So if you pick up your homepod and move it in your room - say from in the middle of the table to near a wall, it will change its sound profile (after about half a minute) to lower bass and minimize reflective frequencies from the wall. Having an omnidirectional speaker blast into the wall would not sound good without that kinda calibration, as you would get reflective sounds from the wall and too much bass.
It does further calibration like this one put in a stereo pair to make sure _both_ homepods are outputting the best sound together.
The audiophile equivalent of this is getting a good mic, hook it up to your $5k stereo, and then use the manufacturer provided software to calibrate it. Then never move anything around your room again or hang new art of throw down a rug, because if you do that you have to recalibrate again.
The homepod is really some crazy audio engineering. One of apple patents describes some of stuff that probably went into the Homepod [1]. There is also a fun review [2] that was posted on the reddit audiophile back when the homepods first came out.
1 - http://appft1.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=.... 2 - https://www.reddit.com/r/audiophile/comments/7wwtqy/apple_ho...
https://www.hifiberry.com/docs/hifiberryos/hifiberryos-room-...
https://www.hifiberry.com/shop/boards/hifiberry-dac-dsp/
They maintain a list of supported microphones.
You can even bake the configuration into the HifiBerry DSP once done, it doesn't need the Pi attached to apply the room correction. The included HifiBerry OS software has a setup process that makes calibrating the room with mic just as easy as the Sonos system.
I was huge into Sonos ecosystem, but recent actions with how they treated owners of earlier equipment have left me cold on it. This works forever once set, assuming you don't move the speakers. Works with any old speaker/amp combo you can output a phono/optical signal to.
its purely opinion etc, but I am just as happy with results from this system with nice pair of bookshelf speakers as I was a pair of Sonos 1s, and it will work as long as the board lasts.
I am shocked hifiberryOS hasn't found more fans, its really impressive for what it does for little money with a supported DSP. The hardest part of this is cloning an image to an SD card, rest is plug and play. You could eBay the calibration mic once done too. If you intend to move your speakers a lot this is no good of course, but my experience is people often set these things in one place in their home.
It's probably just a matter of time before pretty much every speaker can self-calibrate to some degree. Most mid-range bluetooth speakers already have a microphone and some basic DSP abilities, which is really all you need.
HifiberryOS is new to me and looks pretty nifty - I'll have to check it out.
Obviously we have to put some trust in corporations if we're not to live a purely analog existence, and so it stands to reason that we can put a little more trust in a company whose business model is selling premium hardware (and which increasingly sees privacy as a competitive advantage) than a company whose business model is selling your personal data to advertisers.
They see privacy as a marketing advantage, however they collect data as they see fit. It is also important to note, that they are indeed in the ad business and even if it is no match to their hardware business they are profit maximizing. So even if they don't sell your data now this can change and your record on that big corp will become known to whoever pays enough.
Side question: Does Google directly sell personal data to advertisers? (For Google applies what I said above anyway)