Strange devices that MAKE YOU pay attention.
AURAL Exciting Psychoacoustic Projecting Harmonic Enhancer. Any little black box you might come across with any combination or derivation of the above phrase stamped across its front panel is very likely to be one of these.
One of what?
Well, that's the first problem.
If I were to mention the term "aural exciter" then the following topic would be neatly encompassed. However, what I have to say is Aural Exciter as the term is a registered trade mark of Aphex.
In the mid seventies, the Aphex Aural Exciter was an awe inspiring and legendary device that could be hired by the top recording studios to give a mystical presence to their productions. As a technique it was met with some scepticism, largely by people who had not used it and partly because its precise method of operation was kept a secret. Nowadays, there are a handful of other devices on the market which can produce similar effects and, although a lot of the mystery surrounding them has been blown away, to listen to them work can still seem quite magical.
Commonly referred to as "exciters", these devices can be used to enhance more or less any sound source, but they are of most use in situations where high frequency reproduction may be in jeopardy. They affect only the top end of the audio spectrum. With a cursory listen it might appear that someone has simply whopped up the treble, but their real contribution is far more subtle and effective. The various makes on the market all vary slightly in their operation, but basically this is what they do.
The high end of the input signal is fed to a harmonics generator which produces another set of harmonics higher than the original sound, but with frequencies which are still related to it. These new frequencies are then compressed a little and fed back in small proportions to mix with the original sound. In consequence the resulting sound will contain more top end than when it went in. This type of treatment is just the ticket if, due to track bouncing or tape copying, a recording has lost some of its high frequency content. Increasing the treble would not have helped as you cannot boost what is missing from the tape. The exciter will actually re-synthesise a top end for you, and although it will not necessarily be the same as the one that was originally there, the subjective appraisal is generally one of improvement.
It is usually the case with most sound equipment, be it studio or stage, that the highest frequencies are the least faithfully reproduced. This is a bit of a shame when we consider that these frequencies often carry a lot of the pleasure for the listening experience. The psychoacoustic properties attributed to exciters are largely due to the fact that these added high frequencies not only increase brightness but also perceived loudness and stereoseparation. Individual instruments when treated with an exciter will take a step forward in the mix without any rise in level being apparent on the meter.
This effect is used to extremes by radio and television advertisers, and contributes to the leaping offensiveness of some commercial breaks. Listen for the sizzle in some television ad voice-overs — this is excitement used to excess! When used musically you may, with experience, be able to guess when an exciter is in play but it should not stick out like a sore thumb.
In use, the simplest of exciters may only have an input or "drive" control and a mix control with all other parameters fixed. The drive determines the level of signal passed for treatment (appropriate levels indicated by LEDs), and the mix controls the level of effect which is added back to the original signal. The temptation is always to overdo the amount of effect mixed in and the ears rapidly become very accommodating towards the excessive excitement, only to be shocked by what they have allowed when listening back at a later date. In other words, a light nibbling is usually preferable to a poke in the ear.
Other controls offered may be "frequency" or "tune" and "width" or "resonance". The frequency controls the area of sound to be selected for treatment. At its highest setting only cymbals and sibilants will be affected. As the frequency is lowered so a larger area is encompassed bringing in voice, synths, guitars and so on. The width control can help to pinpoint the target area.
Possible uses for an exciter are boundless. Most models are supplied as stereo pairs so that complete stereo mixes can be enhanced. Muddy old demo cassettes when copied through an exciter can often end up sounding better than the original. The hi-hat can re-appear as if by magic and the vocals suddenly become intelligible. Improvements can also be made to many instruments both as they are being recorded, and off-tape. Drum tracks especially can be brought to life, and vocals can be given an intimate breathy closeness.
Uses are in no way limited to the studio. An exciter across the mixer outputs of a PA can improve the perceived sound quality in many an awkward venue. They are also of great value in lifting the vocals above the backing with reduced risk of feedback.
An exciter well used is a simple and effective way in which to put the polish on any production.
Feature by Martin Sheehan
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