50
50
Guenter Villnow
50
50
Guenter Villnow
50
50
50
50

In this application note, we show you how to use Room EQ Wizard (REW) and its integration with miniDSP to equalize your subwoofer.

What you will need[Top]

  • A miniDSP processor and plugin that support the REW integration feature. Almost all current processors/plugins have this feature — check the relevant User Manual.

  • A calibrated measurement microphone, for which we recommend the UMIK-1 or UMIK-2.

  • Room EQ Wizard (REW), which is a free download for Windows, Mac OS X, and Linux. If you are using a UMIK-2, get the most recent beta version from avnirvana.com (you will need to register a free account to download). This will ensure that you get a version that supports the UMIK-2.

We will assume that you're already set up with the miniDSP plugin and REW. If you are new to REW, refer to our app note UMIK-1 setup with REW. The miniDSP processors are very flexible and there are a lot of ways they can be set up, so the procedure below might not apply exactly to your system. REW is also very flexible, so we will describe one set of REW parameters; we suggest that you try it the way we describe here, then experiment with different parameters.

1. Make the initial measurements[Top]

  • In the plugin interface, disable all equalization.
  • Usually, you will also want to disable all crossover filters. This is so that the equalization can be applied independently of the crossover.
  • Mute all output channels except the one that you want to measure (i.e. the sub channel).

Run a measurement sweep in REW with the microphone in the center of the listening area. You can proceed with this measurement if you wish. However, since the measured response varies depending on the microphone location, it's often recommended that you make several measurements and average them. Figure 1 shows four measurements in our test system (light colors) and their average (heavy line).

Initial measurements for input to auto EQ

Figure 1. Initial measurements for input to REW auto EQ (displayed on Overlays screen)

(To average a set of measurements, click on the All SPL button, select only the measurements you want averaged, and click the Average the Responses button in the lower left of the display.)

2. Set up parameters in REW[Top]

On the main REW screen, select the average measurement in the list of measurements at the left. Then click on the "EQ" button.

REW EQ button

Set the parameters as shown in the following screenshots.

Equalizer

REW equalization for miniDSP equalizer setting

Select the option that matches your plugin. Here is a summary table:

  Setting    Sample Rate    Nr. of PEQs    Plugin  
miniDSP 48 kHz 6 2x4, C-DSP 6x8, 10x10
miniDSP-96k 96 kHz 5 4x10, nanoDIGI
miniDSP 2x4 HD 96 kHz 10 2x4 HD, SHD, HA-DSP, PWR-ICE
C-DSP 8x12 192 kHz 10 C-DSP 8x12
C-DSP 8x12 DL 48 kHz 10 C-DSP 8x12 DL, DDRC-24, DDRC-88A
nanoAVR 96 kHz 10 nanoAVR

In these cases, REW may generate too many filters. To prevent this, use the EQ Filters window to disable some filters.

Target Settings

REW equalization for miniDSP target settings

Set Target Type to "None" and deselect "Add Room Curve" to set a flat target. (Feel free to experiment with different target settings later.) Set the Target Level so that the desired EQ can be accomplished with cut filters. You will want to experiment with the Target Level as different values can give different results.

Filter Tasks

REW filter tasks

Set the parameters for generating the correction filters. Shown in the screenshot above are the values we found to work best for our example. You should experiment with these values to get the best result.

Since we are working with an average value, there is no need to try and get the graph completely flat.

3. Set manual filters[Top]

Sometimes, it's helpful to set up some filters manually. Click on the EQ Filters button to view the correction filters (initially blank). Here you can select the Manual option for a filter and then set its parameters. Here in our example we set a shelving filter to boost the low-frequency response of our subwoofer:

REW manual filter

4. Match the target response[Top]

In the Filter Tasks section, click on "Match response to target." REW will generate filters to optimize the response. Here is our example with the measured response in indigo, the corrected response in purple, the target in blue and the correction filters in green:

REW EQ screen showing measured and
predicted response with correction filters

You can see the filters calculated by REW by clicking on the "EQ Filters" button:

REW
calculated correction filters

5. Export and import correction filters[Top]

Once you have a correction that looks satisfactory, click on "Save filter coefficients to file" and save to a file. (Note: "Export filter settings as text" doesn't save the filters to the format needed to import into a miniDSP plugin. Make sure to choose the correct option!)

Then return to the miniDSP plugin and open the PEQ block that you want to put the filters in. Set it to Advanced mode and click on IMPORT. Select the file that you just saved, click PROCESS and the plugin will display the correction filter:

miniDSP nanoAVR parametric EQ screen after loading filters

Confirm your result by running your measurement sweeps again. Note that if you equalized to an average, no single microphone location will be flat.

Wrapping up[Top]

Now you can re-enable your crossover filters and do more measurements to fine-tune your integration. Have fun! Don't forget to let us know how you go in our forum.

 


Related Products - Acoustic measurement