Oberheim SEM

Oberheim SEM Image

The SEM was Oberheim's first official analog synthesizer. SEM stands for Synthesizer Expander Module. It was conceived with the notion of being used as a backup synth connected to a sequencer for layering or beefing up your existing monophonic analog synths. The SEM itself was a keyboard-less module with two analog oscillators, a 2-pole multimode filter, ADR envelopes, and an LFO. Each of the two oscillators offer triangle or rectangular waveforms. But unlike the Moog and ARP counterparts of the time, the SEM's 2-pole (12dB/oct) filter was a little thin. The others used a 4-pole (24dB/oct) filter which has a steeper roll-off and so it sounds much better. But the SEM's filter offered many modes in addition to low-pass, including high-pass, band-pass and band-reject.

Although SEM modules and other external controllers could be inter-connected, the SEM is not a patchable synth module like other modular type synths of the time. Its signal routing was more or less, hard-wired. The SEM was for all purposes, an accessory. But Oberheim jumped into the synth market by coupling SEMs with a keyboard and an analog sequencer into a compact, white, little performance synth. That led to the Two Voice, Four Voice and Eight Voice models. And from there, came the rest of Oberheim's history of instruments. Some earlier SEMs have several differences in their circuit design that affects the envelopes, filter, etc. If your SEM has "1080" written inside, it's an early one. If you see "1180", it's the "normal" one that most people know and love.

Oberheim SEM Image

Pictured just above is the Polyphonic Synthesizer Programmer, introduced in 1976. It could be used with the SEM and the Two-, Four-, and Eight-Voice models. The unique feature this programmer had (for its time) was the ability to store the knob settings of a SEM modules parameters. Neither Moog nor ARP could offer memory/patch storage like this at the time. The PSP could accommodate up to 8 SEMs or, in other words, the Eight Voice. SEMs have been used by Jan Hammer, Josef Zawinul, and filmaker/composer John Carpenter.

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17 Visitor comments
OB fan
April 12, 2013 @ 4:21 am
anyone near London have one of these originals for sale?
don j.
February 19, 2013 @ 4:04 pm
this is a crazy review. the (original) SEM has the fattest filter sound around, even slightly better than the arp 2600/4012, which is also very hard to beat. certainly nothing modern comes close to either of these. this reviewer either doesn't know what he's talking about or had a broken unit. maybe if it sounds dull, replace the CA8030s and capacitors and then give it a chance. there are PLENTY of examples on youtube of how good a properly functioning vintage SEM can sound.
September 19, 2012 @ 6:23 am
"The others used a 4-pole (24dB/oct) filter which has a steeper roll-off and so it sounds much better."

Oh my. Great website overall, but comments like this simply illustrate the author's naivity.

What a silly, silly statement.
June 24, 2012 @ 2:34 pm
"The others used a 4-pole (24dB/oct) filter which has a steeper roll-off and so it sounds much better."

As much as I find the SEM filter to be a bit tame and dull, this is a really crappy description, what sounds better or not is highly subjective from person to person, not a fact in any way which they are trying to make it sound like here.
St. Magellan
May 8, 2012 @ 1:21 pm
The SEM is one of the more unique synth modules of its time, with its own highly distinctive voice. Think of it has a mutant hybrid of the minimoog's thick, rich creaminess (though with more emphasis in the midrange) and the ARP 2600's modular flexibility. And while the filter doesn't self-oscillate, it's capable of some monster sweeps that cover the frequency spectrum like no other synth. The SEM should be in the soundlab of every music college: its panel layout is intuitive and it makes sound creation an absolute joy.
VSE Rating

It’s Good

User Rating

Rated 4.28 (260 Votes)

  • Check Price
  • The link above will take you to an eBay search for this synth to see active listings. If you don't find it there, try looking in our forum marketplace or post a wanted classified.
  • Specifications
  • Polyphony - Monophonic
  • Oscillators - 2 VCO's (each with sawtooth or variable-pulse waveforms)
  • LFO - LFO is triangle wave only
  • Filter - 2-pole multimode (low-, band-, hi-pass, band-reject) VCF with ASR (Attack, Decay and Sustain) generator
  • VCA - 2 ADR (Attack, Decay and Sustain) Envelope Generators
  • Keyboard - None
  • Effects - None
  • Memory - Not on-board. External Polyphonic Synthesizer Programmer module stores control voltage settings for up to 8 SEM modules each.
  • Arpeg/Seq - Not on-board. External DS-2 Digital Sequencer option.
  • Control - CV / Gate
  • Date Produced - 1974 - 1979

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