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The Neumann U 47 and U 48
Meet the Neumann U 47, The World's Preeminent Large Diaphragm Condenser Microphone
The Neumann U 47 is the granddaddy of large diaphragm condenser microphones and features a legendary sound that has captured the vocal stylings of the greatest singers in the modern era. The Beatles used it to great effect, as did Frank Sinatra. From Ella to Adele, the Kingston Trio to the King of Pop, the vocal sounds of jazz and rock, folk and pop would not be the same without a U 47 in the studio. Its richness of tone and full body that peaks at just the right frequencies for the human voice has made the U 47 the undisputed king of vocal microphones.
The U 47 was the first mic produced by Georg Neumann GmbH in post-war Berlin, and became the industry standard microphone in the early fifties and beyond.
The Design and History of the Legendary Neumann U47 Microphone
The U 47 created its legendary sound with precision German engineering and the perfect synergy of all the right elements: a large wire-mesh head grille surrounding a capsule design perfected in 1932, amplified by a wartime Telefunken vacuum tube feeding a custom-wound transformer. It was the first mic produced by Georg Neumann GmbH in post-war Berlin, and became the industry standard microphone in the early fifties, when engineers like Rudy van Gelder (who got the second-ever U 47 to appear in the States).
Gelder discovered that the sensitivity of the mic brought a heightened sense of presence and detail to their recordings. Aficionados of his early Blue Note work will tell you how fantastic those recordings sound, due in large part to the character of the U 47. But high fidelity comes at a cost, and the U 47 was originally three times the price of the next-most expensive microphone, the RCA 77 ribbon mic.
The combination of head grille, diaphragm, tube and output transformer created a magical tone that has never been duplicated. Each separate element had a role to play in the creation of a most amazing transducer.
“The U 47, in my opinion, is the number one vocal mic of choice if I️ only had one to choose from. Not to mention they’re outstanding for one, two and three mic drum recording techniques and on nearly any instrument.”
Mike Nehra, Co-Founder, Vintage King
The U 47 was first debuted at the Berlin Radio Show of 1947, hence the model number became 47, (though production delays postponed the manufacture until 1949). The "U" in the model name indicated that it used a plug-in style amplifier tube - in this case the famous VF14.
After World War II, the VF14 was used in radio receivers that could be powered by either AC or DC current (allstrom empfaenger, or "all-current receivers"). The aftermath of the war had left Germany with no standardized electrical current supplies or voltages. Dual-tube radios and 110v (AC or DC) were the most common, so practicality demanded that consumer radios used two tubes in series that each drew 55 volts for the heater, run directly off of mains power!
Broadcasters were in the same dilemma, and Neumann responded with microphones that could also run off of mains supply where necessary. They simply adapted the already common VF14 (made down the street in Berlin) as the tube to power these microphones. The decision had historic consequences both for the tone of the microphones, and for their unforeseen desirability a half-century later.
The "U" in the Neumann U 47 name indicated that it used a plug-in style amplifier tube - in this case the famous VF14.
The Heart of the U47: the VF14 Tube
The VF14 is a pentode tube in a steel housing, of which Telefunken made many styles, (none, unfortunately, are equivalent to the specs of the VF14). In lieu of paying royalties for the patent on this tube, Neumann allowed Telefunken to distribute (and badge) the U 47. In return, Neumann had first choice of any VF14 tubes that were made, and tested them for suitability in microphone use.
Of the 27,548 tubes manufactured by Telefunken in Berlin and Ulm, Germany from 1946-1958, about a third of these passed Neumann's stringent tests for noise and performance and had a white "M" stamped on them to indicate "mikrofon". Of these, about 6700 were used as original equipment in a U 47 or U 48. Neumann made their third and final order of VF14s in 1958, and when the supply finally ran out in 1963, the U 47 ceased production. But this five-year window gave Neumann time to design two new large diaphragm capsules and a new flagship tube microphone, the U 67.
Creating The Signal With The M7 Capsule
As wonderful as the VF14 is, it is only as good as the signal it amplifies. In the case of the U 47, this signal is created by the fluctuations of the dual diaphragm capsule, the famous M7. This capsule can be set for cardioid or omnidirectional mode. Originally designed for the CMV 3 bottle mic, the M7 design has stood the test of time, and is still made today by Microtech Gefell, who originally supplied many of the early M7s from East Germany, prior to the creation of the Berlin Wall.
Initially, the diaphragms were made of PVC at 12 microns thick, with a thin layer of evaporated gold. The membrane was glued to the capsule and edge-terminated around dual backplates made of brass, with 90 precision-drilled holes per side. Although highly sensitive to sound waves, the PVC material could decay over time. As the diaphragm aged the PVC lost tension and strength, shrinking and creating hairline cracks in the film. This allowed moisture to penetrate, causing dropouts due to loss of conductivity.
The new design used a single backplate and held the diaphragm in tension with 12 screws in a brass mounting ring.
