TV-sound through Sonos for stereo speakers

A bit of tech: The “impedance rating” of a speaker is a judgement call by someone. A speaker’s actual impedance varies instantaneously with frequency. Sometimes the rating assigned is the absolute low point that typically occurs in the 60Hz range. Other times whoever makes the assignment will pick an “average” (unspecified) frequency in this range, measure the impedance, and assign this number, but there could be a lower point (typically) below this frequency. Very high end speakers are notorious for having one of these low points. The result is that a very low note, say 30Hz, might present a 2-Ohm (or lower) load to the amplifier. Some high end amplifiers will tolerate this better than modestly priced amplifiers because the expensive high end amplifier might have originally been designed as a (much more expensive to produce) 2-Ohm amplifier. Certainly, if this high end amplifier is paired with a speaker that exhibits a 2-Ohm dip, the amplifier will sound much better on that very low frequency note.

Earlier SONOS amplifiers had very stern limits and would instantly shut down if the speaker impedance slipped below 4-Ohms at some frequency. This is a great feature and, as described above, protects both the speaker and amplifier from abuse. AMP is a more flexible, intelligent design and will tolerate brief dips below 4-Ohms without raising a fuss, while also preventing clipping. If you try to fake out AMP and connect a speaker that really should be rated bellow 4-Ohms, AMP will figure this out and shut down.

I don’t have experience with the whole universe of speakers, but I have not been seeing reports of AMP balking while driving speakers that are known to fluster amplifiers.