How much does "sensitivity" matter?

[Adam Gold]

In a recent discussion with the guys at Beachtek, one of their techs said:

"the NTG 2 has relatively low sensitivity at only 15 mV/Pa. A more sensitive mic like the Sennheiser ME66 at 50 mV/Pa would work much better. This will give you a strong signal with far less hiss."

So I looked around and found a variety of mics running the gamut from below 10 mV to more than 50.

How much does this matter? Is he right? I guess I always assumed these numbers were like lux ratings, a meaningless single number used to fool gullible customers for marketing purposes. How important is this in the mix of things to consider?

[Marco Leavitt]

Mic sensitivity is just one factor here. There is also the internal noise of the mic itself, the preamp on your mixer, and the recording device. Assuming your mixer and recorder are top end, you can crank the gain without a lot of problem. If the mic is noisy, your still going bring up the hiss though. The ME66 is generally useful when your recorder and mixer (if there is one) aren't that great. That's why it became so popular with the DV crowd when people were plugging it straight into the camera. So long as what you were recording wasn't excessively loud (which would overload the camera's preamps), you could turn the gain on the camera down, lowering the internal noise of the camera. What's your application?

[Adam Gold]

In this particular case, it was mounted on the cam (yeah, I know), one of four in a multicam shoot. This cam was at the rear of the theater about 60 ft from the stage (yeah, I know), going into the Beachtek DXA-FX (the powered one) and then into an FX1000. Huge hiss from the Beachtek because I had the cam on auto gain (yeah, I know). Beachtek said to keep the manual gain on the cam below 3, and when I did that, the hiss went away but so did the sound from the mic. Hence the comment about the sensitivity.

This is only one of about 7 sound sources from the shoot (one on each cam, two into our Zoom at the front of the stage, plus the board feed) and is mostly just used for synching the video, but it would be great to get the best sound possible, given our limitations (well detailed in other really boring threads, among them this one: http://www.dvinfo.net/forum/all-thin...-opinions.html).

[Marco Leavitt]

It looks like that Beachtek doesn't boost the signal, and I guess that your NTG 2 doesn't have enough output for you. You really need a way to boost the signal, like a mixer or something. The Juicedlink is designed for this if you can live with its limitations.

[Colin Rowe]

The only way to good sound is to have your mics as near to the sound source as possible. I appreciate this cant be acheived every time, but even the best shotgun mics need to be right in on the action

[Adam Gold]

Yeah, I know. Unfortunately, not possible. Just trying to make the best of a bad situation, as detailed excruciatingly in the other thread.

[Steve House]

You can't fool Mother Nature. Just FYI, those mic sensitivities typically reference the mic's output when they're exposed to a sound pressure level of 1 Pascal or 94 dBSPL. To put that in everyday perspective, that's roughly the sound of a jackhammer operating 6 feet away from you. Recording 60 feet away fro mthe stage at the back of the hall, there's really nothing you can do nor any mic you choose that's going to give acceptable results.

Here's a couple of good sounding concert clips that I like where the mic'ing techniques used to get the good "concert sound" is readily apparent on-screen. Note the headworn mics on the vocalists and the individual instrumental mics, overheads on the drums, etc.

YouTube - Celtic Thunder - Take Me Home
YouTube - Celtic Woman - The Voice

[Adam Gold]

Yeah, at this point I'd just love to hang some mics over the stage low enough to actually pick up some sound... but they won't let me.

As mentioned in the other thread, placing the Zoom right in front of the stage helped immeasurably. Still debating what additional mics to use but we're slowly making progress.

[Steve House]

I'm trying to understand why they won't let you fly mics ... dropped down from the proscenium, or the ceiling over the pit area or parterre, they'd be well above the audience sight-lines.

[Paul R Johnson]

boundary mics on the stage edge usually work better than flown mics, as people always project forwards, rarely upwards. Flown mics can work if they are upstage, where boundaries can't quite reach - but frequently have a slightly odd sound as much of what they are hearing is reflected off the stage floor.

