I am trying to simulate a current driver using TIP31 transistor for a speaker with known resistor and wattage. Can anyone please help me find a PSpice library for speakers? If there is not a library, how can I simulate the speaker only with information about its wattage and its resistor?

  • \$\begingroup\$ It depends on how much DC current you apply and offset the cone and reduce magnet strength , cone excursion , distortion and what speaker you're using. Given this is just a low gain NPN power transistor, in class A mode , both will be fairly inefficient. Show your worksheet of values and photos of parts, Vmax, Z etc \$\endgroup\$ May 17, 2020 at 0:32
  • \$\begingroup\$ The problem with common emitter is horrible damping factor going from a current source instead of a true voltage source. bad idea. you can use negative feedback for low quality but better to use push-pull with Op Amp or a real driver \$\endgroup\$ May 17, 2020 at 0:35

1 Answer 1


If you only want some reactive load that resembles a speaker (I presume electrodynamic), then a simple series RL will do the job. Try 0.15 mH and 7 Ω for an 8 Ω full-range speaker. If you also want to model the resonance, add a parallel RLC in series with that RL, with, say 50 mH, 50 Ω, 150 μF. At this point, the most you could do is add some parallel resistors, or other parallel RL cells in series with the load to mimick a different slope for higher frequencies. Or you could complicate a bit by adding a would-be transformer between the series RL and the parallel RLC, to mimick some sort of transfer based on magnetic field. You could also add an enclosure, but things get complicated from here on. Here is a quick example with what I said:


The values, as they are now, are not too far off from some Fostex full-range from some ...years ago (as best as I can remember). It's a good enough approximation for a test. Choose your own values for whatever speaker you wish to model after.

  • \$\begingroup\$ Thanks for you answer. I am going to use only the reactive load. The resistor of the speaker is 4Ω and the wattage is 30 watt. I don't really know, how to calculate the inductor? How did you measure the L1 15mH for a 8Ω full range speaker? \$\endgroup\$
    – Bornak
    May 16, 2020 at 21:27
  • \$\begingroup\$ DCR of speakers are typically near 40% of rated impedance give or take 10%. Then the inductor is damped by air pressure with R= 50%Z for a low Q response . But you have DC power mainly on idle. \$\endgroup\$ May 17, 2020 at 0:38
  • \$\begingroup\$ @Bornak Even 20 years ago there was information on the Internet about Thiele-Small parameters, but the manufacturer's datasheet should provide some, if not all. Here is a random Fostex full-range speaker that has some of the parameters. If you want to simulate an amplifier, then it's better to include all those 5 components (if not add more), instead of only the series RL. The values, judging by the rounded numbers, are just the result of a neuron belch. It's up to you to know what you want and how you can achieve it. \$\endgroup\$ May 17, 2020 at 6:43

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