By 1960, a replacement material was found in Mylar® (a type of polyester), which became the diaphragm for the new K47/K49 capsule used in the later U 47 mics, and in the M 49. The new design used a single backplate and held the diaphragm in tension with 12 screws in a brass mounting ring.
Originally, the best of these capsules, with the tightest tolerances between diaphragms, were designated K48/49, to indicate better performance in figure-eight mode for the U 48 and M 49. Eventually, the production tolerances became so good that the designation lost all meaning, and any later capsule was officially designated as K47/49. Microphones delivered with the new capsule were usually indicated as U 47a, starting around number 4800, which is also when the transformer changed.
“At the studio, we have a bunch of great vocal mic options, but the one that goes up first 95% of the time is our U 47. It works best across the broadest range of vocals for what we do. It sounds the most natural, musical, and "biggest" which is what we tend to look for most often.”
Ryan McGuire, President, Vintage King
The Neumann U 48 and Other Variants
One variant of the U 47 appeared in 1955 (with some examples as early as 1953); the U 47P. This was a standard amplifier and body with an old-style torpedo mount to hold an M 48 omnidirectional capsule. The M 48 was essentially the same aluminum capsule as in the small diaphragm tube condenser KM 53 (which debuted in 1953). The demand for the aluminum capsule was high enough to justify making a version that would thread onto the still-prevalent Neumann CMV 3 bottle microphones. Their unique use on the U 47 amplifier was coupled with an output impedance strapped for 600 ohms, also very unusual for a U 47. The letter "P" designation indicated that these were a special order for Philips corporation. Only a few were made in the mid to late 50s, and they can be converted back to a normal U 47 configuration by swapping the torpedo head with a KK47 assembly.
The most important variant of the U 47 is the U 48, released in 1957, (with some examples existing as early as 1950). Approximately 800 U 48s were made before the model was discontinued along with the U 47. The main difference between the two is that the U 47 is cardioid and omni, and the U 48 is cardioid and figure-eight (the "8" in the model name refers to a polar pattern variant on a U 47, and not to the production year). In cardioid mode, the mics are nearly identical, whereas the signal-to-noise ratio in figure-eight is higher, due to a low polarization voltage. The pattern is created by splitting the 105V supply voltage from the tube between both diaphragms, leaving 52.5v instead of the ideal 60v. The later units, after the introduction of the BV-08B transformer, also suffer from the 4-6 dB output loss inherent in that design. Nevertheless, the U 48 does have its advantages, and George Martin sent Abbey Road's U 47s back to Berlin to be modified for figure-eight pattern, to take advantage of tracking harmony vocals on the same mic at the same time. These mics were changed by Neumann to indicate U 47/48 model number.
Originally the U 47 had a long body (made of brass, and later aluminum); this was shortened about an inch and a half when smaller components were used and the transformer was mounted horizontally. Up until the middle of 1957, about 3250 "long bodies" were made, (240mm long, 60mm in diameter), after which the remainder are "short bodies", (200mm long, 60mm in diameter). Also, the head grille was available in two finishes: chrome (for studios) or matte (for TV and film). The special construction of this grille imparted a very musical tone to the sound of the mic, as well as enhancing the "proximity effect" of a low-bass boost when the sound source was close to the microphone. The U 48 appeared after the amplifier body was shortened, so that all of them are short bodies. The entire head grille and capsule assembly of a U 47 (called KK47) can be used on a U 48 body, but not vice-versa, (the third pin for the figure-eight voltage prevents that), so that all three polar patterns were possible with a complete U 48 and a spare KK47 head, (the letters mean Kapsel Kopf, or "capsule head").
The main difference between the two is that the Neumann U 47 is cardioid and omni, and the Neumann U 48 is cardioid and figure-eight (the "8" in the model name refers to the polar pattern, not the year of its release).
Among the many variants in the history the Neumann U 47, one of the other constant sources of change have been the logo badge placed on the microphone. No more than 300 of the first U 47s had the so-called "large badge"; a chrome diamond shape with the Neumann logo and the serial number, mounted on the front of the body. This was replaced with the "small badge", a metal diamond with black lacquer finish and the Neumann (or Telefunken) logo. The serial number badge was separate, and was either a rectangle placed at the bottom rear of the body, or a semi-circle placed on the face of the bell. Some rare specimens of U 47 exist with a Siemens badge, special-ordered from Neumann for use in broadcast work. These various bodies, badges and grilles made for five different versions of the U 47 cosmetics, based on the badge type, plating, and body size.
Looking to get the sound of a vintage Neumann U 47 without breaking the bank? Don't let the high price tags of vintage ones discourage you! There are many great U 47 replicas including the Flea Microphones 47, The Mic Shop MS47 Mark II and the Telefunken Elektroakustik U 47. Additionally, the Slate VMS Microphone System and Townsend Labs Sphere L22 offer up incredible plug-in emulations of this classic microphone.
