Apple has included this stereo pair limitation between two generations of HomePod models due to their internal differences
Apple’s official press release of the 2023 HomePod stated the following right at the end. For those that do not know, a stereo pair is when you have two HomePod models placed in any corner of the same room. Both these devices will be running the same sound, creating a left and right audio channel, resulting in an immersive and high-quality experience. This process can be completed through the Home app. As for why Apple introduced this limitation, 9to5Mac believes that it is likely due to the hardware differences between the first generation and the latest version. For instance, the two HomePod models have a varying number of tweeters, plus different chips. Additionally, the software changes incorporated might result in a different form of the audio emanating from the two smart speakers, which can degrade the user experience. Sadly, it does mean that you will have to spend more money to experience stereo pair, but there is some benefit for the consumer. When Apple launched its first HomePod, it shipped to customers for $349. The newest member is available for $299, so you are saving some money, even if you have to purchase a second one down the road for that immersive sound.
