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Electronic Musician Review: Ohmforce Ohmboyz

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Ohm Force's multiplatform effects plug-ins OhmBoyz 1.20 and Predatohm 1.10 deliver some unusual twists to two common digital signal processing (DSP) effects: multitap delay and multiband compression. For example, you can morph between presets, you can control all parameters with MIDI, and most parameters have their own dedicated LFO. That level of control makes these plug-ins capable of a variety of extreme effects. On Ohm Force's Web site, you can download demos that work for six hours before noise is introduced into the signal. While you're there, pick up a copy of the free Frohmage, an unusual multiband filter plug-in (see the sidebar, “It's the Cheese”).

The Ohm Force plug-ins come in a bewildering assortment of styles and formats. For this review, I tested the VST versions on a Mac G3/300 MHz with Steinberg Cubase VST/32 5.0 as the host. With some feature limitations, I also used them in Emagic Logic Audio 4.8.1 and BIAS Peak VST 2.62. In all cases, the sound quality was excellent and the CPU drain was surprisingly low.
 

THE MANY FLAVORS OF OHM

OhmBoyz and Predatohm are each available in 20 versions spanning three platforms, three plug-in formats, two levels of DSP quality, and two graphic styles (or skins). You can obtain most versions only as downloads, and the Ohm Force Web site is a little difficult to maneuver. On your first visit, figuring out exactly what you want and how to get it can be a daunting task.

All plug-ins are available for the Mac in VST format and for Windows in VST, DirectX, and Winamp formats. VST versions are also available for BeOS on the PC. MOTU Audio System (MAS) and Real Time AudioSuite (RTAS) versions should be available soon.

The Standard-quality versions support 16-bit audio, but they don't allow MIDI automation. Standard versions also do not include a commercial license, so you're not permitted to use them in music that you sell. The Expert-quality versions support 24-bit audio as well as MIDI automation and do include a commercial license. If you produce music mainly for free online distribution in a compressed format such as MP3, RealAudio, or QuickTime, the advantages of 24-bit processing will be lost in the compression anyway. At $9.95 the Standard versions are an incredible bargain.

The Standard and Expert versions provide one skin in one plug-in format on one platform. Bundled versions (which are called Professional) are available as well. When you buy a Pro bundle, you download whatever format you need immediately, and Ohm Force will send you a CD-ROM that includes all skins, plug-in formats, and platforms.

The Funky skins have large controls that aren't always identified clearly and have somewhat whimsical graphics and layout. The Classic skins are more compact, with smaller controls arranged in a standard fashion. I chose the Classic skins for the illustrations in this article because they're easier to understand and describe. Don't overlook the Funky skins, though; the onscreen controls respond much better to the mouse, and the goofy graphics might even inspire a little creativity. Unfortunately, you're required to make a choice before you buy; full-size illustrations of both styles are available on the Web site.


BOYZ UNDER THE HOOD

OhmBoyz begins with a stereo, four-tap predelay (see Fig. 1). Each tap has its own level, stereo balance, and delay-time controls. You can set delay times in milliseconds or in note increments synchronized to MIDI tempo. There is no feedback in the Predelay section; its main purpose is to feed the parallel feedback delays that follow. Because each parameter of each tap has its own LFO, you can produce interesting results with the predelay alone. For example, if you apply zero, quarter, eighth, and three-quarter beat taps to quarter-note snare or cymbal patterns and add a little random LFO for the tap levels, OhmBoyz produces a great ghost-16th feel that's much like the effect of a drummer playing light 16th notes throughout a pattern.

The Predelay section is followed by two parallel delay lines, each with multiband filter, distortion, and high-shelf filter stages. The predelay's left channel is fed into the first delay line, and the right channel is fed into the second. You can turn off the second delay line to save CPU cycles, in which case both predelay channels are fed into the first delay line.

The controls for the Delay section of the delay lines include level, pan, delay time, and feedback. The range of delay time is from 1/64 beat to 4 beats at tempos as low as 60 bpm, which amounts to a maximum four-second delay. (When syncing to MIDI tempo, OhmBoyz doubles tempos below 60 bpm.) Short delay times with high feedback, when applied to percussion, produce a plucked-string effect that sounds physically modeled. You can hear an example of that and other techniques in the MP3 file Ohmboyz.mp3. (I produced all of the online effects from the same four-measure percussion loop with a single pass through OhmBoyz.)

