Electrical Recording

You cannot appreciate what electrical recording fixed without meeting the constraint.

1. Build a simple acoustic recorder: a horn ending in a diaphragm with a stylus attached.
2. Cut a groove in a soft wax or acetate disc rotating on a turntable.
3. Try recording a loud voice close to the horn, then a quiet one further away.
4. Try recording two people at once.

Only the loudest source close to the horn registers at all. The sound's own energy has to move the stylus through the medium, so there is no gain anywhere in the system and no way to balance sources. Performers were arranged by loudness rather than by musical sense, brass players stood at the back, and string sections were replaced by a Stroh violin with its own horn because a normal violin simply did not record.

A moving-coil motor again, now driving a stylus instead of a cone.

1. Mount a small coil in a magnetic gap, as in the moving-coil microphone.
2. Attach a cutting stylus rigidly to the coil.
3. Provide a compliant suspension that centres the stylus but allows lateral movement.
4. Add mechanical damping — a rubber or felt element bearing on the moving assembly.

Damping is what separates a cutter head from a loudspeaker motor. An undamped moving system rings at its resonance, and a resonance in a cutter head is carved permanently into the groove. Maxfield and Harrison's contribution was as much about applying electrical filter theory to the mechanical system — treating springs and masses as circuit elements — as about adding amplification.

Gain is the thing acoustic recording never had.

1. Connect microphone, amplifier and cutter head in a chain.
2. Record the quiet source that failed acoustically, turning the gain up.
3. Record two sources at different distances and balance them by moving the microphone rather than the performers.
4. Record with the gain deliberately too high and inspect the groove.

Put a number on the improvement rather than asserting it.

1. Feed a swept tone through the electrical chain and cut a test groove.
2. Play it back and record the level at each frequency.
3. Do the same acoustically, driving the horn from a loudspeaker at constant level.
4. Plot both curves together.

Joseph Maxfield and Henry Harrison at Bell Telephone Laboratories developed the electrical recording system, licensed to Victor and Columbia in 1925. The industry converted within about a year, and the change was so audible that record companies advertised it directly — Victor’s “Orthophonic” and Columbia’s “Viva-tonal” were marketing names for the same underlying Bell system.

It is a systems achievement rather than a single invention. The condenser microphone existed from 1916, the valve amplifier from the 1910s, the electromagnetic cutter was straightforward. What Bell Labs contributed was analysing the whole chain — including the mechanical parts — as one electrical network with a designed response, and the discipline of matching each stage to the next.

What it did to the recording business. Acoustic recording could not capture an orchestra, a piano, or a soft voice. Electrical recording could, and within a few years the entire classical repertoire was being recorded, crooning became possible as a vocal style because a singer no longer had to shout into a horn, and the microphone became an instrument in its own right.

Its honest limits at the time: the disc was still a disc, so playing time stayed at around four minutes, surface noise remained high, and the frequency range, though doubled, was still modest. Those three problems drive the rest of this batch — magnetic tape solves duration and editing, the LP solves playing time and noise, and stereo adds a dimension none of them had.