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McDSP FILTERBANK 1.04 (TDM/AUDIOSUITE)

November 1, 1999
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The conventional wisdom seems to be that plug-ins, although good for many applications, just don't deliver great-sounding equalization and compression. It's not uncommon to see producers and engineers routing their Pro Tools tracks to vintage outboard EQs and compressors and then back into Pro Tools, rather than relying solely on plug-ins for these important tasks.

It's true that no plug-in is a perfect replacement for vintage outboard EQ and dynamics processors, but McDowell Signal Processing (McDSP) has made a significant step in that direction. Founded by one-time Digidesign employee Colin McDowell, McDSP is making its debut with the FilterBank equalizer, easily the most comprehensive EQ plug-in I've seen.

The program is available on a CD-ROM that contains both TDM and AudioSuite versions, though as of this writing it operates in real time only on the TDM platform. I tested the TDM version, which requires Pro Tools 4.0 or later software and Pro Tools PCI, 24, 24/ Mix, or 24/PowerMix hardware. The software is compatible with Mackie's HUI as well as Digidesign's ProControl hardware controllers.

The informative, comprehensive, and well-organized electronic manual (which comes in both PDF and HTML formats) is packed with JPEG screen shots. Although I prefer paging through traditional paper documentation to reading a manual in a Web browser, I had no trouble learning to use FilterBank with these electronic documents.

SOFT SLIDERSLooking at FilterBank's design, it's immediately clear that this plug-in is unusually flexible. The software's high and low shelf EQ, parametric EQ, highpass and lowpass filters, and bandpass and band-reject filters are available in both stereo and mono versions and in 2-, 4-, and 6-band configurations. You can control frequency, gain, peak, slope, and dip (explained shortly), over a frequency range of 20 Hz to 21 kHz.

You get a minimum of 22 bands of EQ per DSP chip on a Pro Tools PCI system and between 42 and 48 bands on Mix and Mix-Plus systems, which is generous. McDSP says that the TDM version of FilterBank keeps the noise floor at -144 dB by calculating the values with 48-bit precision.

Sliders are the controller of choice in the FilterBank interface, along with bypass buttons that have been amusingly styled after '70s Sequential/Korg LED switches. When you apply equalization, a white line displaying the selected cut or boost curve appears in a Display Graph, which is a black rectangular window with a fixed blue horizontal "zero" line.

GETTING STARTEDAfter a fairly painless installation process (the program is copy protected, offering a choice of challenge-response or key-disk authorization), FilterBank is ready to go. As with any TDM EQ, using FilterBank in its most basic form is simply a matter of instantiating it and adjusting its frequency and gain controls to boost or cut the desired frequencies. FilterBank includes mono and stereo versions; instantiating it on a mono or stereo track in the host program (such as Pro Tools or a TDM-compatible digital audio sequencer) will bring up the appropriate version.

Thanks to the program's wide range of possible configurations, things get much more interesting from here on. The next order of business is choosing the right configuration for the material that you're equalizing. Nine EQ configurations are available (see the table "FilterBank EQ Configurations"), but I'll focus on the four that best show the plug-in's flexibility: E6, P6, F2, and B1.

COMPLEX CONFIGURATIONSFilterBank's E6 configuration (see Fig. 1) is probably the most versatile and has the widest range of musical applications. It contains highpass and lowpass filters (20 Hz to 21 kHz), high-shelving EQ (5 to 21 kHz), low-shelving EQ (20 Hz to 5 kHz), and two parametric EQs (20 Hz to 21 kHz).

Except for the highpass and lowpass filters, which have no gain controls, each section of every FilterBank configuration has its own gain slider, frequency slider, and bypass switch. Additional controls are provided for specific filter types.

For example, the shelving EQs' Peak, Dip, and Slope parameters provide extra shaping power that helps to distinguish FilterBank from other EQ plug-ins. The Peak control determines the amount of added punch or emphasis near the shelving frequency. The Dip control does just the opposite, reducing the amplitude of frequencies near the shelving frequency. Naturally, increasing one of these controls decreases the other automatically. The Slope parameter controls the gradient of the shelved response (that is, the transition between the shelved and nonshelved bands). Using these controls, you can simulate some of the characteristics of classic analog equalizers (more on this subject in a moment).

The highpass and lowpass filters in the E6 configuration offer you a choice of either 6- or 12 dB/octave attenuation. They also provide an input-level control with a phase-reversal switch.

PARAMETRIC POWERThe P6 configuration consists of six identical parametric equalizers whose frequencies range from 20 Hz to 21 kHz, with possible Q settings ranging from 0.2 to 4.0 (see Fig. 2).

I used this configuration often, especially when dealing with tricky, heavily processed sounds containing unwanted peaks and dips at multiple frequencies. As you might expect, having a 6-band parametric EQ allows you to focus on specific frequencies with even more precision than is possible with conventional 4-band parametrics. In fact, with individual Q controls for each band, in addition to frequency and gain controls, you often have more control than you need. (I'm not complaining, of course!)

BOTH HIGH AND LOWThe F2 configuration (see Fig. 3) comprises highpass and lowpass filters, each ranging from 20 Hz to 21 kHz and offering 6, 12, 18, or 24 dB/octave attenuation. Both filters have Peak and Frequency controls. Peak lets you adjust the amount of resonance at the cutoff frequency by up to 24 dB, depending on the attenuation curve selected.

High- and lowpass filters with this level of flexibility and control are invaluable, allowing for drastic frequency changes. This makes them very good for corrective applications (eliminating stray low-end rumble from a live recording, for instance) as well as for special effects. You can create quasi-bandpass effects by setting the highpass and lowpass cutoff frequencies close to each other, or you can deconstruct sounds completely.

PASSING THOUGHTSThe B1 configuration allows either bandpass or band-reject (notch, if a narrow bandwidth is selected) filtering with very precise control. It's intended as a corrective tool for removing hum, buzz, or other narrow-band noises from a signal without heavily compromising the signal itself. As with F2, though, you can create interesting effects with this tool, such as the ever-popular "telephone EQ" vocal effect, to choose an obvious example.

SPECIAL FEATURESSeveral other aspects of FilterBank are noteworthy. For example, when the plug-in is instantiated across a stereo track, separate left and right controls appear for each slider. You can stereo-link them absolutely using the Stereo button, or link them relatively using the Link button. When you use an absolute stereo link, changing the value of one channel changes the other to maintain the same value. When you use a relative link, changing one channel alters the other by the same relative amount, but the two can have different values. The left and right channels can be unlinked using Dual mode.

Another interesting feature is FilterBank's Analog Saturation Modeling. This algorithm ensures that FilterBank will not produce digital clipping when overloaded. Instead, it exhibits a distortion similar to that of an overloaded analog equalizer. In practice, this feature works pretty well: it's far less obnoxious than digital clipping. This is indeed a welcome feature in the digital audio universe.

FROM SUBTLE TO EXTREMEThroughout the review process, FilterBank's sound proved quite smooth, even at extreme cut or boost settings. The plug-in can make very subtle tonal changes, as well as totally drastic sound alterations, and it generally had a decidedly musical character. I now use it for virtually all applications that call for an EQ plug-in.

McDSP includes a large number of presets, some of which are designed to emulate the sounds of various well-known analog equalizers by companies such as Neve, GML, and Avalon. Although I didn't have these devices and could make no direct comparisons, the presets sounded musical and pleasant and were, in fact, reminiscent of high-end analog equalizers. I think it's safe to say that this is the best-sounding TDM equalizer yet.

MY TWO CENTSMy gripes are minor and few, and mostly pertain to graphic design. First of all, the screens for the more elaborate configurations, such as P6 and E6, look a bit cluttered. One such example is the lack of clear graphic distinctions between the parts of a configuration; perhaps color coding them would be helpful.

I'd also like to see a more intuitive layout. In the E6 configuration, for instance, the highpass and lowpass filters are in the lower-left portion of the FilterBank window. I expected to find the lowpass filter at the extreme left and the highpass filter at the extreme right.

It would be helpful if the currently selected EQ curve didn't disappear from the Display Graph window when Bypass is engaged. It's annoying not to be able to see the current EQ setting constantly while toggling Bypass to gauge the effect of EQ on the current track. But as I said, these are minor points.

Fortunately, there is a partial solution for the E2, E4, E6, P2, P4, and P6 configurations. Holding down the Control key while instantiating one of these configurations will bring up a simplified version of the user interface, which still includes dual phase-reverse switches and input sliders. Although this alternate user interface doesn't solve the layout problems, it does reduce clutter.

Finally, although the $495 price tag is not unusual for a TDM plug-in, it is over the top for an AudioSuite plug-in.

A FINE FILTERJudging by its excellent sound and flexibility, a lot of thought and effort clearly went into designing FilterBank, and I was very impressed by its performance. I did not test the AudioSuite version, which offers the same basic features but does not operate in real time.

Fortunately, McDSP plans to release a version of FilterBank and the newly announced CompressorBank for Digidesign's new Real-Time AudioSuite (RTAS) plug-in architecture sometime during the fourth quarter of this year. (For more information on RTAS, see "Stop the Presses" on p. 40 of the October 1999 issue of EM.) The company is also working on support for Pro Tools for Windows NT but has not yet announced a release date.

FilterBank is subtle and musical enough to use on acoustic instruments and vocals, yet it allows you to create drastic sound-design effects. I wholeheartedly recommend it to any TDM or AudioSuite user who needs a serious equalizer.

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