EQ: A video about all forms of equalizers

https://www.youtube.com/watch?v=CLAt95PrwL4

by robinhouston • 9 months ago

263 77 9 months ago

olooney• 9 months ago

Videos don't do well on Hacker News, but I encourage people to at least watch the first couple minutes of this one. The oscilloscope visual overlay is interesting and the editing is really good.

Also, given the topic (audio equalizers) there's no way it could have been a blog post.

IndySun3• 9 months ago

Good point. The bandcamp link to Posy music is equally pleasant. Nice to find actual mellow music.

creer• 9 months ago

I would hope mostly what doesn't do well is useless titles - like one word, or a pithy joke that makes sense only in retrospect. Unfortunately there is also that guidelines which discourages doing better.

gus_massa• 9 months ago

Usually the subtitle is fine:

A video about all forms of equalizers. From one-click bass buttons to advanced studio correction.

That can be reduced to:

"Equalizers: From bass buttons to advanced studio correction."

PS: I'd try to keep the original title too, but in this case it doesn't look nice

"EQ: Equalizers - From bass buttons to advanced studio correction."

cwillu• 9 months ago

It's pretty common for blog posts in this arena to just include samples that you click to play.

nutjob2• 9 months ago

Videos are harder to watch at work since it's obvious they're not work related compared to blog posts.

layer8• 9 months ago

Also the hardware presented is just gorgeous.

mock-possum• 9 months ago

Ah but I’ll always make time for a Posy video

IndySun3• 9 months ago

A pleasant, if muted, layman's 10 minute journey to explain sound, eq, and speaker response. It gets juiciest on room eq correction/compensation, approaching the 9 minute mark.

kragen• 9 months ago

I'm not sure Posy is a layman.

moffkalast2• 9 months ago

Afaik the dude is a professional audio engineer with a retro soundsystem hoardin.. ahem, "collecting", hobby.

IndySun3• 9 months ago

I'm not sure Posy is a layman

I mean/meant pleasant for average (layman) interest. A compliment, in other words.

tverbeure3• 9 months ago

Very first sentence: "This is pink noise... if you measure it, you can make it look like a straight line."

He then shows a horizontal straight line: that's white noise?

lelandbatey• 9 months ago

Pink noise distributes energy logarithmically in a way that matches the the sensitivities of the human ear. The graph which he shows on screen is ALSO in that same logarithmic space, hence why it shows pink noise as flat: it's flat as far as how humans hear it. White noise is not perceptually flat to humans. Thus when testing audio, it's important to use pink noise instead of white noise.

https://en.wikipedia.org/wiki/Colors_of_noise#Pink_noise

tverbeure3• 9 months ago

The graph which he shows on screen is ALSO in that same logarithmic space, hence why it shows pink noise as flat

Does this also mean that audio equipment in general will display a spectrum with this kind of logarithmic offset adjustment?

Acen2• 9 months ago

The main difference between white and pink noise, is white noise has the same level of power across all frequencies. Whilst pink noise has the same level of power across an octave.

There are more frequencies in the high-range, so it naturally sounds considerably higher pitched.

i.e. a C6 on a keyboard sits at around 1Khz (1046.502 to be exact) and a C#6 is 1108.731 KHz (a difference of 62.229 Hz)

While a C3 is 130.8128, and C#3 is 138.5913 (a difference of only 7.7785 Hz).

Then using an entire octave as an example, C3 (130.8128) to C4 (261.6256) = 130.8128 (0Hz up to C3)

vs C6 (1046.502) to C7 (2093.005) = 1046.503 (0hz up to c6 +- 0.001hz)

esafak• 9 months ago

In the 70s/80s every home stereo system -- racks of stereo equipment stacked a meter high -- had a dedicated equalizer. It was not just for audiophiles!

billfor• 9 months ago

There was a company called DAK in the 80's that sold all sorts of interesting stuff and I still use my BSR EQ-3000 which is an equalizer with a spectrum analyzer display fed by a microphone that you walk around the room with to confirm your settings. It even has a pink noise button that injects that into the amp so you have a uniform pattern to equalize. Sort of like an analog Sonos Trueplay I guess. We could do all of this in the 80s :-)

SanjayMehta• 9 months ago

I built my own 10 band equaliser using instructions from Elektor (I think) back in the 80s. The dream was to acquire a spectrum analyser but real life intervened.

Not sure when I even powered up my stereo system. Probably doesn't even work now.

JetSetIlly• 9 months ago

I suspect HiFi culture was slightly different in different parts of the world.

In my part of the world, the original HiFi guys rejected the EQ units. I was influenced by that I think (my father was an original). I still have a metre high stack of HiFi, in almost daily use, and have never felt the need to have an EQ unit.

