancellation between the subwoofer and speaker. Trying to correct a cancellation such as this may result in the speaker or subwoofer being driven harder than really necessary, resulting in distortion.)

In addition to inverting the phase, try changing the time delay on the subwoofer output channel, or on both speaker output channels. Finally, trying a different location in the room for the subwoofer may yield a better result.

Note, however, that if a couple of changes do not yield a satisfactory result, it would be better do your measurements with Room EQ Wizard (REW) instead. This way you do not have to swap between the plugin and the Dirac Live app each time you make an adjustment. See the app note 2.1 Subwoofer Integration with miniDSP and REW.

6. Run Your Dirac Live Calibration[Top]

Run your full Dirac Live calibration using 9, 13 or 17 measurements. Adjust the target curve to suit your preference. For example, this screenshot shows a target curve with an elevated bass level, which many people prefer:

SHD subwoofer integration - after optimization

Then proceed to the Export tab and load your correction filters into the miniDSP processor. Play some music and have a listen! You can turn Dirac Live on and off with the miniDSP remote to hear the difference.

Wrapping up[Top]

That's it for this app note! Have fun, and please let us know how you go in our forum.

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