Review: Sound Radix Drum Leveler

Powerful Dymanics Plug-In
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Drum Leveler applies combined upward and downward compression or expansion to drum hits, adjusting them to your desired level. It does this by processing only those beats with amplitudes that fall between two adjustable threshold settings.

If the above paragraph didn’t quicken your pulse, it should have. Drum Leveler is way more powerful than your average compressor or expander. Imagine, for example, boosting the level of slightly weak snare hits without affecting loud hits, grace notes, or mic bleed. Slammin’ drum tracks, here we come!

The cross-platform Drum Leveler affords mono, dual-mono, stereo, and mid-side operation, and has both 32- and 64-bit frameworks. At the center of the GUI, the Main Display plots scrolling signal-levels against time on an x-y axis; the vertical or y-axis shows levels (Figure 1). Input-signal levels are gray; post-processing gain boosts appear as orange peaks, and attenuated levels are light blue. You can zoom the x-axis in and out, changing the scrolling speed. In dual-channel configurations, the display can be made to show the left, right, mid, or side channel, or the sum of left and right, or mid and side channels. The plug-in’s controls adjust parameters for whichever channel or channels are being displayed.

Set high and low thresholds by dragging respective blue-colored nodes vertically in the Main display; processing is initiated in the range between the thresholds. Drag a third node (gold) to set the target level. In Compression mode, beats within the processing range that peak below the target level will be boosted (effecting upward compression); those that peak above the target level will be attenuated (downward compression). In Expansion mode, beats within processing range that peak below the target level will be attenuated (downward expansion), and those that peak above the target level will be boosted (upward expansion).

You can compress the level of all beats within the processing range so they become exactly equal to the target level, but that’s not always appropriate. Use Drum Leveler’s rotary Compression control to adjust the extent that levels will be changed. (Positive values produce dynamics compression, and negative values produce expansion.) For example, a value of +50 percent (compression) will adjust a drum hit’s level only halfway toward the target level. A value of -100 percent (expansion) will double the number of decibels a hit differs in level from the target level; if, say, the hit were 6 dB below the target level, it would be attenuated to be 12 dB below. A concentric ring around the Compression control serves as a circular meter, lighting up orange to indicate the amount of gain boost and light blue to show the degree of gain reduction applied.

You can set an absolute limit, in decibels, to the Compression control’s action using the Gain Range control.

The Min. Retrigger control sets the minimum time between drum hits required for Drum Leveler to process the following hit. A Hold control adjusts how long gain change is applied before the dynamics processing begins to release. The Recovery control’s setting determines how long it will take for the processed hit’s level to revert back to its unprocessed amplitude after the hold time has expired.

Drum Leveler also includes two steep internal sidechain filters: bandpass and bandstop. The bandpass filter passes only frequencies between the low and high cut-offs you set. The bandstop filter does the opposite, cutting everything in its range and passing all frequencies above and below it. You can solo the sidechain signal to hear either filter’s effect.

Fig. 2. Drum Leveler applies upward compression to weak hi-hat strikes. The sidechain’s bandstop filter removes just enough energy from bleed to keep it out of (above or below) the processing range set by dual thresholds. Input and output faders and associated quasi-bar graph meters are provided for left, right, mid, and side channels, depending on the plug-in’s configuration. The meters show bars in various widths and colors to represent the different portions of the frequency spectrum; for example, bass frequencies are shown as wide, red bars (Figure 2). You can link a pair of input or output faders and they will maintain any preexisting offset. Any channel can be independently muted. A and B workspaces and facilities for factory and custom presets are provided, but undo and redo functions are not included in Version 1.0.3.

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When setting up Drum Leveler on a track with heavy bleed, I found it easiest to start with the plugin bypassed while I listened to the soloed track play back; bypassing Drum Leveler displayed the scrolling, unprocessed levels in gray and helped me judge which signal peaks were being produced by the miked and variously bleeding kit pieces. (Props to Sound Radix for keeping the Main Display functioning as usual with processing bypassed.) Alternatively, the gray-colored signal peaks represent levels in the sidechain when processing is enabled and the sidechain activated, filtered, and soloed; it let me visually compare my threshold settings to what the plug-in’s detector was hearing and acting on.

My first challenge was on a stereo track for drumroom mics that was heavily processed with a Slate Digital VMR module, the FG-116. Like the UREI 1176 FET compressor it emulates, the FG-116 tends to hype hi-hat and overhead cymbals when using high ratios to explode a drum room. I wanted to boost the track’s understated kick drum and toms while leveling the occasional overstated snare hit and— this is critical—do so without hyping the cymbals further. I switched Drum Leveler to Mid-Side mode and selected the mid channel for processing (Figure 1), as that’s what had the most signal. I set the Compression control to 100 percent—to completely level the traps—and set my low threshold just below the amplitude of the weakest kick and tom hits; with my target level set higher than the low threshold, the weak kick and tom hits were boosted. Next, I applied a bandpass filter between 20 and 1,438 Hz in the sidechain to attenuate all cymbals to a level below my low threshold setting, so they wouldn’t be boosted. Setting the high threshold above the target level and the loudest snare hits downwardly compressed those hits, leveling them. The kick and toms were boosted, the snare hits became uniformly loud, and the cymbals’ levels were virtually unchanged—all with beautifully preserved transients. A final tweak: I lowered the Recovery time to 85 ms to make the room pump hardcore. Fantastic!

Next, I used upward compression to smooth level fluctuations on a hi-hat track and discretely boost the hat’s overall level (Figure 2). To prevent downward compression, I adjusted the target level and high threshold to the same setting. At first, it was hard to prevent bleed from also triggering the processing. I could filter out all the traps’ shell resonances using a sidechain filter, but there was no way to winnow out their stick hits, which produced high frequencies in the same range as the hi-hat. The solution was to preserve midrange energy in the sidechain so that rack tom and snare hits would remain louder than my high-threshold setting, while removing enough deep bass to attenuate the quieter kick-drum and floor-tom bleed below my low-threshold setting. A bandstop filter between 20 and 252 Hz did the trick. I also set the Min. Retrigger time long enough that only hi-hat hits falling on quarter-note beats (not eighth-note and shorter beats) would be processed.

Drum Leveler solves problems no other plugin can: It tames fluctuating levels or adds punch to discrete kit pieces in drum subgroups and stems without audibly affecting bleed. And the processing is very transparent—unless you purposely go for a radical effect. At a price of only $149, this is a product every mix engineer should own.

Unique problemsolver. Excellent sound quality. Thoughtfully designed GUI. Comprehensive and powerful control set. Provides mid-side mode and internal sidechain filters. Inexpensive.

No undo or redo.

Sound Radix Drum Leveler: $149

Michael Cooper is a recording, mix, mastering and post-production engineer and a contributing editor for Mix magazine. You can reach him at and hear some of his mixes at