Test Drive: Compassion and EQuality from DMG Audio

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by Steve Cunningham

No, this is not about world peace. It’s about DSP, because Dave Gamble has been writing DSP code for years, for companies including Focusrite, Sonalksis, and my current favorite specialty plug company, Brainworx. While helping these companies develop sophisticated DSP-based audio products, Dave decided to strike out on his own. In early 2009, Dave founded DMG Audio to develop and market his own software processors. His latest efforts include a compressor and a couple of equalizers, all of which sport features that illustrate Dave’s penchant for thinking well outside the box.

This month we’ll have a look at two of them: EQuality is an equalizer, while Compassion is a compressor. Both are available in all the major plug‑in formats on both Mac and PC. For Windows there’s VST and VST3 in both 32- and 64-bits, and 32-bit RTAS. For Mac there’s VST, VST3 and AU as in both 32- and 64-bits, and 32-bit RTAS. OS versions supported include Windows XP, Vista and Win 7, along with Mac OSX 10.4, 10.5, and 10.6.

CompassionMain

THE COMPASSION INTERFACE

Let’s first tackle DMG Audio’s more complicated plugin, the compressor cleverly named Compassion, and I’ll try to explain what I believe Dave Gamble was trying to achieve in designing it. Dave has taken the concept of modeling a specific compressor in software, and has exposed all the inner wiring of the model for you and me to play with. So instead of providing a series of presets, each of which mimics a specific compressor brand and model, Dave has provided control of the parameters that are used to generate that specific compressor model, but are usually hidden behind the preset. If that makes sense to you, then you will understand the extensive front panel controls, which are split into three sections.

What is commonly labeled the title bar of the Compassion plug is known as the Clutter Bar, and is the first of the three sections. It consists of toggles to engage, disengage, and route the sidechain input in various configurations, buttons to copy and compare changed presets with the originals on which those changes are based, a setup menu to configure and calibrate the various meters, and an advanced button that reveals the third section.

The “second” section is really the main display, and shows the customary compression controls. You will get along with these quite well at first, before you dive into the deeper elements of Compassion. These standard compressor controls are supplemented with graphical elements which, on the left-hand side, describe the Knee Response curve and the Compressor Response curve, which can be wildly complex. On the right-hand side is an innovative audio graph that displays the input waveform scrolling right to left, while above and below it the amount of gain reduction is illustrated by the thickness of a band that is alternately green or red, depending on whether the compressor is in its attack or release phase. The threshold level is shown by a white line, and you can choose to view the input or side‑chain waveform superimposed on the output waveform. This is joined by a more conventional vertical bar‑graph VU meter. The many extra controls for detailed configuration are accessed in an optional panel below the main window (the third section), where they are organized into panes.

This is the Advanced section, and it’s a multifunction panel whose contents depend on which of the advanced functions you’ve selected. These functions include Attack and Release parameters, Main and Sidechain EQ, Threshold and Ratio tweaks, and a full Transient Shaper. The end result is that Compassion can be tweaked to behave like almost any hardware compressor, as well as doing a great deal that no hardware unit can. For example, many compressor plug‑ins let you adjust the extent to which the left and right side‑chain signals are summed (to control the degree of stereo linking) but Compassion goes much further. Moving two dots around on an X‑Y graph allows you to graphically set a separate L/R sum for each channel of the mix. Likewise, side‑chain EQ is a common feature of dynamics plug‑ins, but not the way it’s been implemented here. You can even choose to have the compressor act only on the filtered sidechain signal, leaving the rest of the audio alone, enabling Compassion to be used as a sophisticated de‑esser.


TOO MANY CHOICES

The Attack and Release parameters are configurable in ways you can’t imagine. You can specify a “curve law” that modifies the “shape” of the transient response to transients, decouple and reverse the order of the attack and release circuits, and introduce a Hold parameter to delay the onset of the release phase. There’s also an adjustable auto‑release algorithm. Should attack transients themselves escape the attention of the main compressor, you can also engage a fully specified transient shaper and peak limiter, each of which has more parameters of its own than some dedicated plug‑ins do.

The Threshold and Ratio parameters can be tuned in yet more different ways, some tailored towards the possibility of mimicking typical analog circuits, others offering advanced dynamic control. A variable Knee control can be combined with a Bleed parameter, helping to create a dbx‑style “over easy” effect. You can specify a Ceiling, or maximum amount of gain reduction, and a Ceiling Curve that governs whether this operates as a “brick wall” or as a gradual limit. A complementary Depth parameter specifies a maximum amount of gain reduction that will be applied when Compassion is used as a gate or expander.

Of course Compassion can be used as an Expander or a Gate. Actually, it can simultaneously perform conventional expansion or gating, upward expansion (which increases the dynamic range of signals above the threshold) and upward compression (which makes the audio below the threshold louder while leaving peaks untouched). The main Ratio control runs from 1:1 at the leftmost extreme, through infinity:1 (hard limiting) at about two o’clock, after which it goes into negative compression, whereby the gain range of the signal is inverted. If there’s one thing that’s missing, it’s the ability to set a different threshold level for the expander from the threshold used by the main compressor. This can be a useful feature where you want to compress signal peaks while reducing low‑level noise, but leave the central part of the dynamic range alone.

