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Spectrum Synthesis

On the Emax Hard Disk Sampler

Article from Sound On Sound, September 1988

Unlike some samplers, Emax has stayed the course since its introduction over 18 months ago and has developed into a mature, well groomed specimen. Having released a Hard Disk version of the machine almost a year ago, Emu Systems have recently given Emax yet another lease of life with their Spectrum Synthesis upgrade, which turns the sampler into a powerful additive synthesizer. David Hughes tries it out

Unlike some samplers, Emax has stayed the course since its introduction over 18 months ago and has developed into a mature, well groomed specimen. Having released a Hard Disk version of the machine almost a year ago, Emu have recently given Emax yet another lease of life with their Spectrum Synthesis upgrade, which turns the sampler into a powerful additive synthesizer. David Hughes tries it out.

I reckon I must be showing my age, for I'm slowly forming the opinion that samplers are starting to look distinctly old hat. How long ago was it that, suddenly, all my muso contemporaries could talk about was this genius of an instrument called a 'Fairlight' and how it could 'grab' sounds of 'real' instruments and perform all manner of musically useful operations on just a stream of numbers? It must be well over seven years ago, way back in my 'undergrad' days...

The sampler has obviously come a long way since then. Much for the better in my opinion. However, I believe that the sampler is now poised to enter its next phase of evolution. Already, phrases such as 're-synthesizer' and 'Fast Fourier Transform' are being casually tossed about, often without any real consideration for what such an instrument might be and how it might achieve such a miraculous feat.

Looking at the SE retrofit for the Emu Systems' Emax, it is evident that this process is already well under way. However, let me start with a brief recap on what the Emax actually is and what it does.


The Emax sampling keyboard has already been reviewed in the January 1987 issue of Sound On Sound - the one with Peter Gabriel on the front. It boasts eight independent outputs, 12-bit sampling resolution, a built-in disk drive, quite a bit of memory, and a 16-track polytimbral sequencer, which is still pretty impressive 18 months on.

For the purposes of this review I was provided with an Emax rack module rather than the keyboard version. At first I found this a little difficult to work with. Due to size restrictions, its front panel is not as well laid out as the larger keyboard version and the printing on the front is too small to read from three feet away. However, the module did have an extra which Emu have also recently introduced - a hard disk unit. This I felt, made up for the bottles of Optrex I got through.

A hard disk is essentially the same as a floppy disk, except that it's hard. That isn't really a very useful description, so here's a better one. A hard disk is an aluminium platter coated with a ferro-magnetic material which is housed in a sealed container and spun at very high speeds, typically of the order of 3600 rpm. A hard disk is also a great deal more fragile than a floppy disk and does not enjoy even the most playful of knocks (does any piece of computer gadgetry?).

This is due to the fact that, because the disk spins at such great speeds, the disk heads - that is the elements which write and read the information to and from the disk - float rather like a hovercraft on a cushion of air only a few microns above the surface of the disk. Any form of contamination - a smoke particle from a cigarette for example, which is actually twice the size of the gap between the heads and the surface of the disk - will spell instant death for the hard disk. Hence the need for an air-tight container. Fear not though, the hard disk used by Emu Systems is built to 'military specifications', and if it's good enough for good old Ronny Reagan then it's good enough for the likes of you and me. (You do want to be able to sample after the four-minute warning, don't you?)

The principal advantage of using hard disks is that they are fast. Very fast, in fact. When you see other samplers loading their sounds in from floppy, you suddenly realise how painfully slow they actually are. Watching the Emax load in a whole bank of sounds from hard disk in a matter of three or four seconds really must be seen to be believed. The hard disk also has a huge amount of available storage space; in this instance, about 36 disks' worth, all available within three or four seconds.

The quality of the samples supplied with the review model hard disk are the usual pot-pouri of the good, the bad, and the useless. As you might expect, there's a fairly good collection of sampled voices, strings and horns, the occasional orchestral stab, and a number of excellent percussive sounds.

I have one reservation concerning the Emax hard disk unit - there doesn't seem to be a 'parking area' on the hard disk. The 'parking area' does not, in fact, refer to a suitable location for dumping a beaten up old Ford Escort but instead refers to an area to which the disk heads retreat at the end of a read or write session. The parking area is designed to minimise the risk of a read/write head coming into contact with the disk surface. I say this because there does not seem to be any provision for moving the heads into the 'shipping' position, which is common on most hard disk drives for computers. After all, the last thing you want is your disk heads banging up and down on the surface. I guess this should be all taken care of since the drive is of robust military specification. I had no documentation concerning the care and precautions required when dealing with hard disks and would welcome some form of clarification.


However, the hard disk isn't really the subject of this review, although they are really nice to have. The subject of this review is the SE software upgrade, which Emu Systems describe as a 'complete digital additive synthesizer'. The software also contains a number of fixes to the old operating system. The upgrade kit comprises a handy little ring-bound manual, three floppies containing the SE software and re-worked operating system, and two stick-on labels of a distinctly tatty nature which reflect the changes in the Digital Processing section of the Emax menu.

