Fauxberheim Xp-6

my recreation of the Oberheim Xpander

(17 Votes)
C 3b (Updated 7 months ago)
February 15, 2021
Reaktor 5 or lower


“The Oberheim Xpander is a six-voice desktop unit that is one of the most flexible non-modular analog synths ever built”, paraphrasing an article about this beautiful beast, and my obsession for a little over 2 years while I learned “how to Reaktor”. I wanted to post an original old version that will run in Reaktor 5 or its Player so folks who haven’t upgraded could also enjoy it.

Please, enjoy the sound library! It is rather diverse and fun and may transport you to the 80’s without warning. ;)

I am well aware that my build is not optimized, some methods non-standard to say the least. Yet it all seems to work, so I’m ok with that because I always wanted an Xpander and this gives me about 95% of that experience. I’m sorry now that I didn’t share this with the community back when I first completed it.

General description

2 VCOs with 3 mixed waves each, one with Noise
Oscillator Sync
FM to VCO1 or VCF

Multi-Mode VCF from 4-pole LP
(Similar to the Modal pickups from R6’s ZDF Toolkit - I wish I’d had this back then!)

5 ENVs with several custom modes
LFO Triggering

5 LFOs with Retrigger point & Lag
typical waveshapes + Random & Noise
Sample In from other mod sources, including self-mod

LAG function (portamento for keys and other mod sources)

3 TRACKing generators (5-point shaping for mod sources)

4 RAMP generators, also with LFO Triggering

extra VIB LFO just for normal live application, I suppose

simple Voice Panning

*special features*

- Analog Pitch knob to simulate oscillator drift

- Mod Sag knob to simulate a side effect when using MANY modulations on the original; all mods could drag a bit under the load on the processor

In Oberheim Xpander user forums, two common complaints were the speed of the envelopes and the exponential curve on the amount of modulation going to a destination - so I changed both!

- envelope times “go negative”, for faster than original Attack, Decay and Release

- linear control of modulation amount (or original Xp Scaling)

B Panel
FULL Modulation Matrix with 27 Sources & 47 Destinations

The Xpander also allowed the user to reapply a mod source to the same destination, so I made this Over-Mod feature to cover the cases where this occurred when copying presets - 5 extra knobs of mod amount! Mostly used to obtain values between settings on the Xp scale.

Reset Matrix to start from scratch

[I finished this up in mid 2015, dusting it off to add a few more presets and some refinement before I had to, at long last, return the gracious loan of a Matrix-12 keyboard to its owner.]

I recall that I borrowed a few techniques from others along the way… pretty sure the heart of the ENV started out somewhere else before I modded it. I grabbed the hardware knob & button art on the internet and customized those as well as creating the rest of the UI in the excellent KnobMan software.


In this ensemble I have copied (by hand, one at a time) the values of every preset from the Xpander factory library, some of my favorites from the Matrix-12 factory set, and a bunch of choice selections I found online in SysEx libraries. This process also helped me further fine tune the interaction of all the parts.

Have Fun, Make Music



Thomas Alenfors
5 months ago
Wow! Fantastic!!
Jake Bell
6 months ago
Someone finally did it! Awesome! Thank you very much!
Abdullah Said Uslu
6 months ago
Thank you very much! Really nice sounding synth!
Thomas Clement
7 months ago
Bégnon Frédéric
7 months ago
Very nice sound, 10000 thank's. The string preset is fabulous. Yamaha CS80 it's possible ?
Michal Wolski
7 months ago
Fantastic work!!!
7 months ago
This is amazing. Thank you so much!
andrew aronson
7 months ago
dunno if have access to version six, but the stock core NLB ladder filter is basically an oberheim filter. also the stock core oscillators in V6 have better anti aliasing than primary versions. might be good to consider an updated version as a companion or sorts
James Domine
7 months ago
Sounds great! Using it all the time. Very versatile.
andrew aronson
7 months ago
honestly, not a bad bread and butter poly synth
7 months ago
Thank you, Troy - but please zip your upload to a smaller size.