how to make homepod remember speech volume level

I have a HomePod which is great, however when Siri answers me it’s always quite low volume so it’s hard to hear from the other side of the room. I tell Siri to speak to me at loudest volume, which it does, however it never seems to remember this and less than a day later the Siri volume has gone right back down again. How do I get it to remember max volume setting?