A huge amount of blind tests have been carried over the years. You can find them doing some research. All tests have proven that 99,9% of people cannot tell the difference between an AAC or MP3 file at 256kbps. Even if using very expensive audio systems. People will tell you they hear a difference, but put them into a blind test and they will fail. In any case, through earphones or headphones, I challenge you to find someone who will be able to tell the difference. To really hear the bass sounds as they were created and are intended to be heard, an earphone or headphone has to 'cheat' on frequencies to give you the illusion that you're hearing bass frequencies. Physically, lower waves need space to develop. Test that yourself by walking away from your speakers. As you move away, you hear the bass sounds better. This is normal. People crank up the volume in their cars to hear the bass sounds better, but people outside the cars hear the bass sounds very well, much better than the driver. With a headphone or earphone, there is no space between the earphone and your ear to develop a bass sound, as there is between a speaker and the listener. This is a huge marketing campaign.