RIAA question

[Guest]

RIAA is the standard by which LP's are recorded, and use the following formula

Picture1.png (11.88 KiB) Viewed 555 times

and produces the red curve.

RIAA-EQ-Curve.png (42.07 KiB) Viewed 555 times

Can anyone show me how to modify the formula to produce the blue curve?

this is what I have used in excel so far

=(10*LOG10(1+(1/((4*PI()^2)*(C15^2)*($D$11^2)))))-(10*LOG10(1+(1/((4*PI()^2)*(C15^2)*($D$10^2)))))-(10*LOG10(1+((4*PI()^2)*(C15^2)*($D$12^2))))

where:
C15 is f
d10 is t1
d11 is t2
d12 is t3

Yours Simon M.

[Guest]

It is impossible to say for certain without seeing the equations for both curves but it looks to me like the blue curve is the red curve rotated around the x-axis.
That is, if the red curve is y= f(x) then the blue curve is y= -f(x).