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Author Topic: Parametric EQ frequency resolution  (Read 3178 times)

Weogo Reed

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Parametric EQ frequency resolution
« on: February 27, 2018, 09:52:57 pm »

Hi Folks,

I work with some Old Time bands that will sometimes wail away in the key of A.
When you get Bass, Guitar, Banjo, Mandolin and Fiddle all sitting on A, it can start to roar a bit, even on good systems.
So I go to the offending A(usually 220, sometimes 110 or 440) and make a narrow cut in the monitor mixes, and occasionally the house mix.

I used to work on a couple different analog mixers with infinitely fine frequency adjustment.
In reality, the knobs were small and a few degrees rotation probably moved up or down the frequency scale quite a bit.

The first digital mixer I worked on, an 01V96, had 1/12 octave steps for the parametric EQs.
For A-440, 450 is the nearest frequency option.

The Midas MR18 has 1/20 octave steps.
432.7 or 447.9 are your choices.

Allen & Heath QU goes even closer, to 439 and 441.

All of these options are far better than a 1/3 octave graphic EQ, at 400 or 500, and have worked fine for me in a variety of situations.

Some mixers, like the Mackie DLs, have one Hertz steps, except down low where they have 1/10 Hertz resolution, and way up high where they round off a bit.
I can go right to 440.
Maybe not a big deal, but nice just the same.

When looking at new mixers, is this a consideration for you?

Thanks and good health,  Weogo
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Luke Geis

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Re: Parametric EQ frequency resolution
« Reply #1 on: February 27, 2018, 11:48:21 pm »

I can't say that I have ever really considered it an issue or concern. I typically mix with my ears and while I am sensitive to frequency within a few Hz, I am not so sensitive that I have ever said darn, I wish this EQ would allow me to center on 433.789hz. The biggest reason I guess it has never been an issue is that when I center around the offending frequency I also utilize the Q to shape the tonal quality of the filter. So while the exact center of the filter may be 5hz or more off of the actual offending frequncy, the Q can be used to dial in something that I can be happy with.

The question may really be is the resolution problematic at the higher or the lower frequencies? If the resolution of the filter is 5hz, then at lower frequencies it may be more obvious? Higher frequencies are much more difficult to determine a 5hz shift with wide band audio signals. Again with adjustable Q it can pretty much a moot issue.

What you might consider a narrow Q, I may not? Typically with musical / tonal changes you use a wide Q filter that is perhaps 1 or wider. While for problem frequencies you will typically go with a filter Q of 1 or narrower. A filter Q of 1 is usually a good starting point. This is a rather wide filter in the grand scheme of things being ( usually ) around 1-1/3 octaves wide. A few db in cut will usually sweeps out a large range of frequencies both musically and with adequate precision starting with a Q factor of 1. Need more precision, narrow the filter Q. Need more musicality widen it.

The only test I have ever really done with the EQ's is to see if the numbers they say are accurate. If I center the filter on 400hz and raise or lower it, does the RTA reflect that change at 400hz and with the degree of cut or boost I present.  My finding has been that there is no short coming of modern digital EQ's and they will pretty much perform at a degree of precision higher than our ears can audibly detect under practical conditions. Obviously if you boost +15db with a very narrow filter you will hear the change if you shift the frequncy up or down even a couple hz. That would be unpractical though.

I might agree that a finer resolution would be better because in theory and practice it is, but I have never been behind a mixer and said this EQ is inaccurate and not fine enough to acquire a desired result. I think in reality it is a non issue, but your values may be different. I say if it is good, then it is good.
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Ivan Beaver

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Re: Parametric EQ frequency resolution
« Reply #2 on: February 28, 2018, 07:29:09 am »

You could always "ask" them to change their tuning to match your console-----

YEAH, good luck with THAT!
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Caleb Dueck

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Re: Parametric EQ frequency resolution
« Reply #3 on: February 28, 2018, 07:43:25 am »

It's something I assume is relegated to older/cheaper consoles and thus no longer an issue. 

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Dave Garoutte

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Re: Parametric EQ frequency resolution
« Reply #4 on: February 28, 2018, 01:15:55 pm »

The instruments described, when on A, are probably playing three different octaves, so the 440 cut may not be the ultimate fix.  Plus the mando is out of tune anyway.
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Nathan Riddle

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Re: Parametric EQ frequency resolution
« Reply #5 on: February 28, 2018, 01:41:31 pm »

I mostly just have pet peeves with non rounded numbers. Even if the freq of choice was 438.0972745 Hz I'd rather put the EQ right at 440 or 438 NOT 439 or 437.

