Digital EQ Fact & Myth.

[rhythminmind]

I would like to get some technical examples of EQ algorithm differences. I understand compression algorithms. These can be drastically different. How one digital EQ is actually better then another gets fuzzy. I'm not talking about features or interface but audio integrity.

The Digital EQ variables that i am aware of are
Internal resolution
Oversampling
frequency response
filter slope / Q
& phase

I have been able to recreate the the slope, phase, & sonic characteristic of the Duende & CSP with built in native EQ . Or with any fully variable parametric EQ for that matter.
As i said compressors are a different story. Duendes program dependent comp is it's own beast

Besides linear phase, internal bit resolution, or to free cpu with external DSP i'm now questioning why anyone needs anything but there native EQ.
I can't find technical reasons.
Please inform.

[dbjp]

Originally Posted by rhythminmind

I would like to get some technical examples of EQ algorithm differences. I understand compression algorithms. These can be drastically different. How one digital EQ is actually better then another gets fuzzy. I'm not talking about features or interface but audio integrity.

I have recently switched to sonar 7PE. This has made me reevaluate my plugin arsenal.
I have been using Christian's plugin analyzer to compare my EQ's
Christian’s Blog » Programs

I have been comparing the
Duende channelstrip
urs CSP
Sonars Native mixer EQ
VC-64 (kjaerhus audio GAC-1 port)
& LP-64

The EQ variables that i am aware of are
frequency response
filter slope / Q
& phase

I have been able to recreate the the slope, phase, & sonic characteristic of the Duende & CSP with built in native EQ . Or with any fully variable parametric EQ for that matter.
As i said compressors are a different story. Duendes program dependent comp is it's own beast

Besides linear phase, internal bit resolution, or to free cpu with external DSP i'm now questioning why anyone needs anything but there native EQ.
I can't find technical reasons.
Please inform.

I have no idea, and I'm sure someone will give you a proper answer, but to me Waves' eq (ren) sounds bright, whilst McDSP sounds dirty, if that makes any sense. So I use them accordingly. I doubt I could null them no matter how much tweaking I 'd do. Maybe someone else will prove me wrong.

[Dean Roddey]

The differences that aren't always emulatable are:

1. Pre/post filter ring
2. Harmonic content generation

Filterbank letsyou control #1, which is why it can emulate so many types of EQs, but most EQs don't provide any user control over this, it's just a part of the algorithm implemented, or they might have some kind of musical/surgical type of simple mode selection that does have an effect on ringing, but usually not any direct control.

Harmonic content generation is something that would be pretty hard to emulate in a generic, user selectable sort of way.

[ssaudio]

Originally Posted by rhythminmind

i'm now questioning why anyone needs anything but there native EQ

Yup, I've been saying that for years.

[macleodgrant]

i think we need a few eq's with different characteristics but not many...perhaps 3 to 5?

essential in that group for me are

sonnox eq (nice and clean)
renn eq (clean but unusual and very flexible and surgical)
a linear phase (where other eq's just don't do the trick due to filter phasing - this is real)
waves studio classics (v-series is my choice, fixed Freq & Q so it's a different approach to eq)
and one more characterful eq (i'm waiting on the TG Mastering pack for AU)

other than that, do we need more?

i think not

the main difference is the filter phase which can have a huge impact on the sound. it can make things sound either smeary, punchy, glitchy or just perfect

there is also harmonic content as has already been mentioned

[rhythminmind]

So your saying you couldn't recreate the sound of all the other eq's with the sonnox?
I'm not finding anything but interface preference differences in the digital relm. Besides linear phase

[macleodgrant]

Originally Posted by rhythminmind

So your saying you couldn't recreate the sound of all the other eq's with the sonnox?
I'm not finding anything but interface preference differences in the digital relm. Besides linear phase

well if you believe in linear phase, then you must believe that eq's that aren't linear phase must phase differently depending on their programming

in that case it's not hard to understand why eq's sound different.

there is a very interesting eq by DDMF called the LP10. this eq has 10 bands but you can literally change the phase of each filter so with this EQ, theoretically you could emulate all other EQ's that don't include harmonic enhancement or saturation

**** DDMF-The home of Equalizers-DDMF ****

[rhythminmind]

I understand the phase differences that EQ can have. But the digital eq's i have been testing once i match the Q and filter slopes the phase plots are the same.
I'm not matching dial setting's, those will vary from plugin to plugin but using an analyzer i've have been able to match every digital parametric in the freq,slope/Q, & phase relationship.
None of these have harmonic or saturation quality's. i use dedicated tools for that. But maybe the waves models add harm/sat stages. But even with that the EQ dosen't seem to be whats causing a different color.

[synthoid]

I understand the phase differences that EQ can have. But the digital eq's i have been testing once i match the Q and filter slopes the phase plots are the same.

