Help me out here: Obviously the pickup pattern and frequency response of a mic are directly related to how prone to feedback they are in a live-sound situation. But if those two things are equal, I fail to see how the sensitivity of the mic relates, despite very frequent references to that on the internet. E.g. which discusses the transformerless-57 mod to SM57's: the mod reduces the output of the 57 by ~10dB and the video host (whom I like and appreciate) suggests that the mic may not be appropriate for live sound use in feedback-prone situations as a result. Why? Feedback relates to the overall system gain, so you turn your preamp up 10dB and now you have the same overall system gain, and the same chance of feedback, no? Ironically, you hear this arguing the opposite direction as well: "microphone X is very sensitive, so it's not great for live sound use" -- again, turn the preamp down, now you have the same overall system gain and the same risk of feedback. Again, that's with frequency response and pickup pattern being the same: a "sensitive" mic might be sensitive in more ways than just overall sensitivity: they might be using the word as a proxy to mean that the pickup pattern is wider. It's not just that video, of course; I hear stuff along these lines again and again. One argument I could understand is that a less sensitive mic requires more gain, which brings a bit more noise, which may in turn seed a feedback loop more readily, but this seems like pretty nitpicky reasoning. This whole subject just seems like a rebranding of the classic sound guy myth that if you turn down the gain trim on the board and turn up the fader, you lower the feedback "sensitivity" of the mic (or the frequency response). Remarkable how common that myth is, as well. As a guess, perhaps the general overlap in mics that are more sensitive (in the technical sense) with mics that aren't designed for stage use (e.g. studio-oriented LDCs) lead to people associating true sensitivity with being prone to feedback, because it was a reliable-enough pattern, even though it's not actually the sensitivity causing the feedback risk. Am I missing something?

But sensitivity is more complicated than that, no? Isn't it the amount of pressure required to produce voltage? So no amount of preamp gain can compensate for that. Frequency response is a big consideration too.

I think the idea that a high output mic is more sensible to feedback comes from condenser mics. They have a considerable higher output, but usually also more high content. And some even have a pronounced peak in the higher frequencies which makes them even more prone to feedback. But if you compare condensers with dynamic mics with an even frequency curve and the same pattern , you'll get the same sensitivity to feedback, albeit at different gain levels.

The only factor not talked about here is directionality. I don't give a crap what the mic's output volume is, once they are all leveled. I agree, I don't understand why people think some mics are more 'prone to feedback'. If they have a louder high end, sure. But you have an EQ on the mixer for many reasons.. one of them is to balance all the mic's tonally. The only feedback consideration I have setting up mics is to put hypercardioids as the far left and right mics where the speakers are set up (ahead of the mics, of course). This way if they tilt the mic by mistake, there's a little more room before it starts to pick up the speaker. I also make sure these are background vocalists so no one notices the huge high cut I do to be extra cautious. It works out both for feedback issues and also to give the lead vocalist more space in that frequency range to stand 'over' the rest of the band. Also feedback destroyers work really well, I've used this guy before and loved it. Unobtrusive, objective-oriented gear:

Clepsydrae, About feedback detection and correction, I have a good experience using systems from TC-Helicon, in special the small box "correct XT". It's not magic of course, but what I do, is increasing the volume until it rings, letting the unit detect and cut the frequency, then I increase even more, until it cut the next. From there I just turn down the volume a bit and I am set. Really handy if you are a vocalist, you never know which kind of sound reinforcement and "audio engineer" you will find on live situations...

Thanks for the tip; i'll check that out.

As with all things, a competent tech with a decent quality system set up correctly and properly "rung out" should have 99.9% feedback-free system. And for the 0.1% when some dork points a mic at a monitor or falls over and knocks the stand sideways, you really dont have many faders to grab. :D Speaking for myself I HATE "feedback destroyers" with a passion as they always seem to work by inserting predetermined notches in the frequency response of your system, which sort of defeats the object of buying a good system and setting it up properly in the first place!

icicles bicycles ricicles test-ing this microphone....

Arran, can you detail more what you propose as a way to set the feedback destroyer? I usually do what you mentioned (gain up, ring, done), with acceptable results, but I surely would love more headroom (heavy metal singer :P). Do you turn up the gain while standing in front of the mic is that it? And continue the testing while speaking/singing?

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