Quantec Room Simulator
Realistic digital reverberation is still only available from effects devices at a somewhat prohibitive cost. Granted the introduction of the R1000 digital reverb from Yamaha has now provided a low-cost alternative, at around £500, but the reverberation obtained from is is ridiculously unrealistic when set side by side with that Quantec Room Simulator. This difference in quality and flexibility is justifiably reflected in the price differential too, for you could buy twelve Yamaha units for the cost of a Quantec (but still be unable to simulate one tenth of the facilities it offers)!
Basically, the Quantec is a very high quality stereo digital reverb unit (with a built-in stereo echo) capable of simulating virtually any enclosed acoustical environment. It is best to think of the unit as a room containing two loudspeakers (the sound source ie. inputs), with four microphones located one in each corner (outputs), that pick-up the ambience created by the sound from the loudspeakers being reflected off the boundary walls of that room. The characteristics of this imaginary room can be modified totally using the parameter controls on the Quantec, allowing the simulation of anything from a wardrobe (empty or full of clothes) to a cathedral.
The circuitry by which all of these wonderful 'rooms' can be created, is housed in a lightweight 2U high case that can be mounted in a 19" rack. All connections are rear panel mounted, whilst the black brushed aluminium front panel contains the reverb program controls. LED bargraph meters provided for the Left and Right inputs and four channel outputs are clearly calibrated from -72 to +12dB (clipping).
The centre section is given over to the parameter controls which define exactly the characteristics of the acoustic environment. Each has an associated LED display readout that is clearly visible. Parameters can be set in two manners; either by stepping through the possible settings using the '+' and '-' pushbuttons when fine control is required, or by an infinite turn, 'click stop' rotary control that provides coarse adjustment once one of the ' +/-' nudge buttons has been touched on the relevant parameter to be modified. This is a precise, neat arrangement that keeps the front panel free of unnecessary knobs.
There are eight parameters: 1st reflection, which can be varied from a 1 to 200 millisecond delay (in 1ms steps) with its own level control (-30dB to 0dB, plus 'off') and reverb pre-delay, which also has 1 to 200ms time and level parameters.
The reverberation itself has three variable settings; reverb time (variable from 0.1 to 100 seconds in 41 different steps). This is modified by the HF and LF controls which determine the reverberation decay at high and low frequencies, as natural decay of sounds occurs at a faster rate at high frequencies, dependent upon the acoustic treatment of the room surfaces. Thus by selecting a fast decay at high frequencies a room with soft, absorbant materials in it, can be simulated. The decay controls act by multiplying the basic set reverb time by a coefficient selected on each parameter - HF ranges from 0.1 to 10 (in 11 steps), for example. Between them, virtually any character of room covering can be produced and in conjunction with the last parameter - room size - can simulate any environment.
Room size can be defined from 1 to 1 million cubic metres in 6 steps - 1, 10, 102, 103 etc. These decade steps seemed far too coarse on initial appearance but turned out to cover every conceivable requirement quite adequately when used with the other parameters.
Using these controls a reverb 'patch' can be created and then stored in any one of 64 possible memory locations which are non-volatile ie. they won't be erased when power is switched off. This is achieved via the remaining group of memory function buttons to the right end of the panel.
The memories are configured into 8 'files' each with 8 'locations'. These are dialled up simply by pressing the button marked with an asterisk (*) or an equals sign (=) for file or location respectively. A red dot appears in the LED window and then the file or location is selected by pressing the required button numbered 1 to 8. Each time a memory program is called up the stored parameter values automatically appear in the various displays. This is excellent as it removes the need to jot down settings on paper, whilst also teaching you subconsciously how particular values sound.
Once displayed any value can be modified. However, such editing can only take place in memory location 1 of any file, thus, in order to edit a program it must be copied to location 1 first. This is a simple enough task achieved by pressing button '6', the equals (=) button, and then button '1', if you wish to modify program 6, say. To edit, you then press either nudge button (+/-) for the parameter you wish to alter and increment or decrement the setting using a combination of nudge buttons and rotary knob. The parameter display being modified 'blinks' to identify it.
Once completed editing, the modified program can be re-stored in any memory location of the file. All locations from 2 to 8 are automatically protected from erasure as only location 1 is active, which provides a fine degree of security. For convenience when mixing tracks, the required reverb programs can also be copied from one file to another and placed in a logical order ready to be called up - a practical touch that proved a godsend on complicated mixes.
The final front panel controls have been left until last as they provide a range of effects that turn the Quantec into more than just a digital reverb unit. The four buttons are labelled Enter, Mute, Freeze and Enhance and between them they initialise the 'Freeze' and 'Enhance' modes of operation.
