The top audio equipment makers are teaming up in a massive deal. Sound United, owner of the Polk Audio and Definitive Technology speaker brands, announced today that it’s acquired D+M Group, owner of the Denon and Marantz receiver brands plus Boston Acoustics speakers and Heos multi-room audio.

The combined companies will be known as Sound United, led by its existing CEO Kevin Duffy. Terms of the deal were not disclosed. Sound United is part of DEI Holdings, a portfolio company of Boston private equity firm Charlesbank. D+M Group was part of Bain Capital’s Tokyo corporation K. K. BCJ-2.

“D+M Group’s portfolio of brands and Asia Pacific/European footprint is a perfect complement to Sound United’s goal to drive global growth” Duffy tells TechCrunch. “The product and technology portfolio is complementary and supports efforts reaching into new market segments—like A/V receivers.”

Sound United will now have a wide presence across the custom installation, high-end audio, and consumer audio markets. The acquisition extends the partnership struck between the conglomerates back in 2014 for D+M to distribute Sound United brands in Europe.

Duffy tells TechCrunch that “At this time, no immediate changes to the current product portfolio, employee roster, or company locations are known. As we know more, we will continue to inform our partners and customers.”

Rather than directly competing, Sound United’s products could differentiate to address more of the market, and could share hardware science advances. As competitors from the tech world like Amazon Echo, Google Home, and Sonos encroach on the audio business, the new alliance could help defend Sound United’s traditional brands.