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I think the title on HN is misleading. Sadly I’m not sure what’s the short and clearest title :( The video is very nicely made and it focus on sound systems /

I think the title on HN is misleading. Sadly I’m not sure what’s the short and clearest title :( The video is very nicely made and it focus on sound systems / boomboxes frequency response and behavior of included filtering modes. So when talking about EQs with “all forms” in mind, you should consider: - EQ is merely combination of one or more filters. - There are many common filter designs, the video isn’t about that, it also doesn’t mentioned Low-pass/High-pass/band-pass/bell or common structures, but it is only showing them. - Filters made and behave differently - Most filters (including the ones in the video) are done on the time domain (vs spectral one) - Phase, this is the biggest missing piece in the video imho. Naive filtering is “smearing” the signal to achieve the different tone balance. By doing so, they also most likely change the phase (unless using linear phase filters) - Filtering might result delay in time.

atoav 1y ago
You have a slight misunderstanding here about the phase shift bit. Technically filters don't cause phase shift, phase shift causes filters. That means in the analog world all realtime filters come with phase shift, if they didn't you wouldn't have a filter. In the digital world there is a thing called linear-phase mode where clever people found ways of building filters that shift the phase of the whole signal the same way (involves running the signal through forwarwards and backwards through special filters). If you now have an audio program that deals correctly with the latency introduced by each effect, you can shift the rest by the same amount meaning you bought yourself a linear phase response with added latency (a small delay) on everything. Remember: Humans can't really hear phase smears unless they happen in relation to another thing that is in phase. This only happens when you mix two signals. The result of that mix is yet again a filter (e.g. comb filters). With filters everything is a trade off all the time, but again phase shift is not a just a bad side effect of a filter, it is the mechanism by which it does the work. And sometimes the phase shift introduced cannot be heard.
- Aldipower 1y ago
  And also linear phase isn't for free, besides the latency, it also adds pre-ringing, which especially in the lower frequencies can be very audible and annoying.
  - atoav 1y ago
    There is no such thing as free lunch after all.
    - Aldipower 1y ago
      I once saw a place with free beer, then I woke up.
- Sesse__ 1y ago
  FWIW, you don't need to run forwards and backwards to get linear phase. Any symmetric FIR filter will do.
  - rcxdude 1y ago
    Yeah, there's a difference between linear phase (which you can achieve with a causal filter, i.e. one that is running in real-time) and constant-phase, which requires that you have more or less the whole signal before you filter it (you can approximate it to the extent you're willing to add more latency).
  - atoav 1y ago
    Good addition. I mentioned the forward/backward bit as this was a way to achieve linear phase in analog times eith more conventional filters (although the cost here was even higher with the additional added noise floor due to tape noise ad the extra work involved).
JKCalhoun 1y ago
> Phase, this is the biggest missing piece in the video imho. It's why I like full-range speakers—no crossover. At most you might throw a cap on a super-tweeter (yes, even so-called full range need help on the top and bottom ends of the spectrum—so super-tweeters + sub-woofers). Complicated crossovers destroy the phase. Without crossovers/EQ the more stripped-down full-range setup preserves what the Hi-Fi nerds call "soundstage". (A good full-range setup: imagine the "soundstage" you get from wearing headphones—but without wearing headphones.) Those seeking a full-range setup (especially with a tube amplifier) are kind of adjusting for EQ simply by the type of speakers/drivers and placement. (And to be sure they're not going for a flat, studio-monitor response but what sounds good).

atoav 1y ago

You have a slight misunderstanding here about the phase shift bit. Technically filters don't cause phase shift, phase shift causes filters. That means in the analog world all realtime filters come with phase shift, if they didn't you wouldn't have a filter. In the digital world there is a thing called linear-phase mode where clever people found ways of building filters that shift the phase of the whole signal the same way (involves running the signal through forwarwards and backwards through special filters). If you now have an audio program that deals correctly with the latency introduced by each effect, you can shift the rest by the same amount meaning you bought yourself a linear phase response with added latency (a small delay) on everything. Remember: Humans can't really hear phase smears unless they happen in relation to another thing that is in phase. This only happens when you mix two signals. The result of that mix is yet again a filter (e.g. comb filters). With filters everything is a trade off all the time, but again phase shift is not a just a bad side effect of a filter, it is the mechanism by which it does the work. And sometimes the phase shift introduced cannot be heard.

Aldipower 1y ago
And also linear phase isn't for free, besides the latency, it also adds pre-ringing, which especially in the lower frequencies can be very audible and annoying.
- atoav 1y ago
  There is no such thing as free lunch after all.
  - Aldipower 1y ago
    I once saw a place with free beer, then I woke up.
Sesse__ 1y ago
FWIW, you don't need to run forwards and backwards to get linear phase. Any symmetric FIR filter will do.
- rcxdude 1y ago
  Yeah, there's a difference between linear phase (which you can achieve with a causal filter, i.e. one that is running in real-time) and constant-phase, which requires that you have more or less the whole signal before you filter it (you can approximate it to the extent you're willing to add more latency).
- atoav 1y ago
  Good addition. I mentioned the forward/backward bit as this was a way to achieve linear phase in analog times eith more conventional filters (although the cost here was even higher with the additional added noise floor due to tape noise ad the extra work involved).

JKCalhoun 1y ago

> Phase, this is the biggest missing piece in the video imho. It's why I like full-range speakers—no crossover. At most you might throw a cap on a super-tweeter (yes, even so-called full range need help on the top and bottom ends of the spectrum—so super-tweeters + sub-woofers). Complicated crossovers destroy the phase. Without crossovers/EQ the more stripped-down full-range setup preserves what the Hi-Fi nerds call "soundstage". (A good full-range setup: imagine the "soundstage" you get from wearing headphones—but without wearing headphones.) Those seeking a full-range setup (especially with a tube amplifier) are kind of adjusting for EQ simply by the type of speakers/drivers and placement. (And to be sure they're not going for a flat, studio-monitor response but what sounds good).