Speaker quality can make all the difference when listening to music. Good speakers will produce sound that sounds crisp, clear, and with fidelity, while poor speakers can sound watery and distorted. Even if you have cheaper speakers, there are a few ways to adjust some audio levels to make the sound as good as possible given the hardware.
Turn down the volume. Cheap speakers are generally smaller (though not always) and are made with flimsier parts. By pouring too much juice into the speakers, the internal components will be unable to handle the volume and vibrations, resulting in distortion. It doesn't have to be quiet, but bringing it down from the highest volume level is a good start.
Install bass blockers on the speaker wires. These are capacitors that filter out the lower frequencies of the audio. Cheaper speakers tend to have small or cheaply designed subwoofers that cannot handle much of the lows.
Rearrange the speakers in the room to provide for optimal acoustic effect. If you only have two speakers, try to aim them for ear level (either for sitting down or standing, depending on the most common position for that room). The more direct the direction of sound the less unnecessary resonance created, which can distort the sound.
Listen to music that is higher resolution and less compressed. Many mp3 files are formatted to be 128 kbps. While this may not be as detectable on small ear buds, speakers will reveal that compression as sounding quite watery or murky. Using higher-quality audio files (such as .aiff or .wav files) or just less compressed mp3s (like 256 kbps) will make the speakers sound better.
Adjust the frequencies on the speakers from the audio tuner. No one setting will work for all speaker setups, but by raising and lowering the highs and lows you will find a setting that produces the best clarity possible.