The Neumann U 47 is without a doubt the most sought-after, legendary, and unfortunately rare microphone in the history of the recording arts. Known primarily as a vocal mic, it is equally impressive at a wide variety of tasks: from acoustic guitar to upright bass to room sounds for everything from orchestration to drums. The high end response is silky-smooth and the low frequency reproduction must be heard to be believed.
The history of these amazing mics begins at Georg Neumann GmbH as far back as 1928 with the production of the CVM 3 microphone, sometimes refered to as the “Neumann Bottle” mic and seen in historical films of speeches from that era. During World War Two, the Neumann factory was bombed and they were forced to move to Thueringen, while their offices stayed in Berlin. Eventually, in the 1950′s, the East German Government seized the factory and produced microphones there, at first under the “Neumann” name and then under the name “Microtech Gefell”.
Back in Berlin, the “actual” Neumann company, with the financial help of AEG Telefunken, was back inbusiness and began development of the U 47 in 1945. The design was completed in time for the Berlin Radio trade show in 1947. Early models have a Telefunken logo, while others were distributed by Siemens. Eventually, Neumann took over sales and put their own name on the mics.
Before the U 47 appeared, the most popular mics for recording or broadcast were the RCA Ribbon style (more on Morrisound’s RCA Ribbon mics in another article!). The U 47 had unmatched fidelity and presence, making it ideal for a recording and broadcast market with rapidly improving sound quality standards.
The letter “U” was used in the model name to represent a “plug-in” style vacuum tube, as opposed to “M” for a “soldered-in” type. The U 47 was based on Telefunken’s VF-14 pentode steel tube developed for German field radios in World War Two and uses a single supply voltage. The only similar replacement tube would be the EF-14 which uses the more common two-supply voltage design. To use these tubes, a new power supply would need to be manufactured, meaning incompatibility with the supply for the standard U 47. Telefunken kept the VF-14 in production until sometime in 1958. By that time, Neumann was the only customer for these parts, so as Neumann ran through their stock of tubes, they began the design of the eventual successor, the U 67, in 1960.
The U 47 was the first microphone with a switchable pick-up pattern. The M 7 capsule was originally developed for the CMV 3 microphone and incorporated two diaphragms. By manipulating the polarization voltage on the rear diaphragm, the mic can achieve either a “cardiod” or an “omni” pattern. A nearly identical microphone was also made, the U 48, whose only difference was a different method of diaphragm switching which allowed for “cardiod” and “figure-8″. The U 48 can be seen in numerous photographs of John Lennon and Paul McCartney singing together on early Beatles recording sessions. Rumor has it that EMI’s Abbey Road Studios even sent some of their U 47s back to Neumann to be modified into this configuration. Far fewer of these mics were sold, and considering how rare U 47s are, U 48s are even harder to find. It turns out that the U 47 in “cardiod” configuration is roughly 5 db louder than in “omni”. This is essentially due to the fact that in “omni” the rear diaphragm is disconnected and in “cardiod” both are on.
Later U 47s, from 1958 on, were built using a newer capsule, the K 47. The M 7 diaphragms were made from PVC with gold “sputtered” on a disc on either side. The K 47 was used a metalized polyester diaphragm. Many people have their favorite version, based on which capsule was used, but the majority of users seem to prefer the M7, assuming it’s in good condition.
We here at Morrisound have a wonderful microphone that was made in East Germany’s Neumann factory in the mid 1950′s, called a CVM 563 (shown here to the right). This mic also uses the famed M7 capsule but uses an entirely different amplifier design. A similar sound to the U-47 in some regards, but different enough to provide another wonderful “flavor”!
Another key component of the U 47 design is the use of an impedance matching transformer, the BV-08. An especially large transformer, the method of mounting the BV-08 in the body of the U 47 was partially responsible for the long and short body versions. Around 5,000 U 47s were made, 3200 as “Long Body” model, the rest “Short Body” with no electronic differences.
Here at Morrisound, we have acquired a Neumann U 47 (Long Body) to replace the Telefunken U 47 that was stolen in April 2011. We feel privileged to have this mic in our collection. As far as memory serves, the Neumann sounds just as good as the Telefunken. I suppose we will never know, but I do know that this one is a wonderful sounding microphone and a collector’s item with few equals!