**Voltage Drive, Impedance Determines Watts**

Then I finally wrapped my brain around how (for today's solid state amps, not tubes) the volume level sets the voltage level, which is constant for the source signal and no matter what the power draw is. The impedance of the speaker, which is a varying curve through the frequency response, determines the power drawn from the amp in watts.

**Questions**

**Impedance Curve is Almost Inverse of Sensitivity Curve?**

So you wouldn't power a speaker with 1w and get a flat curve. I imagine that if you could keep it at 1w you'd have a frequency response that varied as impedance does?

**Speakers are Easy, Even with Big Dips?**

Now I'm having trouble understanding how speaker reviews that measured impedance and acknowledge a dip to 3 or 4 ohms in mid-bass, but the average impedance is over 7 ohm, say "This speaker is easy to drive with an average receiver."

Take this Stereophile review of the Klipsch RB-15: http://www.stereophile.com/content/klipsch-rb-15-loudspeaker-measurements.

"It drops to around 4 ohms in just two regions—around 80Hz, the port tuning frequency; and in the lower midrange—and though the electrical phase angle is quite high at times, this is always when the impedance magnitude is high, mitigating any negative effects. The speaker will therefore be well-suited to being driven by inexpensive amplifiers and receivers."

I do not see how it's easy to drive, if between 200 and 300Hz it's 4ohms, so we could say the sensitivity is 3dB less than the measured 90dB, so 87dB. It takes all of 100w get get to reference level from 12 feet, and that's with the more generous 3dB loss double-distance and figuring in-room. That seems to be on the ragged edge of a typical receiver. So why is this speaker well-suited to cheap receivers (which I imagine to be realistically 50wpc)?**Phase Angle**

Here's a Stereophile review of the Klipsch Palladium P-17B that's more damning because of the phase angle: http://www.stereophile.com/content/klipsch-palladium-p-17b-loudspeaker-measurements

"[Impedance] drops below 3 ohms between 128 and 265Hz, with a minimum value of 2.6 ohms at 170Hz. There is also an amplifier-frightening combination of 4.5 ohms and –50° electrical phase at 104Hz, a frequency where music has high energy levels. So while the Klipsch will play loud with a low-powered amplifier, that amplifier will still need to be able to deliver goodly amounts of current."

How could one determine by

**phase angle and impedance what the watts drawn**will be?