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SPL Stereo Vitalizer

Psychoacoustic Enhancer

Since its launch just a few years ago, the SPL Vitalizer has made a major impression on many of those who have used it. Paul White tests the new stereo version, which features a simplified control panel — and a lower price tag.

The Vitalizer is one of those products that falls into the nebulous realm of psychoacoustic enhancers — those devices whose sole aim in life is to make a recording sound bigger, brighter and better than it originally was. Most use either harmonic synthesis or some form of sophisticated equalisation; the Vitalizer falls into the latter camp, though its Harmonics control has a very similar subjective effect to its counterpart on a harmonic enhancement device.

Now the Vitalizer has a dedicated stereo companion, which doesn't replace the original but rather offers a lower-cost alternative for those who require only to process stereo signals rather than independent mono channels.

While the original Vitalizer had two completely independent sets of channel controls, its new sibling uses a single set of ganged controls to adjust both channels simultaneously, which results in a much simplified control layout. There's a Sub-Bass control to provide a choice of either hard or smooth bass EQ, a Mid-Hi Tune control to determine which part of the mid-range is to be processed, and a Harmonics control to add sparkle to the top end. The overall depth of effect is determined by the Process control, while the Active switch enables the process to be bypassed for rapid A/B checking. Like the original Vitalizer, the Stereo version has a Surround Processor to increase the effective stereo width of a mix (see box), and one useful inclusion, absent on the original, is a separate Active button, which independently bypasses the Surround Processor.

Physically the unit is quite ordinary, its 1U casework finished in black with cream screen printing. The review model was fitted with both jack and XLR connections, but a 'jacks-only' version is also available; both can run either balanced or unbalanced. To facilitate connection to systems operating at different signal levels, there's a rear panel High/Low level switch, along with a Ground Lift switch to help avoid ground loops. Front panel Peak LEDs flash when the input signal is in danger of being clipped. A recessed switch enables the unit to be set for either 220V or 115V operation and mains is supplied via a standard IEC cable and socket.


Most of what the Stereo Vitalizer does can be categorised as equalisation, though the circuitry that produces it is radically different to that used by conventional equalisers. It would seem that several signal paths are combined to produce both additions and cancellations across the frequency spectrum, and though the result is in some ways similar to that produced by a dynamic equaliser, the designers claim that no dynamic EQ, in the accepted sense, is used.

Even the Harmonics section is said to work differently to the usual harmonic synthesis systems — though there is a VCA in the circuit and, judging from the type of VCA used, it could well be that new harmonics are generated as a kind of side-benefit. The Vitalizer's chief designer has tried to explain its operational principles to me on several occasions, but because of his difficulty in expressing his concepts in English, and my difficulty in following them, I'm afraid the exact working method still remains as much a mystery as ever.

However, the subjective effect of the controls is rather easier to describe. Taking the Sub-Bass control first, this is a centre-off type of control which produces a full, rounded bass boost when turned anti-clockwise from centre, or a hard, attacking bass sound when turned clockwise. These two options are designated Soft or Tight. I gather that in the Soft direction, the bass boost occurs over a fairly wide region, whereas the Tight option combines bass boost with lower middle cut so as not to allow the effect of the bass increase to muddy the lower mid-range. In practice it works exceptionally well. The Soft setting creates a deep, powerful bass sound which works well on synth 'pedal' notes or dance rhythm tracks, while the Tight setting produces a more focused sense of punch that really kicks. The overall amount of effect is linked to the setting of the Process knob which works roughly (but not exactly) like an master effect depth control.

The Mid-Hi Tune control serves a dual function in that it directly modifies the mid-range and, at the same time, influences the signal fed to the Harmonics section of the processor. A mid-range setting of around 3.5kHz seems best for most material, and frequencies below the value selected seem to remain unaffected. As far as I can tell, the Harmonics processor is fed from a combination of the untreated input signal and the output from the Mid-Hi tune filter. Adjusting the Mid-Hi tune control adds an air of clarity and tightness to the mid range but without adding the sizzle you'd expect from a conventional exciter. This sizzle may be introduced by using the Harmonics control, but the fact that its amount can be varied relative to the mid-range enhancement adds greatly to the flexibility of the unit.