With this many controls available, most users will obviously want to start with simple presets. A number of these are provided, along with another innovative concept known as “mods”. A mod stores a subset of parameters, so when your knob twiddling lands you on the perfect compressor for that used-car commercial client, you can store those tweaks as a mod, then just adjust the normal attack, release, and threshold controls for the specific track you’re working on.

THE SOUND OF COMPASSION

Since Compassion is designed to sound pretty much like anything you want it to sound like, it’s a bit difficult to describe. Its flexibility is illustrated by the mods that are supplied with it, which turn it into everything from a FET design to an optical compressor to a vari‑mu tube circuit, and more. Even without tweaking, it delivered a credible performance on the left/right bus, imparting a smooth tone to a VO track. No doubt that with tweaking it could be made to respond in a hundred other ways. Even with fast attack and release times it was surprisingly free of artifacts. If you want transparent, Compassion will do transparent. If you want “character”, then all the tools are there, although figuring out how to use them will occupy your time for a bit.

The sheer flexibility of Compassion also means that it shines in problem‑solving roles where other compressors simply might not do. For example, I was mixing a commercial track in which the client had specified a particularly aggressive music background. Unfortunately the male voice talent’s tone did not, shall we say, match the aggressive nature of the music. As a result, even though the music was ducked it still seriously detracted from the commercial message. Given that the client was insistent on both the voice talent and that particular piece of music, I was not happy with the mix. Using the side chain input of Compassion, and equalizing that side chain signal to emphasize the midrange tones that were interfering with the message, I was able to tune back the aggression factor in the music without making it disappear entirely.

In terms of quality, I would have no problem using Compassion as my only compressor, especially considering it also handles gating, expansion, de-essing, and even transient shaping. In experimenting with the various mods provided, I was able to get it to be remarkably close in sound quality to my longtime favorite Ren Comp compressor. Do be aware however, that all of this flexibility comes at some cost to CPU efficiency. For that reason, you’ll probably be best off using Compassion across the stereo mix bus to finalize your projects, as opposed to applying it in multiple instances on individual elements.

The documentation is downloadable from the company’s website as a PDF file. It’s quite complete and well written, and you will want to read it to get the most out of Compassion, as well as to understand how some of the more esoteric functions actually work. With a suggested retail price of £149.99, which translates to about $238 in my neighborhood, it’s not the cheapest compressor you’ll find. But if you’re looking for a jack-of-all-compressors, it’s well worth getting a free 30-day demo.

EQuality

EQUALITY

After the tour de force that is Compassion, discussing DMG Audio’s equalizer EQuality is remarkably simple. In this case, they’ve simply settled for creating a great multiband equalizer, with excellent audio quality and a small footprint on your CPU.

EQuality has four bands of fully parametric EQ, plus low and high shelving/bell curve equalizers, one lowpass filter, and two highpass filters. All parametrics and filters are capable of plus or minus 36 dB of gain, which is more than most EQs provide. On parametrics the contour (Q) controls run from 0.1 to over 50, while the filters can be set to slopes from 6dB/octave to 36dB/octave. The entire plug‑in can be run in one of five processing modes: the standard Digital, the superior Digital+, plus Minimum Phase, Analogue Phase and Linear Phase. Both conventional stereo and M/S operation are supported, and there are some unique bells and whistles too. The resonant frequency of the shelving equalizers can be separated from the cutoff frequency, so that at high Q values you can adjust the resonant peak to where you want it. You can also freely adjust the amount of interaction between gain and Q values. This mimics the behavior of some analog designs, where the bandwidth gets sharper as more boost or attenuation is applied.

The attention to detail extends to the user interface, which boasts a number of clever features. As expected, you can drag the EQ points around with the mouse, and you can also Ctrl‑click and Shift‑click to bypass them and adjust their bandwidth respectively. Metering is also informative and highly configurable. For example, there’s a Range slider that lets you scale the response of every band simultaneously, so you can retain the overall shape of your EQ curve while deciding how drastic you want it to be. Another neat touch, which I’ve not seen before in an EQ plug‑in, is the horizontal frequency-shift slider, which allows an existing curve to be moved up or down the frequency spectrum. The curve itself is drawn very clearly, and you can switch in a detailed spectrum analyzer if you want to see the effects of your work in real time. Or if you’d rather not be distracted by visuals, you can turn the graphics off completely.

In sonic terms, meanwhile, I think EQuality lives up to its promise. In its “Digital” mode it is not quite as smooth as I expected, but it’s light on the CPU and an improvement on bundled EQs. However, I like it in its other processing modes; Digital+ is nicely focused compared to Digital mode, while Analog Phase seems somehow is softer and a bit warmer. Linear Phase mode demands additional CPU power, but adds clarity to complex music and effects spots. As with Compassion, the PDF documentation is complete and well-written.

DMG Audio’s EQuality equalizer carries a suggested retail price of £99.99, which around here is about $158 US dollars. It too is available as a 30-day demo, and deserves a check-out. For more information on both Compassion and EQuality, visit www.dmgaudio.com. Steve sez check ‘em out.

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