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

Your HDMI device will typically be an A/V receiver, but you may also have an A/V preamp or a Blu-ray player with HDMI input.

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. Use "Save As" in your browser to save the numbers as a file e.g. 7000343.txt.

The calibration file ensures that your microphone is as accurate as possible. Each microphone has a unique calibration file, which is why the serial number must be entered.

2. Download and install software [Top]

You will need to download and install two items of software:

  • Download Room EQ Wizard (REW) from Home Theater Shack. You should get the latest version from the download area at least 5.01 beta 17 is needed to operate correctly with the UMIK-1.


  • Download ASIO4ALL from http://www.asio4all.com/. Double-click and follow the installation steps. The optional components don't need to be installed.

3. Get connected [Top]

Mount the UMIK-1 into the small stand supplied with it, or if you like, you can use any other microphone stand. Connect the UMIK-1 to your computer using the supplied USB cable.

UMIK-1 connection

Connect the HDMI output of your computer to a suitable HDMI input of your A/V preamp or receiver. Be sure that input is selected, and also check that your HDMI device is set for multichannel output e.g. 5.1 or 7.1 and not to a stereo downmix.

4. Configure Room EQ Wizard [Top]

Start REW. The main functions are 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 Preferencesbuttons and make the following selections (in this order):

  • Under Drivers, select ASIO.
  • Under Sample Rate, select 48 kHz.
  • Under ASIO Device, select ASIO4ALL v2.
REW Preferences

Then click on the ASIO Control Panel button (still in REW Preferences). This opens up the ASIO4ALL control panel.

5. Configure ASIO4ALL [Top]

In the ASIO4ALL control panel, set advanced mode. This is done by clicking on the wrench or spanner icon at the lower right. In advanced mode, there will be additional controls in the window and the spanner will have a red X over it.

In the list at the left, enable the HDMI audio device and the UMIK-1. You should deselect other audio devices to avoid clutter when selecting input and output channels in REW.

ASIO4ALL Control Panel

Audio devices don't always appear with obvious names, depending on the device and the version of Windows. In some cases, the UMIK-1 may appear just as "USB Audio Device." By hovering the mouse over the device you will get a popup window with more information that helps to identify the device. The UMIK-1, for example, will be an input device that runs at 48 kHz (only).

6. Select input and output channels [Top]

Quit REW and start it again. This is to ensure that REW has the latest set of channels in the ASIO4ALL driver. In the Input drop-down selector, select the first channel.

ASIO4ALL UMIK input channel selection

REW will at this point ask you to locate the UMIK-1 calibration file that you downloaded in Step 1. Click on Yes and locate the file.

ASIO4ALL UMIK input channel selection

In the Outputdrop-down selector, you should see eight channels - these are your eight HDMI audio channels. Set it to the first channel:

ASIO4ALL UMIK output channel selection

6. Test and measure [Top]

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

You can use the REW Signal generator to test that all is working correctly. Click on the Generator button and set the signal generator to "Speaker Cal" pink noise and the level at -12 dB, as shown in the screenshot below. Press the green play button. Gradually increase the volume on your A/V preamp or receiver - you should hear sound coming from the front left speaker.

REW Signal Generator

To check all channels, change the Output drop-down selector in the REW Preferences window. (You can leave the Preferences window open to make output channel selection easier.) Here is a typical mapping of HDMI channel numbers:

  • Channel 1: Front Left
  • Channel 2: Front Right
  • Channel 3: Center
  • Channel 4: Subwoofer
  • Channel 5: Surround Left
  • Channel 6: Surround Right
  • Channel 7: Surround Back Left
  • Channel 8: Surround Back Right

Open the REW SPL Meter, and click on the red button to turn it on. Increase the volume in your A/V receiver or preamp until the level reads about 75 dB.


You are now all set to run a measurement sweep. Select the first HDMI output channel again and click on the Measure button. Then use Check Levels and then Start Measuring. You will hear a sweep through the front left speaker, and REW will display its first frequency response graph. Then change the output channel to run a measurement on the next channel.

The UMIK-1, like all measurement microphones, is slightly directional and at high frequencies (6 kHz and above) is slightly less sensitive to the sides. For highest accuracy and repeatability, point the UMIK-1 at each speaker being measured. Alternatively, orient the UMIK-1 vertically (pointed at the floor or ceiling) and use a 90-degree calibration file such as that is supplied when the UMIK-1 is purchased via Cross-Spectrum Labs

After completing all channel measurements, you can view them together in the Overlays window. (Apply some smoothing to the graphs using the pop-down Controls overlay.)

Measurements mode over HDMI

What's next? [Top]

Now that you have the ability to run acoustic measurements, you can proceed to optimize and equalize your system. The following app notes contain information that you may find helpful in your journey: