I am not sure if this should be posted here or perhaps in "Audio Student Engineering", so please feel free to move to this.

Can someone please double check me on my understanding of the mechanics of shotgun mics and why they shouldn't be used indoors?

My understanding is that because of the interference tube on shotgun mics, off axis sound tends to be colored, have uneven frequency response and/or comb filtering. If the on axis sound is reflected off the walls into the side of the microphone it will be colored by the poor off axis response which is undesirable.

I can imagine a situation where you might be outdoors but in an area surrounded by walls where you might get the same effect. An enclosed garden for example.

If (!) this is true, would it then be correct to say that the degree to which a shotgun mic can be successfully used in an enclosed space depends on the amount of reverb in the space and how good or poor the off axis response of the microphone is?

Regards, C.

For a non-technical description of how a shotgun mic works, this summary by Hugh Robjohns (SOS) is reasonable: https://www.soundonsound.com/sound-a...tgun-mics-work

Obviously there are some variations on what is described there (e.g. two-capsule designs).

Yes, you can run into problems outside with reflective surfaces and, equally, indoors have none: for the latter, think especially of sound stages, where shotgun mics are very much at home.

And, yes, the reflective nature and the design of the mic will have an effect on the usefulness of a shotgun indoors. Also, having the mic mounted statically can reduce or, more worryingly (unless ignorance is bliss), reduce the awareness of any negative effects: when moving a shotgun mic around indoors (i.e. booming for dialogue) the problems usually become much more apparent.

For all these reasons, production sound recordists usually swap to a supercardioid or hypercardioid in reflective spaces indoors or outdoors, when their specific shotgun mic isn't suitable.

Cheers,

Roland

indoor vs outdoor imo isn't the only consideration... - i do regularly use shotguns indoors, both in the studio and on amplified stages; as spot mics, as ambis for in-ears, for crowd noise, to pickup tap dancers etc.

Interesting SOS article, it filled in some gaps in what I knew. And thank you both for your answers.

Considering the above, I am really curious how for example the MKH8060 supposedly has better off-axis coloration than the MKH416 (I have never handled an MKH60 or MKH8060); I am curious about how that might be achieved.

Interesting thing Schoeps is doing with the double capsule set up, I didn't know that. I guess at the least it proves that companies that build professional microphones are thinking creatively about how things might be improved.

Regards, C.

And then there are the NPR Tiny Desk sessions where a shotgun mic is often seen...there are exceptions to every 'rule'. I must confess I have never tried one.

Not completely. A large part of the performance problems of an interference tube microphone (aka "shotgun") is about more than just the amount of reverb -- it's also about how quickly that reverb shows up at the mic. That is, the closer to a reflective surface you are, the more likely the sound entering the tube through the slots will interfere with the direct sound coming down the tube that you want to keep.

If the distance to the reflective surface(s) is great enough, an interference tube mic works just fine, indoors or out. Which is why dialog recordists can get away with using them on indoor soundstages where actual reflective surfaces are reasonably far away.

All that said, interference tube mics are nearly always going to sound somewhat colored off axis. It's just how they work. This is perhaps why when non-dialog people want more "reach" and less pickup from off-axis, they use hypercardioids or supercardioids instead.

My understanding from a practical point of view is that they can be used indoors when the reflective surfaces are far away enough - bigger spaces, dead enough spaces - people even use shotguns for narration and voice over work in dead vocal booths...

I used Sennheiser MKH60 shotgun indoors for a big TV series project, because we didn't have a hypercardioid at the time and nobody cared - that mic worked even in some glass offices well enough (but not perfect), but had to rely on lavaliers a bit more sometimes - especially for full shots / establishing shots of the space, when dialogue was happening only in those shots... but mostly - the whole show was recorded with MKH60... I loved that mic - it was my first time using it - my initial thought was "oh, that's how you get the "hollywood" sound", because outdoors and in acoustically nice locations it was "ready made" - immediately sounded proper and as dialogue should. And it was nice enough indoors.

(that's the series: https://www.youtube.com/watch?v=pfSV4zUTKhU or https://www.youtube.com/watch?v=sP1CdKIlCU0 )

Also - I think the dialogue is most delicate - you hear the coloration the most with the voice, at least to my senses.

So, it is useful to have a hypercardioid for indoor dialogue, but I pulled it off with MKH60, too.

A side-note about shotguns being used in Tiny Desk concerts - that "stage" area might be small, but the whole office in which it takes place is huge, walls far away and the desk area itself has a lot of absorbing/diffusing objects (books, shelves, etc.), it is pretty "dry"... and they use MS stereo shotguns... so not really a single mono shotgun - they add "side" a bit and I am sure that helps with a more natural sound, too...

I use shotguns inside in rooms with highly polished concrete and wood and its fine.

It is a Schoeps though...