[psy472]

I use software EQ for major sound changes and my hardware EQ like Lokius for minor adjustments. I realized trying to make major adjustments on the hardware EQ will distort the sound a bit.

I A/B my wires and do noticed a difference between the cheap and expensive ones. The Hardware EQ also have the added bonus of making my cheap cables sound like 3k usd cables with just a slight notch turn.

 

[Hypops]

I use software EQ for major sound changes and my hardware EQ like Lokius for minor adjustments. I realized trying to make major adjustments on the hardware EQ will distort the sound a bit.

Software EQ works the same way as hardware EQ (phase shift), so software EQ has the same basic drawbacks to sound quality as hardware EQ. And even if you use linear phase EQ, you still run into pre-ringing artifacts. No free lunch in audio.

 

[VNandor]

And I also prefer using analog EQ to digital, because the latter has the potential to alter phase. I use digital at the moment though because I need its better precision for my current headphones.

Just to note, analog equalizers not only have to potential to alter phase, they always do alter phase (not that this is a huge problem because headphones have uneven phase responses not just uneven FRs). With digital EQ, you have the choice between using linear phase or minimum phase, some even have settings for "natural phase" and "mixed phase". I think EQAPO only does minimum phase though.

 

[Hypops]

Just to note, analog equalizers not only have to potential to alter phase, they always do alter phase (not that this is a huge problem because headphones have uneven phase responses not just uneven FRs). With digital EQ, you have the choice between using linear phase or minimum phase, some even have settings for "natural phase" and "mixed phase". I think EQAPO only does minimum phase though.

To clarify, the reason EQ alters phase is because that is literally how (minimum phase) EQ works--both for analog and digital. In other words, it's a feature, not a bug. And as you say, minimum phase EQ is pretty much a "freebie" for headphones since phase smearing isn't the issue it is with loudspeakers. No need to bother with linear phase EQ for headphones.

The real distinction shouldn't be between analog and digital EQ, but between graphic EQ and parametric EQ.

 

[ADUHF]

I need to know more on the subject, because it's been my understanding for some time that phase alteration was one of the downsides/Achillles heels of digital EQ vs. using analog EQ.

I don't understand the technical aspects of EQ as well as I like or should. But I'm pretty sure I picked this notion up either from some smarter folks on Head-Fi, or possibly on Tyll's old Inner Fidelity site. I thought that was one of the reasons some audiophiles preferred analog solutions, like the Schitt Loki and Lokius, to other digital EQ solutions. But it sounds like the two of you are saying this is just all wrong. (??)

I'm not sure about this though. And don't really want to point fingers at anyone. Maybe someone else here can explain how this idea might have gotten into my head though, or where it could possibly have originated.

 

[Hypops]

I need to know more on the subject, because it's been my understanding for some time that phase alteration was one of the downsides/Achillles heels of digital EQ vs. using analog EQ.

As I and others have said above, you're confusing analog vs digital for minimum vs linear phase (or possibly for graphic vs parametric EQ).

As we've also said, phase smearing isn't really an issue on headphones, so you can use minimum phase EQ pretty liberally on most headphones. Phase smearing is an issue on loudspeakers because the transducers interact in space, and this might be where you picked up on the idea, but again, this is about the difference between linear and minimum phase, not analog and digital. The only limitation to headphone EQ is the distortion profile of the particular headphones you're EQing.

 

[dstarr3]

On the subject of phase, brief tangent:

Ever since I was a kid plugging in my first speakers, it was made clear to me how important it is to make sure that I make sure all the speakers are phased correctly. Whether they're reversed or not doesn't matter, just so long as they're all the same. Never really asked or cared why, just assumed it's the right way to do it and there's no reason to do it any other way. And then decades later when I started making my own headphone cables, I just sort of carried that wisdom over without thinking about it.

All this phase talk has me thinking about it now, though, and I wonder: On headphones, does phase matter? On speakers, it of course does, because the waves from one speaker interact with the waves from all of the other speakers, and if one or more are inverted, you get interference. However, on headphones, the waves from one side don't interact with the waves from the other, so theoretically there's no interference.

So yeah, can you invert the phase on one side of a headphone without issue? Or is there still some problem that makes it unwise?

 

[Hypops]

On the subject of phase, brief tangent:

Ever since I was a kid plugging in my first speakers, it was made clear to me how important it is to make sure that I make sure all the speakers are phased correctly. Whether they're reversed or not doesn't matter, just so long as they're all the same. Never really asked or cared why, just assumed it's the right way to do it and there's no reason to do it any other way. And then decades later when I started making my own headphone cables, I just sort of carried that wisdom over without thinking about it.

All this phase talk has me thinking about it now, though, and I wonder: On headphones, does phase matter? On speakers, it of course does, because the waves from one speaker interact with the waves from all of the other speakers, and if one or more are inverted, you get interference. However, on headphones, the waves from one side don't interact with the waves from the other, so theoretically there's no interference.

