The Stereoizer is a mono-to-stereo upmixer using Inter-aural Intensity Difference (IID) and Inter-aural Time Difference (ITD).
NuGen Audio, based in the UK, makes a range of stereo-analysis and image-manipulation plug-in tools such as the SEQ 1/SEQ 2 linear-phase EQ and VisLM-H/C loudness meter. NuGen’s Stereo Pack suite ($179) features three imaging tools that offer some interesting new processing ideas.
The Stereo Pack includes the Stereoizer, Stereoplacer and Monofilter. Having used other NuGen plug-ins with great results, I was excited to try this trio, which had recently become available. They handle very specific tasks and tackle some problems you didn’t know you had, doing so with style and sonic integrity, and with engaging and user-friendly GUIs. However, these plug-ins can be CPU hogs, so Stereo Pack includes fidelity controls that let you better manage results in relation to available CPU resources.
Stereoizer is a mono-to-stereo up-mix plug-in. I’ve used these types of processors when restoring old vinyl records to improve the image on stereo playback equipment. In most cases, I’ve found myself tediously tweaking settings and eventually giving up, realizing that the end result sounds different, but not necessarily better.
For example, Logic’s Stereo Spread plug-in has a fundamental flaw in which the processing does nothing to accurately re-create the actual experience of stereophonic perception. Instead, it pans a comb-filtered range of frequencies to the left and right, with user control over the affected range. You twist the dials, listen and hope for the best, with the end result sounding “stereo,” yet a bit odd and phasey. Other stereo-widening plug-ins require stereo source material and simply manipulate the ratio of identical information to unique information between the two channels. This effectively allows adjustments of the mid-to-side ratio.
The Stereoplacer allows frequency-specific panning with a simple click and drag.
The Stereoizer plug-in does a much better job of considering psychoacoustic cues based on reality. Our brain looks at several different qualities of sound to determine the directionality of a source and the way that sound travels through, and interacts with, a given space. The most notable are Inter-aural Intensity Difference (IID) and Inter-aural Time Difference (ITD). When sound is louder hitting our left ear than the right ear, it is obvious that that sound came from the left. Likewise, if sound is delayed in hitting our right ear relative to our left, we could draw a similar conclusion. Using this principle, Stereoizer takes mono sounds and creates believable stereo imagery that is comprised entirely of information contained in the original source.
The results I had with the Stereoizer plug-in are impressive and useful for subtly improving the stereo image in a complete, finished mix. Stereoizer is also great for negotiating space for drums and widely panned, doubled electric guitars in a mix. And even with its controls cranked to over-the-top values, the plug-in never produced weird or phasey artifacts, so the possibilities are really without limits. To help push your sound beyond reality, it offers modulation effects, which can be synched to the session’s tempo for modulation of the stereo image. These effects are harder to predict but certainly add an interesting twist.
The GUI has intuitive controls for adjusting the frequency range and stereo width of each of the perceptual cues, the IID and the ITD. All of the plug-ins in this pack offer great graphics, but Stereoizer is the most fun to look at. Its controls have a slick sci-fi feel. A quarter-circle display represents the stereo image, with the left-to-right range representing width, and the range from center to outside representing frequency. For a great sense of sonic control, you can set the range and width of the ITD and IID independently, and both the ITD and IID displays are coupled with a glowing, dancing representation of the energy distribution in the stereo field. The most equivalent product I’ve encountered in terms of design principles and sound quality is the Waves S1 Stereo Imager. Both plug-ins sound very similar, but it seems easier to get the desired result with the Stereoizer GUI.
The Monofilter tightens low frequencies by forcing them to mono below the crossover point.
The Stereoplacer plug-in offers frequency-specific panning within a user-friendly, intuitive GUI. Frequencies are laid out across a horizontal plot, with a horizontal “flat” line through the center. Clicking and dragging the horizontal line creates a breakpoint at that frequency, where dragging upward pans left and downward pans right. It feels like boosting and cutting frequencies on an EQ plug-in, except boost and cut become panning left and right directionality.
