Fresh out of the box and running through the presets of the Behringer UB-xa, my first impression of the sound of the UB-Xa was that it was very reasonably Oberheim-y, but but no more so than what I can achieve on a number of other hardware and soft synths I already own. Meaning it didn't jump out and immediately make me think "Oh yeah baby, that's the Oberheim sound!" like a vintage Obie or the OB-X8 which I had for a while. And my first impression was a solid 80-85% grade in successfully hitting the 'Oberheim Sound.'
Spent a few days digging into progamming it to capture what to my ears was missing, and rolled my own Saw/PWM string pad, which is one of the classic standout special sounds of the OB-X and OB-Xa for me.
I'm happy to say I'm MUCH more pleased with the result, sound is much closer to the the special character of vintage Oberheims in the string pad timbres. I revise my grade to a 90-95% emulation success of the OB-Xa and OB-8 sound.
The original OB-X is quite a different synth than the -Xa and -8, For the emulation of the OB-X sound, I'd still say 80-85%. Key reasons, the resonance isn't quite right, and the filter is too clean to my ears.
One unexpected disappointment -- I'd mis-interpreted the spec of the Mod Matrix, expecting Osc Cross Mod as one of the enhancements. I thought the "OSC1Fr" was the Osc wave output, but it's the sum of all controlling voltages to Osc 1 frequency via the Frequency Knob & Mod Section settings like LFO to pitch etc. DOH! So, while having Hard Sync is good, lack of Cross Mod is definitely a let down.
I tried to make an "FM" patch anyway ;)