The signal gen on the X32/M32 bothered me. QU is better, SQ is even better.

QU ALWAYS bothers me that I can't get the EQ back to zero dB gain (without reset) UGH, my OCD is kicking in.

Also, the pan L/R bothers me, the lights are in the center, but idk if the value is really zero, or it is slightly to the left or right.

It's stuff that can't be heard I know that. Still bothers me for some reason.
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lindsay Dean

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Re: Parametric EQ frequency resolution
« Reply #6 on: February 28, 2018, 02:27:42 pm »

Sounds like an acute case of splitting hairs😕
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Hanno Meingast

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Re: Parametric EQ frequency resolution
« Reply #7 on: February 28, 2018, 05:56:04 pm »

Hi Folks,

I work with some Old Time bands that will sometimes wail away in the key of A.
When you get Bass, Guitar, Banjo, Mandolin and Fiddle all sitting on A, it can start to roar a bit, even on good systems.
So I go to the offending A(usually 220, sometimes 110 or 440) and make a narrow cut in the monitor mixes, and occasionally the house mix.

I used to work on a couple different analog mixers with infinitely fine frequency adjustment.
In reality, the knobs were small and a few degrees rotation probably moved up or down the frequency scale quite a bit.

The first digital mixer I worked on, an 01V96, had 1/12 octave steps for the parametric EQs.
For A-440, 450 is the nearest frequency option.

The Midas MR18 has 1/20 octave steps.
432.7 or 447.9 are your choices.

Allen & Heath QU goes even closer, to 439 and 441.

All of these options are far better than a 1/3 octave graphic EQ, at 400 or 500, and have worked fine for me in a variety of situations.

Some mixers, like the Mackie DLs, have one Hertz steps, except down low where they have 1/10 Hertz resolution, and way up high where they round off a bit.
I can go right to 440.
Maybe not a big deal, but nice just the same.

When looking at new mixers, is this a consideration for you?

Thanks and good health,  Weogo
Do you readjust the eq when they switch keys?


Sent from my iPhone using Tapatalk
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Josh Millward

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Re: Parametric EQ frequency resolution
« Reply #8 on: February 28, 2018, 05:58:39 pm »

As far as frequency goes, I generally consider 3 digits of resolution to be accurate enough.

For example, I would prefer to see:
25.3Hz   This gives you 0.1Hz resolution from 20Hz through 99Hz.
543Hz   Then this gives you 1Hz resolution from 100Hz through 999Hz.
1.25KHz   Followed by 10Hz resolution from 1000Hz through 9,999Hz.
14.3KHz   And finally 100Hz resolution from 10,000Hz through 20,000Hz, or however high you want to go.

I prefer to see gain settings accurate to at least two decimal places, but often the three digit rule can apply there, too.
As an example, I would prefer to see 5.55dB, but when you start dealing with larger number this can be a pain so -55.5dB would be fine too, though that extra decimal place isn't as problematic with gain settings (-55.55dB) as it is with frequency.

Delays require microsecond accuracy. So, 5.555mS is where I would like to see it. You could argue that different delays are required for different places. For example applying delay to a whole loudspeaker for delay alignment needs about half millisecond accuracy whilst driver alignment should be microsecond accuracy. So, it could be reasonable to assume 25.6mS would be fine for loudspeaker delay, whereas 0.054mS may be required for driver alignment.

I love the features on some devices where double clicking on a control sets it to the "nominal" position. This is especially true with pans and EQ gain where I can double click on the control and it sets it back to zero.
« Last Edit: February 28, 2018, 06:02:17 pm by Josh Millward »
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Weogo Reed

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Re: Parametric EQ frequency resolution
« Reply #9 on: February 28, 2018, 10:53:34 pm »

Hi Folks,

Thanks for all the replies!

Ivan, ever work with Medieval instruments tuned to A432?

Caleb, there are $600 mixers that conform to Josh's rule below.
And there are some fairly expensive ones that don't.

Dave, you are correct, as noted, sometimes it is A220, occasionally A110.

Nathan, I hear ya on rounding numbers.

Lindsay, you might have me pegged.

Hanno, Generally I just leave the cuts in.  They are fairly narrow and nobody has ever complained.

Josh, I like your 3 digit rule.

Good health,  Weogo
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Re: Parametric EQ frequency resolution
« Reply #9 on: February 28, 2018, 10:53:34 pm »


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