The Alesis XTC brings high quality digital reverb within reach of the serious budget user whilst retaining a degree of flexibility not expected at the price.

Though I have termed the Alesis XTC a budget reverb device, that doesn't mean that it is cheap enough to be considered by every budget user. Digital reverb is and will always be more expensive than other effect devices that are easier to manufacture, and though we can reasonably expect the cost of such products to fall further in the next year or so, I think that we still have a while to wait before the first £200 digital reverb hits the market.

The XTC is a stereo rack mounting unit offering a bandwidth and dynamic range that even the most sophisticated units on the market will find hard to match. With a typical dynamic range of 90dB, the XTC has an incredible 16kHz bandwidth and its eight basic reverb settings may be extensively modified to give a wide and useful range of natural, gated and reversed reverb effects. In order to keep the cost down, the XTC is not programmable and therefore has no MIDI control but, as the Pre-delay and Reverb Decay controls are in the form of conventional rotary pots, it only takes a few seconds to set up the sound you need. The maximum reverb time is around ten seconds though there is a hold button for infinite effects and all this flexibility comes in a 1U rack mounting package for little more than half the cost of the Roland or Yamaha programmable units.

Controls

Working from left to right, the first control that you come across is Pre-Delay (up to 200mS) which is quite logical in that the pre-delay happens before the reverb part of the sound. For the uninitiated, pre-delay is introduced before the main body of reverberation to create a sense of space and in real life this corresponds to the difference between the reflected sound's path length and the direct sound's path length, as experienced by the listener.

Next comes the effect selection section which really works in binary — I'll explain. Two push-buttons select reverb algorithms one to four depending on their combination, (ie. both out, both in, or both variations of one in and the other out). If this sounds to be a fiddle it's not really a problem as there are four LEDs which indicate the programme selected. Each of these four algorithms has two variations set by the Mod button which again has an indicator LED, and immediately following this section is another rotary control, this time for Reverb Decay.

Moving on then we have another three buttons and the first one of these is Hold which freezes any reverb sound in memory, thereby generating a continuous loop useful for infinite sustain effects. This type of facility can be a great asset if you have any kind of sampler as you can build up a huge layered vocal chant (for example), freeze it, and then sample it to be used later as a sound source. There is also a button for HF Damping and one for LF Cut. On more sophisticated units these parameters would be variable, but by using the EQ on the effects returns on your desk, you can squeeze as much tonal variety out of the reverb sounds as you are ever likely to need. HF Roll-off is fully variable and this is a 12dB per octave filter operating before the signal enters the reverb processor section and it covers the range 3kHz to 16kHz.

Finally we have the obligatory Input Level control complete with six step LED level meter, a Mix control to set the relative levels of the dry and effected signal, and an Output Level control which allows a maximum output level of +12dB, though it isn't stated whether this means 12dBm or 12dBv. Either way it's fairly academic as you get more than enough level variation to match into any commonly used system, from Japanese home recording equipment up to professional studio and broadcast hardware.

Back Panel

As you might expect, the rear panel is a fairly straightforward affair, with all the signal connections being made on ¼" unbalanced jacks. The input impedance is quoted as being 500KΩ whilst the output is 500Ω so you could plug a high or medium impedance source such as an electric guitar directly into the input. Unusually there are two inputs for stereo use which are applicable where you have a stereo effects send facility. The two signals are summed to mono before being processed but the dry portion of the sound retains its stereo integrity. As with most digital reverb devices, the mono input is then processed to give a stereo output. I was once asked how a mono source could possibly be processed to give stereo reverb and the best answer that I can think of is that you can record a singer in stereo even though he or she has only got one mouth. It's the reflected sound within the environment that gives a sound its spacial identity, not necessarily the source of the sound. If you only have a single input you plug it into the socket labelled Mono which will then feed the same thing into both channels and still give you a stereo output.

There are a further two sockets which form an effects loop enabling you to patch in another processor before the reverb processor. Whatever is connected into this loop does not modify the dry signal. The sort of effects that you might patch in here is extra equalisation, further delay or even a pitch transposer.

The fuse holder is depressingly ordinary and the captive mains lead is well secured by means of a strain relief bush so you needn't lose any sleep over that detail.

"The XTC has an incredible 16kHz bandwidth and its eight basic reverb programmes may be extensively modified to give a wide and useful range of natural, gated and reversed reverb effects."

In Use

And now the bit that you've all been waiting for. After all it doesn't matter whether the thing's affordable or not if it sounds like a dustbin full of nails. Fortunately it doesn't sound like a dustbin full of anything.