BlaDeKke2• 9 months ago

This is a fantastic yt channel!

adzm• 9 months ago

Highly recommend their lightbulb video as well.

encom• 9 months ago

Posy is just one guy.

BlaDeKke2• 9 months ago

This is my favorite: https://youtu.be/eGQQWIbD-nM?si=CtQ-MPIxx8h3vYxH

evantravers• 9 months ago

I knew this was a Posy video before even opening the link.

activexray• 9 months ago

I love Posy's channel so much. Really beautiful love letters to all kinds of vintage tech (plus his own music!).

franczesko• 9 months ago

I tried to post Posy's videos a few times here, but with no bigger interest.

His videos about LCD technology are hypnotizing. Bonus - he makes all the music.

mrheosuper2• 9 months ago

His video always scratch a part of my brain that i event dont know it exists.

ggm-at-algebras• 9 months ago

The history behind vU meters is also fascinating. People used to calibrate off the BBC techs, or off American techs.

No BIPM, no SI units: what the BBC say.

ZeroGravitas• 9 months ago

For the earlier systems with the bass boosts, are the graphs showing what comes out of the cables or what comes out of the speakers?

I would assume they don't care about the very low bass because they were designed as a unit and physically couldn't produce those notes very well anyway. Hence the need to boost slightly higher frequencies to fake bass.

whstl2• 9 months ago

The straighter lines are what comes out of cables.

The more squiggly ones later (eg: 2:45) are what comes out of a speaker. But since he uses a microphone to measure the speakers, so that measurement will also come with room sound. He would need an anechoic chamber to measure "only the speaker".

mrheosuper2• 9 months ago

He also needs to calibrate the microphone, because like speaker, it does not have flat response.

Aldipower5• 9 months ago

Couldn't hear this video, just watch, because I have no sound in the env I am currently in. But some thoughts about EQ.

"EQ isn't phase shift, phase shift is EQ.", a video title I saw once, but hits the nail on the head.

"Nothing is for free.", if you eq some frequencies, you affect some other frequencies too. You can use this to your advantage, if you are aware of this.

"EQ graphs are lying." Lack of resolution and not revealing the phase shift makes most stock EQ graphs not telling the truth.

"My hearing aids sound strange/metallic." This is the phase shift, you are hearing.

Have a nice Sunday everybody!

rock_artist• 9 months ago

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.

atoav3• 9 months 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.

Aldipower5• 9 months 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.

Sesse__• 9 months ago

FWIW, you don't need to run forwards and backwards to get linear phase. Any symmetric FIR filter will do.

JKCalhoun• 9 months 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).

GistNoesis• 9 months ago

Can measurements and calibration be done easily at home to see if your sound system is well calibrated ?

I was thinking of playing a pink noise on the speaker and recording it with a cheap microphone or displaying it with the Spectroid app, but the microphone probably has it's own frequency response.

Is there an App for that ? With each phone model microphone factory calibrated ?

Is there a way to use known fact about physics like harmonics should have a specific shape (timbres) that's should help equalize frequency with respect to each other ? Or from various microphone positions, calibrate it so that any cheap microphone can do the trick ?

LM358• 9 months ago

A UMIK-1 is pretty cheap these days. Also check out REW.

scns2• 9 months ago

but the microphone probably has it's own frequency response.

Spot on. When you buy a measurement microphone, you can download it's specific response from the manufacturer.

behringer• 9 months ago

It's harder than that, because your ears have their own frequency response that can only be measured by your consciousness.

I've found a lot of enjoyment in equalizing as best you can with hardware, and then doing the finishing touches against your ears.

Take a frequency generator, I use a web one, and play a tone that matches your eq knob, and work your way through making sure all the tones are at the same volume. You'll have to do this a few times.

You might be surprised at how good it will sound. Especially the upper ranges which will usually be far too low if you only calibrated with mics and hardware and not your wetware.

KronisLV• 9 months ago

Oh, that's really cool, the channel seems like it has a lot of other nice videos as well!

I wish there was a video that's so nice about compressors, like in Audacity you have all of these settings and most are also present in OBS and other software:

  * Threshold (dB)
  * Make-up gain (dB)
  * Knee width (dB)
  * Ratio
  * Lookahead (ms)
  * Attack (ms)
  * Release (ms)

And I feel like visualizations can really help understanding them better, like: https://codepen.io/animalsnacks/full/VRweeb alongside maybe something that lets you loop an audio sample and see how different it sounds with each change. There obviously already are some videos and discussions and plenty of material out there, but I love a good visualization!

jamesbfb• 9 months ago

POSY is an absolute treasure. The time and effort he puts into his videos is absolutely evident.

