T1 ToneMatch® Audio Engine / Para EQ

Understanding the T1 ToneMatch Audio Engine Para EQ

T4S

T8S

T1

This information is applicable to the T1 ToneMatch® audio engine

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Introduction

This article explains Para EQ (Parametric Equalizer) and delves into the Width Parameter.

This article applies to all ToneMatch mixers (T1/T4S/T8S) except that the T1 has a single Parametric Equalizer per channel, and the T4S/T8S have three Parametric Equalizers per channel.

This started with a question from John Nell ^[1]

I understand the concept of notch filters. I'm thinking the ParaEQ works in a similar way, and I understand Level and Freq options. I'm having trouble understanding the Width function. I understand the bell curve concept around a center frequency, but can someone diagram for me the .20 to 5.00 octave width? Exactly, what does this look like on the bell curve? What do the values, .20 and 5.00 mean visually? A diagram to explain it would be great, but I don't understand the "octave" part of it.

If you set the Frequency to say... E3 and the width to 1.0 octave, then my reading of the of the documentation suggests that the widest part of the curve would be one octave wide, or half an octave on either side of E3.

If you set the width to 0.5 then the base of the curve (on the Y-axis) would be one half octave, or one quarter octave on either side of E3.

In other words, the narrower the width, the more precise the effect whether you are increasing or decreasing the frequency.

I don't think in terms of precisely how many notes on either side the width is affecting - just that the smaller the width, the more highly focused my efforts will be. Or if you like, the smaller the base of the curve will be, or ... smaller width suggests that it will affect fewer notes around the central frequency selected with the middle knob.

Examples

So some concrete examples.

I have a big body jazz guitar that really likes to resonate at about 165Hz. That's an octave above the open (lowest Guitar) E string. So rather than having to mute that string all the time, I just dial up that frequency and set the width as narrow as I can - 0.2 (1/5 th of an octave) and setting the Level to -6 dB. This seems to do the trick, and since this Guitar really *loves* that note, dialing it back just balances things out a bit. I used -6 dB because I needed that much to tame the problem. In real life you fine tune the cut by ear. Use much as you need, but as little as possible.

If you have a wolf tone in your Bass, you could probably tame it with the Para EQ.

Starting with the T1 ToneMatch Audio Engine looking like this

imagine that we are increasing the Width parameter. In the plots below the center point (lowest representing -6dB ) is the Frequency that you select with the middle button, in this case, 165 Hz (E3, not shown in the Simulator). The tick marks on the X-axis are roughly one octave.

The plots below suggest the widening range of notes that will be affected by the Level (-6 dB) as we go increase the Width. The plots point down because we are applying a negative level. The depth of the plot (distance down) would vary up and down as we changed the Level. I have kept these constant so we can focus on the Width parameter.

The following are extremely rough approximations. For anyone reading - there is nothing scientific about these plots. The appearance suggests a level of precision that is way beyond what I did to create these images. (Normal distribution curve, manipulated the standard deviation). Just go for the rough visual impression. Thanks!

	Width = 0.2 Octave (0.10 Octave on either side of the Freq)
	Width = 0.5 Octave (0.25 Octave on either side of the Freq)
	Width = 1.0 Octave (0.50 Octave on either side of the Freq)
	Width = 1.5 Octaves (0.75 Octave on either side of the Freq)
	Width = 2.0 Octaves (1.00 Octaves on either side of the Freq)
	Width = 2.5 Octaves (1.25 Octaves on either side of the Freq)
	Width = 5.0 Octaves (2.50 Octaves on either side of the Freq)