I understand why people like to make generalizations about the 4 ohm nominal speakers and amp requirements, but on ASR, specifically, I would hope we could gradually become more focused on the specific user applications.
Reasons, as I mentioned many times are:
1) Theoretically, except for some poorly designed protective schemes some AVRs may use, such as the "limp mode", Yamaha's seemingly (at least in some of their older models) overly sensitive schemes, can drive 4 ohm nominal speakers that have dips to below 3 ohms at some narrow frequency ranges, usually in the 20-200 Hz range.
2) Mid range models such as the AVR-X3800H, Cinema 60, RZ-50, Yamaha RX-A6A will likely do fine with a lot of 4 ohm rated speakers if the users sit with 2-4 meters to their speakers and listen to spl well below reference, say 10 dB or more below reference, such as never turn the volume dial higher than -15 (based on D+M units just as example.
3) Upper midrange to flagship models are usually fine as stated above.
4) Entry level models my occasionally shutdown, and/or run warm, to hot, even if well ventilated, but an ext. fan may help in that regard, so it is still doable in specific use cases.
5) Not all speakers have the same or similar impedance/phase angle vs frequency characteristics, that's aside from their sensitivity specs that obviously can also make a huge differences, as an example, speakers with 4 ohm nominal, dips to 3 ohm nominal, sensitivity 92 dB/2.83V/m will be easier to deal with by most AVRs than speakers with 8 ohm nominal, dips to 4 ohms in a few points within the 20-200 Hz range and sensitivity 85 dB/2.83V/m. And then there is the other factor to consider, the phase angles.
If we must generalize our response to those seemingly weekly questions on amps requirements for speakers that are 4 ohm nominal, or even 8 ohm nominal but revealed on bench tests that there were dips to below 4 ohms, sensitivity below 87 dB/2.83V/m, then I assume the following generalization might be reasonable, and realistic enough:
- Mid range AVRs by brands that have rated output into 8 ohms equal to or above the speaker's manufacturer's "maximum power", or the high end of the manufacturer's "recommended amplifier power" (typically use by KEF)
- Upper mid range to flagship class such as the Onkyo RZ70, Yamaha RX-A6A, A8A, D+M AVR-A10H, A1H, Cinema 30, SR8015.
Other than the above, I would ask the questioner about their specific use conditions before responding with a yes, no.
The same actually would apple to integrated and power amps too. As an extreme example, a <$120 Fosi amp is rated for 4 ohm nominal speaker and might have been verified on the ASR bench as 2 ohms capable too, but we all know the likes of AVRs such as the AVR-X4800, or even the Cinema 50 will likely do a little better than some 4 ohm rated integrated or power amp (other examples are the NAD C 320, 326BEE, also 4 ohm rated), without using their 4 ohm impedance setting. So again, not a good idea to give a generalized response in such an example case.
