Anybody who comes to your house and sneers at your stereo should, and hopefully will, get a richly deserved beating. Unfortunately, just because the guy’s a douche doesn’t mean, necessarily, that he’s wrong. Your speakers probably suck. In fact, if you listen to music on a tiny little system you got at Best Buy, your stereo speakers definitely suck. Here’s why, exactly.
First, we need to understand the physics of sound. As we all know, sound comes in frequencies: the lower the frequency, the lower the sound. Speakers work by sending those frequencies as electrical impulses to an electromagnet. That electromagnet acts on a magnet, moving a cone back and forth and creating sound by, essentially, pushing air. This whole setup is called the driver.
Your speakers probably suck for two reasons: one, the drivers aren’t big enough, and two, it needs more of them.
It’s really, really hard to get something to resonate across a wide range of frequencies. Your typical driver can do it, but not well, and the more frequencies it has to handle, the worse it’ll do. This is why expensive speakers have tweeters, woofers, and subwoofers, and really high end ones will have supertweeters: they’re designed to handle specific ranges of sound. Bigger drivers can push more air.
Adding to the problem is the equipment inside the speaker and its cabinet or enclosure. Speakers generally need to be hooked up to an amplifier, as we’re talking about insanely tiny voltages here; a good amplifier really can make a difference in sound. Furthermore, that voltage needs to be processed by a crossover: a device that sorts what frequencies go to what driver. Finally, the cabinet needs to be a certain size because sound doesn’t emanate in one direction: the cabinet keeps the back of the driver from blasting sound and ruining your music.
If you want to understand just how bad this can get, play back a song over your phone’s speaker, then listen to the same song on your computer. Both will sound terrible, but the former will sound a lot worse than the latter.
In short, if you got some small speakers from Best Buy, they really are crap. On the other hand, pointing this out at a party you are a guest at is rude, so that beating you dished out was still deserved.