Often an area of great confusion and debate, soundstaging and imaging is a subject that needs to be properly understood in terms of both musical presentation and hi-fi functionality. Over many years now, throughout our research and product development, we have learnt a great deal about 3D soundfield perception, the science of signal behaviour and the reproduction of signals in a stereo context.

Here let’s consider the elements of left, right and central perception. The obvious mechanism is simply a level difference between channels, but the more important one probably, is the phase difference between channels. Phase difference relates to time of arrival; if a sound comming from the left channel arrives with a phase shift ahead of the right channel, it is interpreted as arriving at your left ear before it arrives at the right ear. Your brain decodes this time difference and assumes it is a single wave comming from a specific position to your left.

Interestingly though, if a signal is reproduced purely in the left channel, you can only ever hear it comming exactly from the location of the left speaker. But include some of that signal in the right channel, with a significant phase delay, and the brain translates this as the sound emanating from well outside the position of the left speaker. So ironically, it is by having the correct signal coming from the right speaker, that throws the image out to the left, and vica versa of course. For a good example of how effective this phase-shifting can be, listen to something like Roger Waters in QSound (deliberately enhanced phase shifts). On a good system you easily perceive sounds up to 90 degrees to the listening position. But most surprisingly, for some real gains in understanding and performance, the issues with a central image are perhaps the most important. Equal volumes are part of the process, but an exactly in-phase signal from both channels is the real essence of a crisp central image.

Lets assume we have a track with a rich, well recorded central image, some vocals say, but this track also has lots of supporting music in the mix – there is quite a lot going on. The first thing that is fundamentally important, but so often completely overlooked, is the distance from each speaker to your listening position. Yes, we move them around, thinking of room response etc, which is very important, but the direct propagation distance from each speaker to your ears is essential to consider too. Think of that central image recorded on your disc – the image position is set primarily by it being in-phase from both channels – but if the propagation distance to your ears isn’t equal, you wont hear it in-phase. So it won’t appear to be central, but off to one side.

But there’s more. The whole sound, the tonality of that central image is formed by a composite signal from both channels, and if it does not arrive at your ears with the phase as intended, the signals create an interference pattern, they intermodulate, resulting in a very clearly audible harshness to the tonality of the sound. Yes, lets state that again – if the distance from your listening position to each of the speakers has any appreciable difference, central images will sound harsher than they should do. And what sort of distance are we talking about here? Well, we find that a difference greater than 5mm becomes audible!

You simply have to try this out, to get a real understanding of this effect. With an assistant, and a long tape measure, carefully measure from the front of your chest to the face of each speaker. Keep sat very still in your listening seat whilst the other person goes from one speaker to the other. Adjust the speakers and repeat until you have minimised the difference best as you can. With a bit of practise you can get the error down to under 5mm. Then listen to that good recording again – we are pretty sure the results will speak for themselves. And of course, now all this phase information is arriving at your ears as intended, you should also get a significant improvement in far left and right placement, where images should be much crisper and cleaner. When you now play a complex mix with lots of phase information, the overall results should be much, much better.

But where does this come into the Vertex debate? Well, once you have discovered the significance of phase information, and the issue with speaker placement, you can then very clearly hear massive further improvements when you use Vertex gear. This is because a system suffering from systematic faults adds a lot of its own phase distortion as it play dynamic music. So this again breaks down the imaging and creates intermodulation distortion. Position your speakers correctly and then take those systematic faults away using Vertex equipment, and you will hear truly massive gains in tonality and imaging. Your music simply gets much more realistic and sweet – and really moves way outside the width of your speakers, with smooth and crisp central images too.

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