This information is only meant for a basic understanding of what makes a good loudspeaker system, and to discuss various technologies attempted to achieve this result.
In one simple sentence, a good speaker is the one that faithfully reproduces the sound from the input signal.
In general, the flat panel idea was based on that the sound should not come from a box (vs dynamic speakers), and that using an extremely thin diaphragm as the source to excite the air will yield better transient response and reproduces sound wave closer to the input signal.
The main flat panel speaker technologies are:
Basic operation mode is by using static electrical charges to attract and/or retell the extremely thin diaphragm suspended in between +/- charged stators, which in turn produces sound wave.
Note: A new pool of hybrid electrostatic speakers are now on the market. These speakers uses dynamic speakers for low frequency reproduction, with crossover at around 200 Hz. However, matching different technologies in one package has proven to be a difficult task. (ie www.final.nl)
This is similar to dynamic speaker driver, where strips of magnets are lined up behind a diaphragm. A voice coil "loop" is planted on to the diaphragm. When music signal pass thru the voice coil, it interacts with the permanent magnet and creates motion.
A very thin and light conductive ribbon is suspended in between two permanent magnets and within their magnetic field. Since the ribbon itself is the conductive media, no additional wires/coils needed. This allows for extremely light material for great and accurate sound reproduction.
This is the latest Flat Panel technology pioneered by Eminent Technology. It features true push/pull of the diaphragm with permanent magnets on both side of diaphragm. The diaphragm itself is made of extremely light and strong fiber with aluminum conductive material plated on to the diaphragm as the voice coil. The result is a new design that addressed all the shortcomings of previous designs.
This is the most common type of speaker technology we see from day to day, that usually consisting driver/drivers in one enclosure cabinet. Often these drivers consist of dome tweeter for higher frequency, cone midrange, and cone woofers. The material used, the shape, size, and the position of each element relative to the other, etc, all play major factor differentiating a cheap speaker from a high end system.
Usually made of metallic or fabric materials. The metallic tweeter (ie aluminum or titanium) usually sound sharp and more revealing, and can some times be too bright for the given application. The fabric tweeter (ie silk, mylar) emphasis smoothness. The dome tweeter are usually between 1/2 to 1 inch in diameter and are designed to produce frequencies above 2kHz
usually made of Kevlar, Aerogel or Polypropylene materials, which all have high strength and low on weight. This allows the driver to react quickly during transitions in music and minimizes distortion. The cone midranges are usually between 2.5" to 6.5" in diameter and are designed to produce frequencies between 200Hz - 4000Hz
usually made of very strong material. sizing from 6.5" to 15" in diameter and responsible for frequencies between 20-500 Hz.
Note: New materials are always being tried. Recent perfections including ceramic cones and diamond membranes for tweeters.
An extremely important piece of puzzle that often got overlooked. While different drivers, (tweeter, midrange, woofer) have their responses within their own range of frequencies, feeding full range of signal can cause unwanted interferences. Building of a good cross over network that does not add distortion and coloration isn't an easy task, but higher end speaker builders will also ensure the time coherence so all drivers deliver the sound in a synchronized way. This is essential to reproduce the spatial information of a stereo sound. A cheap speaker might not even have a cross over network.
Alone these different drivers responsible for different frequencies, they are also designed specifically to be installed in different enclosures.
has enclosure that is sealed. It offers
tight and quick bass response at cost of decreased efficiency and bass
output. The relatively small air volume in the enclosure works as
damper as well to radiate the back wave energy within the cabinet to
produce bass frequencies.
Similar to acoustic suspension, however, the air volume inside the cabinet is large enough that the back wave energy can be practically ignored. < hard to find these days as no one buys speaker with HUGE cabinet these days...>
These enclosures are usually "ported" or have "passive radiator" that tune the cabinet to a specific frequency driven by the bass driver and volume of enclosure. When done "properly", improves efficiency and bass output. < many newer modern speakers do this. This was not very popular in the old days mainly because there was no tools to tune the port to the desired frequency range.>
These enclosures are a design in which the driver is at one end of the enclosure, with an internal path which consists of a series of bends or curves that lead to a port at the other end of the enclosure. The length and volume are both carefully calculated so it produces phase shift in the back waves that reinforces bass at low frequencies. Very tricky to implement even with current technologies. < example, Point Source Loudspeakers 30M >
Building these drives that matches to each other in one enclosure is by no means a trivial task either.
While dynamic speakers are not the most optimal form to reproduce the sound, they do not have any inherited problems much like the arcing of ESL, or ribbons moving out of operation range, or the non-linearity of planar magnetic. There is always things that can improve a dynamic speaker, from using newer materials, to slight modification to the way it works internally, all can make great change to the sound reproduced.
I invite you to visit the following websites, and read their white papers on why they design their speakers that way, and why they believe they have the best technology for true sound reproduction.
Before choosing your next pair of speakers, familiar yourself with a wide variety of "un-amplified" sounds by attending live concerts, plays, then audition various speakers and look for the familiar "un-amplified" versions of sound compare with the reproduced version to judge the accuracy of a loudspeaker.
Once the right speakers are chosen, proper treatments are needed at the listening area to fully extract your new speaker's potential.
The treatments of listening area by itself is an extensive topic, which is outside the scope of this meeting. Everyone is welcome to further elaborate on this topic and present it in a different meeting.
A good information on various planar speaker technologies at Eminent Technology website: http://www.eminent-tech.com/Manuals/LFT-8Manual.PDF
Thiel Audio has an extensive library of white papers and technical details on their design philosophy. Download these pdf white papers here.
*ps. horn loudspeakers are not discussed here as they usually require to be played at very high volume and requires very high power that is not typically acceptable for the home use.
Disclaimer: All figures were from the web and used here without permissions. If this troubles original creater, please contact me at milanojess at gmail and I'll have them removed.