Logic for example has both an ordinary and a linear-phase EQ built in. If I read the sentence above correctly, you are saying that, based on what you've seen so far, you would expect Logic's two EQs to have the same behavior?

-synthoid

[rhythminmind]

not at all. Ones a PEQ one is a Linear phase. These are the 2 differences of digital EQ's i know to exist.

[rhythminmind]

Ahh i just got my answer! Thank you algorithmix


Taken from http://algorithmix.com

"The truth is that with a properly designed, fully parametric analytic PEQ, every amplitude and phase characteristic of any other equalizer setup can be recreated. Of course, the contribution of distortions to the specific sound of a particular analog equalizer caused by the respective electronics has to be considered. If the distortions are ‘good’, they may make certain applications sound better. Usually, however, ‘bad’ non linear distortions and other deficiencies like limited dynamic range are surely not responsible for a ‘magic’ sound. Therefore our policy in PEQ design has always been to make the equalizer filters as precise and clean as possible. For controlled generation of distortions (if you really need any), we recommend using enhancers or any other specialized processors with proper built-in anti-aliasing technology."

This has been my method for some time.. Use a clean PEQ of my choice & the URS sat/AM-suite to saturate.

[Dean Roddey]

I do agree in general that you can emulate EQs pretty well. I posted a thread a while back (which I think got lost in the forum crash early this month), where I showed the emulation of the Waves SSL EQ using RenEQ.

The Waves SSL has a built in high shelf starting in the mids, which I assume therefore the real ones also have, which may contribute to their more aggressive sound. It's there even when the EQ is flat.

And their Qs are very broad. The thinner Qs on the SSL EQ were about as big as the widest ones you could get on RenEQ.

And of course that's another thing. Unless you have a pretty flexible EQ, you may not be able to create Qs as sharp or as wide as another one you want to emulate. And since pre/post filter ring can change based on the depth and steepness of the cut/boost, that could take a fair amount of manual twiddling you wouldn't necessarily want to have to do, relative to just using an EQ that already has those characteristics built in. EQs like FilterBank and the Kjaerhus GEQ-7 have a number of settings that allowyou to control these things and get a lot of different types of sounds.

The SSL stuff also I'm pretty sure adds harmonic content, particularly if the analog switch is on, as do the API ones I think, though I've not measured eitther of them.

[rhythminmind]

FYI = URS CSP now for sale
Send me a PM is interested.

[duvalle]

Originally Posted by macleodgrant

there is a very interesting eq by DDMF called the LP10. this eq has 10 bands but you can literally change the phase of each filter so with this EQ, theoretically you could emulate all other EQ's that don't include harmonic enhancement or saturation

**** DDMF-The home of Equalizers-DDMF ****

thx for the link - did not know about that plug in ...
sounds interesting, i will try.
by the way: very brave pricing!!

[jdtrbn]

All minimum phase filters have the same phase relationships. If you can duplicate the filter frequency curve, the result will most likely sound exactly the same (I've tried this). There may be some differences at high frequencies because of the z-transform, if these are meaningful I don't know (nobody uses the really bad algorithms anyway). Linear phase filters can sound different already because of the pre-echo, which is different from any other phase shift we have in EQs. Harmonic content generation, as I understand it is a form of distortion and clean digital EQs don't do this at all. If someone found a nice distortion model, he'd probably make a plug-in of it's own out of it or at least make the amount of distortion controllable (which I haven't seen in EQs).

Personally, I'm very skeptical about any digital EQ differences that are based on something else than filter shapes (BootEQ or some URS stuff) or pre-echo. In the analog world it's a different story, and the sound is also decided by something else than the actual processing (just putting the signal through quality hardware can make the sound better, they say) and distortions actually can become real.

[rhythminmind]

+1.

[Mental Fred]

i m not sure it s easy as that ?

[rhythminmind]

Would be nice to get some other non-biased developers thoughts.

[Dean Roddey]

I thought my old thread had gotten lost, since I couldn't find it with the search, but someone just resurrected it:

Making EQs sound like other EQs

[rhythminmind]

I hope people get some education for future buying/workflow improvements. I wish i tested this out years ago. I should of put 2&2 together from all the digital console mixes that jump around from room to room & my work. They always sound the same from console to console. (digital neve's)

Example switching back to my DAWs native console EQ has nice workflow/visual advantages. The EQ plot & controls are visible/tweakable all the time & more hardware controller friendly. One more free insert for my compressors, saturation, & FX i guess

[rhythminmind]

everyone likes null tests right =)

So i took two supposedly "drastically different classed" Digital parametric EQ's.
The Duende X-EQ, It's even external DSP hosted & compared it with Sonars native Sonitus EQ. I got them to null.

This was the X-eq setup.


This is the Sonar EQ with the setting i tweaked to null




To get the settings i panned the channels hard L&R and matched the frequency response. You can see the 2 overlapping lines. Blue = X-eq, Orange = Sonar. You can see single orange pixels if you look close.



