One of the first and most important digital audio recording fundamentals to learn is digital headroom. It can be very easy to “clip” an input signal at the analog to digital convertor on the way into “tape” resulting in unpleasant and distorted sounding audio. There are those occasions when a brief oversight ruins the perfect vocal take or dialogue recording passing the red lines of no return. In such cases most engineers simply rerecord clipped takes in favour of clean sounding recordings but in situations such as location recording opportunities for second takes are not always available or repeatable. Often poorly recorded audio from a camera, Lavalier or shotgun mic will be kicked down stream to patient post production engineers to sort out as the take is often the only take available and has to be used.
In this test we put three popular de-clipper plug-ins up against each other in a blind listening test. Clipping is a form of distortion artefact… not the type you want. There’s no warmth, character or quality to the sound of clipped distortion compared to “creative” styles of tasteful distortion that you typically get from guitar amp simulators or tape plug-ins. Clipped audio is easily identified by ear, but it’s easier to see by looking at an audio waveform:
You can see the peaks in this waveform are chopped off clean like a pair of scissors have had at it. Quality de clipper plug-ins, such as the three products featured in this test, will repair and reconstruct clipped peaks lost (or not recorded) in the tracking process resulting in audio that sounds cleaner and, most importantly, usable.
Top Tip: De-Clipper plug-ins can be used in a variety of ways. You can insert these in your DAW mixer however using de clippers in real time will introduce a fair amount of plug-in delay on the track it is loaded on which can, depending on your session settings, prove to be too much for technologies such as Automatic Delay Compensation (ADC) in Pro Tools to work properly. The best way to use de-clippers is to bounce in place the process to the audio (Logic) or use AudioSuite or commit up to insert (Pro Tools).
Accusonus ERA De-Clipper
Accusonus offer a range of one knob style plug-ins in their ERA range designed for specific audio repair tasks. ERA De-Clipper is the latest addition to their ERA family. It is claimed to be the world’s first entirely automatic De-Clipper. You don't have to mess with controls such as threshold as ERA De-Clipper automatically detects clipping in the audio and tunes the thresholds for you. There are two quality settings. If High is selected you may find that your CPU will struggle to cope as our 12 core 64 gig machine hesitated to run one instance of this set at maximum attack mode.
Acon Digital DeClipper
DeClip is part of Acon Digital’s Restoration Suite. It’s a very simple plug-in to use and does exactly what it says on the tin. Sadly, DeClip is not sold separately but is included in the Acon bundle of four audio restoration tools that you can buy for a shade under £80, which is pretty good value for money.
iZotope RX De-clip
iZotope have been developing their RX audio restoration suite of plug-in for a number of years now. RX is a hugely popular suite in post production circles and their De-clip plug-in is something quite special indeed. Simple, effective and transparent. The “clipped intervals repaired” hit counter at the bottom is always a point of amusement for me as it always reminds of that scene in Hot Shots 2 where they make fun of a famous Rambow scene. Like Acon Digital’s DeClip, iZotope’s offering to the de clip plug-in world is also not available to buy separately outside of a bundle.
In The Interests Of Fairness
Obviously, each of the plug-ins we used in this test are a little different in design. There was no way to be able to set all the plug-ins in this test to an exact and equal value. We used our ears and judgement to match each outcome from each product to sound as transparent and close in results as possible. Each of the examples output or makeup gain controls were set to -10dB to ensure plenty of headroom for the restoration as possible. If the plug-in had a high quality or maximum setting we used this over standard settings. The -10dB was also applied to the original audio example ensuring that there were no level differences between all the audio clips in this blind listening test.
The De-Clipper Blind Listening Test
Listen to the results of our De-Clipper plug-in test below. Listen carefully to the original clipped audio and the processed examples. Compare the results and vote for the processed audio you prefer the sound of the most:
Which Result Do You Prefer?
If you enjoyed this blind listening test then do check out a previous test we published in which we compared the performance of 4 top noise reduction plug-ins on a poorly recording dialogue clip: