Roger Schult 500 Series EQ Filters

German designer Roger Schult released in September of 2010, a trio of 500 series modules sharing the design and sonics of his mastering parametric equalizer, the UF-1.

Overview

The W2377 Universalfilter set is comprised of three modules:
Low Band Filter: 20Hz to 730Hz
Mid Band Filter: 155Hz to 3.5kHz
High Band Filter: 1.03kHz to 23.2kHz

While a stepped ELMA switch is used to set the Quality control, the Frequency and Level settings use ALPS potentiometers. The Level potentiometer has a center detent and covers a range of -10dB to +10dB.

For some mastering engineers, the non-stepped potentiometers of the W2377 will not be ideal, but for anyone not requiring stepped gain and frequency settings, the versatility of this modular design opens up new and interesting workflow possibilities. Frequencies and gain settings are very clearly laid out on the engraved faceplates so recall has presented no challenges for me thus far.

The W2377 filters have nine different Quality (Q) settings from very broad to very narrow. Either end of the Q rotary switch can be set to engage a frequency adjustable high-pass or low-pass filter. The lower Q settings (0.3, 0.5, 0.7) are quite broad and are excellent as an adjustable slope shelf-like filter. The EQ curves bell more in the mid-level settings (1.0, 1.5, 2.5) and finally go from a gentle to steep notch (4.0, 6.0, 10.0) with the high-pass and low-pass functions at either end of the dial. The high-pass/low-pass filter has a slope of 6dB for the first octave then 12dB per octave thereafter.

The illuminated buttons at the bottom of the module are the Focus, Solo, and Bypass options.

The Focus button inverts the Level setting of a module to reference the selected frequency range. For example, a level of +3dB becomes -3dB (Q is unchanged) when the Focus button is engaged. To my knowledge, this is a unique feature to Roger Schult's designs. A peculiarity of hearing is that it's easier to isolate amplified frequencies then attenuated frequencies, so the option to switch back and forth instantaneously is a real luxury. This feature has been unexpectedly handy in tracking down and treating "ringing" notes quickly. Turn the gain up, sweep the frequency until you find it, invert the gain, make a decision about how it sounds, make a small adjustment, done. I have come to really appreciate the immediate referencing ability of this function over turning the level knob from + to - back and forth.

The Solo function isolates a selected module by engaging the bypass in connected modules via a signal bus on the front panels.

The Off switch engages a true bypass by means of relays.

In Use

While I spend plenty of time with two sets of three filters linked together to make a regular style parametric EQ, I have found numerous uses for single bands, or combinations of filters.

For example, this modular design was helpful recording a viola in Mid-Side.

We used a Low Band filter to "thicken" the instrument's C string below about 200Hz, and a Mid Band to notch some screechy bridge noise at about 2.7kHz (Mid mic). The High Band was then used to bring some size and sparkle into the Side mic by turning the frequency setting all the way up to 23.2 and dialing in a +4dB boost with a Q of .5. *Two microphones, three filters, each doing something very different and working together beautifully. The W2377 provides a fantastic way to audition new workflow ideas quickly.

When boosting low and mid frequencies using broad Q settings, the filters subtly grab hold and energize the selected frequency band. The W2377 really excels at taking a slightly dull sound and gently invigorating it, bringing a liveliness to the track. When rolling off frequencies, the process feels equally gentle. For more extreme notches, I would probably favor digital EQ, but for subtle dips alla 250Hz or 400Hz, this filter really works wonders for softening aural protrusions. Using the High Band filter to notch out mouth noises yields again, a softer effect than digital EQ. If nothing too drastic is necessary, cutting a couple dB with a Q of 4 will lessen syllabic noises while retaining a cohesiveness in a speaker/singer's performance.

In addition to corrective EQing, the High Band filter has been seeing use in some shelving applications. This has been especially useful on strings. As stated earlier, burying the needle at 23.2kHz, then adding 2-4dB of gain with a Q of .3 or .5 enhances the overtones of string music and brings forward a clarity and articulation that a reverberant space does not possess on its own. On electric guitar tracks, attenuating the top a little bit, again with a low Q, can be what enhances the clarity of a track.

Conclusion

Having used these EQ filters for well over a year now, I continue to find new applications where they perform well, and continue to be reminded how versatile they are. While trios of Roger Schult W2377 filters are not inexpensive, they have filled the role of high/low pass, shelving, shaping, and notch filter admirably. I am most impressed by them and feel they deserve high review scores.