Review: Meterplugs Perception

The new tool designed by mastering engineers for mastering engineers has Alan Branch all ears.

Every now and again a new plug-in comes along that makes you think ‘How did I work without this?’ Perception is such a plug-in. It accurately matches the loudness and sync when you’re comparing your master audio to its source in real time, helping to remove the loudness deception when applying a mastering process such as EQ, compression or limiting.

So why is this important? Our brains perceive frequencies and volume in a very complex way and certainly not linear; even subtle changes in gain can make frequencies appear more prominent and tonality less obvious, while causing balance shifts between instruments. The result can be an easy trap to fall into, but by adding a limiter that increases overall volume to a mix, you can be quickly fooled into thinking this is helping the song sound better, but not necessarily for its extra dynamic control. Using Perception as a level controller will help eliminate this problem, so your ears get the best chance at hearing when EQ or dynamic processing is lifting the mix into magic or misery.

In Use

Perception is available in AU, AAX, VST, and Mac and Windows 32/64-bit-compatible versions. Registration is done via the web – email and a serial number – so installation was simple. I tested Perception on a DAW master bus when mixing and when mastering separate stereo mixes. Perception comprises two separate plug-ins – Perception Source and Perception Controller. The Source plug-in slots in at the top of the mastering chain and Controller slots in at the end. The Controller UI is really simple and quick to use – once both plug-ins are in place, the two can talk to each other, calculating timing and loudness differences caused by any processing in between.

Measurement is done by playing a few seconds of the track then hitting the Balance & Sync buttons. Perception Controller enables you to evaluate all master processing by simply toggling the FX Bypass button. All the processing level changes and latency is quickly eliminated as Perception matches levels and timing to be exactly the same as the source audio. Now any adjustment of any processing can be quickly heard before and afterwards – comparison couldn’t be any simpler.

Using this simple method is very quick to adapt to and, even as an experienced engineer, Perception helped my workflow massively as it was so much quicker and easier to hear the changes I wanted. Placing the Source plug-in on multiple tracks can be done to master separate stereo tracks – Perception controller knows when each source is being played, which was very useful for quickly adjusting listening mixes I needed to send to the artist and record company.

Loudness is measured by LKFS (Loudness, K-weighted, relative to Full Scale) an agreed standard ITU-R BS.1770. This means the spectral content of the audio is taken into account; basically it’s tuned and filtered to fit how our ears hear things, not just measuring the RMS level. Perception Controller only takes a few seconds to analyse the incoming level during which time the Balance button is disabled. Once the level is found it is displayed as LU Difference (loudness units) between pre- and post-FX. Balance is continuously monitored and if the difference grows too large the difference error will turn red, meaning it’s time to take a new balance calculation.

Perception is a plug-in designed by a real mastering engineer – Ian Shepherd in collaboration with programmer Ian Kerr of MeterPlugs, which makes the excellent mastering K-Meter and LCAST plug-ins. Both men are passionate about changing the loudness problem caused by overcooked mastering. Because of their background it’s easy to see the thought that has gone into the workflow of Perception. For example, a Source Gain and Snapshots feature enables you to have different input gain settings, resulting in any dynamics processing being pushed a little harder, making comparisons of different source gains instant. There is also a peak to loudness ratio display, a helpful guide to see how much dynamic range is being used up by any processing. This simple-to-see pre- and post-readout makes a brilliant addition to hold your hand (or ears) when applying that master compression. Genius little touches like these make all the difference. Ian Shepherd obviously knows what it’s like to go back and forth between too many screens while trying to keep the focus on hearing.

If you’re still not sure how to avoid the Loudness problem, there are some useful videos on the MeterPlugs website that walk you through the different uses of Perception and explain how to ‘Find the Loudness Sweet Spot’, as well as many examples in which you can easily hear how tracks that have been mastered louder have lost the magic to their dynamics.


Making decisions to a final master can make or break a lot of hard work that’s gone into the writing, recording and mixing of an amazing record, so you need to be careful when applying additional mastering EQ or compression. The Perception plug-in system is without doubt one of the best tools I’ve used to help hear accurate changes when dealing with a master mix. Although Perception was developed and is optimised for mastering, I found it works fine within a DAW but I did get the hint that something specific for mixing is being developed.

Simple to use and operate, Perception eliminates our brain trickery of increased loudness sounding like an improvement – especially important when you’re making vital last-minute changes. If you ever wanted a useful tool to help you become a better engineer, Perception is a must have.