As mentioned, Process Depth behaves roughly like a master effect depth control, but in reality, the nature of the processing also changes as the depth is increased. For example, using a low level of Sub Bass boost combined with a high Process setting produces a different subjective result to using a high level of Sub Bass with a low Process setting. This interactive aspect of the controls is what makes the Vitalizer so powerful, and though excellent results can be achieved with all the controls set close to their vertical positions, a little experimentation often produces very worthwhile results.


The Stereo Vitalizer sounds indistinguishable from the original Vitalizer, which remains my favourite of all the psychoacoustic enhancers I've tried. In building a stereo version, the designers have made the unit easier to use on a stereo signal, but by the same token, it isn't now possible to add different degrees of processing to two mono signals at the same time. Having said that, I nearly always use my own Vitalizer for treating either entire stereo mixes or stereo submixes, so the omission of the dual mono mode doesn't represent a major loss. Perhaps the main benefit of linking the controls is that the two channels are always properly matched, though for many people the reduction in price might be seen as an even more attractive 'feature'.

For those of you who haven't used a Vitalizer before, I feel the main benefit of both versions is that they appear to do for the whole audio spectrum what the original exciters only did for the very top end. All the benefits of increased presence, spaciousness and enhanced detail are present, but these are combined with an effective bass enhancement system and a degree of midrange processing which has the effect of sieving all the unwanted mush out of a mix without making it sound over-processed. Like any enhancer, it can be over-used, but a little experience soon makes it evident how much processing you can get away with.

As always, I'll include a warning: don't expect any psychoacoustic enhancer to provide a complete solution in the case of a desperately bad mix. It's true that some shortcomings can be remedied by the careful application of these devices, but they should be looked upon as a means to transform a good recording into a great one, not as an excuse to produce indifferent work and then attempt to fix it in the mix.

The Stereo Vitalizer still costs more than twice as much as some of the cheaper exciters, but we are now well into the quality-conscious age and it usually pays to buy the best and then stick with it rather than buy something you're not really happy with, only to trade it in at a loss a few months down the line. Of course, you should check the Vitalizer against its numerous competitors before you make up your mind, but I think it offers something just a little bit special that makes it worth the extra.

Further Information

Stereo Vitalizer £652 (jack version); £762 (XLR version). Prices inc VAT.

The Hame Service, (Contact Details).


Effective over the whole audio spectrum.
Useful stereo width expander.
Very flattering sound.
Easier to set up than the original Vitalizer.

Still significantly more expensive than most of its competitors.

An incredibly versatile enhancer for use in mixing, mastering or post production.


For those familiar with the original Vitalizer, the only obvious omissions are the Normal/Deep switch on the bass processor and the Mid-Hi Tune Q control which nobody seemed to use anyway. There's also no Dry Kill switch, which was useful in allowing you to check exactly what was being added to the signal, and also enabled the Vitalizer to be used in an effects send/return loop.

Digging a little deeper, the Stereo Vitalizer has only two input level settings whereas the original has a multi-way level selector switch, and the metering on the original has been replaced by a simple peak LED system.


The Surround Processor is actually a very simple stereo width enhancer based on the principle of feeding anti-phase signals from one channel into the other. Used in moderation (about 2 o'clock on the control knob), the effect is to push the stereo image out, making it appear slightly wider than the speakers, but for some reason, this also appears to make the overall mix subtly brighter. This may be because the anti-phase sounds are high-pass filtered to avoid any phase problems at the bass end, but I have no hard information to confirm this. Whatever the reason, the effect is rather flattering. This type of processing is also thoroughly mono compatible; the act of summing the two channels to mono causes the added anti-phase components to cancel out entirely leaving only the original signal. In addition to being useful for widening complete stereo mixes, the Surround Processor is equally effective in spreading treatments such as reverb or multitapped delays.

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Del Palmer

Sound On Sound - Copyright: SOS Publications Ltd.
The contents of this magazine are re-published here with the kind permission of SOS Publications Ltd.


Sound On Sound - Dec 1993

Donated by: Rob Hodder

Gear in this article:

Studio FX > SPL > Stereo Vitalizer

Review by Paul White

Previous article in this issue:

> Morphology

Next article in this issue:

> Del Palmer

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