Oberheim OB-X8

Oberheim are back, and doing what they do best — making massive polysynths with a massive sound.

Back in the distant past, I owned an Oberheim OB‑X. It was a bit tatty and wasn’t my favourite synth, so I swapped it at a famous London music store for a Prophet T8. With its wide, weighted, velocity and poly‑aftertouch sensitive keyboard, this was far more suited to my needs, so I never regretted the trade. Nevertheless, there was something a bit special about the OB‑X that I only appreciated when I no longer had it.

Later, the opportunity arose to obtain a museum condition OB‑8, so I did, but my retrospective lust for the OB‑X never quite faded. Wouldn’t it be nice, I mused, to have a synth that sounded like the OB‑X, but with all of the facilities of the OB‑8 as well as the keyboard from the T8? I waited for a few years, then another few, and then some more... and then I gave up. But then I learned of the OB‑X8, an 8‑voice analogue polysynth designed to emulate all of the original OB series and then add facilities that extend it in a sympathetic fashion.

When the review unit arrived, I immediately popped it on a two‑tier stand above my OB‑8 and switched both on. At that moment, and for the first time ever, the OB‑8 misbehaved and did something that I would never recommend — it took up smoking. So I contacted The Synthesiser Service Centre in London to arrange an emergency trip to the doctor. But one important lesson had already been learned. While we might revere our old synthesizers, owning them is as much an exercise in curation as it is in making music.

The 21st Century Oberheim?

Visually, the OB‑X8 recalls the OB‑X and the first model of OB‑SX rather than the OB‑Xa and OB‑8. It’s roughly the same width as the OB‑X and, although it’s less deep, the controls are laid out much as before. Consequently, and despite the addition of a small OLED screen and its associated encoders, there are wide spaces between the knobs and buttons that might feel odd to players accustomed to the dense panels of some modern instruments.

As in all previous OB‑series synths, there are two VCOs per voice. At some point, it must have been decided that the discrete OB‑X oscillators were superior to the CEM3340s in later models so, unlike elsewhere in the OB‑X8, there are no OB‑Xa and OB‑8 options. This means that what we have here are OB‑X oscillators with additional OB‑8 facilities; simultaneous selection of the waveforms, independent pulse widths for osc 1 and osc 2, a triangle wave and semitone tuning for osc 1.

Cross‑modulation is implemented as it was on the OB‑X. This means that there’s no way to adjust the amount, although you can now select whether either or both of osc 2’s sawtooth and triangle waves are used as the modulation source. In addition, there’s hard sync, and the filter contour can sweep the frequency of osc 2 as it could on the OB‑Xa and OB‑8. You can engage cross‑mod and sync simultaneously, but the OB‑X8 remains surprisingly well behaved when you do, and doesn’t descend into weird and wacky territory.

The outputs from the oscillators pass to the single filter per voice. This is perhaps where the OB‑X8 will find greatest favour with purists because the 12dB/oct SEM‑style OB‑X filter and both the 12dB/oct and 24dB/oct modes of the CEM3320‑based OB‑Xa and OB‑8 filters are available. In addition, the high‑pass, band‑pass and notch modes from the original SEM filter are provided, which means that the OB‑X8 can make more than a passing stab at emulating the fabulous but unwieldy Oberheim 8‑Voice.

On the OB‑X, there were five buttons controlling the audio inputs into the filter: osc 1 at full level, osc 2 at half or full level, and noise at half or full level. The OB‑Xa and OB‑8 lost the half‑level noise button, and now there are just three — osc 1, osc 2 and noise — and you use the menus to determine the signal level for each of these sources.

Cutoff frequency and resonance knobs are provided, and a dedicated ADSR contour generator performs shaping duties. None of the original OBs offered self‑oscillating filters, and so it is here; the resonance can be pronounced, but it never strays into oscillation. Keyboard tracking is also available, and you can adjust this from zero to 100 percent. The output from the filter then passes to the audio amplifier, the gain of which is controlled by its own ADSR contour generator. At this point it’s worth noting that there were differences between the contours generated by the OB‑X/Xa and the OB‑8, so the OB‑X8 allows you to select the characteristic that you prefer in any given patch.

