78 is the name given today to the format used before the long-playing disc entered the market of mass music reproduction media. These records were 10" in diameter and made out of shellac, which made them quite a bit more fragile than their vinylite sucessors.
78s were also the first commercial incarnation of the lateral recording format developed by Emile Berliner, which back in the day had Edison cylinders and hill-and-dale recordings1 as competition.
The first commercially available discs were recorded using acoustic techniques (ie. no electric equipment involved); performers would gather around a massive horn which served as a primitive mechanical microphone, translating variations in air pressure into the wiggles of a cutting stylus.
On the reproducing end, the principle was essentially the same; a crank-wound mechanism took care of spinning the disc while a steel needle2 picked up the vibrations etched on the shellac, which were piped into horns by acoustical means.
The first crop of gramophones used external horn designs -- it was only later that horns were moved inside cabinets, presumably out of cosmetic (as opposed to technical) reasons.
This presented manufacturers with a number of challenges; horn designs had to be literally bent in order to fit inside the cabinets. Since the technology still relied on acoustical principles, this was achieved with varying degrees of success. RCA Victor's Orthophonic reproducers are supposed to be amongst the best.
With the advent of
electricity, acoustic recordings gave way to new
recording techniques; the appearance of
microphones and
amplification meant that
musicians no longer had to cramp themselves around
horns, being able to
perform in a manner closer to a
live situation.
Reproducers benefitted hugely from this as well; intrincate horns fell in disuse, replaced by more efficient electric amplifiers built from valves. AM radio receivers often accompanied these later models.
Volume was no longer tied to the limitations of acoustical systems. Those died a slow death, however, as they enjoyed a certain residual popularity in areas not reached by power grids.
In order to play 78 rpm records today, a person has several options. Purists insist on using the original machines, a fact which has spawned a not-so-small market for spare parts and restored units (some really interesting exchange of ideas on restoration can be found on the rec.antiques.radio+phono newsgroup).
A more modern approach would consist on using an actual turntable. Needless to say, the unit would have to be able to run at the right speed, something which most modern ones don't do. Some aftermarket kits exist which allow for the necessary modifications to be performed on a stock unit.
A phonograph cartridge with a suitable stylus (or selection of styli) would also have to be accounted for. Shellac records had much wider grooves than contemporary LPs; a stylus with a wider tip is therefore needed unless you want to 'ride the bottom of the grooves', which produces ungodly surface noise.
Finally, keep in mind that by the time the record industry was getting started, there were no standards such as RIAA curves, not even a standard speed. Records ran at about 78 rpm, with some going as high as 80 (the nominal speed was eventually set at 78.26 rpm).
Why, then, would a person want to
concern his or herself with such
obsolete devices?
The answers are many. Some people derive
pleasure simply from the
restoration process. Others insist that the
proper way to listen to the
performances recorded on
78s is by using an
original machine from that
era. Some of the
CD transfers of discs and
wax cylinders certainly leave much to be desired.
1Of these last two it was perhaps the Edison Cylinder (and, somewhat later, the Diamond Disc) which caught on the most after the shellac record. Hill-and-dale was the name given to obscurer formats which used vertical recording techniques.
2Other materials were used besides steel. See, what happens is that by design, a small amount of abrasive powder was mixed into the shellac from which the records were pressed, in order to slowly grind the tip to the shape of the grooves. This provided for better contact which, in turn, provided for better sound -- the downside being that needles had to be changed every few plays. In eventual attempts to overcome this, manufacturers put out longer-lasting needles made from everything from bamboo to tungsten (the latter known as the Tungstone® needle).