Mine are rolled off to subs well before that impedence dip
I know the specs say 8 ohms nominal, but looking at the ASR measurements, it looks more like 4, may be 5.5 ohms nominal at the most.
Still, using single point impedance and amp "power" it not very useful unless one wants to take the most conservative approach and size their power amps based on say 2X the speaker manufacturer's maximum power handling, or recommending amp power numbers. In that case, one can pair the F206 with a 400 W into 8 ohms power amp and call it a day.
Otherwise, we can take a look of a more likely real world application such as the following example I would like to use:
For a good part of the audio band, the F206 impedance appears to reach below 6 ohms, but let's say we want to be on the safe side, and choose 4.5 ohms and do some calculations based on that.
Sensitivity: 88 dB, assume that's for 2.83 V at 1 meter (Revel is not explicit on that but we can agree that is a realistic assumption based on common practice on sensitivity specs).
Listening distance, let's assume 4 meters, that's about 13 ft, and the drop in SPL without room gain is -12 dB.
Now assume the worst case in SPL, hopefully worst case is reference level, so 105 dB peak.
88-12 = 76 dB would be achieved at 4 meters, without room gain and that is at 2.83 V.
To bring it up to 105 dB, by calculations based on 4.5 ohms, the "power" required would be about 1400 W, the current draw would be about 18 A.
Clearly the AVR is not going to make it, not even close. Now if the required SPL is 6 dB below reference, or 99 dB, still very loud I would say, then the power required will drop to 144 W, current would be 5.66 A, for two channel driven simultaneously, double the numbers. That's doable by the AVR, but I doubt it would last long if used under that condition regularly.
So I think the key for trouble free operation of the AVR, with the Revel F206 towers and the matching center, would be to do the following:
- Don't listen to more than 10 dB below reference, master volume at below -15 would seem safe.
- Use a quiet fan to blow from the rear, full time.
- Set crossover at 80 Hz, not lower.
Or, use an external 2 or 3 (better) ext. amp rated at least 200 W 8 ohms, 350 W 4 ohms, and then it will be safe to push SPL to 6 dB below reference.
Or, shorter the distance to say 3 meters, then the AVR can survive normally for listening to 10 dB below reference, so volume up to -10 should be okay.
Now, on the 4 ohm setting:
We already know the 4 ohm setting will limit the amp's output voltage, we don't know for sure how much it drops. If we assume the rated power output would drop by half, then we know leaving the setting for 8 ohms, but lower your maximum volume by 3 dB would have the same results.
Above calculations are very much on the conservative side, as it assumes no room gain at all, and impedance 4.5 ohms instead of Revel's official specs of 8 ohms nominal.
In reality, the load wouldn't be as punishing, though keep in mind the calculations mainly based on one and two channel driven. When watching movies in 5.2, depending on the contents, you can push the AVR to uncomfortable too.
Again, an ext. fan would help a lot.
One thing for sure, those who listen loud, like to near ref level from more than 3 meters should almost always use ext. amps unless their speakers have relatively high sensitivity, such as above 93 dB/2.83 V/m