The OB series had a single, global LFO rather than one per voice. Again, the different characteristics of the vintage models are accommodated and, depending upon which you choose, several underlying attributes are changed. As on the OB‑8, you can choose from seven waveforms, with an option to select between the OB‑X/Xa’s sine wave and the triangle wave that replaced it. However, the OB‑X8’s panel only offers access to five of these, with the key‑sync’ed triangle wave and the unusual Sampled Vibrato LFO wave accessed through the menus alongside things such as LFO sync, tracking and phase. The LFO’s maximum depth is that of the OB‑8, as is its frequency range of approximately 0.07Hz to 50Hz, both of which exceed the narrower ranges of earlier models. The range of LFO destinations is tiny by modern standards, with the chosen waveform directed at one depth to the frequencies of osc 1, osc 2 and the filter cutoff, and at another to the pulse widths of osc 1 and osc 2 and the gain of the audio amplifier. You can switch the modulation path on or off for each of the destinations, but that’s all.

In addition to the master volume and tune, the Master panel contains the Volume/Balance knob, which allows you to program the patch volume or the balance between the Upper and Lower parts in a Split or Double (see below). There are also three buttons. The first (Tune) does what you might suspect — it tunes and scales all 16 VCOs. The second (Hold) latches any notes being played while you depress it but, once it’s released, allows you to play any unallocated voices conventionally. The third (Chord) allows you to save a held chord and then replay it at any pitch. You can define how the chord is held (keyed or infinite) and the range over which the function operates. Unlike the vintage models, chord triggering is now handled correctly and the generated notes can exceed the highest pitch available from the keyboard. Again, you can play any unused voices conventionally.

The Control panel contains two important sound generation controls alongside some of the performance controls. These are the osc 2 detune knob and the Vintage knob that determines the amount by which the oscillators, filters and contours can differ across the eight voices. A third knob controls the portamento time. But the switches in this panel are, for me, three of the most important features on the OB‑X8. The first determines whether velocity is directed to the filter contour depth, the amplifier contour depth, or both, while the second allows you to direct aftertouch to the filter cutoff frequency, the depth of the vibrato LFO (which we’ll come to in a moment), or both. The final button selects Unison mode which, as we will see, helps to turn the OB‑X8 into a much more powerful monosynth than you might expect.

Additional Parameters

Oberheim’s Page 2 concept hails from an era before affordable polysynths had screens and menus, and allowed you to program a second set of OB‑8 parameters from the single control panel after pressing the Page 2 button. Unfortunately, there were no legends for these so you had to keep referring to the manual or a Page 2 diagram to see what’s what. (I’ve been playing my OB‑8 for decades and I still find it hard to remember them.) Nonetheless, they add powerful modulation capabilities to the synth and in my view, which I admit is not fashionable, adding LFO phases and inversions, two contour generators for the modulation depths, LFO keyboard tracking, the ability to contour the LFO rate, numerous portamento modes, variable voice detuning and programmable sustain pedal release times elevates the OB‑8 far above the OB‑X and OB‑Xa.

On the OB‑X8, any Page 2 parameters that are common with the OB‑8 can be programmed in the original manner. It would therefore have been nice if the secondary functions had been silk‑screened onto the panel, although I can understand the urge to remain consistent with the original design. More sensibly, you can access them using the screen and encoders, which leaves the control panel free to carry out its primary functions. Programming the OB‑X8 this way also overcomes the limitation on the OB‑8 that Page 2 parameters are unavailable in Manual mode.

The menu system has also allowed Oberheim to extend the number of Page 2 parameters, and three of these deserve special mention because they turn the OB‑X8 into a powerful lead and bass synth. The first is Unison Voices, which allows you to decide how many voices will be stacked on the single note played. The second is Voice Detune, which allows you to detune voices (rather than oscillators) against one another. The third is the Unison Key Mode, which offers low‑, high‑ and last‑note priorities, each with either single or multi triggering. This removes the low‑note, single‑triggering restriction of vintage OBs.

It’s difficult to overstate just how big the OB‑X8 is, measuring 1028 x 423 x 149mm and weighing in at a substantial 14.7kg.

