Software Review: Universal Audio Manley Variable Mu Limiter/Compressor Plugin

Under the hood of the Manley Variable Mu

In November 2014, when Universal Audio announced that it would release a new software version of the Manley Variable Mu compressor, SonicScoop quickly covered this new design with in-depth behind the scenes story called “How the Emulation Is Made”.

Now, approaching its one year anniversary, and continuing to gain in popularity, I felt it was time to give this plugin a thorough test drive of my own to see if it could supplant some of my favorite existing tools.

I was also fortunate enough to have a hardware version of the Manley Variable Mu right in front of me while I tested Universal Audio’s digital recreation of this modern classic tube compressor.

Sound and Features

Universals Audio’s version of the Manley Variable Mu adds some welcome new features to the original design, discussed below.

Many engineers feel the Vari-Mu exhibits a light sonic touch to the mix but I would say it goes beyond that. To my ears, this compressor has a very definitive sound that can add a lot to a mix, or at times be a bit “too much” for certain applications.

The engineers at UA not only succeeded in capturing the distinctive sonic footprint of the piece but added some very useful features including a Mix knob that allows this compressor to serve on even more sources without adding “too much”.

For this review I started with the compressor in stereo across my main stereo mix passing through an aux track in Pro Tools. The track was a tune called “Tippy Toe” by Life at 3AM and was originally featured on the acoustic EP “Won’t Let Go”.

I set it for an appropriate amount of gain reduction, and my initial impression was that the compression was making this particular track a little too dark overall. So, I engaged the built-in sidechain filter, a new addition for the plugin version of the Variable Mu. This helps keep the compressor from over-reacting to low frequencies by making it less sensitive to frequencies below 100 hz by a 3dB.

This adjustment addressed the darkness to a degree helping to keep the kick and bass from sucking the rest of the mix down and stepping too far forward in the mix. This was a big step in the right direction, but I still felt the sound I was getting was a little thick for the song, so I tried out another of the major features added to this software version: The mix knob. With the mix knob, I was able to use the plugin as a parallel compressor, adding just the right amount of glue while still retaining a sense of openness in the mix.

It was very nice to be able to get the sonic touch of the Manley and have that level of control in applying it. Though the full-bodied tone of the hardware Variable Mu can often be a welcome addition to the sound of mix, in the past, I have had to opt for using a different compressor on a mix because I felt the Manley, with all its wonderful tubes and transformers, was rounding off the transients and providing more of a “classic rock” vibe and less of a modern sound. With the UAD plugin however, I can dial in just the right amount. Because of these two welcome new features, the plugin version of the Vari-mu may be useful in even more instances than the hardware. But to demonstrate just how close they can come when desired, I’ve included some audio files with the Mix on full “wet” for comparison with the hardware.

When I switched on another instance of the Vari-mu as a parallel compressor on the drum bus the drums took on a swampy, brooding feel. I had originally been using a Waves API 2500 for this mix which sounded faster and more aggressive than the Vari-mu, which emulates about 4 tubes per channel, plus transformers. When you push this compressor hard you can get color and presence for days. This plugin certainly would be on the list of compressors to try for parallel compression but like any tool, it’s all about the application.

Manley has also added Mid-Side processing as an optional mod to their hardware units and Universal Audio has included this mod on the plugin which is way cool. The unit can be used as an encoder, a decoder, or an encoder/decoder combo. I tested it as an encoder/decoder, but if desired, you could use it as a decoder, for example, on a pair of drum room mics recorded using Mid-Side technique as a decoder. (The manual includes a chart of switch settings to help you determine the correct switch setting for any application you might need.)

When using the plugin to control the “Mid” image, I was able to get the kick, bass, and vocal to sit up front in the mix a bit more. The low end was tight and thumping and the vocal was both powerful and intimate simultaneously. Out on the “Sides” I was able to give the mix just a hint of glue while still letting the dynamics have their play.

I can’t tell you just how powerful a tool this is with Mid-Side capability built in, you’ll have to try it for yourself! I would warn you however, that you can also cause phase and balance issues with your mix if you aren’t careful with your outputs in this mode.

After listening to the various samples I created for this article I feel that the plugin version has a sound that I actually preferred over the hardware version for many of the instances I encountered and the additional feature sets make this plugin one which I would recommend for any engineer’s tool box.

Thanks to Joe Gigs and American Zen Studios in reviewing this gear.

Rick Slater is an audio engineer who lives and works in New York. Visit him at audiobyrickslater.com.

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