Local files synced from desktop

[swanky_beats]

I have a folder on my PC of MP3s that I have made a playlist out of on Spotify. When playing these MP3s from the folder and through the desktop client, they sound great. However, when I sync the playlist onto my phone and listen to it, the audio quality seems greatly reduced and clearly lower quality.

I have Volume Equalisation off and I'm using extreme quality.

Thank you,