OB-6 vs SEM (new)

[anselmi]

Hi, I already got a SEM, the new, patchable version from Tom Oberheim.

I really like it and used it a lot in my productions but since I´m about to get the OB-6 I wonder if they will overlap too much.

I know the SEM being patchable is more "experimental" and also can interact with other CV-capable stuff, like modular, but no matter the fact that I got a eurorack case I never use them together.

The things I patch the most are to use the oscillators as modulation sources, like oscillator and filter FM, and since the OB-6 can use osc 2 as a modulation source I think this kind of sounds could be covered by it.

what do you think?

[science]

I know guitarist who have more than 10 electric guitars. The best thing is you can have them play at the same time without having to record anything.  If there is much overlap it doesnt matter imo.

[DavidDever]

The OB-6 itself is mono-timbral, i.e., all six voices are assigned to the same timbre/patch, so you might consider using the SEM as a spare voice/part, or to layer with the OB-6 itself in low-note priority to fatten up the bottom end. (I'm assuming that you have the SEM Patch-Panel version, so you'd need an external MIDI-to-CV converter.)

You might also find that prototyping patches on the SEM itself ends up being more intuitive - in this respect, you'd have to pry my SEM (MIDI-to-CV version with custom patch panel) out of my cold, dead hands.

[Grimulkan]

I find use for both the SEM and OB-6. I use a lot of continuous pitch modulation on mono patches for example, so the SEM (with pitch CV input) is necessary. On the other hand, there have always been SEM patches I wanted to add notch, notch/BP or Q modulation to, but this is now actually possible with the OB-6.

I'd say if I had the MIDI-only SEM I'd be less inclined to keep it, but IMO the PP and Pro versions remain relevant if you use CV in any non-traditional way (i.e., other than just MIDI->CV conversion).

[DavidDever]

I find use for both the SEM and OB-6. I use a lot of continuous pitch modulation on mono patches for example, so the SEM (with pitch CV input) is necessary. On the other hand, there have always been SEM patches I wanted to add notch, notch/BP or Q modulation to, but this is now actually possible with the OB-6.

I'd say if I had the MIDI-only SEM I'd be less inclined to keep it, but IMO the PP and Pro versions remain relevant if you use CV in any non-traditional way (i.e., other than just MIDI->CV conversion).

I'm working on a drop-in PCB that exposes the extra two panning VCAs while, at the same time, provides some more sophisticated normalling for the MIDI section than the stock Pro or MIDI-to-CV units, AND exposes the cross-sync capabilities in the same manner as the patch-panel version.

I'm less worried about keeping it stock as the MIDI-to-CV units tend to be less desirable due to the lack of patch points, as well as the incontrovertible fact that you'd have to pry it out of my cold, dead hands.

[autoy]

Interesting comparison. So how would a mono voice from the OB-6 compare to a modern SEM Pro? Are the filters similar? RAW waveforms? Envelope behaviour? If anyone has both I'd be delighted to hear.

[eXode]

Sadly I don't read PCB's etc but someone who is familiar with electronics could perhaps deduce what's going on:

New Oberheim SEM (Only VCO's, VCF, and VCA are relevant):


OB 6 Voice card (see attachment):

[Grimulkan]

I'm working on a drop-in PCB that exposes the extra two panning VCAs while, at the same time, provides some more sophisticated normalling for the MIDI section than the stock Pro or MIDI-to-CV units, AND exposes the cross-sync capabilities in the same manner as the patch-panel version.

Interesting! If you do it, would love to see more details. I'm currently trying to figure out how to add notch & Q CV control to mine using vactrols (or maybe digital pots).

Interesting comparison. So how would a mono voice from the OB-6 compare to a modern SEM Pro? Are the filters similar? RAW waveforms? Envelope behaviour? If anyone has both I'd be delighted to hear.

The oscillators are clearly not exactly the same because the OB-6 has a triangle wave, and also continuously variable waveforms (though that could just be a mixing circuit added on top). I haven't done a spectral comparison or anything, but I prefer the raw SEM oscs. It could be all in my head. I do very much like that I can add extra oscs on the SEM via the ext input, which is impossible on the OB-6.

SEM envelopes behave differently (only 3 env controls with shared decay/release, and fully analog). Doesn't matter much to me as I often use external envs patched in to the SEM anyway.

I want to say the SEM portamento (if you use the Pro or MIDI version) sounds like it has a different transition curve compared to the one on the OB-6.

Filter controls a bit differently, which could be the way the knob ranges are mapped or the gain staging, but I can usually get one to sound "close enough" to the other with a little bit of work.

[autoy]

The oscillators are clearly not exactly the same because the OB-6 has a triangle wave, and also continuously variable waveforms (though that could just be a mixing circuit added on top). I haven't done a spectral comparison or anything, but I prefer the raw SEM oscs. It could be all in my head. I do very much like that I can add extra oscs on the SEM via the ext input, which is impossible on the OB-6.

SEM envelopes behave differently (only 3 env controls with shared decay/release, and fully analog). Doesn't matter much to me as I often use external envs patched in to the SEM anyway.

I want to say the SEM portamento (if you use the Pro or MIDI version) sounds like it has a different transition curve compared to the one on the OB-6.

Filter controls a bit differently, which could be the way the knob ranges are mapped or the gain staging, but I can usually get one to sound "close enough" to the other with a little bit of work.

Of course they are not the same, not only in waveforms but the fact that the OB-6 has a sub-osc and probably different gain staging due to poly. I did hear for Dave Smith that the OB-6 was not a direct transplant form a SEM into the body of the Prophet-6 in the sense that the envelopes for example were tweaked to match the response of Oberheim keyboards (not sure if he referred to SEMs os classic OBs). From you comments I understand that most of the time you can match an OB-6 to a modern SEM, which is a good thing in my book.

[Simonsound]

I just got the OB-6 and I also have the first Oberheim 4 voice in my possession. I'm a bit under the weather but I'll try and do a comparison. The 4voice is a contakerous (but amazing sounding) beast though!