SPEAKERS - Goldmund

2. Preliminary calculations
First we need to determine:
- The force factor Bl
- The mechanical parameters linked to the mobile system: mass ms, resistance Rms and
compliance Cms
- The acoustic equivalent parameters of enclosure, port and losses due to leakage: Cab,
map, Rleak
- The acoustical radiation impedance mar and Rar
These lumped-constant parameters enable input impedance, membrane displacement, as well as
drivers and port volume velocities to be calculated. According to the hypotheses of membrane
coincidence and monopole radiation, they lead to a first estimation of drivers and port radiating
sound pressure.
The figure below shows the example of the Minilogos calculation results:
ohm
m3/s
35
30
25
20
15
10
5
0
6
5
4
3
2
1
0
- Drivers input impedances
- Drivers membrane displacements
- Port and drivers volume velocities
- Port and drivers radiating sound pressure estimated at 1W/1m
DRIVERS INPUT IMPEDANCE
10 2
x 10 -3 PORT & DRIVERS VOLUME VELOCITY
10 2
10 3
Hz
10 3
Hz
10 4
10 4
mm
dB SPL
2.5
“Perfection in an imperfect world”
2
1.5
1
0.5
0
100
95
90
85
80
75
70
65
60
55
50
DRIVERS MEMBRANE DISPLACEMENT
10 2
PORT & DRIVERS SOUND PRESSURE at 1W/1m
10 2
10 3
Hz
10 3
Hz
10 4
10 4