Specifications

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.
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:
V = width (W) x heigth (H) x upper depth + lower depth
2
W
H
UD
LD
OHMS LAW:
R = resistance in ohm, U = voltage in Volt
I = current in Ampere, P = power in Watt
Volume (V) of a pipe:
D = depth (length) r = radius
V = r
2
x 3,14 x D
2
r
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
2
= 1296 in
2
= 0,8361 m
2
1 square foot (ft
2
) = 144 in
2
= 9,290 dm
2
1 square inch (in
2
) = 6,452 cm
2
1 cubic yard (yd
3
) = 27 ft
3
= 0,7646 m
3
1 cubic foot (ft
3
) = 1728 in
3
= 28,32 dm
3
1 cubic inch (in
3
) = 16,39 cm
3
1 pound (lb) = 16 oz = 0,4536 kg
1 ounce (oz) = 28,35 gram
CONVERSION GAUGE - mm
2
Gauge (ga) is an American measure for cable
areas, also called AWG (American Wire Gauge).
1 AWG = 42 mm
2
9 AWG = 6,8 mm
2
2 AWG = 33 mm
2
10 AWG = 5,3 mm
2
3 AWG = 27 mm
2
11 AWG = 4,2 mm
2
4 AWG = 21 mm
2
12 AWG = 3 mm
2
5 AWG = 16 mm
2
13 AWG = 2,7 mm
2
6 AWG = 13 mm
2
14 AWG = 2 mm
2
7 AWG = 10 mm
2
15 AWG = 1,65 mm
2
8 AWG = 8 mm
2
16 AWG = 1,3 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 mean power
BL = The factor of theflux density in the magnetic
gap in the speaker x the wire length of the voice coil
GEOMETHRY:
Circel:
r = radius O = periphery
d= diameter A = area
Radius (r) = O Diameter (d) = O
2π π
Periphery (O) = 2π x r Area (A) = π x r
2
To get the net volume use the inner measures of
the box.
Use measures in dm
and you will get the
answer in liters.
DLS SOUND HANDBOOK - FORMULAS AND FACTS