TANDBERG TC3.0 manual Audio Console application, Equalizer filter parameters, Filter types

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The equalizer

The system has 8 user defined equalizers, each made up of 6 second order IIR sections, see the illustration below. Each of these 8 equalizers can be applied to one or more of the audio input and output connectors on the codec.

The Audio Console application

We recommend using the Audio Console, with the build in equalizer GUI, to modify the equalizers. The Audio Console application is found at the TANDBERG Developer Zone web page.

Go to: http://developer.tandberg.com/web/guest/tools/ integrators/audio-console

The equalizer filter parameters

Each section (1 … 6) of each user defined equalizer (1 … 8) can be modified independently by setting the four parameters:

• Filter type (Peaking, low shelf, high shelf, low pass, high pass)

The filter types

The illustrations below shows the 5 different filter types and frequency response variations dependent on some of the parameter variations. The Q-value for low pass, high pass, low shelf and high shelf filters should be set to 1/sqrt(2) in order to get maximally flat responses. The Q-value (or Q-factor) is defined as Q=f0/bw. Where f0=resonance frequency in Hz; and bw=filter bandwith in Hz.

dB	Peaking filter			dB	Low pass and high pass filters
8
				2
	Gain				Lowpass filter		Highpass filter
6				0
4	Q			-2
				-6
2
				-8
0				-10
-2				-12
-4				-14
-6				-16
				-18
-8				-20
101	102	103	104		102	103	104
	Frequency (Hz)			101
						Frequency (Hz)
dB	Low shelf filter			dB	High shelf filter

• Frequency

• Gain

• Q-value

To switch off one of the six equalizer sections; set the second order section to have a flat frequency response. This can be done by setting the filter type to “none” or by setting the filter type to “peaking” and the gain to “0” (zero).

8

6Gain = 6 dB

4Gain = 4 dB

2Gain = 2 dB

0

Gain = -2 dB

-2

Gain = -4 dB

-4

Gain = -6 dB

-6 -8

101 102 103 104

8
6	Gain = 6 dB
4	Gain = 4 dB
2	Gain = 2 dB
0
-2	Gain = -2 dB
-4	Gain = -4 dB
-6	Gain = -6 dB
-8

101 102 103 104

Frequency (Hz) Frequency (Hz)

The equalizer IIR filter
Section 1		Section 2		Section 3		Section 4		Section 5		Section 6
	b0		b0		b0		b0		b0		b0
z-1	b1	z-1	b1	z-1	b1	z-1	b1	z-1	b1	z-1	b1
a1		a1		a1		a1		a1		a1
z-1	b2	z-1	b2	z-1	b2	z-1	b2	z-1	b2	z-1	b2
a2		a2		a2		a2		a2		a2
D14635.02—MARCH 2010						43					www.tandberg.com