Leapwing Audio recently released CenterOne, which is a centre channel extraction plugin. Whilst the instant use might be assumed to be to be able to change the balance of a mixed piece of music by controlling the level of mono or "centre" image sounds, it is also very useful when it comes to post production sound in multi-channel formats such as 5.1 or 7.1 and upwards.

The Phantom Of The Centre

If you've ever sat outside the "sweetspot" when listening to a stereo system, you'll know that there is an emphasis towards whichever speaker you are closer to, even if the signal is panned equally between the left and right. There's nothing that can be done about this - it's the laws of physics. Unfortunately when your speakers are behind the screen in a cinema, the majority of the audience will be sitting outside the sweetspot. To compensate for this Dolby (and other cinema sound system manufacturers) decided to add a third speaker to the front, directly behind the centre of the screen. This means that wherever you are sat in the cinema, if a sound is panned to the centre, it will appear to be coming firmly from the centre of the screen.

Left, Centre, Right 

Contrary to common misconceptions the centre channel is not designed for dialogue only. Indeed the centre speaker should be of identical frequency response and power to the front left and right speakers. Dialogue, Effects and Music are all designed to be passed through this speaker, and the effectiveness of the front sound image depends on the centre speaker being identical.

"But why do we need to extract a centre signal from a stereo image?", I hear you ask. The answer actually makes a lot of common sense. If you are balancing say music against dialogue, and the music is only coming from the left and right, and the dialogue is only coming from the centre, then if you are sat outside the sweetspot, then the relative balance of the dialogue against the music will be significantly different to what the mixer heard, and indeed what you would hear if you were sat in the sweetspot. Therefore, it is vitally important that the mixer uses LCR signals as much as possible.

The great thing about CenterOne is that you can pick up the "extract" outputs discretely and bring them back in to your mix on aux inputs.

I am routing all my stereo supplied music tracks to an instance of CenterOne on a "dummy" path, which doesn't route anywhere. I have then picked up the Centre output of the plugin and brought it back in on a mono aux input, which is fed straight to the centre. The reason for using this "dummy fader" workflow is to ensure that any treatment that is applied to the stereo music tracks, including level control, also happens to the centre signal.

The Result

As you can see from the screenshot above, CenterOne is very effective and doesn't introduce any horrible latency. The original "4.0" signal is in blue at the top, and the new "5.0" signal is below. The level of centre extract can be dynamically controlled using the aux input return. The bandwidth of the centre extract can also be controlled within the plugin.

Conclusion

CenterOne is a very effective and versatile plugin. Whilst it is very useful within the stereo domain, it is also really handy for use with dialogues, music and effects in 5.1 and 7.1. I have used it extensively in my current feature mix, where I've been supplied stereo music tracks, but as a submix within Pro Tools, so I can't simply use an upmixer plugin. Ignore the centre speaker at your peril - if you do, expect lots of negative dialogue clarity feedback!

Leapwing Audio CenterOne retails at £179, and in my opinion is worth every penny.