The Neumann Model U 67 (1960-1971)
multi-directional tube condenser microphone

The following text is from the March, 1966 Neumann specifications sheets. The U 67 Condenser micro­phone is a newly developed multi-purpose studio micro­phone. It has an attractive shape and possesses first-class transmission properties and a number of new advantages. The U 67 Condenser Micro­phone can be used in a multi­tude of cases in recording, broadcasting, and sound reproduction. From a dimension point of view, it lies between the group of miniature micro­phones and that of the older standard type of con­denser micro­phones. By relinquishing the absolute miniature type of construction, it is possible to use reliable standard components as well as an approved easily replaceable micro­phone amplifier tube with plug socket, a type which can be obtained all over the world.

By means of three switches, arranged at the base of the head assembly, the three directional characteristics, frequency response, and transmission ratio can be adapted to requirements. The frequency response of the micro­phone, also in the upper audio range, is practically linear for frontal sound pickup and does not show the commonly found rise. This enables the micro­phone to be used especially at a short distance away from the sound source without getting an unnaturally sharp sound impression. A new type of circuit considerably attenuates frequencies below 30 c/s already before the control grid of the micro­phone tube, whilst frequencies above 40 c/s are transmitted unaffected. The often feared overloading of the micro­phone tube caused by excessive movements of the membrane due to wind, floor vibrations etc. has thus been prevented. This was not possible with the commonly used rumble filters at the output. If the bass attenuation exceptionally is not desired, frequency response of the micro­phone amplifier can be linearized by disconnecting a small wire bridge in the micro­phone. The limit frequency of this bass attenuation can be shifted to 100 c/s by means of a switch located on the micro­phone (favorable e.g. for recording of speech or in television studios).

When the transmission degree of the micro­phone is reduced by approximately 10 dB by means of the third switch, the micro­phone amplifier will not be overloaded, even with the highest levels occurring in practice. (Application e.g. with pick-up of loud solo instruments from short distance.) The micro­phone tube operates as an anode amplifier into an output trans­former with separate feedback winding. The micro­phone amplifier section may be opened easily without the aid of a screw­driver by unscrewing the fastening ring at its base in a counter­clock­wise direction. This permits the conical housing to be with­drawn. The head assembly may then be removed by pressing lightly against the two length­wise support rails near the head assembly, releasing the latch and freeing the head assembly for unplugging.

Cables up to 165 feet in length may be used between micro­phone and power supply. When longer cables are required, the filament potenti­ometer R6 must be readjusted to bring the filament voltage at the micro­phone back to −6.3 volts. Consistency of operations is also increased by the following measures: Gold-sputtered poly­ester foils used as membranes make the unit highly insensitive to temperature, humidity, or aging. Printed circuit used through­out for stability and shock resistance. Great resistance to moisture due to potting of all grid circuit components and use of Teflon tube socket. Protection against RF interference through use of feed-through capacitors on all leads and RF-protected connectors on inter­connect cables.

The U 67 micro­phone may only be used with the NU 67 power supply. The filament voltage is made independent of mains voltage fluctuations by means of a power-type Zener diode. When the micro­phone is not connected, the power supply unit need not be switched off. Above the plugs for micro­phone cable and AF output is a pair of plug sockets, which permit the application of a test voltage in series with a 60 resistor.* For this purpose a voltage divider of 10:1 has been inserted, which steps up the input resistance of the test input to 600. The audio output socket is a three-pole connector (Tuchel T 3081). The appropriate line connector (T 3080) will be supplied upon request. The unit is fitted with a standard equipment type mains input socket.

*Ohms? It doesn’t say.

Specifications

• Frequency range: 40 to 16,000 c/s
  
  
• Directional characteristics: Omni-directional, Cardioid, Figure 8
  
  
• Sensitivity: Omni-directional: 1.1 mV/µb
  Sensitivity: Cardioid: 2.0 mV/µb
  Sensitivity: Figure 8: 1.4 mV/µb
  
  
• Total harmonic distortion: 0.5% up to 116 dB SPL
  
  

 

Download the 1963 Operating Instructions for this mic.

Download the 1966 Specifications sheets for this mic.

Download the 1992 Operating Instructions for this mic.

Download the background information sheet for this mic.