This is a bunch of stereo image meters that show the lack of phase differnces. I maen LACK of differnces




This is what happens if i bypass one of the EQ's for comparison.

[Nishmaster]

All non-linear phase digital EQs will necessarily exhibit identical phase responses with identical settings. The way EQ works is by phase shifting parts of the signal, then adding it back to alter the frequency response, so by definition if the frequency response is equal, so must be the phase response.

The differences in sound between plugin EQs doesn't come from "more phasey" or "less phasey." Most often, it comes from the differences between what the GUI is telling you is happening and what actually is happening. Less often, some harmonic distortion and noise is added to make the effect more analog sounding.

Paul Frindle and I discuss this in some detail here, as well as elsewhere in that thread.

[Ethan Winer]

Originally Posted by Nishmaster

The differences in sound between plugin EQs doesn't come from "more phasey" or "less phasey."

Agreed. And "phasey" usually means there was comb filtering already present in a track and it was simply brought out by EQ boost.

--Ethan

[Kenton]

Originally Posted by Dean Roddey

The Waves SSL has a built in high shelf starting in the mids, which I assume therefore the real ones also have, which may contribute to their more aggressive sound. It's there even when the EQ is flat.

Sorry but.......

The Waves SSL will null with the original signal if the EQ is flat, so the second part of that statement is incorrect.

K.

[Dean Roddey]

The Waves SSL will null with the original signal if the EQ is flat, so the second part of that statement is incorrect.

Well, you can see the RenEQ high shelf required to get the same frequency response (in my other thread linked to a couple posts up.) So, either RenEQ is dropping the highs and requiring a compensating lift, or SSL is raising them.

Perhaps the SSL only generates that high lift when you engage a broad cut or something. But it clearly is raising the highs up if RenEQ isn't dropping them artificially, as the example demonstrates. I'm not sure it makes a huge amount of difference what it does when the EQ is flat, since most people would use it in order to actually do EQ. If it has the lift when actually used, then for practically purposes it has the lift.

[Dan]

Originally Posted by rhythminmind

Ahh i just got my answer! Thank you algorithmix


Taken from http://algorithmix.com

"Therefore our policy in PEQ design has always been to make the equalizer filters as precise and clean as possible."

.

This statement assumes that there are gradations on how "clean" and precise an algorithm is. Thus digital PEQs can sound different.

Also, if it isn't true, you have to assume that every digital PEQ is mathematically perfect for a given bit depth. I don't have that much faith in software developers. Neither do they, according to their revision histories.

[macleodgrant]

i'm never buying another EQ plugin again

[rhythminmind]

So i decided to take it a step further.
How close could i get to the waves SSL with ANALOG on.
So instead of using sonar & my usual URS saturation I decided to try it with all native Ableton Live plugins. At 1st i was having a hell of a time trying to match the EQ Phase. That is until i turned off Live's Hi quality EQ mode .
Live oversamples with Hi quality on.

Here are the EQ setups.



Frequency Response with saturation.



The left measures frequency differences & the right is phase. Not bad, it's near mono. Pretty cool for completely different tools.

[Dean Roddey]

Of coures in a lot of cases, none of this helps us. Compressors are definitely different, and in the case of all of the new Waves bundles, to get the compressors you get the EQs anyway, so if you have them, and their built in characteristics get you to where you want to go more easily, you might as wel use them.

I found that the API EQs really worked well for me and their automatic proportional EQ really always sounded so good with just a couple twists of the knobs, without me having to figure out the optimal Q for a given depth cut or boost.

So I'd use them often for their interface and how they react to settings as much as for how they actually do their thing inside, even knowing that they really aren't that different ultimately.

[j2j]

I think I have a very simple argument here, proving the op incorrect.


Robin from www.rs-met.com wrote:
vieris wrote:

All properly designed Digital plug-in EQ's are the same.


which is a well known fact:

Document Not Found 0.1.1.23.3931

...assuming, we stick to the standard biquad implementation and demand the gain at Nyquist frequency to be 0 dB.




I don't know anything about c++, or coding computer software, but what are you saying Mr. Robin? There is a fundamental algorithm that parametric eq's share? That is what I think you are saying, that is what I think the OP is saying.



Let us chew on this concept--

Are all airplanes, cars, trains, lasers, surgical instruments, buildings, bridges and etc, the same? All of them share some fundamental concepts. Actually, everything on earth seems to share concepts.

I'm sorry, but to build a bridge you follow some very stringent mathematical formulas. Perhaps the same is for parametric eq's. I fail to see how all bridges are the same.

That said, " All eq's are exactly the same, except for X." Is a pretty weak argument. IMHO...


Even if it is slight difference in the distortion and q....


Well, What about the slight differences between a bullet, and a missile?