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Stereo filters?

4dubs

Stereo filters?
« on: June 21, 2018, 09:31:27 AM »
Perhaps someone can clarify for me . . . while I'm a veteran DSI owner, I have no experience with "stereo filters", which the PX apparently possesses (I believe the Evolver series did too?).  Maybe I'm missing something, but it doesn't appear that the PX has separate controls for each filter, nor does their appear to be a way to offset them against each other (as you would with a Moog Voyager, for instance).  Wouldn't that mean the same filter settings are being passed through either side of the stereo outs?  I'm not seeing the significance.  Is it just something I have to hear to understand? 
DSI:  Prophet 6, Rev 2 16 voice, Pro 2
Other:  Moog Model D reissue, Voyager, Sub 37, Little Phatty Tribute, Nord Stage 2 SW73, Korg Z1, Mono/Poly, Studiologic Sledge Black, Arturia Matrixbrute,

Re: Stereo filters?
« Reply #1 on: June 21, 2018, 10:30:19 AM »
The most obvious use of stereo filtering is to ensure that the stereo image established for a voice before filtering is preserved.  If I start with a stereo sample and have only one filter for the voice then the two channels are summer prior to filtering and there’s no way to recreate the original stereo image.  You can pan the filter output, but each voice would still be a mono signal at a designated position in the stereo field.

So with the introduction of stereo samples it’s really important to preserve the original content.  There are other benefits as well, since a voice is composed of two sampled instruments and two DSP oscillators.  Each of these can be independently positioned in the stereo image prior to filtering.  Being able to have two retuned oscillators in a voice, one panned hard left and one hard right, creates a wide stereo image within a single voice even without considering samples.

Lastly, it is possible to adjust the cutoff of the left and right filters independently.  They’re listed as mod destinations, so any modulation source can adjust them individually.  There is also a “stereo split” parameter that can be adjusted using a soft knob when in the filter section.  This simultaneously increases the left cutoff while lowering the right or vice-versa.

The one thing it seems you cannot do is apply different resonance settings to the left and right filters.  This isn’t a hardware limitation, as they can be addressed independently in 16-voice mode, but presumably for simplicity DSI hasn’t included distinct left/right resonance modulation destinations.

4dubs

Re: Stereo filters?
« Reply #2 on: June 21, 2018, 10:50:25 AM »
Great explanation . . . thanks very much!
DSI:  Prophet 6, Rev 2 16 voice, Pro 2
Other:  Moog Model D reissue, Voyager, Sub 37, Little Phatty Tribute, Nord Stage 2 SW73, Korg Z1, Mono/Poly, Studiologic Sledge Black, Arturia Matrixbrute,

Re: Stereo filters?
« Reply #3 on: June 21, 2018, 03:00:43 PM »
Great explanation . . . thanks very much!

I’m glad you were able to read through the typos and autocorrect-induced quirks!  I’m fond of abusing post-then-edit and evidently by the time I noticed my limited window to fix the quirkier parts had expired.  “Retuned” should be “detuned”, etc.

DMS

Re: Stereo filters?
« Reply #4 on: June 21, 2018, 04:42:23 PM »
 the l/r cutoff filters to the  l/r sliders for some great stereo manipulation

4dubs

Re: Stereo filters?
« Reply #5 on: June 21, 2018, 07:32:42 PM »
the l/r cutoff filters to the  l/r sliders for some great stereo manipulation

Yep . . . that was exactly what I was thinking.   :)
DSI:  Prophet 6, Rev 2 16 voice, Pro 2
Other:  Moog Model D reissue, Voyager, Sub 37, Little Phatty Tribute, Nord Stage 2 SW73, Korg Z1, Mono/Poly, Studiologic Sledge Black, Arturia Matrixbrute,

4dubs

Re: Stereo filters?
« Reply #6 on: June 21, 2018, 07:34:23 PM »
Great explanation . . . thanks very much!
“Retuned” should be “detuned”, etc.

No worries Lady Gaia . . . thanks again
DSI:  Prophet 6, Rev 2 16 voice, Pro 2
Other:  Moog Model D reissue, Voyager, Sub 37, Little Phatty Tribute, Nord Stage 2 SW73, Korg Z1, Mono/Poly, Studiologic Sledge Black, Arturia Matrixbrute,

Shaw

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Re: Stereo filters?
« Reply #7 on: July 09, 2018, 04:53:56 PM »
I’m LOVING these stereo filters.  One of my favorite, “no-brainer” tricks is to use 2 LFOs each set to random, one modulating the left filter cutoff, the other modulating the right.  Again, supe-simple, super-obvious, but amazing sounding.

Another trick I like is using velocity to modulate the mod amounts differently for left and right filters. SWEET!

What tricks are you guys using?
"Classical musicians go to the conservatories, rock´n roll musicians go to the garages." --- Frank Zappa

Razmo

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Re: Stereo filters?
« Reply #8 on: July 11, 2018, 01:21:43 AM »
For you that have the X regarding stereo:

What about the two synth oscillators? ... with the sample oscillators, it's clear that there is a dedicated oscillator firing into the left/right sides of the two analog filters used for stereo, otherwise stereo would not be kept... but do you know how the synth oscillators is done? are they true stereo, and not just the same one oscillator duplicated into the left/right filters? ... on the Evolvers, the oscillators are true stereo... meaning that if you chose a sawtooth for the waveshape, then without phase keysync on, you'd have different phase offsets in left/right (or said in another way; there was a dedicated oscillator for left and right) ... that was what made the Evolver stand out because it could create a very wide stereo sound without introducing beating or detuning, and instead just had the left/right oscillator out of phase.
« Last Edit: July 11, 2018, 01:24:46 AM by Razmo »
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Re: Stereo filters?
« Reply #9 on: July 11, 2018, 07:46:13 AM »
The oscillators are mono sources, but you do have control over their pan position prior to hitting the filters.  So each one can be equally distributed to the two channels, panned hard right or left, or anywhere in between.  If you want the effect you describe it just requires one oscillator panned left and one panned right.

Sampled instruments can also be panned, but there you're starting with a stereo image so you're actually placing two discrete channels with a single pan parameter.

Razmo

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Re: Stereo filters?
« Reply #10 on: July 11, 2018, 08:14:42 AM »
The oscillators are mono sources, but you do have control over their pan position prior to hitting the filters.  So each one can be equally distributed to the two channels, panned hard right or left, or anywhere in between.  If you want the effect you describe it just requires one oscillator panned left and one panned right.

Sampled instruments can also be panned, but there you're starting with a stereo image so you're actually placing two discrete channels with a single pan parameter.

As I would have guessed it would be, since that is how it is with the Prophet 12, from which most of the synth-side of the X was ported... would have been nice if it was true stereo oscillators though...

So in essence, the X is 6 oscillators... 4 sample (working as two pairs) and 2 synth...
If you need me, follow the shadows...