Panning is another strength. Whereas the OB‑8 had eight knobs set into the right‑hand end cheek that allowed you to determine where each voice sat on the soundstage, the OB‑X8 offers five panning modes and a parameter to determine the maximum width of the mode selected. This makes it possible to do things such as position the two patches in Split and Double modes in different spaces, and to spread the voices (however allocated) to create wide ensembles.

Hang on a moment... that’s the second time that I’ve mentioned Splits and Doubles. These bi‑timbral modes, introduced on the OB‑Xa, divided the synth’s eight voices into two groups of four — Lower (voices 1‑4) and Upper (voices 5‑8) — that you can split or layer as desired. The same system has been implemented and extended on the OB‑X8. Once you have selected the patches for the Upper and Lower parts, you can determine their relative volumes, their transpositions, the split point (if used), the detune of the Lower part to further thicken the sound in Double mode, and whether the Hold/Chord, panning, performance and arpeggiator parameters are derived from the Upper part, the Lower part, or are determined in the Split/Double itself. But never forget that a Split or Double doesn’t contain any patches; it only points to those sounds in the patch memory. If you change a sound in one, you’ll change it in all the others that use it.

Unlike its ancestors, the OB‑X8 also has a significant selection of Global settings. Many of these relate to MIDI; for example, which ports are used for MIDI and SysEx, whether the control panel sends MIDI CCs or NRPNs, whether the arpeggiator spews out MIDI notes, and so on. Others fine‑tune the programming and performance characteristics. These include the knob mode, the aftertouch and velocity curves, the sustain pedal polarity and mode (piano‑like release or hold), the pitch‑bend polarity, the arpeggiator clock source, and more. You can also select the desired output mode and your choice of tuning scale, while other options take care of basic housekeeping, and a final collection perform troubleshooting and calibration tasks.

The Performance Panel

To the left of the keyboards on the OB series you’ll find a performance panel. The OB‑X’s was utterly basic, with just pitch‑bend and modulation paddles, narrow/broad options, an ‘Osc 2 Only’ switch for the bend, plus an octave up/down switch. While the OB‑Xa added a dedicated vibrato LFO to this, it was only on the OB‑8 that it reached its full potential by increasing the number of vibrato waveforms to six (including S&H) and adding an arpeggiator.

The Oberheim paddles may seem strange to novices but, if you give them a chance, you’ll find that they are simpler to master than wheels, and highly expressive. The pitch‑bend paddle is to the right, placing it under your index finger, and the modulation paddle (which is summed with the initial modulation depth) is to the left. By default, the effects of both are increased as you pull them toward you, and both are sprung so that they return to zero when released. This means that you can create natural vibratos, or play bends and control the LFO modulation depth in a way that (for me) feels much more comfortable than using wheels. You can also apply the paddles to just one oscillator per voice, making it possible to obtain effects that are hard — or impossible — to achieve on other vintage synths.

The OB‑X8’s arpeggiator is surprisingly flexible. It can be driven by a dedicated internal clock, from an external analogue clock, and by MIDI Clock and, although it’s not obvious from the panel, it offers up, down, up/down and random modes with up to five transpositions. It also offers several playback modes including ‘while played’, latched, latched plus any notes that you add while you add them, and latched but allowing you to play any free voices over the top. Now, why did I say ‘five transpositions’ rather than ‘five octaves’? It’s because you can determine the amount by which each successive repeat is transposed. If you select C1, C2, C3, C4 and C5, you’ll obtain the usual multi‑octave arpeggio but, if you select different notes, the arpeggio can be made to develop harmonically. In addition to all of this, there’s a hidden ‘as played mode’ that can replay eight‑note sequences in the order that you play them. You can transpose these in real time by playing the keyboard while the arpeggiator is running, and things become even more interesting when you add Unison, Splits and Doubles into the equation. Despite its paucity of controls, the OB‑X8 is much more comprehensive in this area than you might imagine.

