| bblackwood wrote on Fri, 20 August 2004 16:11 |
Though there may be other definitions, here's how I break down the two:
Paragraphic - fixed width control (Q), adjustments for frequency and boost/cut.
Parametric - adjustable Q, freq, boost/cut.
I think that parametrics are better for almost every application as the added ability to dial in the specific bandwidth is very helpful. That being said, there are a few good EQ's on the market that have fixed Q...
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Your first definition fits closest to a graphic except (Q). Transition bandwidth is fixed but not Q factor. The way it typically works is the transition bandwidth spreads across 3 bands, the center frequency (control) and the band above and below. A 10 band (sometimes 9), has 10 bands each with a band control at each octave. A 15 band has amplitude control at 2/3 octave intervals, a 20 band has amplitude control at 1/2 octaves and a 30 or 31 band has amp control at 1/3 octaves. All usually still have transition bandwidth fixed at the two immediate side band controls. If you raise a slider on a graphic, the curve sharpens (narrower bell) as the amplitude rises, the curve starts and ends at the band above and below so that a 10 band graphic has a fixed transition bandwidth of 2 octaves, where a 20 band has a fixed transition bandwidth at 1 octave.
Q factor (user controlled or not) is variable so that the transition bandwidth widens as amplitude is applied and narrows as amplitude is lowered. If you have a Q factor of 1 at +3dB and boost it to to +6dB, your Q stays fixed but your transition bandwidth widens, IIRC, an octave on either side of the center freq every + or - 3dB, but don't quote me on that. A graphic doesn't do this because the transition bandwidth stays fixed. As you boost (or cut) your Q factor changes. You can't apply or release amplitude without the transition bandwidth being altered if Q is fixed.
While graphics aren't necessarily ideal for a mastering chain, they do have their uses, if you know their parameters and want to control frequencies within them. For example a 31 band grapic makes a fairly good notch filter if you want to attenuate some material that has some narrow band system noise in it, without affecting too many other frequencies, because the Q factor changes and the transition width doesn't, your curve sharpens with gain cut and you never cut outside of that 2/3 octave. I don't feel parametrics are better for almost every application, because although you have control of Q factor (sometimes only bandpass freq's) you typically have less bands that you can control. Because the center freq contols on a graphic have a 3 slider transition bandwidth, almost any curve can be applied across the spectrum, with a grapic representation of your curve reflected on the very controls that you are setting them on. This exceeds rotary controls in that you can always see your curve and with pots, you are dependent at moving closer and viewing the numbers. Paragrapics are better though, because they combine the Q flexibility of a parametric, with the wider band control of a graphic. But I prefer a 120 band sweeping parametric on most of my apps, because I have the availability to control 120 different center frequencies with Q control on 4 of them.