My immediate thought was to use Stereoplacer to take a mono piano recording, split the stereo image in half with a high and low shelf, and send the highs to the left and lows to the right. I also started playing with the same effect on mono recordings of choirs and orchestras. Stereoplacer did an incredible job, precisely mapping the designated frequencies to the desired spatial locations. In every case, the effect was free of sonic impurities or phase-related artifacts, but the result was unnaturally clean. This was easily corrected by running the processed signal through the Stereoizer, which filled in the missing space.
With the precision of Stereoplacer, I could take mono jazz records and remix cymbals to the left or sax solos to the right. I carved out certain elements of the overall mix based on their fundamental frequencies and redirected them to different places in the soundfield. In all honesty, I was surprised to find that things like that could actually work without sounding unmusical.
The concept behind the Monofilter is simple: As low-frequency energy is perceived with a lack of directionality, it’s inefficient to push unique lows to each speaker in a stereo pair of speakers. Instead, summing all lows to mono and using the force of two speakers to push the bass in phase through two speakers creates the potential for a tighter and more plentiful bottom end. To that end, the Monofilter sums information below the chosen crossover frequency to mono.
From there, you can solo the stereo high frequencies—or alternatively, the mono low-frequency information—so you can make critical judgments about the overall effect. This is particularly helpful when it comes to implementing one of the plug-in’s best features. The bottom of Monofilter’s window displays phase correlation across the broadband frequency spectrum. By listening to the mono-summed signal and referring to the visual feedback offered by this phase scope, you can make manual adjustments to shift the phase relationship of the two audio channels and remove potential cancellations. You can also apply automatic detection and correction. This not only helps make bass tight and punchy by locking in phase-correlated bass and pushing it through a pair of speakers, but it generally helps in correctly summing the mix to mono.
You can implement a very clean bass-management crossover by soloing the upper stereo information and mono-summed lows, each on separate instances of the plug-in processing the same material. Output from the stereo-solo’d plug-in can feed stereo satellites, while you can feed the mono sum discretely to a subwoofer. Having the highs and lows on different channels also allowed me to compress the bass frequencies in a mix differently from the high frequencies. Whether I was treating the 2-bus of a mix or mastering a finished mix, this procedure became a no-brainer. I can’t envision myself ever calling a mix finished without treating it with Monofilter. Plus, with Monofilter you can manipulate the output level of each signal and lows vs. highs. As a result, you can pump up the bass on the output in a way that sounds less colored than, say, simply adding a low shelf to the entire mix.
Once I started using Monofilter on my Logic and PreSonus Studio One mixes, I found myself hesitant to even mix music in Pro Tools for lack of an RTAS version. Thankfully, at the time of this writing, an RTAS version is on the verge of release and a beta version has been a welcome addition to my Pro Tools workflow.
A TRIPLE TREAT
Flatly stated, the Stereo Pack’s plug-ins all work as advertised and exceeded my expectations. However, you’ll need plenty of CPU power to run them in HQ mode. Even so, I found myself enjoying the quality of the plug-ins before realizing that I wasn’t even running the high-quality option. Once I made the switch, I was thrilled to find that the HQ version sounded even better and it was difficult to turn back. In my tests, the combination of stunning visual feedback and high-powered sonic performance often proved more than my 2.26GHz Intel Core 2 Duo MacBook Pro could handle. My CPU easily started to choke running the HQ Monofilter across the 2-bus of a 20-track, 24-bit/44.1kHz mix. Bottom line: Bring your best CPU to this game.
Who would love these processors? As forward-thinking as this set of plug-ins is, I wouldn’t classify them as geared toward audiophiles and mastering engineers. While they would satisfy the most critical listener, they are accessible enough to interest users at all levels of experience. Everyone from electronic musicians, beat-makers, mixing engineers and sound designers can benefit from these plug-ins. They sound great and offer musical results delivered in a creative fashion.
Brandon Hickey records and mixes audio for independent films and teaches audio post.
Click on the Product Summary box above to view the Stereo Pack Plug-In Suite product page.