OB‑X8 In Use

Before I began my tests I upgraded the OB‑X8’s firmware to the latest version. Having done so, I ran the full calibration routine and, while I was waiting, learned the ‘hidden’ panel commands, which proved useful for speeding up programming. I then loaded the Basic Program and put the synth into Manual mode before starting to create new sounds. I immediately noticed that some parameters felt smoother than on my OB‑8 and contacted Oberheim to see whether I was going mad or not. Co‑designer Marcus Ryle confirmed that, unlike the OB‑8 (which uses 6‑bit resolution for all of its potentiometers), the OB‑X8 uses seven or even eight bits, doubling or quadrupling the resolution where this is beneficial. I wasn’t going mad.

I had expected to begin by programming a selection of strings and brass patches, but the OB‑X8 had other ideas and soon led me down lots of unexpected but interesting paths. Reining myself in, I carried out a series of tests that showed that Oberheim have achieved their aim of emulating at least one of the previous OB‑series polysynths. So does it really sound like an OB‑X, OB‑SX, OB‑Xa, and an OB‑8? To cut a long story short, yes it really does... but sometimes it won’t. In direct comparison with my OB‑8 (did I forget to mention that its surgery was a complete success?) I was gobsmacked by the similarity and have to admit that, when stepping through the OB‑8 factory patches on both, I was often unable to tell which was which. Even minutiae such as the unusual interaction of the sawtooth and pulse waves are correctly recreated. But there would probably be greater differences if I were to conduct these tests against an older model, not because the OB‑X8 is deficient, but because I’ve never met two OB‑Xs or two OB‑Xas that sounded the same. There are scores of trimpots inside each of them, and the chances of two units being calibrated identically is as close to zero as makes no difference. The OB‑X8 can’t be expected to sound identical with two synths of the same model that sound different from one another, can it? Nevertheless, I would have liked to have had the opportunity to compare the OB‑X8 with an OB‑X to see whether it recreates the gnarlier bottom end of the early model as well as it does the smoother response of the later one. Since I have already explained where my OB‑X went, I’ll have to leave that to you!

I had the opportunity to discuss this with Tom Oberheim a few weeks ago and he told me, “Marcus Ryle spent many hours in his home studio where he has one of every Oberheim synth, and he was able to A/B each of the originals against the OB‑X8. Interesting enough, the sections that took Marcus the most time were the envelope generators — they are significantly different in each machine.” He then explained how the engineers at Sequential ensured that the characteristics of each vintage synth could be recreated on the OB‑X8. He concluded, “I was pleased when I got a chance to look at the schemas, and in all three of the voice sections the circuitry is largely right out of the old units. Dave [Smith] and his Sequential team did an excellent job.”

Stepping beyond the sounds available from the vintage synths, I was able to create all manner of patches that I would describe as ‘vintage Oberheim but more so’, especially since the addition of the other SEM filter modes makes it possible to emulate sounds previously available only on a 4‑Voice or 8‑Voice. Furthermore, I can’t overemphasise my enthusiasm for using the OB‑X8 as a monosynth. Programming basses and leads is a delight and, after selecting my preferred keyboard and portamento responses and (of course) adding pressure sensitivity, I was able to make it sing! Mind you, it would be nice if the maximum velocity and aftertouch responses were programmable. Come on Oberheim... make me happy!

If you want a bucketful of modulators and a matrix the size of Manhattan, look elsewhere. But if you love Oberheims and the Oberheim sound, there’s something rather special about the OB‑X8.

Conclusions

In addition to the far lower cost, I can think of many compelling reasons to buy an OB‑X8 in preference to hunting down the synths that inspired it; velocity and pressure sensitivity, reliable tuning, extended synthesis capabilities, a comprehensive MIDI specification and more. In addition, all of the components in the OB‑X8 are about 40 years younger, which can only be a good thing. Were you to offer me the choice of one of the vintage synths or the new one, it would take me... oh, a millisecond to choose the latter. Based on a few weeks’ use, it seems better in every way and, while I’m sure that there will be the usual crowd who claim that it can’t sound as good as any of the originals, they’re wrong. It’s not quite the hybrid of the OB‑X, OB‑8 and Prophet T8 that I had envisioned, simply because its keyboard has 61 keys and if offers channel aftertouch rather than poly‑aftertouch. Nor is it a modern all‑singing, all‑dancing synth; if you want a bucketful of modulators and a matrix the size of Manhattan, look elsewhere. But if you love Oberheims and the Oberheim sound, there’s something rather special about the OB‑X8.