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DLS SOUND HANDBOOK - FORMULAS AND FACTS
FORMULAS
It's easier to understand some parts in this book if
you know some of the formulas on this page. They
are also useful at many other occasions.
OHMS LAW:
R = resistance in ohm, U = voltage in Volt
I = current in Ampere, P = power in Watt
GEOMETHRY:
Circel:
r = radius
O = periphery
d= diameter
A = area
Radius (r) = O
2π
Periphery (O) = 2π x r
Box volumes (V):
When caculating the volume of a box you simply
multiply the width (W) x heigth (H) x depth (D).
Use measures in dm and you will get the answer in
liters.
A trapezoid box is calulated as below:
Volume =
width (W) x heigth (H) x ((upper depth + lower depth)/2)
To get the net volume use the inner measures of
the box.
W
UD
H
LD
Volume (V) of a pipe:
D = depth (length) r = radius
V = r
2
x 3,14 x D
Diameter (d) = O
π
Area (A) = π x r
2
r
Use measures in dm
and you will get the
answer in liters.
MEASURE CONVERSION
The following relation between some units are
useful to know of.
1 yard (yd) = 3 ft = 36 in = 0,9144 m
1 foot (ft) = 0,3048 m
1 inch (in) = 2,54 cm
1 square yard (yd
2
) = 9 ft
1 square foot (ft
2
) = 144 in
2
1 square inch (in
) = 6,452 cm
3
1 cubic yard (yd
) = 27 ft
1 cubic foot (ft
3
) = 1728 in
1 cubic inch (in
3
) = 16,39 cm
1 pound (lb) = 16 oz = 0,4536 kg
1 ounce (oz) = 28,35 gram
CONVERSION GAUGE - mm
Gauge (ga) is an American measure for cable
areas, also called AWG (American Wire Gauge).
1 AWG = 42 mm
2
2 AWG = 33 mm
2
2
3 AWG = 27 mm
4 AWG = 21 mm
2
5 AWG = 16 mm
2
2
6 AWG = 13 mm
2
7 AWG = 10 mm
8 AWG = 8 mm
2
SPEAKER TERMS
It´s useful to know what the most common speaker
data terms stands for.
Fs = speaker resonant frequency in Hz
Fc = box resonant frequency in Hz
F3 = approximative lower frequency for vented
boxes in Hz. Often called F-3 dB point = the point
where the power is half.
Qes = the speakers electrical Q-value
Qms = the speakers mechanical Q-value
Qts = the speakers total Q-value
Vas = Eqvivalent air volume. The air volume having
the same aqoustic compliance as the speaker
suspension.
X-max = voice coil length - 2 x thickness of the
inner pole plate.
Sd = the speakers effective cone area
Vb = net volyme of the box
SPL = sound pressure level in dB
Sens. = speaker sensitivity in dB at 1Watt / 1 mtr
Re = speaker DC resistance in ohms
Mms (Mmd) = moving mass
Le (Lbm) = Voice coil inductance
RMS = AC average power value
BL = The flux density factor in the magnetic gap in
the speaker * the wire length of the voice coil
2
2
= 1296 in
2
= 0,8361 m
2
= 9,290 dm
2
2
3
3
= 0,7646 m
3
= 28,32 dm
3
3
2
9 AWG = 6,8 mm
2
10 AWG = 5,3 mm
2
2
11 AWG = 4,2 mm
12 AWG = 3 mm
2
13 AWG = 2,7 mm
2
2
14 AWG = 2 mm
2
15 AWG = 1,65 mm
16 AWG = 1,3 mm
2
2
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