Visual Mixing: A guide to the Phasescope

Introduction

In this modern age of DAW’s, touch-screens, laptops and government austerity packages, we can all get a little hung up on using our eyes instead of our ears. A prime example is when dialling in compression settings; we should be listening to what the compressor is doing to our vocal track when solo’d and in the mix – not just looking at graphs. OK so the graphs and visuals do help but you can see what I mean. Right?

Despite what I’ve just said, there are instances when visual aids offer a distinct advantage and in this post we will cover Pro Tool’s bundled plug-in ‘Phasescope’. Phasescope is a stereo-only metering plug-in that provides phase and level information, it is mostly used as a go-to reference on the master fader and can be found under ‘soundfield’ in the inserts menu (multichannel only); read on to find out more.

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Levelling off

The level meter will display a whole host of metering modes however I would suggest that sticking with the default peak value display will suit most needs. Peak metering has a very fast response and is therefore useful to get an accurate reading of drums for example. RMS (which means root mean squared) is essentially the average level and is therefore much less sensitive. You will find that the majority of meters on analogue desks are RMS meters as they are cheap to manufacture – they are often used just as a visual reference to check whether there is any signal on a channel. A useful feature however is the Peak+RMS value which shows the peak in green and the RMS in blue – check it out!

The peak hold selector is pretty much what it says on the tin. You have three options; 3-second, infinite and no hold.

The level meter also has a level reference mark – this is the rightward facing orange arrow and horizontal line running across the meter. Any signal which is over the reference shows as orange whereas under the mark it is green. This can be a useful tool when mastering or when you have strict level specifications as is often the case in Film and Television.

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Scoping out

The ‘scope’ section of the plug-in is what is known as a Lissajous meter or VectorScope; this displays the relative amplitude and phase characteristics of the stereo signal. In other words, it graphically represents the stereo field so you can detect any phase, mono-compatability or stereo spread issues. As you become more and more familiar with the meter you can even begin to tell what kind of stereo mic technique has been employed!

Reading the scope is daunting at first, but here’s a few key tips:

• Mono audio will show a vertical line
• Out of phase material will show a horizontal line
• Diagonal lines or patterns indicate a bias to one speaker

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Phase Meter

The phase correlation meter is often misunderstood, but it needn’t be; it really is quite simple to use! Here’s what the readings mean:

• 0 value = perfect stereo
• +1 value = perfect mono
• -1 value = perfectly out of phase

LEQ(A)

The LEQ(A) tool displays the weighted average power being measured; it gives a reading in dB and is dependant upon the ‘window’ setting.

In acoustic testing, background noise is measured using this figure, although correctly put it is “L_Aeq” – I imagine Digidesign (yes this plug-in comes from Digi not AVID) went with LEQ(A) for simplicity’s sake. It means the equivalent continuous A-weighted noise level. A-weighted refers to the process of approximating the response of the human ear because of course we don’t hear all frequencies at the same level.

The window setting determines the length of time that the measurement is taken before an average is calculated – incidentally when in infinite mode it is constantly averaging the signal.

• Hold on stop = the measurement window timer will pause and resume on playback start/stop
• Auto reset = the reading will hold upon playback stop and will be reset when playback starts

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Final Words

I hope that given a little time to learn and experiment with the Phasescope plug-in it will become a standard on your master fader. I always use it to check mono compatibility and to see if any stereo width processing is having a detrimental effect on my mixes. If you found this article useful and would like more about the more obscure plug-ins in Pro Tools please let us know either by commenting below on Twitter or via the questions box.