Basically, a six-voice Matrix-12 without the keyboard, the Xpander utilized Oberheim's Matrix Modulation instead of patch cables, to create an incredibly powerful tabletop synth.
In May 2022, Oberheim announced that the company was going to begin manufacturing a new product after nearly 40 years, the OB-X8, an 8-voice polyphonic analog synthesizer that combines all of the main features from their OB-X, OB-Xa, and OB-8 synthesizers. These legendary synths dominated the late '70s and were the forerunners to the next generation of Oberheim synths, the Matrix. The Matrix synthesizers featured their breakthrough design of the Matrix Modulation, an ingenious digital routing control system that allowed users the kind of patching flexibility found only on modular systems.
The first of these synths was the Xpander. The Xpander was a tabletop synth module without a keyboard. Launched in 1984 and discontinued in 1988, the Xpander combined an analog audio signal path with the convenience of digital controls. Around 2000 units were sold and it continues to be used by many artists today. Depeche Mode, Hans Zimmer, Vince Clark, Orbital, Tangerine Dream, Ray Lynch, The Chemical Brothers, and many more have all used the Xpander on countless records and live performances. The Xpander was capable of elaborate patches as each of the six voices were completely independent of each other. Each voice had two voltage-controlled oscillators (VCO) that could generate sawtooth, triangle, pulse, and noise waveforms. The Xpander also included a multi-mode voltage-controlled filter (VCF) which allowed for 8 types of filtering. Low pass, high pass, band pass, notch, and phase shift filters could be combined in different ways to create a truly unique sound. The Xpander also contained two voltage-controlled amplifiers (VCA).
All of these components could be modulated by different digital controls, including ADSR envelope generators, low frequency oscillators (LFO), lag generator, ramp generators, and tracking generators. Each of these controls could be routed to almost any parameter, thanks to the Matrix Modulation, giving the user incredible power over the sound. The Xpander is possibly the most flexible non-modular analog synth ever built. Any of the 27 sources can be connected to one or more of the 47 destinations. Up to 20 connections per voice were possible.
All of these creative possibilities needed a way to be saved to memory and the Xpander answered the call with memory locations for 100 single patches and 100 multi-patches. The multi-patch consisted of 3-zone setups with MIDI channel and note range, splits, layers, volume, transposition, voice assignments, and panning or separate output. Add to that the flexible inputs and outputs on the back panel and you have a production powerhouse. They included left, right, and mono audio outputs, 6 individual audio outputs (1 for each voice), 6 CV/gate inputs, trigger input, 2 pedal inputs, and MIDI in, out, and thru. The CV/gate inputs can be converted to MIDI out.
The Xpander sounds very good. It has a smoother timbre when compared to earlier Oberheims, Moogs, and ARPs. The mellow sound could be due to different Curtis chips used in the later Oberheims.
The Xpander is still a coveted piece of gear commanding extremely high prices on the second-hand market. If you are lucky enough to own one you are in good company and should consider yourself blessed. It will be interesting to see if Oberheim has any plans for a new version of the Xpander in their future line-up.