0xdada• 9 months ago

I have watched 10+ hours of lessons on compressors and I still don't hear it. I understand most concepts but don't use much compression besides side-chaining and the built-in Ableton glue compression.

derriz• 9 months ago

I know what you mean - took me a while too. I understood what it does, how the parameters affect what it does and the mechanics of it, but struggled to "hear" it.

I even bought a cheap $25 Behringer guitar compressor pedal to see what I was missing but it didn't help - later I realized that my guitar playing isn't repeatable enough. So this isn't the way to go.

What made it click was due to an accidental mistake in my normal workflow - I recorded some DAW-less techno jam stuff using GarageBand (normally I just copy the wavs from my little Tascam). While playing back, I noticed that there's a master compressor and I started fiddling with it. With repetitive music like Techno and House, the difference between no compression and full compression suddenly becomes very apparent (although still somewhat subtle compared to other FX commonly used in music production). Also it helped that my recording had no compression on it - comprising just a raw drum machine and mono-synth.

Aldipower5• 9 months ago

It is pretty normal not to hear compression on material that already is quite compressed. But you will hear compression on very dynamic vocals or a snare drum, I am pretty sure.

Slow_Hand2• 9 months ago

That's normal. For engineers and mixers, compression is one of the more difficult phenomena to hear and build an intuition for.

My advice for learning is to totally overdo the compression on a drum track (snare, kick, hats, etc) and play with the settings. Ideally these drums are uncompressed.

Using a 4:1 ratio, lower your threshold all the way down until you're getting > 10 dB of gain reduction and then start playing with the attack time. What do you hear when the attack time is at 0 ms? What do you hear when you start to slow the attack time? 5 ms? 10 ms? 30 ms? 100 ms?

Then do the same with your release time. Start with it set as fast as it will go and then start to slow it down. What do you hear happening?

Once you have the attack time and release time feeling good then raise your threshold so that the compression is less heavy-handed (unless you like it). Set the threshold where the level of compression feels good to you.

scarecrowbob• 9 months ago

I work with audio professionally and it took me a years to get a feel for dynamics processing. Like, it wasn't until I down sat with a nice compressor (in my case a Neve 453) and just did a lot of experiments, and then took my experiences from those experiments to my live gigs.

IME, you can get a feel for what the threshold and ratio are doing pretty quickly, and that's probably enough to be useful. In broad strokes that's all you need to make them "work". If you have the attack set way fast, you'll start to hear the signal get a bit muddy.

But attack and release (especially on a lot of plugins) are a bit funky, and I still can't tell what the knee is doing unless I move the knob around. And I own a couple clones (76kt or gold comp 2a) and a couple of distressors, and they sound different but I still need play around with them to coax them into what I think they should sound like.

Aldipower5• 9 months ago

The House of Kush made me compression rethink. He's the Bob Ross of audio. :-D

https://www.youtube.com/watch?v=K0XGXz6SHco

_odey• 9 months ago

OK, so based on this video, I've turned on EasyEffects, added an Equalizer, set the input source to "Easy Effects Source" in the system settings, started playing pink noise, then tried to adjust the dials until the input looked closer to a horizontal line (it's very chaotic so that is hard to do).

As some sections of the video highlight it ended up needing to dip the mids and boots the lows and highs. This is my end result (so far, I'm probably going to tweak this continuously):

    Preamp: -1 db
    Filter 1: ON PK Fc 27.782795 Hz Gain -3.36 dB Q 1.7848856
    Filter 2: ON PK Fc 49.40557 Hz Gain 1.09 dB Q 1.7848856
    Filter 3: ON PK Fc 87.85691 Hz Gain 5.04 dB Q 1.7848856
    Filter 4: ON PK Fc 156.23413 Hz Gain 6.43 dB Q 1.7848856
    Filter 5: ON PK Fc 277.82794 Hz Gain 3.76 dB Q 1.7848856
    Filter 6: ON PK Fc 494.0557 Hz Gain -1.19 dB Q 1.7848856
    Filter 7: ON PK Fc 878.5691 Hz Gain -5.54 dB Q 1.7848856
    Filter 8: ON PK Fc 1562.3413 Hz Gain -3.96 dB Q 1.7848856
    Filter 9: ON PK Fc 2778.2793 Hz Gain -2.97 dB Q 1.7848856
    Filter 10: ON PK Fc 4940.557 Hz Gain 0.3 dB Q 1.7848856
    Filter 11: ON PK Fc 8785.69 Hz Gain 4.35 dB Q 1.7848856
    Filter 12: ON PK Fc 15623.413 Hz Gain 8.7 dB Q 1.7848856

There's also an Output amp of -2.5dB that does not appear in the export for some reason.

TUXEDO InfinityBook Pro 15 - Gen10 - AMD Laptop Speakers.

