Audio Formulas

The following chart contains commonly used conversions of length, area, and volume. Simply multiply what you want to convert by the number in the last column.

Length

inch to  millimeters X 25.4
inch to  centimeters X 2.54
inch to  meters X .0254
inch to  feet X .0833
millimeters to  centimeters X .100
millimeters to  feet X .00328
millimeters to  inch X .03937
millimeters to  meters X .00100
centimeters to  millimeters X 10.0
centimeters to  feet X .0328
centimeters to  inch X .3937
centimeters to  meters X .0100
feet to  centimeters X 30.48
feet to  inch X 12.0
feet to  meters X .3048
feet to  millimeters X 304.8
meters to  centimeters X 100
meters to  inch X 39.37
meters to  feet X 3.28
meters to  millimeters X 1000

Area

inch2 to  centimeters2 X 6.452
inch2 to  feet2 X .006944
inch2 to  millimeter2 X 645.2
inch2 to  meter2 X .0006452
centimeter2 to  inch2 X .1550
centimeter2 to  feet2 X .001076
centimeter2 to  millimeter2 X 100
centimeter2 to  meter2 X .0001
millimeter2 to  inch2 X .001550
millimeter2 to  centimeters2 X .0100
millimeter2 to  feet2 X .00001076
millimeter2 to  meter2 X .000001
meter2 to  inch2 X 1550
meter2 to  centimeters2 X 10000
meter2 to  feet2 X 10.76
meter2 to  millimeter2 X 1000000
feet2 to  millimeter2 X .000929
feet2 to  centimeter2 X 929.0
feet2 to  inch2 X 144.0
feet2 to  meter2 X .0929

Volume

inch3 to  feet3 X .0005787
inch3 to  centimeters3 X 16.39
inch3 to  meters3 X .00001639
inch3 to  liters X .01639
feet3 to  centimeters3 X 28320
feet3 to  inch3 X 1728
feet3 to  meters3 X .02832
feet3 to  liters X 28.32
centiimeters3 to  inch3 X .06102
centiimeters3 to  feet3 X .00003531
centiimeters3 to  meters3 X .000001
centiimeters3 to  liters X .001
liters to  centimeters3 X 1000
liters to  inch3 X 61.02
liters to  feet3 X .03531
liters to  meters3 X .001

Electronics

In many electrical circuits, the values of components are specified in units with prefixes. This makes the numbers easier to handle without long strings of zeros.

mega = X 106
kilo = X 103
milli = X 10-3
micro = X 10-6
nano = X 10-9
pico = X 10-12

E = Potential Difference (volts)
I = Current (amperes)
R = Resistance (ohms)
P = Power (watts)

Power (watts)
E X I
I2 X R
E2 / R

Potential Difference (volts)
I X R
SQRT( P X R )
P / I

Current (amperes)
E / R
P / E
SQRT ( P / R )

Resistance (ohms)
E / I
E2 / P
P / I2

Resistances in series
RT = R1 + R2 + R3 .... + Rn

Resistances in parallel
1/RT = 1/R1 + 1/R2 + 1/R3... + 1/Rn

Resistances in parallel (2 components)
RT = (R1 X R2) / (R1 + R2)

Capacitances in series
1/CT = 1/C1 + 1/C2 + 1/C3... + 1/Cn

Capacitances in parallel
CT = C1 + C2 + C3 .... + Cn

6dB High Pass
Series Cap = .159 / ( Impedance X Frequency )

6dB Low Pass
Series Inductor = Impedance / (6.28 X Frequency )

12dB Butterworth (high and low pass)
Capacitor = .1125 / ( Impedance X Frequency )
Inductor = ( .2251 X Impedance ) / Frequency

Attenuation Circuit

Attenuation in dB 2 Ohms 4 Ohms 8 Ohms
R1 R2 R1 R2 R1 R2
1 .25 16 .5 33 1 60
2 .5 7.5 .8 15 1.6 31
3 .66 5 1.2 10 2.5 20
4 .75 3.4 1.5 6.2 3 13
5 .83 2.5 1.7 5 3.4 10
6 1 2 2 4 4 8
7 1.1 1.8 2.2 3.4 4.3 6.6
8 1.2 1.4 2.5 2.75 5 5.2
9 1.3 1.2 2.5 2.2 5.2 4.3
10 1.4 .83 2.75 1.87 5.5 3.75


Zobel Network

Resistor = 1.25 X Re
Capacitor = Inductance / Resistor2

Series Notch Filter

Capacitor = .1592 / ( Re X Qes X Fs )
Inductor = (.1592 X ( Qes X Re ) ) / Fs
Resistor = Re + ( ( Qes X Re ) / Qms )

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