- Hits: 4574
The history of sound reproduction shows ample evidence of the electrostatic loudspeaker as an alternative to the electromagnetic speaker. The "actual" electrostatic loudspeaker, in simple form, made its appearance in 1929. This may seem a little late in the piece, but we have to recall that, before 1924 - 25, sound reproduction beyond the necessities of telephony was next to impossible. Two General Electric engineers, Rice and Kellogg (no kidding!) set about the task of creating the first hornless loudspeaker, in the early 1920's. They soon realised that no available amplifier of the time was suitable, and they...but that is another story. We can trace the very beginnings of high fidelity sound reproduction to 1925 and a hornless loudspeaker designed by these two men.
The Rice and Kellogg speaker was quite successful. After all, it was one of a kind for awhile, and had zero competition. They discovered that the speaker had to have a large cone and be quite rigidly mounted for good low-frequency reproduction. Following this trail to its ultimate conclusion, they soon discovered that the speaker became more directional and produced far less output with increasing frequency. Having recognised these problems, the early workers used two different approaches to try to coerce these contradictory and inconvenient phenomena into a workable mechanism. One solution was to divide the cone, mechanically, into smaller sections. At low frequencies the cone moved like a "rigid piston", and at higher frequencies only a smaller, central section radiated. A second solution involved division of the audio band into several spectra, and using a separate speaker for each. The second method, in theory, allows the designer to split the audio frequency spectrum into as many parts as they choose to.
Apart from work on actual drivers, investigations into various baffle systems were carried on, resulting in bass reflex, acoustical labyrinth and folded horn enclosures. Of course, each system claimed to have "the most natural reproduction".
During the 1950's one could attend the various "hi-fi" shows in the U.S. and England, and have a technical discussion with the chief engineer and head of the firm - the same person, very likely! Starting in the early 1960's, the "hi-fi" show was "discovered" and infiltrated by the Recording Companies and their Advertisers. The engineers stayed at the lab and the Sales People went to the shows, and some shows even had the gall to charge an entry fee!
There was at least one interesting emergence from this era, in that Thiele and Small started modelling loudspeakers as though they were electrical filters. This was quite significant, since you can easily model electrical filters using mathematical equations. It took most speaker manufacturers until the 1970's and 80's to indicates or specify Thiele/Small parameters. Today, it is reasonably commonplace, allowing the enthusiast to design and/or build a speaker system to suit their needs.