It does make a positive difference (why don't they teach us this in school? ;) ). Please note I am music illiterate.

EDIT: it looks like changing the input source has no actual effect, just need to make sure the internal microphone's volume is not muted, and have to keep system setting window open while doing this, maybe the microphone is no longer on when the window is closed?. Linux is weird sometimes.

whstl2• 9 months ago

They teach this in audio engineering school :)

But the reason this is not widely talked about is two fold:

First, because those measurements are heavily room dependent and they sound worse than treating a room. Because the room affects the sound in ways that EQ can’t really fix anyway.

Second, because the goal of mixing and mastering is making music sound good in a big variety of speakers and environments.

yapyap• 9 months ago

Posy my beloved

dusted• 9 months ago

My music listening speakers have two built in power amplifiers (one for the tweeter, one for the woofer) and have a DSP feeding right into a DAC, feeding right into those amplifiers.

There's a control box that comes with them, and when you plug a calibrated microphone into that box, and put it in the listening position, you can get it to do some frequency sweeps, one at a time, then they calculate a correction curve for each speaker, based on the actual response of the particular speaker in the particular room, and program that curve into the DSP of the speaker.

It's like night and day toggling the calibration on and off while listening to music.

And yes, as he says, the best hi-fi is just professional audio gear..

My music listening setup is simply a USB->AES converter box that feeds directly into the monitors, the monitors are a pair of Genelec 8050, and then the GLM box and volume knob. Never heard "hi fi" coming even close to it, not at the price, not at five times the price.

Same goes for headphones, you can't get much better than the simple and cheap DT990 (or 770 if you want them closed), sure, you can pay about 10 times as much for some Sennheiser hd800s, and those are pretty good, and I do have a pair of HE1000se, which are not only cheaper, but actually sound better too. But I'd never recommend anyone who's not as stupid as myself to buy anything "above" DT990.. And yeah, I EQ my headphones with a dbx 231x two channel 31 band EQ, and while that's not as scientific as the calibrated monitors, for a headphone listening experience, it gets pretty good.

scns2• 9 months ago

You can get correction settings for headphones at [0]. Peace Equalizer (for Windows sadly) already contains them.

https://autoeq.app

spookie• 9 months ago

JamesDSP (Linux & Android) also provides this.

n_kr• 9 months ago

"The best hifis are professional equipment"

This is gold. I wish so many people understood and used this. Pro equipment is more robust and more versatile. And if you know some people you can get amazing used stuff at bargain prices from your local musicians or sound engineers. Lot of times, people I know (and I too, though I'm not a pro sound engineer) will help you choose and setup just because you showed interest in the things we are interested in. Beers are assumed.

One drawback is that pro audio stuff may look ugly to non pro people. I made my wife listen to the cheapest studio monitors I could find on amazon, equalized with the same pink noise method in this video, and compare it to her bose and marshall speakers. She liked the sound better but my speakers are "yuck ugly" :(

jama2112• 9 months ago

They might look ugly to pro people too, just in a studio it’s function over form. However at home I’m inclined to agree that it being pleasing to look at is important to me.

pfdietz• 9 months ago

Is equaliser an alternative spelling, perhaps in British English? I ask because there's a mathematical entity called an equaliser.

https://en.wikipedia.org/wiki/Equaliser_(mathematics)

nativeit• 9 months ago

Posy’s videos are always incredibly creative and beautiful celebrations of retro tech.

Archit3ch• 9 months ago

From the title, I expected Neve and Pultec, not 90s HiFi and digital EQs. :(

amelius• 9 months ago

These graphs show only amplitude, not phase shift.

Looks like an incomplete approach if you ask me.

ZoomZoomZoom• 9 months ago

The second sentence in the video hides a bit of complexity. Pink noise isn't a straight line on the spectrum analyzer unless a correction slope is active, and the common settings for the slope (3, 4.5) are just a convention.

I guess, that's why it says "you can make it look like a straight line".

jama2112• 9 months ago

I saw this earlier today and it was wonderful, dude has a great sense of humour too

Humbly8967• 9 months ago

EQing for a flat in room response is NOT ideal!

Correcting a speaker requires measuring the *anechoic* response, and only the bass should be tuned to subtract the room's effect.

This video [1] provides a crash course on science of audio reproduction.

[1] https://www.youtube.com/watch?v=zrpUDuUtxPM

Slow_Hand2• 9 months ago

Yes. I work for a company that tunes dozens of speaker systems in high-end recording studios a year and our target frequency response balance can generally be described as this: A spectral "tilt" in which the bass frequencies are +6 dB louder than the highest frequencies. The slope downward should be gradual, from lows to highs. Again, with a 6 dB difference between the bottom and the top octaves.

EQ: A video about all forms of equalizers

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