15" field coil woofer MI 1432a, used in the RCA directional baffle MI-1456. Which was RCA's nomenclature to avoid using the word "horn", because of marketing and patent reasons vis Western Electric. The MI-1456 was a W-type horn that formed the bass section of RCA's Shearer two way horn system.

1428 B Field coil midrange compression driver. This was the first and only cone center voice coil compression driver until the recent developments of Cogent. The MI 1433 uses a 100V field coil, the 1428B uses a 13V field. Steve Schell has written an extremely informative essay which you can read here. It also shows the interior workings of this amazing driver. The best sounding midrange in the history of audio.

The MI 9584a permanent magnet midrange compression driver. A number of different models exist, virtually identical with the version shown here. The primary difference between these models is in the phase plug, which in earlier editions was comprised of a number of holes, and this example, which uses a single slit and hole at the apex of the phenolic diaphragm. This simple looking phase plug is actually extremely well designed, and along with the tremendous build quality, large Alnico magnet, and phenolic diaphragm, accounts for the fact that this may be the best sounding permanent magnet compression driver ever made for its passband- 300hz to 6khz.

The MI 9444 was the field coil version of this driver, produced after the MI 1428B, and before the advent of the permanent magnet version.

Detail of the phasing plug and voice coil gap. Notice the ridge near the gap.

Small format compression driver MI 12419. This unit was discovered in a radial horn prototype made by RCA but never produced. From the Estate of RCA engineer A.J. May.

Harry Olson's design- MI 6234 6" cone wide range driver, typically found in projection booths as a monitor speaker. Many models exist, all utilizing the same revolutionary design- there is NO edge compliance or suspension where the cone would normally attach to the outside of the basket. Instead the periphery of the cone folds back onto itself. This allows the cone far greater freedom of excursion and thus extended bass response for such a small driver.

MI 11419, actually not an RCA built driver at all, but a JBL OEM for the RCA LC-9 horn system.
This driver is essentially a JBL 175 built to RCA specifications.

Extremely rare field coil motor mechanism for the second and last generation of field coil drivers. Just like the earlier generation, the field coil motor could be used with both the midrange compression driver or the woofer.

Push pull 6L6 amplifier BA-4C or MI 11223B. The later version, BA-14 was similar in design but used oil capacitors. A classic amplifier for the LC1 Duo Cone loudspeaker.

BA 14 amplifier.

Two generations of RCA autoformers for converting line level (600 ohms) impedance as generated by the amplifier system in the remote projection booth to speaker/crossover level impedance. The box units on the right are from the early field coil photophone systems. The round units on the left date from the later permanent magnet driver systems. Both make excellent choices for use in crossover networks.

70D Transcription direct drive turntable. This example was setup for cutting transcription discs with a cutting lathe, which is no longer present. This turntable was so expensive to manufacture that it was replaced in the 1950's with a less expensive idler wheel version.

Pickup heads for 78 rpm playback and two versions of RCA tonearms used with broadcast turntables.

RCA SL12 Wide Range Driver. Curvilinear cone with a 1 inch aluminum edge wound voicecoil. The middle size speaker in the short lived Intermatched Components line offered by the Sound Products division of RCA in Camden. See Archive section for more details.

SL8 Wide Range Speaker. The smallest in the high quality line of the Intermatched Range of components offered by the Sound Products division of RCA in Camden. Shown here in a version with whizzer cone and without.

RCA's crowning achievement in a permanent magnet monitor speaker- the LC1 Duo Cone. A 15 inch speaker with separate tweeter with its own magnet structure built into the same plane as the woofer for perfect phase integration. Harry Olson's design, the last version being made by Hans Dietze. See Archive section for more details, as four models were made on this theme, the LC1 A, B, C and preceeding model which only bore an MI number.

MI 6333C speaker. See Archive for literature.