I purchased speakers and amp through Best Buy which is being fulfilled by Ultra Discounts Corp

Each company can be different, I suppose, but I’d still want to go to Best Buy first, if I bought a Mac there. It would be up to them to then point me to Apple, as needed.

Unless you are dealing with an extra warranty purchased through the seller, the manufacturer’s warranty is the responsibility of the manufacturer.  Some retail stores may take the item back after the normal return period, but that’s just for PR purposes (or to shut up an irate customer who is making a scene).  But ultimately, it is the manufacturer’s responsibility. 

In some cases, the retail store can effectively act as the manufacture’s representative and accept the return, or perform the repair, at the manufacturer’s expense.  The obvious example of this is a car dealership, but other dealerships follow a similar model.   

In the case of Sonos, there are no repairs, and I doubt any retailer can accept a warranty (or diagnose if a warranty replacement is needed) on Sonos behalf.  Worth noting though that I think the setup process effectively acts as a registration as far as I know.

All interesting but likely only applies to a new product, how Sonos treats a returned, reboxed and resold unit would be my concern.

Sonos did right by me with the old and damaged devices Best Buy sold me. Once we sorted out the issue that they had been stored for over a year in a shipping container in the Phoenix summer heat, and that Best Buy had sold them to me as new, current stock, Sonos made it right.

That mess also trained me to NEVER trust a store receipt to remain legible over time. The Best Buy ones were so faded it took photographs and tweaking to see the original printing. Now every expensive receipt goes into the copier for an archival copy.

I’m quite sure many can point to a one-off experience. However, I’m only discussing the legal liability that a warranty may cover and the primary party responsible which I contend in a court of law is the manufacturer.

A retailer in some cases will circumvent their official policy regarding a warranty on a product they sell even though they didn’t manufacture the product. See ​@jgatie’s comment.

Sonos has a warranty on all its  (branded) products which can vary by region. In the US It’s 12 months. After that it’s just a 30% discount toward a new product. Sonos can choose to offer a new product but they are legally under no obligation to do so. Sonos now offers a 3rd party warranty (at cost) to cover defects beyond the normal manufacturer’s warranty.

As an aside manufacturers and resellers are careful when circumventing their policies regarding products they manufacture or sell so as not to set precedent that could result in a class action or void their warranty and/or return policy.

Sonos sells products by Sanus but do not warranty them beyond the applicable return window. Ergo at that point Sanus is the responsible party.

Spent some time reading the Sonos documents here and didn't find the answer I was looking for.

Found limits when not buying from an authorized reseller, but nothing directly mentioning used/open-box/returned product from an authorized reseller. Did see the remaining warranty could transfer to a new owner though.

I worked retail big box back in the 90s.  Not Best Buy, but a regional big box store that was similar (Lechmere, throughout the New England area).  They were your typical big box - appliances, electronics, computers, household goods, etc.  Pretty much the New England Best Buy.  They had all the perks - extended warranties, VIP cards, Magnolia type screening rooms. 

It was there I learned all about things like “break in” periods for electronics (that happened to last as long as the no questions asked return policy), “equal cable lengths” so the electrons arrived “in sync”, and “A/B comparisons” that involved a slight nudge of the volume knob in the demo room.  

Anyway, the things we saw when it came to returns and warranties were mind blowing.  We saw returns of Craftsman tools and Kenmore appliances, which were only sold at Sears.  We took them back.  KitchenAid mixers that were at least 30 years old.  We took them back.  Lawn tools with rust and dirt on them.  We took them back.  About the only thing we refused was when people tried to return a bunch of computers that were stripped of their mother boards and hard drives.  The bar was set that low, and it was all for PR purposes.  The suits just didn’t want the hassle of people screaming at customer service.  

I would say that open/box which would be in a retail store would carry the same warranty as new provided the new owner can provide sufficient documentation to the fact that it was an open box purchase.

Products returned to Sonos that can be resold would must likely fall over the refurbished category and still carry a full warranty.

I can concur with what ​@jgatie described during his time at a big box retailer. What was done was strictly PR driven. 

However in the STRICT definition of a Warranty regardless of where the product is purchased the Manufacturer has the responsibility to honor it. Retailers going off message to pick up the mantle outside of a manufacturing warranty is strictly a person choice. Why do you think retailers ( including Sonos) push extended 3rd party warranties as another revenue source.