Eventide H8000FW

Recording Equipment

The following article, Wave Phase and Cancellation - Part 2, covers the physical causees, acoustic impact and solutions to the phenomenon of audio wave phase cancellation.

Wave Phase and Cancellation - Part 2

continued from Part 1

So it is with sound – two very similar (or identical) waveshapes, perhaps from two mics covering the same source, or two identical copies of a sound played together in a digital editor (DAW), can collide unhappily when mixed together, resulting in a wide range of possible effects, from a weakening of the bass tones in the sound, to subtle, or extreme, tonal shifts, as the monitoring is switched between stereo and mono, right up to a radical loss of virtually the entire program sound of the affected tracks, even though each individual waveshape is recorded at a high level. If this happens, and what goes missing is your main rhythm guitar track, or something equally important, the results could be disastrous to your mix. Since any problems caused by acoustic phase won’t show up clearly, unless the signals are actually mixed together, the rule is: Always check your stereo mixes in mono, to show up any unknown troubles.

There are, of course, ways to deal with the problems created by phase issues before they happen, such as the X-Y pair mic technique. Another quick rule-of-thumb for using two mics is the 3:1 Rule, useful when the conditions require that the mics are spaced apart (a spaced pair), rather than close together (a coincident pair), as is the case with the X-Y. Here, place the first mic facing the sound source, at a mid-distance (say, 2 feet/60 cm), and then, place the second mic not less than three times this distance from the other one, or in this case, about six feet, or 180 cm, apart from it, at the same distance from the source as the first mic is. By doing this, there will likely be enough difference between the program content reaching each mic, that any phase issues will hopefully be minimized as a result. While this is not necessarily a perfect quick-fix, and mono checking must still be done, and adjustments made, for optimum results, it is a good starting point to work from. With a bit of effort, a professional-quality stereo recording can be achieved, with coherent phase, and a wonderfully wide, spatial aspect to the sound. If, after a few tries, the adjustment part of this is frustrating you, I suggest placing the mics so that they face outwards, away from each other a bit (even as much as 90 degrees), so that the aspects of each side of the source that each mic captures will be truly unique, giving even better phase consistency in mono.

Just to make a point about mono checks, while many folks rationalize that music nowadays is almost always heard in stereo, and that "their" mix will "never" be played in mono, they are fooling themselves. Most AM radio, some FM stations, many hotel, commercial and institutional applications, and most live-sound systems will take whatever is input, and send it out in mono, so if your mix is not mono compatible, you may get an unpleasant and public surprise, more often than you'd like.

Go back to Part 1 of this article

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Eventide H8000FW

The Eventide H8000FW is a fully-programmable, multi-channel, multipurpose, 24 bit, 96kHz-capable, dual or monolithic (both processors used to support one huge algorithm) topology digital signal processor (DSP) audio effects processor with UltraShifter™ capability. That's a lot of adjectives, but the H8000FW is a lot of processor! It is the flagship of a long, proud line of digital signal processors that stretches back to a time when most audio manufacturers didn't know digital audio from Morse code.

The H8000FW is loaded with features that put it in a class by itself. It has eight AES/EBU digital inputs and outputs, eight ADAT digital inputs and outputs, two S/PDIF digital inputs and outputs, and four analog inputs and outputs, plus a total of 16 IEEE1394 Firewire ins and outs. Routing among them is very flexible. The H8000FW houses two independent signal processors, each having eight inputs and eight outputs (imaginatively dubbed "DSP A" and "DSP B"). The two processors can be run in parallel, in series, or in any mutant variation thereof. In addition, the H8000FW can run "monolithic programs" that use the processing resources of both DSP A and B to run just one large program.

The variety and depth of the programs that the H8000FW possesses are truly amazing, from lush reverbs, to choruses, to flanges, to delays, to pitch shifters, to dynamics, to EQs, to filters, to distortions, to synthesizers, to samplers, to ring modulators, and everything in-between. The H8000FW can do it all. And if that's not enough, DSP A boasts nearly three minutes of sample time in addition to the 44 seconds of delay time found on both DSP A and DSP B!

For the user who is interested in making his or her own programs (if the huge number of onboard factory programs - over 1800 - aren't enough!), the H8000FW continues the "modular programming paradigm" that made the DSP4000 and its offspring famous. Programs are composed of individual building blocks, or "modules," that allow the user to create and custom-tweak totally original programs - each program is its own algorithm. Inspiration and creativity are given no bounds.

If the world's highest-calibre, multichannel effects processor is something your work demands, or, if you want to do sophisticated, integrated effects processing in a 5.1 or 7.1 surround environment, within any type of audio system - even from right inside your DAW - there is only one solution - the Eventide H8000FW.

Contact Rock Shop Pro Audio for information and pricing on the Eventide H8000FW and Eventide products.

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Wave Phase and Cancellation - Part 2

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