Cakewalk Blog: QuadCurve EQ Demystified

Modern = "Musical and warm"
Vintage = "Clinical and harsh"

Time to fill in a bug report


Seriously though, thanks for the cool info, I like the blog!

Interesting, thanks! I think it's wise that you renamed the models, since people looking for "warm and musical" would probably reach for the "vintage" model first without exploring what it really means.
 

 In physics and engineering Q factor means a very specific thing: Q is the bandwidth of a resonant circuit and it is measured at 3dB from Peak.

 In other words the Q parameter is not a number value that can mean many things... In engineering it means one thing, a specific bandwidth measured at a specific place.

 Why does ProChannel offer three different actual bandwidths for the very same Q parameter value?

 The way ProChannel EQ uses the Q parameter value seems like a perpetuation of a labeling mistake made when someone was building some old analog gear.


 Wouldn't it be more accurate to have the actual numeric Q parameter value switch in the text box to an accurate representation of the the actual Q value that we hear when we switch between Pro, Vintage, Modern, Hybrid?

 I don't understand why we are encountering a labeling mistake in 2012 when the actual underlying *digital* math is so accurate that a mistake like this has to be forced upon the transfer function in the form of some correction factor that forces Q to not mean what Q actually means.

 Surely, if the Q we are hearing is wider, or less wide, than the Q factor value shown in the ProChannel Gui then there must be some mathematics under the hood that represents what the actual Q we are hearing really is.

 Why can't we see the actual Q we are hearing, rather than have to view some arbitrarily assigned value?

 I suspect that if one really understands the idea that the Q in ProChannel is just some reference number, a number that is only accurate representation of Q for some of the EQ modes, that one will conclude that switching between the EQ types is a quick way to switch Q values.

 The next thought that may occur is that any of us ought to be able to adjust the Q by ear so that any EQ can sound Pure, Vintage, Or Modern. If you are seeking a good understanding of EQ it can be helpful to know what the actual real life Q value you are listening to is.

 Is there a real benefit to hiding the actual Q factor by leaving it at a fixed value as you actually switch through various widths?

 One benefit is that you can present a regular old EQ transfer function and pretend like it's actually 3 different EQs... which I guess makes it seem like more EQ.

 One downside is that the end user will have inconsistent experiences when listening and trying to relate what they hear to a Q factor, The lack of consistency, and inaccurate display of the parameter value as you switch through the various mis labeled Q factors will make it difficult to keep track of which Q actually is and which Q isn't really.

 So, it seems to that it would be great if the real Q factor was displayed as the parameter value. For example; If you switch modes and the Q gets wider or thinner then the Q number could reflect the change rather than the way the current display perpetuates, and even celebrates an inability of old analog circuits to be as accurate as digital circuits.

 In other words if the Q is 1.0 and I switch modes and now the Q is actually 1.5... I think the parameter value should switch out and read 1.5 rather than suggest that Q = 1.0 can mean different things.

 It's 2012 and control panel labeling mistakes and analog circuit compromises can be easily understood, accurately described, and easily represented using digital processes.

 It is 2012, and the easiest way to demystify some of this stuff would be too provide accurate labeling rather than indulge in the anachronistic practice of emulating mistakes made in the past.
 

 Simple?



 best regards,
mike
 

Q is decidedly NOT subjective.

Engineers (real ones) and Mathematicians have a specific defintion that has been shared and agreed upon for 100+/- years.

It's easy to learn about.


best regards,
mike

And oh dear, caught out again. Looked good for a bit, almost like you actually knew what you were talking about for once, but that idea of changing the labels to the "real" Q number shows you don't.

mike_mccue


Q is decidedly NOT subjective.

Engineers (real ones) and Mathematicians have a specific defintion that has been shared and agreed upon for 100+/- years.

It's easy to learn about.


best regards,
mike

It is subjective because it is relative to its dependency on Gain (see above post). That's why you see different curves on different EQs with the same gain and Q settings.


SP

Sigh. Q can't "actually" be anything in this context.

Seth Perlstein [Cakewalk
]

mike_mccue


Q is decidedly NOT subjective.

Engineers (real ones) and Mathematicians have a specific defintion that has been shared and agreed upon for 100+/- years.

It's easy to learn about.


best regards,
mike

It is subjective because it is relative to its dependency on Gain (see above post). That's why you see different curves on different EQs with the same gain and Q settings.


SP

I can suggest that the curves shown on the graph do represent the actual Q accurately (to the degree to which the graph is accurately drawn) while the numeric value in the text box is the value that deviates from the Q you are hearing.

If the Q value drawn on the graph can change to reflect what we are hearing why can't the Q value written in the text box accurately reflect what we are hearing?

The only reason that I can think of is that this is some sort of anachronistic celebration of the limitations of analog circuits and their inaccurate, yet permanent, silk screen or engraved labels.

