Why does listening to music on my computer sound better than my iPhone 4?

Today, while I was browsing iTunes I decided to listen to some samples with my earphones. I own the regular Apple earphones w/ mic (the ones that come with an iPod). The sounds from my computer had a surprising quality, compared to my iPhone 4. For instance, it sounds more HD, the bass is so much better, etc. But when I play the songs on my iPhone 4, there's hardly any bass and it almost sounds like my earphones are broken when they're totally fine…

Why is this?
Computer/iTunes (High quality sounds w/ bass) VS. IPhone 4 (Poor quality sounds w/ hardly any bass)…

Added (1). Not talking about speakers! I mean, with EARPHONES.

Quite simply, you have better speakers on the computer.

The speakers on the iphone aren't good quality. Like they're ok but think about it; they are only coming out of two tiny holes on the phone. Also, the phone wasn't designed to play music. However with the computer, it's much larger, has bigger speakers and one of the main uses of a computer is to play music. So yeah

Your phone is… Well, a phone, that happens to play music. Apple products tend to be on the lower side when it comes to fidelity (sound reproduction), kind of a shame since they sell so well. Most other portable music players (Sony, Samsung, Sandisk, even Zune) have much better sound than apple, with Samsung being the best overall.
As to your computer, it has the processing power to really take advantage of high kbps recordings.

If I understand correctly, you're talking about listening to music from your computer with your earphones plugged in compared to earphones plugged into the iPhone?

If so, maybe your settings are tweaked on either the iPhone, the computer, or both.

To check iPhone settings go to Settings > Music > EQ - If it's on something other than "Off" at the top, this could be you problem. Alternatively, if the EQ is off, try selecting one of the choices; sure to improve quality if you select the right one. Just try them all.

If the above is NOT the case you can try adjusting your sound settings on your computer. Heck, you may not even have the option but right click the Speaker icon in the bottom right of the screen.
Click Playback Devices > Select the headphones or whatever option is available and click Properties > Enhancements > Equalizer > Select an option at the bottom and try them all.

OR it could just be the fact that the headphones suck lol. In that case, messing with the EQ or Equalizer can definitely improve the sound.

Because the bass speakers are of better quality in your