ADPTR Metric AB review

Covering all your signal analysis comparison bases

  • $199

MusicRadar Verdict

If A/B mix comparison plays any part at all in your production process, Metric AB is a plugin you simply have to try.


  • +

    Effortless A/B comparison.

  • +

    Comprehensive metering.

  • +

    Playback Modes give plenty of options.

  • +

    Filters for frequency isolation.

  • +

    Gorgeous, snappy GUI.


  • -

    Filter presets can’t be edited.

  • -

    Manual is very vague in places.

MusicRadar's got your back Our team of expert musicians and producers spends hours testing products to help you choose the best music-making gear for you. Find out more about how we test.

Five years ago, Sample Magic and UK producer Marc Adamo released the unassuming but helpful Magic AB.

This simple utility plugin enabled instant in-DAW A/B comparison of mixes with up to nine reference tracks, and was followed up in 2016 by the iterative v2, which added host sync and stereo/mono switching. Magic AB 2 is still available, but Adamo, who owns the IP rights, has signed up with Plugin Alliance, under the ADAPTR brand, to release a seriously souped-up and renamed new version. A cursory glance at Metric AB’s delicious GUI makes it clear that this is a far deeper and more versatile proposition than its Magic counterpart, and that improvement is, naturally, reflected in the price (which is more than three times higher). 

Where the Magic happens 

Metric AB’s workflow is basically the same as that of Magic AB. Having inserted the plugin (VST/AU/AAX) on your DAW’s master bus, up to 16 reference tracks (WAV, AIF, MP3, M4A on Mac, AAC or FLAC) are loaded into the slots at the bottom - click a slot to make it the active reference. The output of the plugin is then switched between monitoring the project and the reference track by clicking the big A/B button, which turns blue for the project stream and orange for the reference track stream. The twin meters above show peak and RMS levels for both, and monitoring is switchable from regular stereo to the Mono, Sides, Left or Right channel. 

The launching and looping behaviour of each reference track is governed by its Playback Mode setting - see Playback time - and balancing levels to match that of the project is done manually or automatically with a click of the Loudness Match button. The waveform display shows an overview in the top panel and a scrolling, zoomable region at the bottom, complete with cue, loop and playback position markers. So far, then, there’s nothing here to set Metric AB apart from Magic AB 2 - but we’ve barely scratched the surface... 

From A to B

The Filters section facilitates isolation of specified frequency ranges, with freely editable High and Low cutoff points used as the basis for high-pass, low-pass and band-pass filter modes, at 12 or 24dB/octave roll-off slopes. Five preset buttons also offer instant positioning of both cutoffs for soloing the Low Mid, Mid, High, Bass and Sub ranges - these can’t be tweaked and overwritten, we were perplexed to discover. 

As handy as the filters are, they’re certainly not the main event. No, the big draw here is the five comparative graphical analysers accessed via the row of buttons at the top. Comprising Spectrum, Correlation, Stereo Image, Dynamics and Loudness, these can be set to visualise the currently audible signal, the mix and reference signals side by side in separate panels, or mix and reference overlaid in the same panel. 

Playback time

Crucial to Metric AB’s utility as a comparison platform is the ability to control playback of the reference tracks in relation to the mix being referenced, which is handled by a set of four Playback Modes and a straightforward cue point system. 

The default Playback Mode, Latch, simply starts and stops playback using the host DAW’s transport, with no automatic repositioning of the playhead - click either waveform to position it manually. Cue mode does the same, but with playback always starting at one of four draggable Cue points when the reference stream is activated or playback is stopped and restarted. Sync mode locks playback to the DAW timeline, as if the reference were actually an audio track in the project, with the option to offset the start point if required. The final mode, Manual, unhooks Metric AB from the host and puts it under the control of its own simple transport. 

In Latch and Cue modes, playback can also be set to cycle between two loop points (separately assigned for each Cue), which are adjusted by dragging, either individually or together. The Loop region can be halved or doubled in size at the click of a button, and shuttled forwards or backwards by its own length.

All five analysers animate smoothly and look great. Spectrum is a conventional spectrogram; Correlation reveals phase issues either in real time across the frequency spectrum, or as an averaging History graph; and Stereo Image shows panning power distribution across the spectrum, via separate Range and Average visualisations. The displays for these three are collectively switched between the standard Plot curve and four bar graphs (Octave, 3rd Octave, Critical and crossover-editable Multiband), and various ballistics can be tweaked (peak and average hold times, etc). Plot mode enables vertical (dB) and horizontal (Hz) zooming, and activating the Link button locks the zoom to the middle (band-pass) filter frequency range. This doesn’t currently jump to the high or low range when the filter is in high- or low-pass mode, but we’re told that’s on the to-do list. 

The Dynamics analyser measures the Peak to Short-Term Loudness Ratio (PSR) to continuously ascertain the dynamic range of the source material (pre or post filter). This is then compared to a user-specified target level, represented by a red line: when the PSR drops below the line, it means the source signal is lower in dynamic range than the target, suggesting that you need to back off the master bus compression. 

Finally, the Loudness analyser is as solid a LUFS targeting and metering setup as you could hope to find. Set your loudness target manually or choose one from a range of established and original presets (Broadcast EU, Spotify, YouTube, Loud Master, etc), and view the Integrated, Short-Term and Momentary LUFS values as meters or, in any combination, a history graph. Overs are clearly indicated in red, and True-Peak, RMS and PLR (Peak to Loudness Ratio) readouts are also provided. 

The final analysis 

With its excellent multipurpose metering, Metric AB expands the fundamental concept and remit of Magic AB into a whole new realm of visual comparison. The five analysers are more than good enough to warrant employment in their own right, but when they’re coupled to the A/B referencing system, the whole thing really does come together as a unique and powerful tool, with the potential to improve the working life of any mixing or mastering engineer. 

The filter zooming issue does need addressing, the manual’s not great, and we’d like to be able to reorder reference tracks by dragging them between slots. On the other hand, those are all criticisms that fall under the ‘minor niggle’ category, and don’t significantly tarnish this incredibly useful plugin. 

Computer Music

Computer Music magazine is the world’s best selling publication dedicated solely to making great music with your Mac or PC computer. Each issue it brings its lucky readers the best in cutting-edge tutorials, need-to-know, expert software reviews and even all the tools you actually need to make great music today, courtesy of our legendary CM Plugin Suite.