Q: I have heard that tube microphones should always be used upside down (with the diaphragm at the bottom). This is supposed to prevent heat from the tube from altering the frequency response of the mic. But I have seen a number of newer mics in which the mount does not allow for this. What’s the deal?
A: In general, the mic designer will determine if the heat from an onboard vacuum tube is significant enough to alter the microphone’s overall frequency response. But keep in mind that modern tube mic designs are quite a bit more sophisticated than those from the 1950s. Still, we know a few veteran engineers who insist on using tube mics in the upside-down position only. Certainly it won’t harm the microphone in any way, as they are designed to be placed in all sorts of positions, but in the end, we’d go with what the manufacturer recommends, and what our ears tell us is working best.