Speaker Polarity is an iPhone app that tests a speaker for correct polarity (sometimes called "phase").
See our new demo video of this module. This video was recorded in the simulator, and shows the module running within AudioTools.
To use Speaker Polarity, you need to send our proprietary test signal to your speaker. Then, holding the iPhone near the speaker, the polarity is read using the internal microphone (located on the bottom of the phone). Speaker Pop generates the signal, and as long as you use a stereo tip-ring-sleeve 1/8" audio cable, and not a cable with a 3-ring connector, the iPhone internal microphone will still function.
Also, you can burn the test signal to a CD. The test signal can be generated when running Speaker Polarity just turn on the Output Signal switch, plug an 1/8" stereo cable into the headphone jack, and plug the other end into a Mac running Garage Band, capture the signal, and burn a CD. Or, just go to our downloads page to get the test signal, as a WAV file, and burn that to a CD.
Then, play the test signal through the speaker and read the result. Check the signal strength meter to make sure that you are within the working range -- anywhere above "low" and below "high" should work fine.
Speaker Polarity Main Screen
Here is the main Speaker Polarity screen:
The algorithm used for testing speaker polarity is quite advanced, and is designed to prevent false triggers and bad readings. It will work with any type of speaker, small or large, and will work quite well at a distance, as long as the test signal is strong enough.
Note: Early versions of this app required us to use filters to select the speaker driver type. This was causing false readings due to phase shifting in the time domain. The algorithm now automatically determines the driver type and finds the polarity for any driver. Note that you may need louder signals to test subwoofers.
Signal Files to Download
Download signal files from our Downloads page.
Burn the WAV file to a CD, or you can use the AC3 format file as the soundtrack on a DVD to make a home theater test DVD. Note that iDVD does not support AC3 files, so you would have to use a program like DVD Studio Pro to burn the DVD. We have heard that some versions of toast will burn this signal to a DVD.
We will be making home theater test DVDs available soon. When you play the DVD, the Speaker Pop Signal is sent to all 5 speakers and the subwoofer. Just bring the iPhone near the speaker you want to test (6" to 2' will usually work well) and read the results.
Airport Express and Apple TV
You send the stereo file to either the AE or ATV directly. Just import the stereo signal file into iTunes and play it. But, note that every Airport Express that we have tested or have feedback from inverts the signal! So, you have two choices: if you want the polarity to be correct for other inputs, such as a CD player, adjust all the speakers to read '-', or reverse the wiring on all of your speakers, if you normally only use the AE.