words: Adam Fuest
images: Gavin Roberts
When the Sherman Quad Modular Filter
Bank - or QMF to its friends - arrived at The Mix office, there was a
clamour of excitement and a hoard of eager hands wanting to get hold of
it, and yours truly was the lucky devil who was able to take it home and
live with it, play with it and muck about with it.
'So', you cry, 'what is a filter bank, anyway? And what's so exciting
about the QMF? Filters aren't a new thing to audio and many people make
the association with synthesizers, but every time you reach for an EQ
pot on a desk or a plug-in, tweak the EQ in Logic or VST, or kick in a
wah- pedal you are, in fact, using filters of sorts.
Obviously the type and quality of filters varies dramatically, and the
modern filter has taken on two distinctive forms. Firstly, as an equalizer
in the audio path of most mixers and amplifiers, where they provide the
ability to cut or boost the audio signal at various frequencies, thereby
enhancing the tonal character of the audio. The second use is within synthesizers,
where one will find a very different animal altogether.
The synthesizer filter has become an equaliser capable of manipulating
the signal from (primarily) an oscillator or from an audio sample and,
with the use of feedback loops, band-pass filters and envelopes, totally
remodelling the original signal. For many years people have been putting
audio signals into the backs of old synths and generally mucking about
with them - one need only listen to old Roxy Music and Led Zeppelin albums
to hear what was going on.
If there's a sound on these albums you can't understand or emulate, you'll
probably find it was created in part with a synth filter. And what do
we learn from this? For those of you who may not be into dance music,
Io-fi or big beat, do not rule out tools such as these! Putting a bass
guitar or a vocal through a synth's filter can be an incredible experience.
So, what's the big difference between the QMF and an Arp Odyssey or a
Pro One? Well, fun though those instruments are, they are actually synthesizers,
so to a certain extent one is usually limited as far as facilities are
concerned. The QMF, on the other hand, is designed to be everything but
a synthesizer. For those who aren't familiar with it, we shall briefly
cover the piece of studio gear that gave birth to the QMF: the Sherman
Filterbank.
Original style
The original Sherman Filterbank was
designed to fit a 2U rack space. Now around four years old, it has found
favour with many illustrious users, including the Chemical Brothers, U2,
Apollo 440, Andy Gill, Jamiroquai and Adrian Sherwood. Along the back
it has connections for signal input, FM and ADSR trigger inputs, link
in and out (to facilitate the use of multiple Filterbanks), plus MIDI
in, out, and thru, amplitude modulation input, trigger out and finally,
output one and main output. These are basically mix and effect and effect
only.
Along the front panel we have controls for the following: two independent
low, band and high-pass filters with resonance, frequency and ADSR controls,
which are switchable between parallel or serial operation. The second
filter has a six-octave switch, and is synchronisable with the first filter.
There's also one ADSR generator for these filters with an external output
for use with more Filterbanks or modular systems, one FM input for the
filters - internal or external audio can be used as a source - LFO or
CV, one VCA overdrive with AIR generator and one ring modulator. This
may all be a bit of a mouthful, but to have such facilities from a synth
would require one hell of a machine.
So now we've covered that, let's move on to Sherman's latest monster. The QMF, unlike the original Filterbank, is not rack-mountable. it actually measures just over 21 ", which means it doesn't fit comfortably anywhere in the average studio. This is just fine, because that way it will stick out like a sore thumb, so everybody will notice it and say 'Wow! You have a Sherman QMF - cool!'
The truth is that it is, and you will be. So not only is it too wide but it's also 16" deep, with retro- wooden side panels. Down the left-hand side of the unit are found all the input and output sockets for each channel, and to the right of these are the four (near) identical sets of controls for the QMF. These are, in fact, four Filterbanks in their entirety complete with all physical inputs, outputs and triggers, and of course those lovely little link sockets so all four Filterbanks can operate independently, or they can be chained together for serious action - giving up to 96dB filter slopes!
There are some subtle differences in the units. Units three and four each have six additional switches, and these are as follows: Bright boosts high frequencies at the input. The next switch is Limit, which clips input signals at a lower level. Therefore, setting the input level extremely high will not blow your speakers to bits - an interesting phenomenon which the novice can easily achieve.
Next we have the Slow switch. When engaged, the Slow position gives the envelope followers the characteristics of the original Filterbanks, whereas when Slow is switched out the envelope followers are five times faster. Octave simply doubles the centre frequency of both filters.
The QMF is one of the most interesting tools we have ever had the chance to work with and it is impossible to describe fully just how much this box can do for your music. in the week we had the unit in the studio it was used constantly. Whenever a particular sound or track was feeling a little lacking you could just plug the QMF in and fiddle.
The most important thing to do was to record whatever we did every time because it was nearly always useful. For example, a bass that was recorded via a preamp was sounding remarkably dull and lifeless within a track, but after putting it through the QMF, adding a little overdrive on the input, a soupcon of envelope, a touch of resonance and just a hint of LFO on a band-pass filter... Boomshanka! We had one grunting, snarling mofo of a bass with so much attitude it would bring tears to your eyes and ears.
Another example is when we were presented with a track to mix, What was really required was a drum loop, but unfortunately the rhythm track was not up to scratch, although it was well-performed and inspired. So out comes the QMF, in goes the drum ambience, and out comes this pumping, squelching rhythm-glue that fitted into the track like a hand in a glove.
On a vocal we were able to create a shimmering whisper that sounded as if it were going through some Io-fi Leslie. And as for the Triangle! If you mix, then this box is for you. And if you can't get the QMF, buy a regular Filterbank. This is an essential item already and we haven't even got round to the external triggers and MIDI bits yet.
This mucking-around mentality is what the QMF is all about. if you visit their website (www.ping.be/sherman/) you'll find a list as long as your arm of addicted users in the 'Known Sherman Filter Bank Abusers' list. That said, you can be very sensible with the QMF and put dull digital keyboard parts into it, trigger it from the MIDI notes and enhance the hell out of it.
In this way it's possible to make a Korg M I electric piano - possibly one of the most emotionally destructive sounds known to man, in fact a sound responsible for such acute depression that it has been banned from all but the most Eastern of Eastern European studios - and make it sound like an overdriven Waldorf Microwave. Now that, in our book, is a gift to mankind.
On the downside, however, there's no form whatsoever of storing your patch other than using a pen and paper, which is strange. One would have thought that with such a retro bit of gear one would at least have cassette backup or something like that. Never mind - if you like what you create with this brute you'd better record it, because one twitch of a knob will have the QMF grunting and groaning off in another direction like some bad-tempered adolescent in a Cosworth, leaving skid marks on your tweeters and bootprints on your woofers.
Is there an alternative? Well, you could go out and buy half a dozen analogue synths, turn them on and leave them for a few days to get nice and hot and possibly stable (but there's no guarantee of that) and then fumble about with patch cords and MIDI-to-CV converters and DCB8 boxes - you might learn something about air conditioning while you're at it but even then you won't be anywhere near reaching the potential of the QMF.
Simply put, there is nothing else to compare with the QMF. The bad news is that Sherman, in their infinite wisdom, have decided to make only one hundred of these naughty boxes available worldwide, so if you're up for one and have a couple of grand to spare, best get your name on the list ASAP, as this is undoubtedly the first major collector's item of the new millennium.
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