The miniDSP PMIK-1 is the perfect pocketable companion to audio analysis programs running on your tablet or even your smartphone. In this application note we will show you how to set up the PMIK-1 for use with the AudioTools app and Smaart® Tools from StudioSix Digital, running on an Apple iPad.
Please note: miniDSP cannot provide support for third-party applications or hardware. This app note shows you how to set up the miniDSP PMIK-1 to use with AudioTools but other functions of the Apple iPad hardware or the AudioTools app are beyond the scope of miniDSP support.
1. Get your calibration file [Top]
Go to the PMIK-1 page and enter your microphone's serial number. It is in the form xxx-yyyy and labeled on the microphone.
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.
*1000Hz -32.1 20.00 -3.9 20.55 -3.6 21.11 -3.2 ...
2. Get connected [Top]
The PMIK-1 simply plugs into the headphone jack of the iPad. The microphone body is oriented at 90 degrees to the plug, which makes it easy to use your iPad in landscape mode and point the microphone towards the sound source:
As suggested by the photograph, we recommend that for the most reliable and repeatable measurement results, the included wind/pop filter be removed from the PMIK-1. If the pop filter is used, be aware that the response above 10 kHz will read up to a few dB low.
To generate audio output from the iPad for the purpose of measuring system response, connect a cable from the rear of the PMIK-1 to the system being tested. At the PMIK-1 end, the cable will have a 3.5mm stereo jack. A 3.5mm to RCA socket adapter is included with the PMIK-1 to make it easy to use regular RCA cables to connect to the system.
3. Calibrate [Top]
If you haven't already, install the AudioTools program on your iPad from the App Store.
Open the app and go to the Settings menu, and then select Microphone Setup. You will see see two choices: Low Range and High Range. Select Low Range.
Then tap on the "i" icon to the right. This will bring up the microphone calibration screen.
In the screenshot above, the name of a PMIK-1 calibration file is shown. Initially, however, this will be blank, so you will need to load the calibration file to the iPad and select it. Tap on the Calibration File link and then on the Files link at the bottom right. This will bring up a screen with information on how to transfer the calibration file from your computer to the iPad:
On your computer's browser, enter the address shown by AudioTools on the above screen and upload the calibration file to the iPad.
Back in the AudioTools interface on the iPad, tap Done and then on the name of the calibration file and tap Apply. The calibration screen will change to display the name, as shown above.
The Trim parameter can be adjusted for correct SPL readings. Unfortunately, because different devices will have different sensitivity on the microphone input, it is impossible to provide a standard adjustment to get correct SPL readings. You will need to use an external sound source with a known SPL. With our iPad mini, we used the value 2.5, so you could enter that as an approximation if you wish. Then tap on Done to close the calibration screen, and on Done again to go back to the main AudioTools menu.
4. Measure! [Top]
AudioTools has a number of modules. A powerful tool for measuring system response is the FFT tool. Tap on the Acoustics icon at the left and then on the FFT icon. To measure system response, we will need to generate a pink noise test signal. Tap on the small sine wave icon at the bottom of the screen. A control panel will pop up; set it for pink noise and tap the button at its top left. (Note: make sure to turn the iPad output volume or your system volume down first, and then increase it gradually.)
With pink noise playing through the system, the FFT shows the frequency response of the system as measured in the room. You can adjust the frequency resolution using the selector at the lower left.
To use Smaart® Tools, you will need to purchase the Smaart® plugin from within AudioTools. From the home screen, simply tap on Acoustics then on Smaart® Tools I. You will be asked for your App Store credentials so you can make the purchase.
With that done, click on the spanner/wrench icon near the bottom of the screen to set the parameters. Here is a typical example set of settings:
Below is an example screen showing the Smaart® module in action. Here, we have enabled the dual display mode, and are displaying an RTA, spectrum, and a spectrogram while monitoring music playback: