This app note shows you how to set up the miniDSP UMIK-1 and Room EQ Wizard (REW) on the Mac, together with a device with HDMI input such as an A/V receiver or a miniDSP home theater processor. This enables you to select individual output channels for use in measuring and equalizing a home theater or multi-channel surround system. You can use a Mac with an HDMI output port or a Thunderbolt port.

This app note assumes that you have already downloaded and installed REW.

1. Get your calibration file [Top]

Go to the UMIK-1 page and enter your microphone's serial number. It is in the form xxx-yyyy and labeled on the microphone. Ensure that you download both the regular calibration file and the 90-degree calibration file.

The calibration file ensures that your microphone is as accurate as possible. Each microphone has two unique calibration files, which is why the serial number must be entered. The regular calibration file is used when the microphone is pointing at or between the speakers, and the 90-degree file is used when the microphone is pointed at the ceiling.

2. Get connected [Top]

Mount the UMIK-1 into a microphone stand. For home theater applications, it's easiest to point the microphone at the ceiling and use the 90-degree calibration file. Connect the UMIK-1 to your Mac with a suitable USB cable.

Connect your Mac to a suitable HDMI input of your A/V receiver or miniDSP home theater processor. If using a Mac with an HDMI output port, you can use a regular HDMI cable. If using a Mac with a Thunderbolt port, you can use a Mini DisplayPort to HDMI adapter cable. Check that your receiver is set for multichannel output e.g. 5.1 or 7.1, and not to a stereo downmix.

The photograph below shows a MacBook Pro connected via the Thunderbolt port and adapter cable.

UMIK-1 connection

3. Configure[Top]

Double-click on the REW app to run it. You will see a screen asking if you want to use the UMIK-1. Click Yes.

UMIK-1 detected

Answer Yes to the next question about the calibration file:

Use cal file?

Use the dialog box that appears next to locate the 90-degree calibration file that you downloaded in Step 1 above. It will have a name like "7013462_90deg.txt". (This assumes that you have pointed the UMIK-1 towards the ceiling.)

The main functions of REW will now be accessible from a row of buttons at the top of the window. This screenshot highlights the functions we will use in this app note:

REW buttons

Click on the Preferences button:

REW Preferences

  1. Check that the sample rate is 48 kHz.
  2. Set Output Device to the HDMI output device.
  3. Verify that Input Device has been set to the UMIK-1.

4. Test [Top]

Before proceeding, turn down the volume on your A/V receiver.

Click on the Generator button:

REW Signal Generator

Set the signal generator to Pink Noise and select the "Full range" radiobutton. Set RMS Level dBFS to −20.0. Drop down the Output selector and select channel 1, then press the triangular green Play button. Gradually increase the volume on your A/V receiver - you should hear sound coming from the front left speaker.

Click on the SPL Meter button. Click on the red button to turn the meter on. Increase the volume on your A/V receiver until the SPL reads about 75 dB.

REW SPL Meter

Press the Play button again to stop the signal generator. Change the channel selector to 2 and press Play again. You should hear sound from the right speaker. Continue through the remaining channels to check that they all work as expected.

5. Measure [Top]

You are now all set to run a measurement sweep. Click on the Measure button:

REW measurement window

  1. Check the start and end frequencies.
  2. Check that the level is -20.0 dB.
  3. Drop down the channel selector for Output and set it to channel 1.
  4. Click Check Levels.
  5. Click Start Measuring.

You will hear a sweep through the front left speaker, and REW will display its first frequency response graph. Repeat for all channels by clicking on the Measure button and changing the channel selector each time to 2, 3, and so on.

Channel selection

We recommend that you change the name of each measurement as you go to keep track of which is which. After completing all channel measurements, you can view them together in the Overlays window.

Overlays button

Apply some smoothing to the graphs using the pop-down Controls overlay. You can turn the display of individual graphs on and off with the checkboxes underneath. You should have a result like this:

Measurements mode over HDMI

What's next? [Top] [Top]

Now that you have the ability to run acoustic measurements, you can proceed to optimize and equalize your system. Check out the acoustic measurements and home theater tuning app notes on our web site. Have fun! Don't forget to let us know how you go in our forum.


Related Products - Acoustic measurement