Feedback is adjusted as a percentage of the incoming level; that is, each successive echo's level is a percentage of the previous echo's level. Because no dry signal is present at the delay line output, a feedback setting of zero results in no output from the delay line. That is slightly annoying, because it makes it impossible to use the delay lines as single-tap processors. With too little feedback, you don't hear the echo, and with too much, you hear it several times.

The multimode filter section of the delay lines is one of OhmBoyz's most interesting features. Highpass, Lowpass, Bandpass, and Peak modes are available. For all modes, the frequency range is 40.00 Hz to 10.24 kHz; consequently, the first three modes always have some audible effect. For the peak filter, the resonance (Reso) control determines the amount of boost or cut, and you can eliminate the filter by setting it to zero. For the Peak and Bandpass filters, the Q control sets the bandwidth; it has no effect on the other filter modes.

The distortion and high-shelf stages hold no surprises. Distortion is a waveshaper with a variable curve that is continuously adjustable from an S shape to a sine wave. It can simulate everything from common overdrive to nearly white noise. It is most effective on pitched material, especially guitar tracks. You can set the high-shelf filter from 200 Hz to 20 kHz with maximum attenuation around 96 dB and 6 dB-per-octave rolloff.

When you use both delay lines, a balance control lets you cross their feedback. With four taps of predelay, two cross-feedback delay lines, complex filtering and distortion, and 39 LFOs, OhmBoyz can generate some pretty dense effects. When you add MIDI control and morphing between presets, things quickly get out of hand (in a good way). Fortunately, the six banks of factory presets give you a good head start, and more are available on the Ohm Force Web site.


PREDATORY PRACTICES

You can think of Predatohm as a 4-band compander or a 4-band dynamic equalizer (see Fig. 2). It divides the frequency spectrum into four user-defined bands and then applies distortion and independent compression or expansion to each band.

Setting up Predatohm's frequency bands is a piece of cake. Simply move the three band sliders at the top of the control panel. The Main Edit window above the sliders shows a slider's position in hertz as you move it. You can reduce the number of bands by pulling the sliders completely to the right. When all of the sliders are completely at the right, you have a single-band compressor.

Each compression band has controls for level, compression or expansion shape and threshold, and the type and amount of distortion. The Character knob controls the compression type; the left half of the knob controls compression, and the right half controls expansion. The Intensity knob determines the compression threshold. The Distortion Type knob selects among 13 types of distortion: hard clipping, 6 tube simulations, and 6 waveshaping curves.

The output of the compressors is mixed and passed through a resonant lowpass filter with variable shape and cutoff frequency. A Feedback delay stage follows the filter. The delay time is displayed in hertz to indicate the frequency at which feedback resonance occurs.

Predatohm's last stage is a stereo simulator. All Predatohm processing is in mono; stereo signals are mixed down to mono at the input. The Super Stereo stage sends the raw signal to the left output channel while sending an inverted and delayed copy to the right output channel. The Phase control sets the delay time. Super Stereo will introduce mono incompatibilities (including total cancellation when the delay is zero), so when that's a consideration, simply turn it off.

One of the most useful features of Predatohm and the other Ohm Force plug-ins is their ability to morph between presets. As many as eight presets can be stored using the preset buttons. Recalling a preset causes the controls to change to the preset values during the indicated morph time (ranging from 0 to 99 seconds). As settings morph, you can watch the controls gradually change their values. I recorded the MP3 example Predatohm.mp3 in one pass using two ten-second morphs.

As cool as the morphing feature is, it is a pity that you can't synchronize the morph time to MIDI tempo and that you can't recall (and therefore morph) presets using MIDI Program Change messages. Rather than being able to bounce a morph completely within the digital domain, you must manually click on the preset buttons while you route the audio out and back into the computer.
OM FOR OHM

I liked both plug-ins and found them useful for a wide range of digital-signal processing needs. Of the two, OhmBoyz is the more interesting and is capable of a huge variety of effects. Predatohm's compression seems a little heavy-handed, but if you happen to be into distortion, it makes an excellent choice. The Standard versions are an incredible bargain, and the Expert versions seem fairly priced (though it would certainly be nice to get both skins).

The ease of using OhmBoyz or Predatohm depends on your choice of platform and host. On the Macintosh, in everything but Cubase VST, the Classic skin controls are touchy and difficult to use. Cubase is also the only host that supports MIDI control and tempo synchronization — two key features. Nevertheless, the sound quality is uniformly good, and both plug-ins are eminently usable in all hosts. Original from emusician.com

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