Chromecast Audio enables wireless music streaming for your old-school speakers
theverge.com
theverge.com
Personally, I use my iPad in this manner. Plug it into my speakers and play Spotify. Then use my iPhone to control the Spotify music. Which is actually a killer feature of Spotify, with the same account you can control music playing on other devices.
(I'm assuming this is a genuine question, and you'ra aware that a small $35 dollar device to do what you're doing with a large $350 dollar device is an improvement in itself).
I didn't buy an iPhone or any phone so I could play music but it's a good feature.
I might not be the norm but I certainly have a good use for this.