With the miniDSP UMIK-1 or UMIK-2 USB measurement microphone, you have an easy way to get started with acoustic measurement: to optimize and equalize your subwoofer, to correct for room effects, or even to design your own speakers! Each UMIK is individually calibrated for accuracy. In this application note, we'll show you how to get up and running with the UMIK-1 or UMIK-2.

Here are the key differences between the UMIK-1 and UMIK-2:

  Model    Sample Rates    Connector  
UMIK-1 (original) 48 kHz USB Mini-B
UMIK-1 v2 48 kHz USB-C
UMIK-2 44.1 to 192 kHz USB-C

1. Get connected [Top]

Mount the UMIK-1 or UMIK-2 (we'll just call it the "UMIK" from now on, unless there's a reason to specifically indicate which one) into the small stand supplied with it. For optimum results, look into obtaining a mic stand with a boom arm, readily available from online retailers. To make measurements, you will need to:

  1. Connect the UMIK to your computer, and

  2. Get audio out from your computer into your stereo or home theater system.

UMIK-1 (original)

If your computer has a USB Type-A port, connect the UMIK-1 (original) to your computer using the supplied USB Type-A to Mini-B cable:

UMIK-1 connection USB Type A to mini-B

If your computer only has USB-C ports, you can use a USB-C hub to connect, like this:

UMIK-1 connection using USB-C hub

Alternatively, you can use a USB-C to Mini-B adapter cable.

UMIK-1 v2 or UMIK-2

If your computer has a USB Type-A port, connect the UMIK-1 v2 or UMIK-2 to your computer using the supplied USB Type-A to USB-C cable:

UMIK-1 connection USB Type A to USB-C

If your computer has USB-C ports, you can use a USB-C to USB-C cable, like this:

UMIK-2 connection using USB-C cable

Note that while the USB-C connector is used, the USB protocol supported by the UMIK-1 v2 and UMIK-2 is USB 2.0. Therefore, you only need a USB-2.0 compatible cable with USB-C connectors on it, which is cheaper than a USB-3.x cable.

Alternatively, you can use a USB-C hub together with the supplied USB Type-A to USB-C adapter cable.

Audio output

You will need audio output from the computer into your stereo or home theater system. If you are using a device with USB audio input, connect it to your computer as normal using a USB cable.

You can use the analog audio output from your computer if it has one i.e. a line or headphone output. This is typically a 3.5mm stereo connector so you will need an adapter cable from stereo 3.5mm to RCA plugs. Connect the RCA plugs to your preamp.

Audio connection

For connection to an A/V receiver or processor over HDMI, see the app notes on using a UMIK-1 or UMIK-2 and REW with HDMI output on Windows or Mac.

2. Get your calibration files [Top]

Go to the UMIK-1 or UMIK-2 page and enter your microphone's serial number. It is in the form xxx-yyyy and labeled on the microphone. Two calibration files are downloaded:

  1. The regular or "on axis" calibration file has a name that is the same as the serial number e.g. "8100002.txt". Use this file when pointing the microphone towards the speakers.

  2. The 90-degree calibration file has "_90deg" in the name e.g. "8100002_90deg.txt." Use this file when pointing the microphone towards the ceiling.

The calibration files ensure that your microphone is as accurate as possible. Each UMIK has its own unique calibration files, which is why the serial number must be entered.

3. Set sample rates [Top]

Set the input and output devices to the sample rate that you want to use.

  • If you are using a UMIK-1, set the output device to 48 kHz. (The UMIK-1 can only be set to 48 kHz.)

  • If you are using a UMIK-2, set both the UMIK-2 and the output device to the sample rate that you want to use, between 44.1 and 192 kHz.

Windows

Open Control Panel, then Hardware and Sound, then Manage Audio Devices. On the Playback tab, click on the output device and then Properties. Drop down the selector to set the sample rate.

2x4 HD sample rate setting in Windows Control Panel

If you are using a UMIK-2, go to the Recording tab and click on the UMIK-2 and then Properties. Drop down the selector to set the sample rate. (The UMIK-1 can only operate at 48 kHz.)

UMIK-2 sample rate setting in Windows Control Panel

Mac

Open the Audio MIDI Setup application. Click on the output device and drop down the menu to set its sample rate.

2x4 HD sample rate setting in Audio MIDI Setup

If you are using a UMIK-2, click on it and drop down the menu to set its sample rate. (The UMIK-1 can only operate at 48 kHz.)

UMIK-2 sample rate setting in Audio MIDI Setup

4. Set up Room EQ Wizard [Top]

Download Room EQ Wizard from roomeqwizard.com. 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.

Once installed, start REW. You will see a screen asking if you want to use the UMIK-1 or UMIK-2. Click on Yes.

UMIK-1 or UMIK-2 detected

Answer Yes to the next question about the calibration file.

Use cal file?

Use the dialog box that appears next to locate one of your calibration files:

Select UMIK-2 cal file

Open the REW Preferences window. Select your output device (in our example the 2x4 HD), and select the UMIK-1 or UMIK-2 as the input device. Set the sample rate to the same as you set above. This is the result:

REW Preferences set up for UMIK

Note: be sure to use the "MICROPHONE" setting for the UMIK and not "Default Input." This is because REW stores calibration files for these two choices, and the dialog box just above loaded the cal file into the "MICROPHONE" input for the UMIK-2. Furthermore, the MICROPHONE input must be used for proper SPL readings. Click on the Cal Files tab to view all devices and inputs and their stored cal files.

5. Set levels [Top]

The UMIK is automatically calibrated by REW for sound level (this information is in the calibration file). You will want to set your system to generate a suitable signal level, though. Click on the Signal Generator button:

REW signal generator button

Set the parameters as shown below. -20 dB is a good starting point for the level.

REW Signal Generator

Position your microphone at the listening position and turn the volume of your system down. Then click on the Play button (green triangle), and turn the volume up until the test signal is at a comfortable level.

Click on the SPL Meter button:

REW SPL meter button

Click on the red button in the lower right corner to turn it on, and adjust your system volume until the meter reads about 75 dB. Alternatively, change the output level in the REW signal generator. Close the SPL Meter window when done.

REW SPL Meter

6. Run a measurement sweep [Top]

Click on the Measure button:

REW measure button

Check that the level is set to the same as used in the Signal Generator (–20 in our example). Set the frequency range for 20 to 20,000 Hz and check that the output channel is the one you want. Click on Check Levels. As long as it doesn't have any errors, click on Start.

Making a measurement

REW will make a "whoo-oop" sound through your speakers. A short time later, you should see your first in-room measurement!

Example measurement

You may want to apply some smoothing from REW's "Graph" menu. Here is the same graph as above with 1/6th octave smoothing:

Example measurement REW measurement with 1/6th octave smoothing

What's next? [Top]

Now that you're able to do an acoustic measurement of your speakers and room, there are lots of interesting things you can explore. Check out the app notes on our site:

Have fun, and don't forget to let us know about your experiences in our forum!

 


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