It's 2012... we can have EQs that actually do what the parameter values say they are doing.

best regards,
mike

There's no such thing as an "actual" Q value. Can anybody hear me? Am I a ghost?

"Your concept of, 'Q @ 1 always equals x value',"

It's not my concept. It's a engineering concept that is shared all over the world in the universal language of mathematics.

"If you want to use an EQ where a Q of 1 always equates to a specific curve in the graph, well, I suggest you find another EQ to use, because that's not how the QuadCurve EQ works." 


But it can work that way.... doesn't one of the 4 choices work that way?

I think it's what Cakewalk calls the "E".




It's the other 3 that seem "mystifying" because they arbitrarily alter the Q value without displaying the alteration.

 
best regards,
mike

Oh my. No. Q is a relative value. It has no absolute meaning. 

Hi Mike,no offence sincerely,but you should be a politician.....You can not always be right!Best.Roby

In mah house voltage does not always equal 120 volts..it is either 105V or 135V....

This almost reads like one of those discussions wherein one has the idea that it is the circuit itself that makes for a good amplifier or the parts used.

To me Q is an arbitrary construct anyways...

"Look at the widths at 0db of the different curves at each of their gain settings. The reason they are different is their Q/ Gain dependencies are different, so each modes curve will look and sound different even when their Gain and Q settings are identical."

Hi Seth,

Here's an illustration that shows where Q is measured. The width at the 0dB line is just the result of some particular Q at some particular gain level.



Which is why I equate the E which is described as "minimal Q/ Gain Dependency" to what an engineer calls *Constant Q* or in this case maybe *near Constant Q*

The Q, measured at -3dB from peak stays [nearly] constant (because it is effected by gain "minimally") and so we can observe that while the width at 0dB expands and contracts the Q is effected minimally with gain.

So, in the case of "E" a Q label may actually be what it says it is... or at least onl minimally different.




In the other examples gain dependency can occur and the bandwidth at -3dB from peak will reflect that relationship.

The bandwidth at 0dB is merely the result of the Q at some particular gain level. Q is measured at -3dB from the peak.

If the value of Q is dynamically linked or dependent on gain level then the Q is still measured at -3dB of peak regardless of what is happening at 0dB.

The bandwidth at 0dB is only a result of the current Q factor and the current gain level.

If the graph in ProChannel was sized larger, the drawing would be easier to view at -3dB from the peak and we could see that on the whole your explanation of the effects of gain dependency seem accurate.

I imagine that it seems easier to illustrate the effect at 0dB simply because it is easier to view in the drawing. Unfortunately, that is not where Q is measured so the observation at 0dB is purely incidental.

It would be more accurate to speak about Q where Q is actually measured. This practice may highlight the fact that Q actually has a well defined meaning in engineering and mathematics.

all the best,
mike

mike_mccue


"Look at the widths at 0db of the different curves at each of their gain settings. The reason they are different is their Q/ Gain dependencies are different, so each modes curve will look and sound different even when their Gain and Q settings are identical."

Hi Seth,

Here's an illustration that shows where Q is measured. The width at the 0dB line is just the result of some particular Q at some particular gain level.



Which is why I equate the E which is described as "Q/ Gain Dependency" to what an engineer calls *Constant Q* or in this case maybe *near Constant Q*

The Q, measured at -3dB from peak stays [nearly] constant (because it is effected by gain "minimally") and so we can observe that while the width at 0dB expands and contracts the Q is effected minimally with gain.

So, in the case of "E" a Q label may actually be what it says it is.




In the other examples gain dependency can occur and the bandwidth at -3dB from peak will reflect that relationship.

The bandwidth at 0dB is merely the result of the Q at some particular gain level. Q is measured at -3dB from the peak.

If the value of Q is dynamically linked or dependent on gain level then the Q is still measured at -3dB of peak regardless of what is happening at 0dB.

The bandwidth at 0dB is only a result of the current Q factor and the current gain level.

If the graph in ProChannel was sized larger, the drawing would be easier to view at -3dB from the peak and we could see that on the whole your explanation of the effects of gain dependency seem accurate.

I imagine that it seems easier to illustrate the effect at 0dB simply because it is easier to view in the drawing. Unfortunately, that is not where Q is measured so the observation at 0dB is purely incidental.

It would be more accurate to speak about Q where Q is actually measured. This practice may highlight the fact that Q actually has a well defined meaning in engineering and mathematics.

all the best,
mike

That's nice that you went to the trouble to research and post what you posted, but the blog post was not meant to be a white paper. It was meant to explain the different modes in the QuadCurve EQ. 


The blog post is probably not for you since you are familiar with Q/ Gain dependency and all that. If you wish to use an EQ that displays its Q setting how you describe, I would suggest you look for another EQ.

However, if you want an EQ that faithfully represents some of the most sought after console EQs of the past half century, then use the QuadCurve EQ.

SP