Loudspeakers are the most variable elements in any audio system, and are responsible for marked audible differences between otherwise identical sound systems. Loudspeaker performance or accuracy in reproducing a signal without adding distortion is significantly poorer than that of other audio equipments.

Some important men who made history
Ernst W. Siemens was the first to describe the dynamic or moving coil transducer, with a circular coil of wire in a magnetic field and supported so that it could move axially. He filed his U. S. patent application for a Magneto electric Apparatus for obtaining the mechanical movement of an electrical coil by electrical currents transmitted through it was granted patent No.149797 on April 14, 1874.

Oliver Lodge filed for British patent No.9712 on Apr. 27, 1898, for an improved loudspeaker with nonmagnetic spacers to keep the air gap between the inner and outer poles of a moving coil transducer. This was the same year he applied for a patent on his famous radio tuner.

Thomas Edison was issued a British patent during 1881, for a system using compressed air as an amplifying mechanism for his early cylinder phonographs, but he ultimately settled for the familiar metal horn driven by a membrane attached to the stylus.

Harold Arnold around 1925 began program at Bell Labs to improve phonographic sound recording. The first priority was the electronic amplifier using the new vacuum tube, second was the microphone, and third was the loudspeaker that would improve the balanced armature units developed for public address.

Bell Laboratories in 1931 developed the two way loudspeakers, called divided range for the demonstration by H. A. Frederick of vertically cut records. The high frequencies were replaced by a small horn with a frequency response of 3000 to 13,000 hz, and the low frequencies by a 12 inch dynamic cone direct radiator unit with a frequency response within 5db from 50 to 10,000 hz.

How the loudspeakers used to work
The first loudspeakers used electromagnets because large, powerful permanent magnets were not available at reasonable cost.

The coil of an electromagnet, called a field coil, was energized by current through a second pair of connections to the driver. This winding usually served a dual role, acting also as a choke coil filtering the power supply of the amplifier to which the loudspeaker was connected.

AC ripple in the current was attenuated by the action of passing through the choke coil. However, AC line frequencies tended to modulate the audio signal being sent to the voice coil and added to the audible hum of a powered up sound reproduction device.

The quality of loudspeaker systems until the 1950s was, by modern standards, poor. Continuous developments in enclosure design and materials have led to the significant audible improvements. The most notable improvements in modern speakers are improvements in cone materials, the introduction of higher temperature adhesives, improved permanent magnet materials, improved measurement techniques, computer aided design and finite element analysis.

Home speaker building can be rewarding and gratifying whether it is a one time undertaking or a full blown hobby. Warning: Many who tackle a loudspeaker building project for the first time become hooked and develop a serious dependency on do-it-yourself (DIY) speaker building. These people can often have speakers in every room of their home. A large percentage of the loudspeaker building community believes assembling a speaker system from various components and a DIY cabinet or enclosure will offer a better sound quality than a retail speaker costing an equal amount. The enjoyment of creating speakers is another factor which draws many to the hobby. Building speaker enclosures allows the builder to tailor the finish of the cabinet to suit their taste. The more advanced loudspeaker building hobbyist can tweak the crossover to reach a specific design goal. A more pronounce midbass may be desired, for example. The experienced builder can alter the response of the speaker to suit their desired outcome.

The scope of this writing is not to be a tutorial for speaker building. Basic electronics and beyond, woodworking skills, plus other abilities will serve the DIYer in assembling a speaker. The internet has many forums and sites which will be of help to a beginner. The best path for learning the hobby may be to read some of the books that are dedicated to the subject. Many hobbyist recommend Speaker Building 201. Besides learning the concepts for home speaker building, you will have eleven tested and proven speaker designs included in the book to choose from.

A vital part of a speaker is its crossover network. If a speaker has multiple drivers, in most all cases electronic components are used to divide the audio frequencies and send them to the appropriate driver. For instance, tweeters receive high frequencies, mid-range drivers receive the middle frequencies and the bass driver receives the lows. Designing the crossover network to perform with the selected drivers and its parameters is at the heart of creating a quality speaker many enthusiasts believe. One final thing to add, loudspeaker building need not be an endeavor which entails constructing everything from scratch. Speaker kits can be purchased. If you would rather avoid building a speaker cabinet, speaker kits that include the enclosures may be your best option. Kits can also provide pre-assembled crossover networks. If you are uncomfortable with your soldering skills, a kit with a pre-assembled crossover may be an option also.