We misunderstood each other, sorry.

Passing the channel on `init` is good,
But then we should store the channel type in a `_channelType` private variable.

```
    if (_channelType && (this._audio.mozAudioChannelType !== channel)) {
     this._audio.mozAudioChannelType = channel;
  } 
```

Should live in the `ensureAudio` method so we don't create the audio object too early.