Shotgun Microphone

[Cougar]

Hi

 

I have been asked to help specify a microphone to record at a distance of around 30m on as wide a frequency band as possible with as tight a polar response as possible. To give what background I know, it is to record a source that will be around the same level as a person talking to a computer sound card or similar. The Mic itself will need to be positioned in a relatively noisy area so minimising side and rear lobes is a priority. The recording end processing is sorted apparently they only require suggestions as to model of microphone. In what I have done in the past I have never needed to use shotgun type microphones and thought this would be a good place to start enquiring. I did search but found nothing that really was suitable. Budget is apparently not an issue at all but as I don't quite believe that I am looking to suggest options at the top end as well as in the middle and bottom of the ranges.

 

Thanks in advance

 

Evan

[Bobbsy]

The classic "long gun" mic is the Sennheiser MKH816...though unfortunately this is not in the current product list. They do still crop up on the second hand market from time to time and are excellent mics.

 

The closest present alternative is the MKH70 (details HERE ).

 

Something to be careful of on both these is that the lobar/hypercardioid pattern DOES give some pick up lobes to the back of the mic.

 

Do be aware that, although these are about the best mics around, even they can't work miracles and if you're trying to pick up a single soft audio source in a noisy environment you may well not be happy with the results. The only way I know to get an even more directional recording would be to move to a parabolic dish microphone...but this will give directional performance at the expense of quality.

 

Bob

[StevieR]

Ooo - not an easy one at all. We had a similar enquiry from a customer looking to record from a distance. We ended up specifying a Sennheiser MKH70 long shotgun and it seemed to do the job. However, the distance in your application would seem to be too great even for a mic such as this. Also, although shotgun mics have a narrow pickup pattern and good off-axis rejection, the further the distance from the capsule, the wider the pickup area will be.

 

An alternative may be to use a parabolic reflector such as those used at sports events. I have not used these myself though so I hope someone else may be able to offer advice on these.

 

Is there no option for getting a closer position for the microphone?

 

Steve

 

Ah - I see that I'm not the only one with these thoughts....

[paulears]

30m!! even the full length rifle like bobbsy mentions isn't much cop at that distance. Many issues.

you want to record soft speech from 30m with the mic in a noisy area? With full bandwidth if possible.

 

most rifles are really wide at the bottom end anyway, so to get better directivity, that has to go for a start. Assuming you have a mic with preamps quiet enough, it isn't realistic to hear a distant quiet source when localised noise is far greater in level. You could go for a dish - the bigears style ones are popular for sporting events,but they are small, and as bandwidth is a function of wavelength, a small dish won't give you much low end - and even if it did, 30m worth of wind may well drown out what you are after. My guess is a really big dish - a 3m commercial satellite one might be good copuld work, but would be difficult to hide! I experimented with a system using a couple of these close to where I live about 12 years ago, and we got speech to work between two dishes at about the distance you want to cover speaking into the dish at the focal point could be clearly heard with an ear at the focal point accross a lake. This is with a dish at both ends, only having one, would cut the distance considerably.

 

I reckon the chances of making this work without very specialist eavesdropping kit are slim in the extreme

[Ekij]

30m in a noisy environment, you're into professional spying equipment.

Bounce a laser off a reflective object beside the speaker and measure the Doppler effect in the frequency shift as the object vibrates due to the speech. Very expensive. :D

[david.elsbury]

Can you not use a wireless lav or similar?

[jamesperrett]

Bounce a laser off a reflective object beside the speaker and measure the Doppler effect in the frequency shift as the object vibrates due to the speech. Very expensive. :blink:

 

That's exactly what I was thinking. I heard stories about the security services using similar devices to eavesdrop on what was going on during a hostage taking crisis. The only problem was that they couldn't get enough of a reflection from the window of the room in which the hostages were held so they devised some way of sticking bird droppings to the window which did the trick.

 

Cheers

 

James.

[Cougar]

Thanks for that guys very much the answers I expected my first thought had been that they should be speaking to spy's rather than me but still. Hopefully I can help them a bit. And for reasons I don't quite understand closer is not a option. If anyone has more suggestions they will be welcome.

[Ekij]

Why can the person in question not wear a radio mike?

(or have one placed close to them)?

They do know they are being miked don't they!? :blink:

[Cougar]

The radio Mic option is not viable as there may be more than one source not all of which will be people that was just used as a indication of frequencies and level. Also the source may not be known before hand or with enough time to fix a tie clip or similar discrete microphone to the person. (and yes they do know it is being recorded don't worry about that).

[mackerr]

The radio Mic option is not viable as there may be more than one source not all of which will be people that was just used as a indication of frequencies and level. Also the source may not be known before hand or with enough time to fix a tie clip or similar discrete microphone to the person. (and yes they do know it is being recorded don't worry about that).

While shotgun mics, like the Sennheiser MKH70, are often used to record dialogue for TV or movies, the mic is usually less than 1 meter from the actor, and it is on a quiet sound stage. The likelihood of getting usable audio from 30m in a noisey environment is pretty slim. If you can't put a mic on the people, is there a way to put a mic closer to the action? Mics hidden in furniture or flower arrangements that are close to the person speaking are more likely to be successful.

 

Mac

[paulears]

I've just spotted that Canford audio show the big ears spec (585mm dish) as 800mm target diameter at 30m, depending on mic.

 

Part number is 53-399 and price is £1330 + vat plus mic

 

freq response quoted as 1000-15000Hz, using a lav type mic.

[Bobbsy]

Obviously we don't know the full details of what is being filmed, but unless this is some kind of super-clandestine project, you've probably better off trying to solve this using some creative mic technique rather than a (possibly non-existant) technological solution.

 

What I'm thinking of is things like hiding the sound man behind a counter or under a table near the subject so the mic is close but not in shot. If this isn't possible, a small lav radio mic hidden someplace in shot can often work. If you're able to mic one person but not a second, putting the RF lav a bit farther down the shirt than normal can sometimes give useful (though not perfect) pickup from both the person wearing it and the one opposite.

 

You'd be surprise how many places I've managed to hid mics (and even sound men) in or near shot!

 

Bob