Selecting this causes all reverberation to cease and pressing Mute cuts the output signal and clears out the memory. Freeze mode is similar to an 'infinite repeat' facility on a digital delay and simulates a sound source that is trapped within a non-decaying room where the sound is continuously bouncing from one wall to the next without dying away. Any number of signals can be sent to the 'room' using the Enter button. The effect produced is stunning when a vocal harmony is built up and 'frozen', for example. Great fun was had by freezing sounds, then letting them decay slightly ready to be refrozen. On a synthesised chord this treatment sounded tremendous.
This second special effect mode sets the Quantec apart from other digital reverb devices in a similar price range. What it does is simulate a room acoustic with no perceptible reverberation. This is very hard to imagine, but the closest thing to it would be hearing yourself speak whilst having a cardboard box over your head! It is this mode that lets you simulate the sounds heard inside a wardrobe or metal tank, to take but two unusual examples.
Enhance is also capable of synthesising 'dummy head' binaural recordings if monitored on headphones, and can produce an effect similar to an Aphex Aural Exciter, compressing and intensifying input harmonics which really pushes a treated sound to the foreground of any stereo mix. I used this mode on lead vocals to great effect, whilst on a Roland TR808's bass drum it produced a dynamic, punching sound that cut through a rather 'muddy' mix very effectively.
The Quantec was put through its paces at the Newcastle Media Workshop Studios (see review in this issue) whose quadrophonic monitoring system via Tannoy Ardens proved an ideal way of evaluating the various interconnection possibilities of the device.
As the Quantec is a stereo unit it really needs to be fed from a stereo echo send on a mixer, connected to the XLR input sockets on the rear panel. Outputs 1 and 2, which include the mixed-in 1st reflection information, are best used as Left and Right returns patched into two spare input channels of the mixer and panned hard left and right. For quad use, all four XLR outputs are required naturally. One especially useful facility of the device is the reverb level control. This is best used to control the gain of the reverb return signals, instead of the mixer's own return control, as it can be stored in memory for various settings and will not require adjustment during a multi-track mixdown.
The reverb 'tail' response was superbly smooth in use, absolutely free from the incessant 'boing' sounds associated with reverb spring devices and the 'hiss' produced by echo plate units. The internal circuitry accepts signals with a dynamic range up to a staggering 150dB, so signal overload is out of the question unless levels are mis-set in the first place. When changing settings whilst an input is connected, the output is very nicely muted to prevent unwanted switching noise - a vital requirement if stepping through memory programs in real time during a mixing session.
The quality of the room sounds is phenomenally good. In a quadrophonic monitoring set up, a tape of a drummer played back through the Quantec gave you the unbelievable impression that the kit was directly in front of you. On headphones, with a small room size and Enhance mode operational, you could have sworn that your head was actually inside each of the drums - who needs Zuccarelli's holophonic trickery when you've got a Quantec!
My favourite reverb program though, was the 'Taj Mahal' preset that comes with the unit. This sounded like the largest cathedral you could imagine, with a reverb decay time of some 400 seconds! When you compare that with the Yamaha R1000's maximum 2.4 second reverb time, you begin to understand the £6000 price tag.
Internally, the Quantec Room Simulator is a delight, consisting of 9 glass fibre PCBs, beautifully soldered with the highest quality components available. Edge connectors are used wherever possible in place of cabling to reduce possible hum and RF pick-up. Virtually all space on the circuit boards is taken up with memory chips but this is understandable when you learn that the Quantec has a breathtaking 2 Megabits of RAM (compared with 48K of a Spectrum computer)! The high quality of reverberation effects is only to be expected from the 16 bit analogue-to-digital converters (one for each of the stereo inputs), whilst the 20 kHz sampling rate determines the fairly limited 8kHz bandwidth, which was never really apparent in use.
The facilities available from the Quantec make possible the creation of highly realistic acoustic environments whose size and acoustic treatment can be controlled completely. Operation is simplicity itself (which is more than can be said for other digital reverbs) and performance quality is beyond reproach.
As a reverb unit alone, the Quantec is extremely good value for money in view of what it's capable of doing, but the inclusion of the special effects section makes it far more attractive proposition. For those who can afford the asking price, then the Quantec must be on your shopping list. For those who can't, there's some consolation in the fact that the cost of memory chips and 16 bit processors is the only thing that prevents the Quantec from having a selling price nearer £1000. The price of such technology will certainly be dropping in the near future, making devices such as this Quantec accessible to a larger number of people. In the meantime, keep your eyes open for the HSR Room Simulator project in our 1994 issue...!
Further details on pricing, availability and demonstrations from. Syco Systems Ltd., 20 Conduit Place, London W2. Tel. 01-7242451.
Review by Ian Gilby
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