How can i improve the sound of Iphone 11?

I use an Apple Lightening to USB adapter from my iPhone to a Dragonfly Red to drive my Hifiman planar ‘phones and it improves the sound significantly over using the iPhone itself.  Specifically the soundstage expands and clarity and detail are greatly improved as well.  In short, it brings back all the audiophile goodies that make music more enjoyable.  I don’t think you’d be disappointed by the sound, and it’s easy to use on the go.  The Lightening to USB3 adapter is supposed to sound better and gives you the capability to charge your phone while listening, which is nice to have.  And the Cobalt might sound even better although I haven’t felt the itch to upgrade from the Red.  

One thing I’d recommend is trying Qobuz — I switched from Tidal and am much happier, and no MQA crap to deal with.  Anyway, hope this helps, and best of luck. 

Im also using the SE846 direct to my iphone. The sound sounded “dead” without the Audioquest Dragonfly Cobalt. Sounds perfect with it. I also use the Lavricables pure silver lightning to usb A adaptor. It gives that effortless air in the sound. 

I have a Dragonfly Black with the Jitterbug and it improves the sound of all phones I've tried it with. The Red or Cobalt are probably even better. I also have an iFi Nano but it sounds about the same, it is just much bigger and hard to carry.

Switch it off.

I have a PS Audio Dectet conditioner and I've been happy with it so far. It also helps with power surges.