5 band graphic equaliser project

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p.gholap93

Member

• Jul 17, 2011

• #1

I am making a 5 band graphic equaliser project. For that I'll be using 5 second order band pass active filters using opamps,1 power amplifier,1 summer and a preamplifier. I have divided the audible frequency range into 5 centre frequencis viz-50Hz,250Hz,1kHz,4kHz,16kHz. Now the problem I don't know the "boost" and the "cut" level that should be applied? Is there any standard levels for that?(I read at most places as 12dB)

 

4pyros

Well-Known Member

Most Helpful Member

• Jul 17, 2011

• #2

Start Here;
https://en.wikipedia.org/wiki/Graphic_equaliser#Graphic_equalizer

 

crutschow

Well-Known Member

Most Helpful Member

• Jul 17, 2011

• #3

What's the power amplifier for?

 

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p.gholap93

Member

• Jul 17, 2011

• #4

crutschow said:

What's the power amplifier for?

Click to expand...

It is for impedance matching with loud speaker.

 

crutschow

Well-Known Member

Most Helpful Member

• Jul 17, 2011

• #5

p.gholap93 said:

It is for impedance matching with loud speaker.

Click to expand...

OK. Normally when the term "graphic equalizer" is used it means a device that works just with the low level audio signals. So what you are building is an audio amp with a built-in equalizer.

 

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carbonzit

Active Member

• Jul 17, 2011

• #6

Looking at your frequencies, 16kHz seems quite a bit too high, as it's really about at the outside of the audible range (actually well outside it for some of us old farts). Even 10kHz is probably too high. How about an octave above 4kHz?

 

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KeepItSimpleStupid

Well-Known Member

Most Helpful Member

• Jul 17, 2011

• #7

The 16 kHz might be used to get rid of hiss, not so much as tone control.

The OP should look at a "parametric equilizer" rather than a "graphic Equalizer". In the former the center frequency is varied and there are very few bands.

 

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carbonzit

Active Member

• Jul 17, 2011

• #8

KeepItSimpleStupid said:

The 16 kHz might be used to get rid of hiss, not so much as tone control.

Click to expand...

I'd say it's too high even for that; 16kHz is barely at the upper threshold of hearing for us humanoids. Now, if you're designing a graphic equalizer for dogs ...

I agree that a parametric equalizer would be even better. 3 bands would probably be plenty.

 

4pyros

Well-Known Member

Most Helpful Member

• Jul 17, 2011

• #9

All points I was trying to get acrossed in post #2

 

Sceadwian

Banned

• Jul 17, 2011

• #10

carbonzit, what are the cutoff frequencies for a 2nd order bandpass filter at 16khz?

 

Last edited: Jul 17, 2011

audioguru

Well-Known Member

Most Helpful Member

• Jul 18, 2011

• #11

Most people with normal hearing can hear 16kHz and higher as the "sizzle" in music. Vinyl records and CDs go a little higher than 20kHz. FM radio and TV are down only -3db at 15kHz.

The bandwidth of a second-order bandpass filter is very broad. If it peaks at 16kHz then it will still have plenty of output at 2kHz.

A boost of 12db is 8 times the power that has no boost which is enough to destroy a tweeter.