Understanding FM #2 - The magic of sidebands and the origin of all those cool sounds
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- Опубліковано 28 вер 2024
- If you want to start at the beginning of the series, there's a playlist you can follow: • Understanding Frequenc...
Now we get to the meat of FM, where all those lovely rich sounds come from...and also those clangorous, in harmonic sounds. It all starts with the generation of sideband frequencies coming out of the modulation of frequency.
A lot of what we're going to talk about from here on is going to involve understanding how harmonics come together to create more interesting sounds. If that's new ground for you, check out this video first: • Oscillators, harmonics...
I've known for a while that FM sounds 'nicer' when you use integer divisions of the carrier frequency for the modulating frequency, but that makes a lot more sense now that I know about the sidebands.
@stogoshuffle - Exactly! Not the next video but the one after, I'll be digging into those ratios, there's some neat stuff going on in there.
THANKS A LOT! there's so much misinformation at youtube than i feel i need a fresh start to actually understand whats fm
These are so valuable! I'm learning a lot. You really can't overstate the value of an oscilloscope. Seeing what's happening visually makes all the difference.
I do agree with the other commenter about text on the screen that doesn't match what you're saying. Some great advice I heard a while back about presentations is not to make the audience read and listen at the same time, cause they can't do both. What I do now is make each slide either a picture or a single word, or at least as few words as possible, specifically avoiding sentences.
Why does UA-cam always always always push pt2 instead of pt1?
really enjoying this so far. good call on breaking it into shorter videos. even short videos you have high information density with this topic so it gives people who are following along food break points to kinda onboard each set of concepts
You are one of the best teachers on UA-cam. Thanks!!
Wow, thank you so much!
you mentioned "DX", they are actually PM synthesis not having any sidebands below the route and the same go's for most digital FM synths. they all should be called PM synths.
+10 for the shot of the CX5M, my first FM synth. Still have it with the big keyboard.
@rockrobertson5776 - That keyboard was surprisingly decent! Cool that you still have yours. It deserves a video all it's own, I wonder if I can find one locally...
clangorous ❤
@ValirAmaril - It's a great word :)
Very nice series, thank you for your effort! I'm very curious though, what's the story with the carrier frequency dropping & disappearing? Is there another video perhaps about this? Alternatively I'd appreciate if you could share any relevant reading material about that. Thanks again!
@Act1v1st - Yes! That is really interesting. I will be digging into this, but it's a couple videos out still. In the mean time, you can check out Bessel functions -- they basically describe how the sideband levels evolve over time. Also, there's an element of destructive interference that happens when those sidebands go down below zero and "reflect" back over sidebands that are already there. I'll start discussing that last one just briefly in the video that should be out tomorrow morning. The details get involved though, so it's going to take just a bit to get everything lined up for it.
Really enjoying these. I've been testing these examples using a VCO2600 as carrier (utilizing it's fm inputs) and the two independent outputs of a cre8audio chipz.
WTF... mate this gold - thank you soo much - instant subscribe.
By the way the opsix is a great cheap tool to show FM and so on.
@zebarzebra - Thank you so much! I think I need to check out the Opsix.
I program bright fm sounds but im trying for darker sounds.
Mind blown! Please keep them coming!
@shey87 - IKR? Video #3 should be out within 48 hours I think.
By far the best FM video i've seen in ages. High five.
Ermmm… well this was pretty great. Am I actually, finally going to understand how FM works by the end of this series? Fantastic work here, thank you so much, I’m devouring these episodes!
Looking at how the sidebands are symmetric, it just occurred to me that the ones to the left of the carrier are actually undertones, and that this must be one (just one) of the reasons FM timbres often sound inharmonic.
@modalmixture - Ah! We're going to get there! You're right, they are undertones, but in video #4 I think, you'll see something cool where actually the undertone becomes the fundamental for a new 'virtual tone'. But that only works when the carrier & modulator frequency are in a nice ratio to each other. When they aren't? Inharmonic city.
Glad you're enjoying the series. #3 should be out on Friday morning I think.
This is the best explanation I've ever seen. Great job
Wow, thanks!
Are there any inharmonic frequencies in between like natural sounds?
@epiphoney - Yes! That's what the next FM video is going to get into, how you can pick values for carrier & frequency that will be more or less harmonic/inharmonic. And leading up to that is a general video on "why some pairs of notes sound nice (harmonic) and some don't (inharmonic)" to lead into that FM one. That one should be out in about 24 hours or so.
I'm not a fan of videos with spoken tekst and different written text at the same time, but I was a brave little boy and managed it. Thanks for the excellent visuals and explanation!
First of all, beautiful video! This may well be the clearest explanation of FM creating sidebands I’ve seen. I tried to work through Bristow’s text back in the 80s but didn’t have the math depth to really get the Bessel functions. It took a broadcasting tech class in college for me to really get it.
What are you using to display the sidebands? Looks great!
@Bent6 - Thank you so much! Actually, the sideband spectrum display - along with a lot of the waveform displays, etc. - are all animations that I've done myself, in Python and Javascript.
@@SoundVoltageI’m even more impressed knowing you have programming/graphics chops too! Nice work!
Great series! The minimalist design works really well here and the pace is just right.
Agree with tychoclavius, that when what is written is different to the spoken, my brain goes brrrr.
Another thing that came to mind, perhaps you could additionally display the oscillation below the frequency analyzer or on another "slide".
Great video, this cleared things up a lot for me. Just out of curiosity, is that spectrum display reacting to the audio from your modular or is it an animation? I noticed that none of my analog modules are capable of producing a sine wave as pure as shown in the graph, even the self-oscillating filters have a few higher harmonics at around -60 db, which makes it a bit more difficult to see what's going on with the side bands.
@nilskozstum8256 - It is being generated by the audio coming out of the modular rig, but since I wrote the code, I get to make decisions about how big frequency spikes have to be before I include them in the animation. Generally speaking though, I'm not intentionally cutting anything out. The only sine wave I've really a real extra frequency component in is the Nonlinear Circuits CEM 3340, and in that case you can distinctly see a little sharp peak right at the apex of the waveform. I'll have to check things again though.
@@SoundVoltage thanks for clearing that up! I guess it's down to how the sine is generated, my main oscillator that I use for FM is the Instruo Cs-L, where one of the oscillators is a triangle core and the other a saw core, which then get filtered/sent through comparators to generate the other waveforms. You can clearly see on the spectrum that the same harmonics that you get in the core waveform are still present, just much more toned down. I don't mind this at all, I love the sound of these oscillators. I was expecting the filters to be cleaner then they are though. Cleanest sine I could get from MI Plaits, unsurprisingly digital will get you the most mathematically pure sine.
Such a valuable explanation!
Thank you! I'm glad it helps.
tbh i don't think I would have understand it if I didn't already before I saw the video.
The text to speech and different information on the screen makes it very confusing even when you know what's going on.
Not actually text-to-speech...