The main reason is that the Ohm rating of speakers is a marketing tool, not a true specification.
A speaker is not a restive device but a reactive device and the actual rating varies with frequency and possibly power levels. So a speaker rated at 4 Ohms might actually vary between 3 and 6 depending on what is being played.
Sonos picked a safe number to publish for general use. For Sonance speakers they worked with the manufacturer to create speakers designed for Sonos use.
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What does it mean that these speakers are optimized for Sonos Amp?
When these speakers are connected to Sonos Amp, the Amp will automatically detect them, and automatically adjust the sound to be best for that speaker. This is only possible because we designed the speakers from the ground up with Sonance. This also means the indoor models (In-Wall and In-Ceiling) are the only passive speakers to support Sonos’ Trueplay tuning, which tunes the system to the room environment.
How many pairs of speakers can be installed together on a single Sonos Amp?
The Sonos Amp has been designed to power up to three pairs of Sonos Architectural speakers on a single Sonos Amp.
It turns out one of my sets of speakers is 8 ohm and the other is 6 ohm.
Parallel wired this is 3.43 ohm - still below the stated 4 ohm limit of the AMP but way above the Sonance 2.67 ohm that works.
As the speakers are quality (Polk and Monitor Audio) not some off-brand rubbish I’m minded to give it a go. Anyone got any thoughts on this?
Cheers
The quality of the speakers is not the issue. If you’re in the mood for research, you could see if the manufacturer, or an audio reviewer, published measurement graphs of ohms vs. hertz, for each speaker. In theory, you could overlay them to see if they just happen to *not* coincide. IOW, you would sum the two graphs, which might give you reason for hope.
But nobody here will advise you to (potentially) try to pull too much power out of your Sonos Amp -- you have to take that upon yourself. The problem with your conjecture that 3xSonance ==2.67Ω is that nobody here (yet, so far as I know) knows *exactly how* “the Amp will automatically detect them” and what limitations the Amp puts on itself as a result. I would expect it does some kind of auto bass reduction if it calculates being near its limits -- but I know nothing! That would mean you could safely try your speakers in parallel and keep listening for distortion & checking equipment temperature, vs. volume control, while playing your Rammstein or whatever -- but I know nothing! Sonos and Sonance don’t disclose this info and restrict TruePlay use just because they want to pull as much money as they can from the custom installation budget.
[Oops, sorry @jebr , didn’t mean “sum” the graphs literally, my mistake -- meant “calculate the (effective) parallel resistance, despite knowing full-well that it’s a complex impedance”. Forum won’t let me edit the post above. But whatever the result, merely connecting them won’t hurt the amp. It’s just when you try to drive them, especially turning up the volume, that might result in distortion, with its consequent or co-incident potential damage somewhere in the chain.]
Also annoying would be one set of speakers being loud and the other being quiet, and you not being able to do anything about that. For example, I paralleled a set of Cambridge SoundWorks Ensemble (showing my age here!) and a pair of Paramount outdoor burial speakers on an old ZonePlayer, and it was unbearable inside when it was barely loud enough outside. I didn’t push it. Bought a multi-speaker switch box which inserted resistance when more than one speaker set was in use, and that helped, but still uneven.
You could try that if you are risk-averse, something like a Niles SS-4, with the “Protection” switch pushed in.
