Unlikely. Are both crackling or only one of the two? You can use the balance slider in the App to find out that.

One of them quite a lot and other is marginal. I bought another pair and they seem fine. I’m returning the original pair to a local repair centre and will update on what the outcome might be. Thanks

 Speakers are damaged via under powered amps and by running them at higher sound levels than they are designed to deliver. Therefore as long as this is not being done, a 20W amp is more likely to cause damage than one that is 100W.

By looking at the damage, the service shop should be able to tell you if excess power supplied to them by the Sonos Amp was the cause.

Is that relevant in this case, I understood the Sonos amp, although not stated, runs nominally at 125w per channel?

It can deliver up to 250 watts per channel if the speaker impedance drops to 4 ohms; it is a powerful amp. A good analogy is a car engine - a small one will always run at close to limits with little in reserve for emergency overtakes, while a powerful one will have power in reserve to get you out of trouble while overtaking etc. But used irresponsibly, the powerful engine can land you in a lot of trouble.

Ah, I think I understand, so I have most likely played music to loud and I have blown the speakers?

With this in mind, is it wrong to pair the AM1 speakers with the Sonos amp is out of balance and is to powerful

It is fine as long as the volume ccntrol is in responsible hands. And even this issue that can be addressed by setting the volume levels for the Amp to 50% in the Sonos app. Until you hear from the service centre, I suggest you do this.

If these speakers are used outdoors and are not close to the listening areas - that is the bigger potential problem in the long term. Sound levels drop rapidly with distance for speakers outdoors and to address this issue you may be running them too loud. 

Yes, I’d agree, I’ve set the volume limit to 70% already, thanks for the advice

So an update. The speakers were kindly repaired under warranty. One was good the other required the midrange/woofer replaced. Begs the question, now I have  two pairs is it possible/advisable to run them in parallel via the Sonos amp, advice please, thanks in advance.

Yes, AMP will support two pairs of AM1’s wired in parallel.

Wiring speakers is similar to wiring lamps. You can keep adding lamps until the circuit limit is reached. An individual lamp draws its power and is not aware of the others.

We don’t know exactly how the speaker failed. It’s possible that there was a manufacturing defect or that your average level was too high. It’s easy enough to determine this by inspecting the failed speaker.

The outside “room” is rather large and if you were attempting to be assertive out there, you may have been running the level too high. Assigning safe speaker power levels, unfortunately, is not an exact science. It’s typically more marketing than science. If you buy a “50W” speaker and use a 25W amplifier, safety is not guaranteed.