#145

Question.

13%20PM

How does the middle filter respond to freq movement. The LP and HP will move with the FREQ left and right, does the middle BP Filter just stay constant? or does it just grow and shrink in the middle.

And in Formant mode, what does the 3 band pass filters do? They stay where the Span settings are? or does it move left and right like a LP or HP would do.

I’m assuming the image above is when FREQ knob is at noon. what would it look like if all the way CW and CCW.

can’t quite visualize it.

#146

I think in both images above, the Freq is whatever you have that set to, via knob and 1v/8 in. That includes Center. So, everything moves up and down w/ Freq.

In both Crossover and Formant mode, Span controls how far the Low and High filters are from that center.

In Formant mode, the Centre filter has a distinct peak, as shown and is more like a narrow BP. In Crossover mode, the Centre filter is all frequencies between the Low and High peaks, so essentially a wide BP (or not that wide depending on your Span settings).

The images would continue to look like that, but the frequencies they’re covering would be different. I don’t believe the response character changes as the 3 collective filters move towards lower or higher frequencies.

So like this. Note that the 12kHz number is completely made up. Crossover behaves in a similar manner but this was easier to Photoshop.

3sisresponse

None of this speaks to the inverse Q response, which I’m not going to begin to try and illustrate as I have no idea what it would look like :slight_smile: Also, //////// correct me if any of this is wrong.

#147

Okay, so its basically like a venn diagram.
36%20PM
So the center is only the cross over.

Also, is the sense of scale about right in your photoshop? I know 12kHz is made up, but if in formant mode and FREQ is full CW, does all 3 BP only represent the top halfish frequencies only in all 3 inputs?

#148

Possibly, though I’m not familiar with ‘cross over’ as an engineering term. Centre is a filter whose center frequency is defined by Freq (I can’t believe that sentence). In Formant, that’s just a BP filter at that frequency. In Crossover, it covers all the frequency range between the Low and High filter peaks. If that’s ‘cross over’ in engineering speak, then yeah. (I guess that would make sense given the mode name).

I believe the diagram in the manual (which I photoshopped) is illustrating a scenario where the Span is relatively narrow. I unfortunately don’t have a good spectrograph - that would be amazing for this sort of thing - but the peaks are further apart from each other if span is ‘wide’ (CW) and closer the more towards CCW you get. Note that the low and high basically align with center at about 9:30, and more CCW than that, Low is actually higher than Centre, and High is lower than Center. They cross over each other, in other words.

One thing to note is that, if you are listening to Centre, and in Formant mode, Span has no effect at all. Centre’s location always matches Freq (that’s what Freq is, really), and in Formant, Centre is a bandpass filter, so changing Span does not change Centre. In Crossover mode, changing Span affects how much of the frequency range Centre is covering, so you do get an audible effect in Centre if changing Span while in Crossover.

I think this is actually easier to hear than to visualize. I would crank up Quality so that the three filters oscillate, and then put it in Formant and either monitor all the outs through All, or 2 at a time, until you understand better how they ‘move’.

4 Likes
#149

Also, for the slopes and range, try feeding some pink noise into ALL.

I have a couple of visualizers I use for this sort of thing. MOTU included some nice software along wtih my interface and Logic Pro has decent metering too. There probably have to be a few good free plugins out there too if you don’t have something to work with. Never cared as much until I started using synths more and it has made the journey much easier. :+1:

1 Like
#150

Have you tried inputing white noise into 3Sis and monitoring all the outputs with a spectrum analyzer? I think this would be the most intuitive way to visualize the filters.

edit 1: oops too slow.

#151

I think the Venn diagram is not really the right way to think about it, unless you have 3 circles instead of two.

Behold my terrible design skills (sorry moving fast, need to get back to work! and I know about 2-3% of Photoshop)

3sisoverlap
3sisoverlap.png2000×2000 113 KB

Where red is Low, green is Centre, blue is High, if that’s not clear.

8 Likes
#152

More succintly, maybe:

In Formant, it is literally 3 bandpass filters, positioned with Centre by Freq, and then with a spread from each other defined by Span. The 3 BP filters may have some frequency overlap, or not, depending on the width of Span.

In Crossover, Low and High are more like traditional LP/HP filters. Centre is a BP filter in this case, but it always has overlap at its boundaries with the LP and HP filters, and so it may be quite wide if Span is set wide. The center frequency of Centre is determined by Freq. The center frequency of the LP and HP are determined by Freq plus or minus the “width” given by Span.

I’m not sure that’s much better, TBH? :slight_smile:

5 Likes
#153

I get it now. The light has been turned on! For some reason I thought LP/HP/BP were moving independently and not as a unit.

So if looking at the original image in the manual, the center will always follow the FREQ knob up and down the spectrum and move all as a unit.

So like when you detune voices in a OSC to get that fat sound, you can basically do that here with FORMANT and SPAN but with 3 different sound sources? MIND BLOWN.

Even just 1 audio going into ALL and then FORMANT wide SPAN is pretty sweet!

Wow, this is something! :smiley:

@xenus_dad Thanks! Thats what I meant but have no photoshop skills :smiley:

1 Like
#154

TBH this helped me understand it better for myself. Also, I might have gotten some stuff wrong! Hopefully folks will set us right.

But yeah, the three peaks never operate independently of each other. They’re always centered according to Freq on Center.

Yeah. Easiest way to hear that is to monitor ‘All’; crank up Quality so the filter is self-oscillating; turn Span CCW to about 9:30 until you hear the three tones converge; then turn slightly in either direction. That’s the direct equivalent of the slightly detuned oscillator.

#155

I’m pretty sure LOW is the only one which accurately tracks v/o (plus influence of span, of course).

2 Likes
#156

Just want to say this.
Sister -> FORMANT
FREQ 9oclock

MI Marbles. t1-> LOW, t2->CENTER, t3->HIGH. Any X to FREQ.
LOW Out-> VCA 1, CENTER Out-> VCA 2, HIGH Out-> VCA 3.
Maths CH 1 & 4 on Cycle, different attach/release on VCA 1,3

SEXY.

4 Likes
#157

I tried out this patch for myself, pretty amazing. The harmonic fluttering that Just Friends adds is hypnotic. My patch was nearly identical to yours except I used a DLD instead of an Echophon, and added a tanh3 in the signal chain.

Thank you for sharing.

23 Likes
#158

gosh, this is wonderful. thank you for capturing it and posting. wowowowow.

2 Likes
#159

this weird nature scene was captured halfway through a patch dismantle, so no notes beyond six sisters in feedback with each other, cold mac wavefolding, let’s splosh! exciting with processed LFOs.

these filters, y’all.

46 Likes
#160

holy frog, this is wonderful :star_struck:

1 Like
#161

Oy, all the diagrams above are lovely… I’ve always been totally mystified by how exactly the Sisters work, basically have just been turning knobs and enjoying the sounds, albeit with a pretty strong desire to know a bit more about what the hell’s going on haha.

Also @kbit & @dan_derks those clips sound fantastic :heartpulse:

3 Likes
#162

whale song is the best synthesizer music and this gets super close

2 Likes
#163

Can you say more about Let’s Splosh? That looks nuts!

#164

Is there something that would be useful for limiting the levels out of Sisters when you are sweeping? I find I have to ride my mixer pretty carefully to manage the resonance swells when I am jamming with Just Friends. :thinking: