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Vesta Fire GAE-110 Graphic Analyser/Equaliser



Historically the preserve of the acoustics technician and loudspeaker designer, the Spectrum Analyser is still a rare sight in the majority of semi-pro studios and is unlikely to be found on many home recordist's equipment shopping list. The reason being due to a lack of understanding about the benefits of such a device and more specifically the previously prohibitive price.

This latest unit from Vesta Fire changes the latter situation, combining, as it does, both a spectrum analyser and a graphic equaliser into one package costing a few hundred pounds, with the added attraction of 'computer control' ie. it's fully programmable.

Before I move on to describe the GAE-110 unit in detail, now is probably an opportune moment to say exactly what a spectrum analyser is and why it is useful.

Basically, a spectrum analyser is an electronic device that splits the frequency content of any sound into specific frequency bands, and displays this information visually. It is a useful way of representing a sound and thus discovering more about how it is constructed. These devices have found their way into PA system applications recently, as well as in studio monitoring, where they are used to discover how the loudspeakers inter-react with the natural acoustics of the room in which they are located and their combined effect on the sound. Once a display (or analysis) is available of where the signal energy is located across the frequency bands, a graphic equaliser can be used to boost or cut the level of each band to achieve an overall 'flat' response. Such a response is generally what you are looking for from every device in the monitoring chain, be it amplifier, mixing desk or loudspeaker. Without this flat response, the sounds heard will be unnatural, distorted and 'coloured'.

This causes problems when recording because you need to rely on and accept what you hear through your speakers as being a 'true' representation of the sound at source. However, if your speakers colour that sound, then this will not be the case, but you could employ a spectrum analyser and graphic EQ to compensate for the deficiencies of the speakers and/or the sound modifying effects of an untreated room, to produce a more realistic picture.

Ironically, the spectrum analyser is probably most needed by the home recordist rather than the professional studio, as the latter has the time and money to ensure that speakers and amplifiers have the best and flattest frequency responses, and that the detrimental effects of room acoustics are minimised from the very start. However, the average home recordist beavering away in his back bedroom, is probably monitoring his/her recordings on a grotty pair of highly-coloured hi-fi speakers in a room with absolutely no acoustic treatment, totally unaware that the recording is drowned in bass because the speakers are deficient in this area. When the recording is subsequently played on a correct, flat monitor system, there will be too much bass and the recording will be ruined!

Well that about covers the theory and uses of a spectrum analyser, now let's take a look at what the Vesta Fire unit offers.

GAE-110



The unit is smartly finished in a 19" x 3½" (2U) rack-mounting black case, and incorporates a ten band graphic equaliser with program storage capabilities, and a real-time analyser with built-in pink noise generator (more of this later). Although configured for stereo operation, the left and right channels are not independent, but share the equalisation characteristic set by the one graphic.

The device has obvious uses for hi-fi set-ups and not unnaturally, connections are provided on the rear panel specifically for tape playback facilities, in the form of phono sockets and jack sockets. Line In/Out sockets are also provided for general connection within your recording set-up.

The front panel is dominated by ten 12 segment LED meters that have a bright response when programme material is fed into the device. The outermost meters also double up as Left and Right output level indicators. The graphic/analyser share the one display and cover a ten octave frequency range from 31.5Hz to 16kHz in octave (double frequency) leaps. Each meter refers to its respective frequency band, and has an individual selector button below it.

To the right of these meters are two 'windows'. The top one has a green readout for the current equaliser program, ranging from 0 to 9, and the lower one displays the direction in which the graphic's LED fader will move, dependent upon the selection of Up/Down status via the pushbutton to its right. This is indicated by a green, illuminated arrowhead.

Input level to the unit is determined by the Mic and Line selector buttons, and the level controlled by a horizontal slider labelled 'Volume'. If used as a graphic equaliser, input will be at line level. Mic input will only be used when the spectrum analyser is operative and a ¼" jack-socket is fitted to the front panel to accommodate the connection of a microphone when undertaking an analysis.

Output is switchable between Line or Pink Noise, the latter being necessary for the analysis mode only. Operation mode is selected via one of three front panel pushbuttons, the choice being: Equaliser, Real-Time Analyser or RTA + Level, and with all modes a red LED lights to indicate your choice, whilst the meter display changes to the relevant readout.

To help with comprehension, the display decay ie. how long it takes each frequency meter to return to zero level, can be set for slow or fast. This is only of use in the analyser mode and with 'fast' chosen, the meter functions in a similar manner to a PPM in that it responds well to signal peaks, whilst it resembles a VU meter's 'average' response when 'slow' has been selected.

The final button, Bypass, lets you hear the equalised or direct signals for quick comparisons and is a necessary inclusion, as the human ear quickly adjusts to changes in EQ, with the result that you can forget what the original signal sounded like in the first place. Bypass lets you use the direct sound as your reference, so there should be no over-use of EQ - a common fault.

