The best-sounding Alexa speaker, according to the search results, is the JBL Authentics 500. It has been praised for its high-end features and premium design, offering excellent audio quality in a retro-style form factor. Additionally, the Amazon Echo Studio is noted for its superior sound quality, with a robust combination of five speaker drivers, including a front-firing 1-inch tweeter, two side-firing and one upward-firing 2-inch midrange drivers, and a 5.25-inch down-firing woofer. This speaker is capable of producing a powerful bass punch and can even be used as a soundbar.
Considering a balance between sound quality and voice assistant capabilities, the Amazon Echo Studio is also mentioned as the best-sounding Alexa speaker, matching the performance of the discontinued Google Home Max in terms of bold bass and a room-filling soundstage.