In order to assess the unit in context, I set it up along side a Klark Teknik DN780 and a Yamaha REV7 so that I could see how well it was able to emulate the effects created by its more expensive counterparts. Using the straight reverb settings I was able to get closer to the sounds created by the Klark Teknik than to the REV7, the latter seeming to possess a somewhat harder quality. As expected, the Klark Teknik was quieter, smoother and more flexible than the Alesis, but then it does cost five or six times as much. Nevertheless, when the reverb sound was evaluated within the context of a complete mix the simulation was very convincing.

It's possible to simulate both plate and room acoustics quite convincingly, and though the reverb is a little grainier than its upmarket counterparts when examined in isolation, the overall effect definitely works well, and that's what really counts.

Although the Klark Teknik has only got a 12kHz bandwidth as compared to the Alesis's 16kHz, it was still capable of producing an equally bright sound when required to do so and I can only put this down to the extremely high density of reverb that the Klark Teknik can generate, which the Alesis can't reasonably be expected to match. The Alesis is more than bright enough for any reasonable application and you will often find yourself using the HF Roll Off control to reduce the effective bandwidth.

The gated mode is excellent - really brash, and in this mode the Decay control sets the length of the reverb burst giving more than adequate range for any standard gated effect. I actually preferred the gated effect to that produced by any of the other reverbs I have checked recently, regardless of their price. The reverse mode also sounded more like the Klark Teknik than did the Yamaha but it falls slightly short in this department in that it would be useful to set the decay time to be shorter than the minimum allowed. You can get a good long reverse effect but on a fast drum track, you might just want to shorten the effect and become frustrated by the lack of range. As reverse reverb is a strictly artificial effect, I can't say which of the units produced the best result as they were all subtly different and all very good.

In terms of user-friendliness, I found it easier and quicker to set up a sound from scratch than to call up a preset on a programmable unit such as the REV7 or the Roland SRV2000 and then modify it. I think that to some extent we've fallen foul of the scientific calculator syndrome where we end up paying for features that will seldom or never be used but that we are told we must have. After all, a few years ago plates were used for everything and they only had a decay control, if that!

"It is possible to simulate both plate and room acoustics quite convincingly."

One unexpected omission though, is the lack of a bypass button which would have made life a little easier when it comes to setting up an effect and then comparing it with the dry sound. Having said that, you must have a mute button on your mixer effects return line or something similar that will do the same job.

The specification suggests that this unit should be quieter than the Yamaha in operation and similar to the Klark Teknik. In practice, the Yamaha and the Alesis were both very quiet but with the Klark Teknik being noticeably better than either. With the input gain control turned right down, the Alesis XTC was incredibly quiet but when I turned up the send level on the desk, the hum and noise increased. This transpired to be noise generated in my mixer and not in the XTC so it's quiet enough for any serious application with the possible exception of mastering for Compact Disc!

The HF roll-off control is instrumental in offering a wide tonal variety but I couldn't get the LF cut button to produce any appreciable effect at all. Either it's very subtle or it wasn't working on the review model but having said that, whatever it's supposed to do, I didn't miss it.

The fact that pre-delay and decay are on rotary controls really does make for easy setting up; without any of this increment decrement nonsense. If these controls are adjusted when a signal is being processed, slight glitches are audible but this is technically unavoidable and you wouldn't normally want to change these parameters during a mix. More serious is the glitching that occurs when the hold function is used, as it renders any subtle sounds such as soft vocals difficult to freeze. This problem is present to different degrees on different reverb settings and it shows up more on some types of programme material than others so experimentation is the order of the day.

Conclusions

In virtually all respects this is a versatile unit capable of producing excellent results and has the added attraction of a relatively low selling price. My only real criticisms concern the glitchy hold function and the lack of range on the reverse setting where the short decay may not be short enough. In fairness these are not serious limitations when the price is taken into account.

All the standard reverb effects are both flexible and useful with a good stereo depth and the gated effect is really first rate. Drums always seem to present the most demanding challenge to these machines so a lot of the testing was done using a Roland TR707 but vocals and other instruments also sounded duly flattered when subjected to the Alesis treatment. Vocals in particular benefit from the extended bandwidth of this unit and really sparkle.

In purely subjective terms I liked this unit very much, its performance compares well with machines costing up to and over three times the price and I didn't really miss the lack of programmable features at all, at least not in a recording environment. It's not going to put AMS or Klark Teknik out of business overnight but it is going to be a great asset to small studios and presents a cost effective alternative to the budget programmables currently available without compromising on sound quality.

The Alesis XTC will retail for around £699 and further details may be obtained from: Sound Technology, (Contact Details).