Equaliser Memory



There are ten non-volatile memories permitting the storage of equalisation settings defined by the EQ curve display. A memory is selected by pressing the 'Memory' button adjacent to the number display. Repeated pressings step through the memories in ascending order, 0 to 9 then back to 0. Each time the memory increments, the graphic display shows the frequency settings programmed into that memory, and the equalisation is imposed on the signal passing through the unit, immediately.

I found it of immense educational value to have the facility to preset bass, mid or treble boost, for example, and see and hear, the changing effect of the different equalisation. Using the GAE-110 in this manner is an enjoyable way of learning more about the effects of EQ and its possible applications. With any signal going through it, you soon learn which frequencies are the best to boost or cut for a particular sound.

Unlike a conventional graphic, where the 0dB or 'flat response' position is set in the centre of each slider control, with the Vesta Fire unit it is arbitrary. As there are 12 segments per meter in total, and each one represents a 3dB change in level, you can set your 'flat' position at the bottom of the meter and effectively allow yourself 36dB of signal boost (but no cut) - or any permutation within the limits of the meter's range.

The graphic is easy to use. Modifications can be made to any memorised program at any time, as the unit is permanently in the write/edit mode. You simply select Up or Down, then press the selector button(s) below the frequency band(s) you want to change, and the illuminated LED segments) will step up or down producing an immediate boost or cut in the programme signal.

Once you're happy with the necessary EQ curve, you can store the final setting in the memory (indicated in the top right display) by pressing the 'Write' button once. You then recall that equalisation by dialling up the relevant memory number.

Real-Time Analyser



This function is used to equalise your monitor speakers to a flat response in order to compensate for the colouring effect of the playback room's acoustics.

To do this you select 'R.T. Analyser' mode on the front panel and push the 'P. Noise' button. This sends a continuous burst of pink noise (noise containing equal energy per octave frequency change) to the line level output sockets, the level of noise being controllable from a small, rear panel-mounted rotary control. The noise then feeds the monitor speakers which must be set at the same playback level as when mixing music or whatever.

An omnidirectional microphone, with a very flat response of its own, should be set up in the same position in which you'd be sitting when monitoring, and connected to the socket on the front panel. This picks up the sound of the pink noise coming from the monitors and displays the response on the unit. You should be able to see the colourations caused by a combination of the monitors and room acoustics as peaks and troughs in the readout. The ideal display would indicate a flat frequency response with all ten segments in a straight line.

To achieve this you need to switch to Equaliser mode and set the curve to be a copy of the analyser's readout. Obviously, the fact that the GAE-110 only has ten frequency bands, each divided into 3dB increments, means that the unit cannot perfectly equalise a room, but it is certainly better than nothing at all.

A professional studio will employ the likes of a pair of 27 band, one-third octave graphics (due to their extra degree of accuracy) to equalise the room, incurring considerable expense in the procedure. To tie up two very expensive units permanently in this way is a necessary evil of studio life, as very few studios can attain a flatly equalised control room without resorting to graphics.

The silly thing is that as soon as the acoustic environment of the control room alters, for example, by four band members entering the room all wearing woolly jumpers, the flat response will disappear, as the jumpers will provide a source of high frequency absorption. Strictly speaking, the room should be continually analysed and the equalisation curves updated to compensate for any changes, but this is impractical so a compromise results.

Conclusions



A large section of this review has been devoted to the theory and uses of spectrum analyser/equalisers rather than specifically to the Vesta Fire product. This is partly through necessity and partly because the GAE-110 is such a good unit, for which I have nothing but praise, that fault could not be found with it. Construction is good, the unit is extremely reliable and, put simply, works!

This model is essentially a direct copy of the dbx 20/20 computerised equaliser/analyser which sells for ridiculous sums of money. In operation it was extremely quiet with very little noise emanating from the unit. As a package it is hard to beat for the price. If it contained only a ten memory programmable graphic, it would still be good value. The fact that it contains a good quality spectrum analyser/pink noise generator as well, just makes it even better value.

If you've never looked at the possibility of a spectrum analyser in your studio, or even for PA use, then think again and check out the Vesta Fire GAE-110. Highly recommended.

Price of the GAE-110 is £713 inc VAT.

Distributed in the UK by MTR Ltd, (Contact Details).



Previous Article in this issue

Aphex Aural Exciter - Type B

Next article in this issue

Using Microphones


Home & Studio Recording - Copyright: Music Maker Publications (UK), Future Publishing.

 

Home & Studio Recording - Apr 1984

Donated & scanned by: Mike Gorman

Review by Ian Gilby

Previous article in this issue:

> Aphex Aural Exciter - Type B...

Next article in this issue:

> Using Microphones


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