There is no doubting HEOS had Sonos firmly in its sights. HEOS launched with a product line-up perfectly aligned with the Sonos range. HEOS 3, 5 ,7, Amp and Link vs. Sonos' Play:1, Play:3, Play:5 and Connect: Amp and Connect.

Headlines such as "Denon's Sonos Killer" certainly fuelled the fire too.

It may have taken a few months but Sonos overnight announced they have filed a lawsuit against Denon's parent company, D&M Holdings in the state of Delaware USA, over Denon's HEOS wireless home audio product line. They added further that D&M Holdings infringes on at least four of its patents.

Craig Shelburne, Co-Founder & General Counsel for Sonos said in a recent blog post, "We have watched as several companies have entered the wireless home audio space with product features, designs and messaging strikingly similar to Sonos, without truly moving the experience forward in any way."

"For anyone who has looked at Denon’s Heos product line, you will recognize many of the same elements found in Sonos products, with little or no effort to differentiate features or functionality. Beginning with its product name and messaging (which in some instances they have just copied word for word), Denon borrows liberally from virtually all aspects of the Sonos story."

Sonos seem willing to work through the matter amicably however, likely to avoid an Apple vs. Samsung style fight. "This is not an action we take lightly, as we’re not fans of resorting to the courts to resolve disputes. As a next step, we will offer to sit down with Denon, explain our views and give them time to modify their products. We are not asking for a royalty or other license fee – we just want Denon to build an experience that isn’t copying ours."

We'll watch with interest as this progresses. As a number of manufacturers have entered this category over the last year and even more recently, it will be interesting to see where Sonos will draw the line on what they consider their own technology.