VERTICAL
4.2: POSITIONING
This is the monitor equivalent of a wheel alignment. Where do you aim the speakers to give you the smoothest and most consistent sound, and how far apart do you place them to give you a good stereo image? The basic rule is to follow the layout of an equilateral triangle. The distance between the two monitors should be roughly the same as the distance between one monitor and your nose in the listening position where you are leaning forward on the console armrest. See the following diagram.
Now, if you were to follow the all too common practice of lying your two way monitors on their side to give you better sight lines over your meter bridge, you can see (and hear) what will happen. With the monitor on its side, moving your head horizontally means you are now moving through all those rays, or lobes, where the wavefronts from the woofers and tweeters interfere with each other. The midrange frequency response will be different for each head position. All two way component monitors, no matter who manufactures them, need to be used with the multi-driver axis vertical (that�s just the way it has to be when you�re in the near-field). And if you�re wondering how three-way near-fields work with a whole bunch of speakers stuck all over the baffle, well... you�ll quickly realise why we stopped at two way speaker systems.
The speaker axis (shown on the diagram) should be aimed at the halfway point between your furthest forward and the furthest back listening positions (as indicated by the two heads on the diagram). This is typically a range of about 24" (600mm). If you can, you should line your ears up with the vertical speaker axis (half way between the woofer and the tweeter). Remember the earlier drawings showing your ears and the speaker, these were to get your normal listening position lined up in the best spot possible. If this would have you resting your chin on the console, you could tilt the monitor back slightly. This keeps your head in the sweet spot whether you�re leaning forward adjusting level or EQ, or leaning back and listening to the mix. Don�t go crazy trying to get this exact to three decimal places, within a few inches will suffice. Your Tannoy monitors have a wide sweet spot both horizontally and vertically to reduce the variations in sound quality as you move around doing your recording engineer stuff. Turning the monitors in like this has an added benefit of keeping the high frequencies from reflecting off the walls and outboard gear.
4.3: CONSOLE REFLECTIONS
The number one killer of smooth near-field monitor response is the mixing console. Most people park their near-field monitors on top of the meter bridge, which makes the console top the most influential reflecting surface for the sound you hear when you�re mixing. How important is that reflection? If it were such a big deal, wouldn�t people have done something different by now? Let�s face it, this industry is not exactly quick to acknowledge a situation that makes it apparent we�ve ignored a problem for the ten years or so since near-fields became popular. So you still have reservations as to the significance of this reflection? OK, dig out your pink noise generator, it�s time for an experiment. You�ll need an assistant from the audience for this. Have your assistant hold your monitor up in the air about 600mm (24") from the top of the console while feeding pink noise through it. Make sure you�re listening right on the speaker axis (that line between the woofer and tweeter), and have your assistant slowly lower the monitor onto its perch on the meter bridge. Hear that change in midrange character as it gets within the last foot of the console? How different did it sound when it was up in the air. There�s two significant things happening here. The first problem is comb filtering (interference) caused by the reflection from the console top taking a fraction of a second (and a tiny fraction!) longer to get to your ear than the sound directly from the speaker. And you thought you couldn�t afford a Flanger for your studio. You may have noticed that in the last foot prior to touchdown on the console the main sonic change was in the midband area. There is a real cruelty associated with laws of physics, the speed of sound in air gives us wavelengths in the midrange area that just seem to coincide with the dimensions of everything we mount speakers on, maximising the problems created by these reflections. The previous diagrams (horizontal and vertical) that show the interaction between a separate woofer and tweeter also demonstrate the problem generated by the reflection. Substitute the reflection for one of the drivers in the diagram and you�ve got a pretty good picture of what happens when the original wavefront and the reflected wavefront meet. The big problem with this comb filtering is that you can�t fix it with any terrestrial equaliser, once the waves cancel there is nothing left to boost. You may also notice that as you move your head, the filtering changes, so any equalisation you attempted to apply for one position would be detrimental to all the other listening positions. We mentioned that there are two things happening here. The second thing is a change in directivity caused by the addition of a boundary (the console top). When you want to shout at someone outdoors you cup your hands around your mouth to increase the directivity of your voice. By placing the monitor on the meter bridge, you�ve done the equivalent of putting one hand to your mouth. In the lower midrange (200-800Hz), where the wavelength is long enough at 400mm-1400mm(16"-55") that you don�t get cancellation, you get the wavefronts adding together. This causes an increment in the level over the lower midrange area at the same time that holes appear in the midrange from comb-filtering effects. Now that you�ve begun to believe it is impossible to use near-fields on a console top, we�ll talk about what you can do to help alleviate these problems. The first thing you need to do is be able to identify the surfaces that are close enough to do serious harm. You can do this at great expense by using a real time analyser, and spend a few months learning to use it, OR, you can grab a length of string, some gaffer tape, and a mic stand, and get set for another experiment.
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