So yeah, can you invert the phase on one side of a headphone without issue? Or is there still some problem that makes it unwise?

Some folks don’t even notice when loudspeakers are out of phase. And I have to admit, there have been times in my life while listening to music over speakers where I ask myself: wait, something is off. Are my speakers out of phase? Sure enough, cable polarities were swapped. Throw in subwoofers, reflections, room shape, etc, and you discover that most people’s speaker listening is riddled with all kinds of phase issues. You could even argue that room correction is actually a form of phase correction. Even recording engineers mess with phase (not just for EQ), and final masters of recordings can often be out of phase to greater or lesser degrees.

However, the general sense is that phase interactions don’t matter much for headphones (for the reasons you stated). There are many other issues to worry about when you EQ headphones, but “phasiness” isn’t one of them.

I’m also curious what would happen if you inverted phase on one channel on a set of headphones. There would be no physical interaction between the waves, so you wouldn’t get cancellations or boosts. But it might affect subtle things like imaging, tonality, and staging. Dunno. How it sounds would be totally up to your brain’s response. The human brain is excellent at compensating for funky audio and timing cues, so it may just realign phase/timing by itself, and you’d never know the difference. I’d try it for myself if I could think of an easy way to do it

 

[ADUHF]

As I and others have said above, you're confusing analog vs digital for minimum vs linear phase (or possibly for graphic vs parametric EQ).

As we've also said, phase smearing isn't really an issue on headphones, so you can use minimum phase EQ pretty liberally on most headphones. Phase smearing is an issue on loudspeakers because the transducers interact in space, and this might be where you picked up on the idea, but again, this is about the difference between linear and minimum phase, not analog and digital. The only limitation to headphone EQ is the distortion profile of the particular headphones you're EQing.

It's not the difference between PEQ and GEQ, I think. More likely the linear vs. minimum thing. But I'm not sure.

So do hardware-based analog EQ's (like Loki) generally use linear phase then, and do you think that's how I might have gotten a bit confused on the subject?

I can let the subject go until I find the original article or discussion on this. But I distinctly recall hearing somewhere that changes in phase were more likely to be a potential issue on the digital side. Just can't remember exactly where or why.

 

[ADUHF]

So yeah, can you invert the phase on one side of a headphone without issue? Or is there still some problem that makes it unwise?

Give it a try and see! I think it will sound like poop though, and mess up the stereo imaging in the headphones.

I believe I did this once, when I accidentally soldered some wires the wrong way on a pair of my headphones. And the results were a bit strange, and amusing. But not somethin I'd want to listen to.

 

[Hypops]

It's not the difference between PEQ and GEQ, I think. More likely the linear vs. minimum thing. But I'm not sure.

So do hardware-based analog EQ's (like Loki) generally use linear phase then, and do you think that's how I might have gotten a bit confused on the subject?

Loki is a minimum phase graphic EQ. It is also analog. It is also hardware. Those are three mutually exclusive things (therein may lie the confusion). As far as I'm aware, linear phase correction can only happen digitally (maybe adding to the confusion), but minimum phase correction happens commonly in both.

Another way of saying this is that if you see something labelled as "EQ," chances are very high that it is doing minimum phase correction (whether analog or digital). You typically have to go out of your way and purposely seek out linear phase EQs, and they are not beginner friendly IMO.

I can let the subject go until I find the original article or discussion on this. But I distinctly recall hearing somewhere that changes in phase were more likely to be a potential issue on the digital side. Just can't remember exactly where or why.

That's above my paygrade since I'm neither an audio designer nor an engineer. But that doesn't sound right to me. It's easy to shift the phase of a signal using just passive analog components (that's in fact how an analog EQ works). But I have no idea how digital might be different, whether for better or for worse.

 

[VNandor]

m also curious what would happen if you inverted phase on one channel on a set of headphones. There would be no physical interaction between the waves, so you wouldn’t get cancellations or boosts. But it might affect subtle things like imaging, tonality, and staging.

It absolutely does affect the way you hear things if you invert only one of the channels even on headphones. You really should try it, it sounds surprisingly "different" (bad IMO). I used audacity to do the phase inversion.

I can let the subject go until I find the original article or discussion on this. But I distinctly recall hearing somewhere that changes in phase were more likely to be a potential issue on the digital side. Just can't remember exactly where or why.

Either you remember this incorrectly, or the people who discussed this didn't really have an idea of what they were talking about. I'm also 100% sure Tyll wouldn't get something like this wrong by the way.

