C32 EQ (Lows begin at 383 Hz ??)

[MLS]

The EQ section of C32 seems to be false at the lows.
It shows as the smallest value ".04" which would translate 
as 40 Hz. The knob goes under this value therefore it has to be 38 Hz,
but it shows 383,5 Hz !
At the filter section, the HPF shows as smallest value ".02" which translate as 20 Hz
and this is shown by Mixbus as 20 Hz - the correct value.

So what's the deal with this false value for the lows ??

[sunrat]

What version of Mixbus do you have? This is an old issue which I thought was fixed several years ago.
Actually I just checked my v6.2.407 (haven't updated to 7 yet) and it has the issue, low EQ values are shown at 10x their actual value in the scribble strip. Note it is only cosmetic, the actual values applied to the audio are correct.

[Dingo]

There is a long conversation about the 32C EQ display and how the modelling of resistor values in the real hardware made the mapping to digital display very difficult.
Making it more complicated is the way in which the Harrison proportional- Q design changes the EQ range based on gain.
Sorry cannot find that thread.... yet.

If you engage bell it will display the mid point EQ accurately, when shelf is selected the display is showing the highest point of the shelf filter, not the midpoint.

I tend to look at the knob position rather than the read out on the channel, although that is handy at times.

[MLS]

Thank you !
Yes with engaging bell the values are correct.
It seems that with shelf engaged the display is showing the (rightmost) edge value.
That way it makes sense.

[sunrat]

There is a long conversation about the 32C EQ display and how the modelling of resistor values in the real hardware made the mapping to digital display very difficult.
Making it more complicated is the way in which the Harrison proportional- Q design changes the EQ range based on gain.
Sorry cannot find that thread.... yet.

If you engage bell it will display the mid point EQ accurately, when shelf is selected the display is showing the highest point of the shelf filter, not the midpoint.

I tend to look at the knob position rather than the read out on the channel, although that is handy at times.

I remember that conversation but IIRC it didn't quite resolve satisfactorily. Be good to locate that old thread @Dingo. My search-fu failed.
I noticed the Hi EQ doesn't exhibit the same behaviour when shelving. Should it not show the lowest frequency affected by the filter?

I tend to not look at the display much either, knob position for coarse adjustment and ears for fine tuning.

[Ben@Harrison]

This is a very complicated topic, and I apologize because I was directly involved in making it complicated

In the analog 32C circuit, the relationship between the frequency knobs and the resulting frequencies was complicated. That was inherent in the 'voicing' of the eq and the taper of the potentiometers used. The frequencies on the knobs were only rough indications of the frequency. The original console had a strange discrepancy where the knob was labeled for the 'bell' mode (to match the 2 mid-bands) but the default operation was shelving, and no frequency text was provided for that mode which was quite different. But since 32C is intended to be a recreation of the hardware console, we copied the labels verbatim, warts and all.

The circuit model was created using the knob-travel of each knob, to correctly recreate the exact taper and sweeping behavior. In the original versions of Mixbus32C (up through v5 I think), the text display would show 0.0 -> 1.0 (or 0..100%, I forget) in the readout. That value represented the percentage of knob travel, as used by the circuit model. So a value of 0.4 in the automation meant "40% knob travel" not "0.4k = 400 hz"

The original console lacked any text readouts, of course, so we didn't anticipate so many people would be interested in this aspect of the software.

A few (vocal) people complained about that, so in later versions we made an effort to display the frequency and gain values in Hz and dB in the channelstrip readout. However, this was complicated by the fact that we share a lot of code with the open-source community but we did not want to share the internal operation of the 32C algorithm. So we used an approximation in the graphics code.

To further complicate things: the 32C 'shelving' filters are a different shape than a typical parametric eq, and in an attempt to convey that, I chose to print the 'frequency where the shelf reaches full gain" so for example you might see values like "+6 at 23k". That is somewhat weird but, again, necessitated by our desire to keep the internal operation proprietary.

In practice, none of this affects the 'sound' ... because turning the knobs will accurately represent what the original console did. It's just that the text-readouts (which the original console lacked entirely) look strange compared to a typical parametric eq.

In our 'plugin' versions of the 32C (32C Channel, Vocal Flow, etc) we have full control of the GUI and the DSP, and we've recognized that users want this information; so the knob labeling, text entry, and text displays are far more accurate. (the sound-algorithm itself is the same in all cases)

Best,
-Ben

[sunrat]

Thanks for the explanation, Ben. It helps to understand exactly what the numbers mean. I recall the earlier thread explained this to some extent but people were still asking for frequency display and now there seems to be a similar amount of complaints and confusion about that as there were originally for the knob position display.
It doesn't really bother me as I rarely look at the text readouts anyway. I grew up on analog consoles.

[Theotherguy]

Yes, thanks Ben, I hope your explanation answers everyone's questions.
Like Sunrat, I grew up on analogue consoles, so it was all about knob position.
Like hand - eye coordination, it's knob - ear coordination.