I spend lots of time listening to music on my iPhone. I don't consider myself an audiophile but I'm always on the lookout for ways to tweak the quality of the audio coming out of my device. The built-in iOS Music app provides quite a few stock equalizer settings to choose from, and I've looked at a few other audio-enhancing music apps, but I can't help thinking that there's something better out there. So I thought I'd give GoodHertz's $3 CanOpener - for Headphones a spin.
CanOpener is unique because it addresses a problem that's inherent with listening to music through headphones (or "cans" as they're sometimes called). As the app's documentation explains, when you listen to stereo music through external speakers, sound from the left channel hits your left ear first, and then a portion hits your right ear a split second later, and vice versa. This crossfeed effect helps music from speakers sound fuller and more natural than headphones which completely isolate the left and right signals.
CanOpener seeks to solve this problem by mixing a bit of one channel into the other and letting you adjust both the amount and angle of the crossfeed effect. It also provides highly customizable EQ options to further enhance the audio. CanOpener contains a database of several popular brands of headphones and earbuds and provides built-in tweaks for those particular models. The app still works with any model of headphones or earbuds but without those added enhancements. (If your headphones aren't included, you can add them to your database if you know their sensitivity and impedance settings.)
CanOpener can access your existing music library but, because of limitations imposed by Apple, it can't apply audio enhancements to streaming tracks. So, to make full use of the app, your music must be stored directly on your device. Like other iOS music apps, CanOpener can handle music in MP3, AAC and Apple Lossless formats, but it goes a step further and adds support for FLAC, an open-source lossless format that's popular among audiophiles.
While a track is playing, tapping on the Crossfeed option displays two sets of icons: one for the current left/right balance and another for the amount and angle of crossfeed. If you select from the various pre-set options, such as Lifelike or Wide Soundfield, for example, this will adjust the icons on the screen accordingly so that you can visualize its effect on the audio signal. You can also adjust these effects manually, either numerically by category or by dragging the icons directly.
Tapping on the EQ option provides a colorful equalizer graph that you can adjust in a similar fashion. There are useful presets to choose from or you can adjust the settings manually. Tapping on the icon in the upper-right toggles CanOpener's EQ and crossfeed effects so that you can compare your current settings with the unmodified audio signal.
The app also provides a dosimeter (loudness meter) for supported headphones. Not only does it display the current volume level, but it keeps tabs on your total listening time along with the average volume level over the life of using the app. This can help you determine if you're exceeding recommended volume levels and possibly damaging your hearing. (Note: the app shares this data anonymously with the developer, but you can disable this in the app's settings, if you want.)
I found that CanOpener's EQ options work very well across the board, but the crossfeed effect is extremely variable depending on the type of music you listen to. For hard-panned tracks (common in older stereo music), CanOpener provides a dramatic improvement in the quality of the audio. But the app's effects are much more subtle in music that's recorded with a more dynamic stereo soundstage.
As a music player app, CanOpener's interface is a little quirky, but that's not necessarily a criticism. For example, the progress meter/scrubber is a circle, rather than the straight-line scrubbing control you typically find in other music apps. At first this seemed a little odd, but it actually makes perfect sense if you've used the old click-wheel iPods, as it provides much more control when scrubbing back and forth.
CanOpener is a universal app which means that its interface is optimized for both the iPhone's and iPad's screen sizes. However, on the iPad, it runs only in portrait mode and really doesn't seem significantly different from the iPhone app's interface. It would be nice to see the larger screen used more effectively.
If you have lots of older tracks that need crossfeed tweaks in order to sound acceptable through headphones, or if you have a large library of FLAC-formatted audio that you want to play on your iOS device, then CanOpener is a no-brainer. But if you think your music already sounds fine through headphones, then you may find the app less compelling. However, sometimes you don't realize something needs fixing until someone points out that it's broken. At the relatively low price of $3, there's little harm in giving the app a shot and seeing if it offers some improvement to your music library. Life's to short to listen to bad music.