I've been using DATS to test a few drivers and inductors I have lying around. I also tried measuring the Focal Profile 918s and made a startling discovery. The minimum impedance is around 2.3 Ohms! Also, the impedance between 75 and 250Hz remains below 3 Ohms.
No wonder these speakers can tell the difference between a mediocre and stout amplifier. They are just ridiculously difficult to drive for their class.
This low impedance is probably a direct result of the crossover topology, 2.5 way means that the mid/woofer and woofer are both working in the bass. Since both are about 6 Ohm devices this would imply a minimum impedance of half this. Ouch.
Please note the maximum and rising impedance in the treble are probably my fault. I've made some EQ changes to the treble which means this is probably not what a stock speaker would measure like above 1 kHz.
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