Upgrading to the full SE spec is very simple and the manual describes the process very well. In fact, the manuals provided with the Emax and the upgrade really are first rate. It's a shame certain other manufacturers don't put as much effort into something which is so absolutely essential to the user.

The SE software isn't the end of the goodies. There a few highly useful additions that allow your Emax to open itself up to the outside world. You can now modify samples received via a MIDI Sample Dump protocol, such that they can be re-sampled at one of Emax's own slightly restrictive sample rates. I'll discuss these features in greater depth a little later on, but there is also now the provision to connect to a CD-ROM player for fast access to over 500 Emax samples.

That's a basic description of the package but what do you actually get? The upgrade itself is centred around a complete digital additive synthesizer. 'Additive synthesis' - like Yamaha's FM synthesis - is quite complex mathematically but in reality is actually very easy to use. If you're a bit confused by the terminology, 'subtractive synthesis' (which is the reverse of additive synthesis) removes components from a musically complex sound using some kind of filter to make a less complex sound. So, logically, additive synthesis functions by starting with a number of harmonically simple waveforms, such as sine waves, and then mixes them together to form a more complex sound. A 'spectrum' is essentially a graph of the relative amplitudes (volume levels) of each of the frequency components and, in general, the more components there are in the spectrum, the more complex the final waveform will be.

Emu describe their method of sound generation as 'Spectrum Interpolation Synthesis'. At a guess, this probably translates into a system which is quite similar to those used by PPG in the Wave series and Sequential's 'Vector Synthesis'. The basic principle is that the user defines a series of 24 sound spectra - these may be of the user's own making or selected from the onboard palette of 100 - and then chains them into a sequence of waveforms referred to as 'time-slices'. The object of this system is to simplify the process of sound creation and development. And it does look quite impressive. The 64,000 dollar question is how easy is it to work with and what do the end results sound like?


The first stage is to define the length of the required sound, which is dependent upon the amount of memory remaining at that instant. The available memory is then divided into 24 equal elements and each element, or 'time slice', represents the sound spectrum at that point. A spectrum may then be created from 24 individual sine waves and each sine wave may be tuned to any ratio of the fundamental frequency. Each sine wave is in fact a partial, and the amplitude and frequency of the collection of partials determines the final timbre of the sound. The wonderful thing about this system is that, once a sound has been created, it may then be treated just like any other Emax sample. Furthermore, using Emax's Dual Mode, a sound may be further modified to incorporate the attack portions of other sampled instruments to create D50 type sounds.

Actually creating a sound seems, at first, to be a very complex process. However, you are supplied with a number of useful starting points on the SE disk. These specimens are pretty amazing. Some very abstract, some very useful. All very PPG-like. I was impressed.

The first thing to do is access the Synth Options menu and then press function key 1. This is the fun bit. You are then presented with a specimen spectrum. Hitting F1 again puts you into Draw Mode and then, having selected the spectrum you want to draw, you press Enter. After a short countdown, you simply 'draw' in the spectrum as required using Emax's data entry slider. The cursor steps from left to right automatically. After drawing the spectrum there is then the option of editing and copying the newly created waveform. Dead easy!

But the really clever bit comes next. There is no need to draw a separate spectrum for every one of the available time-slices. You simply select a time-slice some way into the sample, say TS24, and repeat the above process. If you then select the 'Interpolate' facility, Emax will calculate the spectra for each of the time-slices between your two end points. This takes only a matter of seconds but to hear the sound you've just defined you must then move to the 'Synthesize' option. This is where Emax does most of the hard work. Up until this point, Emax has been working with a mathematical model of your sound - more than likely based on those wonderful Fourier coefficients - and must now convert that model into a real sound. This takes time, and it does pay to work with shorter sounds while you're learning.

The sound designed in the manner described is built up from a number of discrete packets which may or may not have a number of violent changes in their respective harmonic content. Emu Systems provide the user with an option to modify the way in which the sound changes from slice to slice, which may smooth over some of the more jagged changes. There are two modes, Stepped and Smooth. Having selected the required response, the machine then goes into its calculations. Emax calculates the frequency spectra for each time-slice between the two points you have specified and the display tells you how many slices there are left to calculate. This does take some time, but if you're used to waiting 20 to 30 seconds for the disk drive to load a bank of data then this wait doesn't seem like too much to put up with.

When the calculations are complete you can try playing the pseudo-sample. In general, I was quite pleased with my efforts. Once 'synthesized', you can then resort to the normal Emax sample edit facilities to set looping points, filter levels, etc. Like most samples, the higher the frequency, the shorter the sound, and so some form of looping is essential if the sound is to sustain at all in the higher registers.

