Audio Digital Audio Players Reviews

In the App Store: CanOpener

Editor’s Note: shotgunshane delivers our first iOS app review!

There are a lot of iOS music players and equalizers in the Apple App Store, so many that it can become quite confusing on which purchase. It is very easy for quality apps to get lost in the noise of the many App Store offerings.  CanOpener, by Good Hertz, is certainly an odd name for a player and one that could be easily and regrettably overlooked but it shouldn’t!  It’s a unique and beautifully designed app that contains many useful functions not found on any music app that I’ve tried, and I’ve tried many.

The overall look and feel of the app are completely different from any music player I’ve used on iOS.  The main functions offered are crossfeed, equalizer, and a noise dosimeter (sound level meter), along with some not-so-obvious improvements like 15-second fast forward and reverse steps, a manual fast forward/reverse scroll wheel, as well as true decibel volume control.  All functions include preset options and well as complete manual control.

CanOpener, a versatile music player app for iOS.
CanOpener, a versatile music player app for iOS.


I’ve not seen crossfeed offered on any other music player.  Previously, my only experience with crossfeed has been with hard implementations on a few different portable amps. Those hardware implementations tend to reduce soundstage width by pulling the music in from the sides.

With CanOpener’s software implementation, the user can set the amount of crossfeed as well as the as the angle/placement of the crossfeed, enabling the user to maintain soundstage, and with some settings, selectively enlarge or decrease the soundstage.

The supplied presets are very useful and tasteful, especially the ‘Lifelike’ and ‘Modern Music’ presets.  Other buttons let you switch to mono, reverse left and right, reverse polarity and even control the left and right balance.

CanOpener also provides a convenient toggle to turn on/off all of your settings, which is very useful for seeing how far you’ve taken the sound away from stock.  The software implementation really does sound great and I don’t ever see myself using the hardware-based implementations on my portable amps again.

Users can flexibly adjust crossfeed settings.
Crossfeed presets
Presets are also built into the crossfeed function for those that don’t want to slowly tweak.


The equalizer function is rather simplistic, only allowing you up to two equalization points.  CanOpener divides your choices between bass and treble, letting you choose one point for each.

For bass, you can choose anywhere between 31 Hz and 250 Hz, while for treble it ranges from 2 kHz to 16 kHz. You can increase or lower your chosen frequencies in 0.5 dB increments.

There are also a small handful of presets and a colorful spectrogram to choose from.  So, if you only need simple EQ, like bass boost or treble cut, CanOpener can perform the job admirably, but if you need several equalization points or more precise options, like Q settings, you’ll probably want to look at another app.  I look at the equalizer function as a nice bonus to an otherwise very useful music app.

Eqaulizer inputs
EQ adjustment is a two-point system divided into bass or treble, but can be specified for frequency.


Probably my favorite function of CanOpener is the dosimeter.  Have you ever wondered how loud you’ve been listening and how loud your average listening volume is over extended use?  Wonder no more!

CanOpener has several models of headphones and IEMs already programmed in for selection like the Apple EarPods, Bose QC15, Etymotic HF5, Sennheiser HD600, and others. If you’d like to see more presets added, the development team welcomes user feedback and suggestions. They’ll be adding more as quickly as they can get them tested.

How accurate is the dosimeter?  Here is a response I received from the development team on that question:

“For headphones we have measured, the dosimeter is typically within ± 3dB (Leq) of the true sound pressure level. Performance for in-ear headphones can be slightly more unstable, mostly due to being improperly seated or fitted. We also measure each iOS device in the lab, so in addition to the headphones data, we have very detailed data on the audio performance of each iOS device.”

They’ve also added some generic presets for headphones, IEMs, and earbuds:

The generic models are as follows:

  • Generic Headphones: 64 Ohm Impedance, ~100 dB/mW Sensitivity
  • Generic Earbuds: 32 Ohm Impedance, ~100 dB/mW Sensitivity
  • Generic In-Ear: 20 Ohm Impedance, ~105 dB/mW Sensitivity

One of the best updates to the app has been to input your own parameters and save them as a preset.  If you have the manufacturer’s specifications for sensitivity (dB/mW) and impedance, you can create presets for all your headphones and IEMs.

With the latest update, you can input your own earphone's sensitivity and impedance settings for an approximate sound exposure estimate.
With the latest update, you can input your own earphone’s sensitivity and impedance settings for an approximate sound exposure estimate.

Other Functions

My other favorite function is the true decibel volume control.  The iPhone only has about 16 steps in volume control from the side toggle buttons, and while you can attempt to make smaller increments with the tiny software slider in the stock player, it’s not an ideal way to go about fine volume control.  Overall, the lack of fine control over volume is in my opinion one of the biggest weaknesses of the stock player.  While CanOpener does not change how the iPhone side buttons work, you can control the volume from -72 dB all the way to 0 dB inside the app, giving you precise control over your listening volume.

Volume control in true decibel steps gives you very fine control over volume, a huge step up over the default iOS volume control.
Volume control in true decibel steps gives you very fine control over volume, a huge step up over the default iOS volume control.

Now that Apple has opened up USB audio capability to the iPhone (just as they have on the Pad), allowing you to connect non-MFI specific USB DACs to iDevices running iOS 7, this volume control capability is a necessity.  Some DACs utilize the representation of digital volume control on your iDevice to reflect the internal volume adjustment of the DAC, but when this happens, the stock interface’s volume steps jump from not loud enough, to way too loud, in just one click.  I experienced this with my Resonessence Labs Herus DAC. CanOpener’s volume control makes it the perfect pairing and have improved my enjoyment of this portable set up.

Other notable functions include the ability to fast forward and rewind in 15 second increments, and to pixelate or show clear artwork on the main player screen.


All in all, CanOpener is a very well thought-out design, and with a new approach to the music player UI, making it both a joy to use and to view.  Functions like true decibel volume control and dosimeter, along with an excellent crossfeed implementation, make this music player easily recommendable app that can quickly become a permanent replacement for the stock Apple player.

For more information on CanOpener, please visit:

Cute Effect: pixelated album artwork!
Cute Effect: pixelated album artwork!

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