With the miniDSP UMIK-1, 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 loudspeakers! In this application note, we'll show you how to get up and running with the UMIK-1.
1. Get connected
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.
Connect an audio output from your computer to your sound system. With most computers, you can use the line out or headphone output with a suitable cable. It is advisable to connect into your system at the preamp inputs, so that the preamp volume control can be used to manage the signal level from the computer.
2. Get your calibration file
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.
"Sens Factor =-16.273dB, SERNO: 7000343" 20.396 -0.376769317 22.242 0.434645133 24.255 0.819522375 26.4503 0.869646823 ...
3. Set up Room EQ Wizard
Download Room EQ Wizard from Home Theater Shack. You should get the latest version from the download area as at least 5.01 beta 14 is needed to operate with the UMIK-1.
Once installed, start REW. You will see a screen asking if you want to use the UMIK-1. Click on Yes. (If you don't get this screen, go to the REW Preferences window and set the Sample Rate to 48 kHz.)
Answer Yes to the next question about the calibration file, and then locate the file that you saved above.
4. Set levels
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 and set the parameters like this (the top frequency parameter, "24,000" in this example, isn't relevant, you can ignore it):
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.
Now open the REW SPL Meter. 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.
5. Run a measurement sweep
Click on the Measure button near the top left of the main REW Screen. Check that the level is set to -12 dB, and click on the Start Measuring button.
REW will make a "whoo-oop" sound through your speakers. A short time later, you should see your first in-room measurement!
Note: if you're measuring primarily bass frequencies, it's better to run both speakers at the same time. If you're measuring full-range and looking at from, say, 200 Hz and up, it's better to run just one speaker - just disconnect one of the cables. Depending on the type of measurement, you may also want to apply some smoothing to it from REW's "Graph" menu.
You're well on the way now! 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 following app notes:
- Loudspeaker measurements with REW. Learn how to perform basic loudspeaker measurements. A great starting point for anybody who just acquired the UMIK-1.
- Subwoofer Integration with miniDSP. Use the measurement capabilities you now have to accurately integrate your subwoofer into your system. No more guesswork!
- Auto-EQ tuning with REW. Use the Auto-EQ feature of REW to generate correction curves for your system based on your UMIK-1 acoustic measurement. Just load the result right into a miniDSP plugin.
- Building a 2way crossover. Use the UMIK-1 to measure your speakers accurately in order to make an active 2-way (or 3-way, or 4-way) loudspeaker system.