5 Band Graphic Equalizer

[NSLogan]

Ok, i'm hoping to build a 5 band graphic equalizer for use with the two channel LM1876 so, as expected, i have a few questions.
1. First off, i know very little about graphic equalizers and have been searching google for a few hours now. I found a 3 channel graphic equalizer (http://www.circuitstoday.com/categor...ircuits/page/3); so, my question is: how did the creator of this circuit come up with the frequencies this adjusts (50Hz, 1kHz, 10kHz)?
2. Continuation of 1: if i understand how these values were calculated, could i add two channels/adjust these values to adjust what i want?
3. To equalize two channels, would i have to duplicate the RC circuit for both channels and just use input from the 5 pots for both circuits?

[Artie]

Go to the National Semi home page and get the data sheet for the LME49720 chip. It has exactly what you're looking for. Its near the end of the sheet, but shows how to make an EQ, up to 10-bands.

[ChrisA]

Originally posted by Artie
Go to the National Semi home page and get the data sheet for the LME49720 chip. It has exactly what you're looking for. Its near the end of the sheet, but shows how to make an EQ, up to 10-bands.

They leave off one important part of the design. What to do with frequencies above the hgh band and below the low band? The end bands need to not have a second cut off. Look at the last (at the bottom) section of this "classic" design. This might be the first equalizer ever sold. I think it might be 60 years old but the idea still applies today. (yes I might build this some day.)

http://www.triodeel.com/images/b9b.gif