Less sensitive mics need more gain from somewhere, and if the pre-amps are a bit weak, then the hiss can be quite bad.

[Adam Gold]

They won't let us fly mics because they find them "visually distracting" even if they're out of the sight lines.

And as I mentioned in the other thread, the boundary mics were worse than useless -- all they picked up were footsteps. Loudly.

For now the best solution seems to be what I proposed in the other thread -- the Zoom and some additional mics on stands on the floor right in front of the stage lip.

[Jon Fairhurst]

Mic technique aside, the Beachtek has no gain (as mentioned above). Often, Beachteks are used as the front end for camcorders with so-so preamps. If that's the case, then mic sensitivity is critical - even with perfect recording techniques.

Considering equipment only, the solutions are to use a more sensitive mic, and/or get a powered preamp with gain, like a juicedLink or SoundDevices mixer. Personally, I'd go with a different preamp. It can make low-sensitivity mics sound good, and high-sensitivity mics sound great.

My experience with a passive Beachtek and 5D Mark II with Magic Lantern firmware is that anything short of a close placed, high-sensitivity mic gives an hissy result.

[Bill Davis]

Just to reinforce the central issue that attends all audio decisions....


Sore sensitivity is great. Unless it's not.

The point is that in any recording environment you want the RIGHT amount of mic sensitivity - not just "the most" or "the least."

Clearly, if you're in the outdoors trying to capture bird songs, sensitivity is your friend. Particularly if it can be coupled with very low self-noise.

OTOH, if you're recording in a retail store, that same sensitivity can mean your dialog gets messed up with the sounds of the AC. shopping carts rumbling by, other shoppers talking, etc, etc, etc.

Mic sensitivity (or for that matter ANY single microphone spec) is just one ingredient that makes a contribution to good sound.

And just as all good cooking doesn'g universally feature chicken - all good sound recording situations don't call for any one particular level of mic sensitivity.

Another reason there are so many, many kinds of mics out there!

For what it's worth.

[Jon Fairhurst]

The only way that high sensitivity would raise the background sounds in the final mix would be if the sensitivity forced you to move the mic further from the source.

The Beachtek is passive and includes a variable pad. If the signal is too hot, just turn down the Beachtek. Based on my testing with the Beachtek into the 5D Mark II (with Magic Lantern Firmware to set the camera gain), there's no such thing as a mic with too much sensitivity.

The only exception is with super high SPL sources, like bass drum mics and recording Saturn V rockets. But that's really a dynamic range issue, rather than a sensitivity issue.

Here's the first video in my six-part test including multiple mics and 5D2 recording options, including a passive Beachtek:

1. Canon 5D Mark II Audio Exposed - Boom Mic (juicedLink, Zoom H4n, Microtrack II, BeachTek) on Vimeo

Note that there are links to uncompressed audio clips for most of the videos. (Follow the Vimeo link to find the wav files and other five videos.)

[Jeff Kellam]

Originally Posted by Adam Gold

In a recent discussion with the guys at Beachtek, one of their techs said:

So I looked around and found a variety of mics running the gamut from below 10 mV to more than 50.

How much does this matter? Is he right? I guess I always assumed these numbers were like lux ratings, a meaningless single number used to fool gullible customers for marketing purposes. How important is this in the mix of things to consider?

Adam:

The AT 4073a open circuit sensitivity is -23 dB (70.8 mV) re 1V at 1 Pa. I think it's probably the hottest mic out there. Like the other posters said, you need to be close, but this mic is the closest there is to performing long range sound pickup miracles when there is no other option.

I have had one for about a year, and I can tell you it will ocassionally perform actual miracles, but don't count on it. Also expect to keep gain pots at 1/4 or less. I think the low self noise and keeping device gain pots very low contributes to very low noise results.

Unfortunately, it's discontinued though.