# What's the Theory behind Equalisers (sound)

#### trunks14

Joined Apr 22, 2007
15
Hey all,
I want to design & develop an equaliser. It is the design part in which I need your expertise , as this requires a very good understanding of the theory behind them.

In your opinion, what knowledge is required to design a basic equaliser? A parametric EQ?

For example, what areas of mathematics are needed to do some design work? (Fourier analysis...?).

#### syed_husain

Joined Aug 24, 2009
61
Hey all,
I want to design & develop an equaliser. It is the design part in which I need your expertise , as this requires a very good understanding of the theory behind them.

In your opinion, what knowledge is required to design a basic equaliser? A parametric EQ?

For example, what areas of mathematics are needed to do some design work? (Fourier analysis...?).
first, u need to understand the "transfer function" of electronic circuit which is the heart of "frequency domain analysis". from that u need to understand the "electrical filter" theory e.g high-pass,low-pass, bandpass and band-reject.equalizers are nothing but a bunch of filter combination. if need basic understanding on circuit theory, u can try "Fundamentals of Electrical Engineering by Charles Alexander and Mathew Sadiku" (cover both basic circuit theory,transfer function and also Fourier analysis).

As for math, u need to have firm knowledge of complex algebra bcos 100% of the material are based on complex algebra. for that u can try Basic Engineering mathematics by Stroud and Booth or Technical mathematics by Allan Washington.

#### AMIT_GOHEL

Joined Jul 13, 2010
67
Every bar of equilizer indicates a perticular frequency/frequency range.

For such a purpose you need to learn discreate furrier transform.

#### marshallf3

Joined Jul 26, 2010
2,358
I've only seeen a very few that were actually based on any math unless they were done in octaves:
30 Hz, 60 Hz, 120, 240, 480, 960, 1920, 3840, 7680, 15360
but as you can see when it comes to audio these aren't ideal breaks.

Most are separated as bass, mid bass, mid, mid high and high and can have any number of steps as the manufacturer desires.

An example of a good EQ with some theory might be:
http://www.jbl.com/resources/Brands...atedDocuments/en-US/OwnersManual/GTX47 om.pdf

They used to have the schematic for this online, not there anymore though.