CanOpener review: fine-tune the audio output of your iPhone’s headphones

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I am a huge music fan. If it is possible to have such a thing as eating, sleeping, and breathing music, I do it. I am also fairly picky about what my music sounds like. Unless I’ve got my iPhone connected to an external speaker, I tend to avoid using it to listen to music.

CanOpener is a processor app that allows you to tweak, adjust, and fine-tune your iPhone to offer the best possible quality of audio output through just about any type of headphone on the market…


The first thing you should do is connect your iPhone to your headphones. Whether you use ear buds, over-the-ear studio quality headphones, or the most basic of headsets, you can set the app to match the output device you are using.

When you are playing your music, you can adjust the crossfeed and equalizer by tapping one of the sections listed at the bottom of the screen. The features are gesture based. If you want to fast forward through a song, drag your finger in a circular motion on the pixelized version of the album art. To adjust the crossfeed, drag your finger from the left or right to the center where the headphone icon is. To adjust the equalizer, drag the line upward or downward to increase or decrease the bass and treble frequencies.

When you tap the album art icon, you’ll see the title of the song, the name of the album, and the band or artist. Tap the album art again to go back to your current adjustment screen.

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App Use

This app is specifically designed to optimize your audio quality when listening to music on your iPhone or iPad using headphones. While I love being able to carry hundreds of hours of music around in my pocket, the one thing I have always had a hard time with is sound quality. I listen to a lot of thrashy, distorted music that is already heavy on the high end. When listening to bands like Gauze, D.R.I., and M.D.C. on an iPhone, everything just sounds tinny and overly bright.

CanOpener makes it possible for you to make minor (or major) adjustments to the bass, treble, and crossfeed of individual songs in order to give a boost to high-end songs, or bring up a little brightness to muddy songs.

The app will first ask you what type of headphones you are listening to. I tested it using my Apple EarPods. However, you can also select from some name brand devices, like Technica, Sennheiser, and Shure. Don’t worry. If you don’t see your headphone brand, just pick a generic model that most closely resembles what you are using.

The next thing is to pick a song, album, or playlist to begin listening to. You can also set the app to play a shuffled playlist by tapping the “rand()” button in the upper right corner. Once you’ve picked your music, you can begin adjusting the sound quality.

The app will automatically switch to the home screen where the crossfeed, equalizer, and dosimeter settings are. Tap the Crossfeed tab to adjust which ear you hear the music out of. It is also great for altering the surround capabilities. You can make your headphones sound like the music is coming from out front, or from behind. Adjust the left/right balance by dragging your finger from the “L” or “R” button toward the center of the screen.

You can also turn off stereo quality by tapping the Mono tab. This will essentially flatten out your music. If you want to switch the audio from right to left, tap the Flip tab. This will reverse the sound output.

Invert the phase of the crossfeed by tapping the Polarity tab. This will help make mono recordings have a bit more fullness.

The Crossfeed section also includes a list of presets. Chose your crossfeed by “Music Before 1970,” “Likelike,” “Modern Music,” “Wide Soundfield,” “Car,” or “No Crossfeed.”

In the Equalizer section, you can fine-tune the bass and treble of your music. You’ll be able to increase or decrease the amount of bass and center the frequency. Plus, change the amount and frequency of treble. The app does not clip the signal when you boost bass or treble.

To adjust the equalizer, touch the graph and drag your finger up or down. This will alter the amount and frequency of bass and treble. Drag your finger upward on the left side of the screen to increase bass. Drag your finger downward on the right side of the screen to decrease treble.

The equalizer also has a list of presets to make adjustments easy. Choose from “Bump,” “More Air,” “A Lil’ Mo Hi-FI,” “Warmth,” “Brighter,” “Darker,” and “Flat.”

The Dosimeter section predicts the sound pressure that is affecting your eardrum for the current headset you are using. It displays the current sound pressure levels (SPL), plus the lifetime SPL to calculate an equivalent continuous sound level to give you a better understanding of how loud your music is.

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The Good

This app actually works. I tried it out with my CD transfer of an MDC album, which sound particularly tinny. After setting the Polarity and increasing the bass a bit, it turned an otherwise annoying sound output into something listenable. Now, I just have to get over how much those Apple EarPods hurt in my tiny little ear holes.

The Bad

While worth the money, this app is a bit expensive. Most five dollar apps are console-quality games or integrated business apps with multiple security options. This app is a bit pricier than others like it.


CanOpener costs $4.99 to download. While it is worth every penny for someone like me who is picky about listening to music through headphones, it may seem unreasonable to casual music fans. It will certainly make every song sound better through your tiny little ear buds, but if you don’t do the work to fine-tune your music, the effects don’t matter.


If you are the kind of person who goes out of your way to avoid listening to certain types of music on your iOS device because you think it sounds crappy or gives you a headache. This app will make everything a whole lot better. It is worth the five dollar price tag to make it possible for you to listen to your favorite metal bands from the mid 1980s without it sounding like the high-hats are smashing your brain in. Download it for the iPhone, iPad, and iPod touch in the App Store today.

Related Apps

Equalizer is an app that lets you adjust the bass and treble of individual songs. EQ 10 is a 10-band equalizer for your iOS device that also offers 32-bit depth processing.

Do you listen to music on your iPhone with headphones? Do you use apps fine-tune your experience? Make sure to share your tips in the comment section below.