The MartinLogan ElectroMotion ESL tower speakers are what's called an electrostatic speaker. In an electrostatic speaker you have three main components: the diaphragm, stator and the spacing spars. The diaphragm is what makes the speaker move to create sound. In an electrostatic speaker, its similar to the look and feel of Saran Wrap. Very expensive Saran Wrap. The stator is what gives the gives the signature hi-tech look. It's layered in front and behind the diaphragm material. Similar to a transformer, it converts the receiver’s output into signals that are opposite in polarity. The spacing spars are strips of non-conductive material that stiffen the panel. This is so that movement only happens within the diaphragm. Combined, you have a speaker technology like none other.
But the ElectroMotion ESL also has a conventional driver at the bottom of the tower. This makes it somewhat of a hybrid speaker. This speaker drives the mid to lower end of sound, from 42 Hz to 500 Hz. Frequencies that are above that are powered by the electrostatic speaker. Since bass requires a lot of movement to reproduce the lower frequencies, electrostatic panels aren't ideal. This is why they use a normal driver to power the lower frequencies that the panel is not capable of reproducing efficiently.
The MartinLogan ElectroMotion ESL produces beautiful tones. Its incredibly balanced and has zero harshness to it's sound. They're clear, detailed and smooth. The bass was great as well. Remember that the bass is powered by a conventional driver. The bass driver beautifully matched the tones of the panel. But if you listen to heavy bass or music with lower frequencies, you might want to consider adding a subwoofer.
In the end, the Electrostatic speakers are great. They're pretty rare, and pretty expensive. But despite being a entry – mid level hybrid, people love them.
Take a look at Household Audio's full line of Best Floorstanding Tower Speakers for your home theater.