The Altec 670A
multi-directional ribbon microphone
The 670 Microphone is a general purpose microphone of broadcast quality having a frequency range that covers the complete audio spectrum. It consists of a ribbon element and a controllable acoustic labyrinth.
Microphone courtesy of Jeff Rudisill
The microphone has three basic directivity patterns as illustrated below.
- P pressure (omni-directional)
- C cardioid
- R ribbon (bi-directional)
These basic patterns may be modified by placing the selector on the back surface of the microphone in intermediate positions. Such placement will result in a compromise between the adjoining patterns.
The impedance selecting switch is located underneath the name plate on the front of the microphone. Position 1: 30 to 50 ohms. Position 2: 150 to 250 ohms.
Quoted from the Altec Lansing Corporation Operating Instructions, Part No. 12182
According to Mr. Bill Hayes at MicroMike Laboratories in Anaheim, California, there is a Model 670B that employs a slightly thicker, stiffer ribbon, which modestly improves the frequency response over the A series. Our thanks to Mr. Al Pushkin for contacting Mr. Hayes and tracking down this information.
November, 2006: I have managed to track down a 670A and a 670B, and record them simultaneously, although under rather adverse conditions. Apologies for the ambience. It was this or nothing. References to channels 1 and 2 represent left and right channels of this stereo recording. The 670A is on the left, while the 670B is on the right.