When testing my new HomePod earlier today, I noticed that if I streamed a track with Spotify to HomePod over AirPlay, then listened to the same track from my purchased iTunes to HomePod, it sounded noticeably louder and filled the room more streaming from iTunes than Spotify. Even with Spotify streaming quality set to Extreme, music sounded louder and “fuller” streaming from iTunes. I finally figured out what the issue was. By default, the Spotify iOS app playback settings has the Enable Audio Normalization option turned on. This option in Spotify applies volume adjustment on every track so they all consistently play at around the same volume. My research on this audio normalization setting found that having it turned on applies a compressor to the music you’re listening to, reducing the dynamic range. It might be good to have normalization turned on when listening to music with headphones, but definitely turn this off when streaming Spotify to HomePod.