Are you interested in simulating speakers? Manufacturers sometimes give some basic info about the driver's physical characteristics that can be useful to start the modeling process, but my example was taken from my work from a few years ago with a prototype subwoofer that I was then developing. One gets in the ballpark by starting with the parameters from any model of a vaguely similar speaker, or by calculating the first cut parameters from the equations. After that, it is not too much trouble through trial and error to adjust the parameters to get a near perfect fit to measurements. I measured the proto subwoofer's impedance and response on an Audio Precision analyzer and I went looking for a way to model it so I could simulate an equalization scheme that uses positive feedback of coil current. Almost all of the models I found were set in the acoustical- mechanical domain and didn't capture actual performance all that well anyway. So I came up with a much more EE friendly model to match the data. -- analog spiceman Here is an example of a SPICE model that very accurately mimics measurement. It is for a speaker with both an actively driven cone and a passive radiator cone. First some definitions (skip to the end for a quick peak at the results). Bl Electromechanical motor constant of the voice coil - this factor depends on magnet strength, gap geometry and turns in the coil. It relates coil displacement force to coil current (newtons/amp). Rvc Rvc is the dc resistance of the voice coil. Rvc1-3 account for the frequency dependent increase in resistance due to eddy current losses in the voice coil and surrounding pole pieces. Lvc Voice coil inductance - decreases with increasing frequency due to flux squeezing resulting from eddy currents. Les Cone suspension compliance equivalent inductance: Les = Cm*(Bl)^2 Cm is the mechanical compliance in m/N. Cem Cone mass equivalent capacitance: Cem = Mm/(Bl)^2 Mm is the mechanical mass in kg. Res Cone suspension loss equivalent resistance: Res = (Bl)^2/Lm Lm is the mechanical losses in inverse seconds. Fa Acoustic output factor - goes up with cone area and motor efficiency and goes down with cone mass, but has almost no effect on electrical impedance. Note: RLesa and RLesp are added to avoid convergence problems with SPICE and Ro allows summing the current dependent current sources that model the acoustic output factor of the two cones in the system. The Model: / Voice \ / Active \ Air in / Passive \ / Coil \ / Piston \ Box / Piston \ Rvc Lvc0 Leb o--./\/\/`--+--@@@@--+-------+-------+--@@@@@--+-------+-------+ 3.8 | 4.5m | | | 62m | | | / | | | | | | Rvc1 \ | | | RLeb | | | 3 / | | +-./\/\/`-+ | | | Lvc1 | | | 200 | | | +--@@@@--+ | | | | | | 3.0m | | | | | | / | | | | | | Rvc2 \ | | | | | | 15 / | | | | | | | Lvc2 | Cema | (@ Lesa | Cemp | (@ Lesp +--@@@@--+ === (@ | === (@ | 2.0m | 0.5m | (@ 200m | 1.5m | (@ 110m / | | | | | | Rvc3 \ | | | | | | 75 / | | / / | / | Lvc3 | | \ RLesa \ Resp | \ RLesp +--@@@@--+ | / 1m / 80 | / 1m 1.3m | | | | | | / | +---+ | | +---+ Resa \ Faa | ,!. | | Fap | ,!. | 90 / [i]( I ) | | [i]( I ) | | 588m | `+' | | -235m | `+' | | | | | | | | | o------+-------------+-------+---}---+----+----+-------+---)---+ _|_ | / | / / / Acoustic | Ro \ 1 ohm | Output | / | Vo o--+--------+----------------+ The Results: Speaker Impedance 100 +-----------+-----------+-----------+-----------+ | ' | ' | ' | ' | | ' | | | ' | ' _| ohms | - - + - - | ! - l - | - - + - - | - - + _," | | ' | l ; : | ' | _,-" | | ' |; : ; ` | ' _,-" ' | 10 +-----------+--\-;---\--+-------_,-" -----------+ | ' _/| v ' \ | _,-" | ' | |~----**"" | ' "*--" ' | ' | ohms | - - + - - | - - + - - | - - + - - | - - + - - | | ' | ' | ' | ' | | ' | ' | ' | ' | 1 +-----------+-----------+-----------+-----------+ 1Hz 10Hz 100Hz 1kHz 10kHz Acoustic Output 1V +-----------+-----------+-----------+-----------+ | ' | ' | ' | ' | | ' | ' _.--.._ ' | ' | 100mV | - - + - - | - -__.-"- | - -`+~._- | - - + - - | | ' | / ' | ' `~~..__ ' | | ' | ; ' | ' | `~~..__| 10mV +-----------+-y---------+-----------+-----------+ | ' | | ' | ' | ' | | ' __| ; ' | ' | ' | 1mV | - - -,-" \/- - + - - | - - + - - | - - + - - | | _,-" | ' | ' | ' | | / ' | ' | ' | ' | 0.1mV +"----------+-----------+-----------+-----------+ 1Hz 10Hz 100Hz 1kHz 10kHz