That's just plain wrong, because putting any small speaker down there forfeits a major share of its sound quality.
Ex-movie theater projectionist Steve Guttenberg has also worked as a high-end audio salesman, and as a record producer. Steve currently reviews audio products for CNET and works as a freelance writer for Stereophile.
I cringe every time I see a small speaker sitting on the floor. It all but guarantees they'll sound dull because most of their midrange and treble detail will never make it up to your ears.
The one good thing about putting speakers on the floor is their bass output will be boosted, relative to what a bookshelf, satellite, monitor, or Bluetooth speaker will deliver when placed on a table, shelf or floor stand. The "boundary" reinforcement of floor placement maximizes bass, but putting a speaker within a few inches or centimeters, or directly up against a wall will also aid bass reinforcement.
Ideally, you should have the speakers placed so their tweeters are as close as possible to the same height as your ears when you're listening. Hey, it's easy enough to experiment with different placements and see if you hear a difference, and I'm sure you will. Ideally, you should be as close as possible to the same distance from the left and right speakers.
You might also want to try different locations in the room, each of the four walls if possible, and chances are good that each location will sound different. Sometimes a lot different, and one will be the obvious best.
If the speaker isn't bass shy, try moving it away from the wall behind it in 6-inch (15.24 cm) increments. I find most speakers that produce satisfying bass sound best placed 12 inches (30.48 cm) or more away from the wall behind them.
Play the same one or two songs over and over again as you experiment with these placement scenarios, so you can more easily track the differences. You may be amazed by how much better your music can sound when you find the perfect location for the speaker. Share your experiences below.