My one grievance with the Emax SE concerns the manner in which spectra are drawn and edited. Essentially, editing a spectra is a graphic process. Sadly, Emax is smitten with a tiny LCD display - only 16x2 characters in size - which means that if the amplitude of a frequency component is less than 14% of the full level, then it isn't displayed. The manual does apologise for this shortfall and, sadly, there isn't an easy solution short of providing the extra hardware required to link the machine to some kind of VDU. (This is one reason why I like the latest Roland samplers, the S550 and S330.) To be fair to Emu, I didn't really find anything wrong with it once I'd become more conversant with the SE system. There is an awful lot for the user to tinker with and I've only just covered the basics. In fact, I almost feel guilty by not going into greater detail.


As I mentioned a few paragraphs ago, there is now the facility to modify the sample rate of a sound already in memory, and this is pretty useful if you're good at using up every last byte of available storage in the machine. This feature is a form of 'down-sampling', another buzzword which has been much abused of late. Another possibility is to modify a sample received from another sampler via the MIDI Sample Dump protocol which may not have been sampled at a sampling rate native to the Emax. This does take time to execute, however, and the Emax display is very friendly in that it provides you with a precautionary estimate of the amount of time in minutes that the process is likely to take.

There is also the facility to change the pitch of a sample. I found this useful as a means of generating flange effects without the need for an external sound processor. The range by which you can shift the pitch of the sample is given as plus or minus 35 cents, which should be more than suitable for most applications. Again, this option takes some time to compute and Emax gives you an indication of how long the process will take.

The final enhancement is the addition of the wonderfully titled 'Transform Multiplication'. The manual initially defines the TM process as a 'powerful and fascinating' function. However, it then says that TM is 'hard to describe and the results hard to predict'. This sounds like the invention of a fast-talking sales executive who doesn't really understand what the development engineer has just put in front of him and so invents a name which he hopes no living soul on God's earth can understand. This I had to try!

The manual goes on to say that 'TM is easy!'. Actually, there isn't much for you to do other than to choose two samples which appear interesting and then set the machine running while you go off to make a cup of tea. Happily, there are some examples of TM supplied on the software disk. TM does indeed sound excellent. Very unusual indeed and highly innovative. The sounds are not natural at all (well, the examples I came up with were not!). There is a limit to the size of the sample that you can process with TM. Both samples must be less than 32k in length, and I guess this restriction is probably due to the amount of processing time and memory used in performing the calculations.

The manual is really cute about the delays in processing time and invites you to contemplate the early pioneers of digital synthesis, who had to wait days before they could hear the results of their efforts. Thankfully, you don't have to wait quite as long as that.



As everyone knows, a sampler is only as good as its sound library and this is where Emax really scores. With well over 300 disks in the official Emax Sound Library, containing literally thousands of different samples, there's a good chance that the sound you want has already been committed to disk. To get you started, the Emax Hard Disk unit comes with the following 30 sounds ready installed:

Grand Piano, Arco Strings
Rock Kit, Rock Organ
Big Brass, French Horn
Mixed Chorus, Kyodai Synth Collage
Rock Guitar, Marimba/Vibes
Pop Bass, Electric Grand
Multi-Synth Combo, Woodwind Ensemble
Steel String Guitar, Tine Strings
Pipe Organ, Harp/Karplus Strings
Harpsichord, Tremolonde Strings
Spiccato Strings, African Instruments
Pizzicato Strings, Solo Arco Cello/Violin
Rock Percussion, Male Voices & Synth Orch
Sitar, Sarod
Sarangi/Tabla, Tambura (Sitar/Sarod)

I was very impressed with Emax before I began my review of this upgrade. At first I didn't feel that the rack module I was using was as ergonomically laid out as its larger keyboard brethren but I became quite used to it after a while. (I'm due for a visit to the optician's anyway!) I can finish by saying that I'm still impressed with Emax. The SE software makes Emax look very attractive indeed, even if there are other instruments available or which will be available in the near future that do much the same for slightly less money. The reason for this is simple: the Emax sampler is not a closed system. It doesn't just stop with Version 1 like so many Japanese instruments these days.

If you're already an Emax owner, then simply don't hesitate. If you're looking for a sampler with that extra something which makes it stand out above the rest, then the Emax SE is a very good bet. The fully expanded system is a little on the expensive' side but it is not ridiculously over-priced. SE is a lot of fun and will teach you a lot about the sounds you're making in terms that don't require a maths degree. The only thing that SE/TM does seem to require is a bit of patience. The sounds that it makes are unique and, more importantly, musically useful.

Once I'd leafed through the preparatory documentation and started to work my way around the system, I started to formulate the opinion that SE isn't really an upgrade to a system. It feels more like a completely new instrument. It shows that, having done an excellent job on the Emulator III, Emu Systems have not simply sat back and neglected their old customers. They've said, 'this instrument is good, but it can do more'. How many companies will do that for you?

Price SE Upgrade £199 inc VAT. Emax SE Hard Disk Rack module £2999 inc VAT.

Contact Emu Systems Ltd, (Contact Details).

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

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Sound On Sound - Sep 1988

Gear in this article:

Sampler > Emu Systems > Emax SE HD

Gear Tags:

12-Bit Sampler

Review by David Hughes

Previous article in this issue:

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