Quote:
brucek wrote:
 Yeah, I do mean (and changed) that the impedance will be riding up and down as shown in the first diagram. Its lowest point is around 12Hz, so the current will be the greatest and so the applied power. The phase curve shows where the load becomes near purely resistive when it reaches 0 degrees. I think the power used will be close to the inverse of the impedance curve, will it not.
brucek |
Hi Bruce,
I wanted to jump in as this matter is one often confused. Despite common terminology and specifications, we drive speakers with Voltage, not power. Power ratings on amplifiers are defined by driving specific, resistive loads (nothing earth shattering here). Real electromechanical devices have impedances that vary with frequency. Nominal impedances are about as precise as a "2x4" is 2" x 4"
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You are correct that actual power dissipated in the voice coil is inversely proportional to the impedance curve for a constant Voltage input. The feedback from the creaters of WinISD might have been from confusion of terms. "Power" input could be, and by their description might be, defined by Voltage into the Re or Dcr of the driver. Different programs handle input signal a little differently in how you specify it, but the results should be the same when using the same modeled Voltage.
In short, if you want to correlate the driving signal to a theoretical vent velocity, you want to measure RMS Voltage. Many meters are not True RMS meters, and you will have less confusion in calibrating the Voltage at 60Hz with the meter and then using the frequency response measurements of the electrical signal to extrapolate from there. In taking such measurements, do be sure to include some casual observation to correlate what you are modeling and observing. For example, from the above model you would expect to see ~1/2 the excursion at the tuning frequency as at ~20Hz.