It's hard to find an article that's specifically only about analog equalizer's phase shift because it's sort of "common knowledge". Here are some links that support this notion however:

https://ethanwiner.com/EQPhase.html
If you look up who Ethan Winer is, you'll find that he is (or used to be?) an active member of AES with plenty of published works. He is a very reliable source of information when it comes to audio.

Here's a link to a paper published on IEEE that was written when linear-phase EQs were still relatively novel. In the introduction section, it also off-handedly mentions that analog EQs cause phase distortion, no matter what.
paper: https://citeseerx.ist.psu.edu/docum...&doi=69dbedbca6b3ab8a4f49676619813d70ac5732cf
IEEE: https://ieeexplore.ieee.org/document/641062

Link from Roland:
https://proav.roland.com/fr/solutions/case_studies/consoles/2859/
As I said, the article doesn't really focus on phase shift caused by analog EQs, it just mentions it as an aside. For an article that's published by company with something to sell, it's surprisingly well done.


Bonus video on how to actually do linear phase equalizing with analog EQs: in short, you have to utilize the EQ to do forwards-backwards filtering so while it's possible to do linear phase equalizing with analog EQs, it's impossible to do so in real-time.

That's above my paygrade since I'm neither an audio designer nor an engineer. But that doesn't sound right to me. It's easy to shift the phase of a signal using just passive analog components (that's in fact how an analog EQ works). But I have no idea how digital might be different, whether for better or for worse.

The principle behind the basic digital filters is to create a phase shifted (where the amount of phase shift depends on the frequency) version of the input and mix that phase shifted signal with the input to create the output. This causes a varying amount of phase cancellation in the output. Wherever the phase shifted signal and the input signal is out of phase you get attenuation, whereever they are in phase, you get a boost. Linear phase EQs are based on convolving the input with an impulse. The symmetry of the impulse is what guarantees both the phase linearity and the pre-echo.

 

[ADUHF]

Appreciate the replies from both of you on this, Hypops and VNandor. And have read and looked at all of the above material you've referenced.

I think there is still something about the differences between EQ-ing in the digital and analog domain that I'm missing in this discussion. And will probably have to go back through some previous threads to maybe find it, which could take some time.

I think this video helped me to understand and visualize a few of the concepts discussed here a little better though, fwtw.

 

[ADUHF]

This video goes over my head, but seems to get more into some of the nuts and bolts of the technical aspects of EQ.

 

[Hypops]

Appreciate the replies from both of you on this, Hypops and VNandor. And have read and looked at all of the above material you've referenced.

I think there is still something about the differences between EQ-ing in the digital and analog domain that I'm missing in this discussion. And will probably have to go back through some previous threads to maybe find it, which could take some time.

I think this video helped me to understand and visualize a few of the concepts discussed here a little better though, fwtw.

No doubt. I've become increasingly fascinated by (and more than a little obsessive about) EQ over the past year or two. It's one of the few areas in music that brings together music creation, production, reproduction, and listening. It's incredibly technical and incredibly subjective at the same time. Every recording engineer has their own unique philosophy of EQ (as does just about every armchair EQer).

Now you've got me intrigued by this mystery explanation. As far as I understand minimum-phase EQ, digital just does digitally what analog EQ already does: shift phase to attenuate or boost certain frequencies. @VNandor reaffirms above what I had assumed. Digital sounds functionally identical to analog. But that doesn't mean there isn't more nuance than that, and like I said above, seemingly every recording engineer has their own philosophical dogma when it comes to EQ. Just like there are diehard analog-only audiophiles, there are probably similar divisions among recording/mastering engineers. But that's just a guess. Now you've got me super curious to hear the case against digital EQ. I'll have to do some digging...

It absolutely does affect the way you hear things if you invert only one of the channels even on headphones. You really should try it, it sounds surprisingly "different" (bad IMO). I used audacity to do the phase inversion.

Whoa. I just tried inverting phase in one channel using Roon's "Speaker setup" filter. Not what I expected at all. Not only is it audible; it is way more audible through headphones than it is on speakers! Weird. I guess that means our brains are good in the other direction. Rather than realign the two different phases, your brain makes them even more distinct than when they interact in space. And more bizarrely, the waves don't interact in space, but they do interact in your head. Complete with phase cancellations and everything. I mean, they're neural signals at that point. They're no longer sound waves, but they still interact as if they were... The effect is even more pronounced than it is in space. Wow. Speaks strongly in favor of folks who argue that our ears/brains are more sensitive to timing imperfections than we assume.

If I understand this correctly, then, the reason that minimum-phase EQ works well on headphones without the same "phase smearing" that can happen with speakers is not because a headphone's channels are isolated from one another. Based on what just happened when I inverted phase, the reason you can EQ headphones so well is actually because there's no "room" to worry about and therefore you can EQ both channels identically... which means you don't adversely affect their phase alignment. Maybe? I really dunno. I'm just hypothesizing. I think that makes sense, though.