How much does "sensitivity" matter?
 

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?

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?

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).

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.

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

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

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

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.

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.

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.

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.

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.

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.

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: 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.)

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.

The AT4073a lives on as an upgraded model, BP4073

Steve:

The specs, features and pickup pattern are a lot different on the BP4073 from the 4073a.

I don't know why AT has to try to confuse everybody with using almost the same name on different products.

There are still some new 4073a mics for sale too I just saw.

They're not THAT far different and what has changed makes the BP4073 look significantly improved at about the same price.

AT changed many of its mics. Isn't one of the main reasons the mics were "upgraded" was to make them legal to sell in Europe under the new laws? Or is this not accurate.

4073a SPECIFICATIONS
ELEMENT Externally polarized (DC bias) condenser
POLAR PATTERN Line + gradient
FREQUENCY RESPONSE 30-20,000 Hz
LOW FREQUENCY ROLL-OFF 150 Hz, 12 dB/octave
OPEN CIRCUIT SENSITIVITY -23 dB (70.8 mV) re 1V at 1 Pa
IMPEDANCE 100 ohms
MAXIMUM INPUT SOUND LEVEL 126 dB SPL, 1 kHz at 1% T.H.D.
NOISE 14 dB SPL
DYNAMIC RANGE (typical) 112 dB, 1 kHz at Max SPL
SIGNAL-TO-NOISE RATIO 80 dB, 1 kHz at 1 Pa
PHANTOM POWER REQUIREMENTS 11-52V DC, 3.2 mA typical
SWITCH Flat, roll-off
WEIGHT 4.0 oz (114 g)
DIMENSIONS 9.13" (232.0 mm) long,
0.83" (21.0 mm) diameter
OUTPUT CONNECTOR Integral 3-pin XLRM-type
ACCESSORIES FURNISHED AT8405a stand clamp for 5/8"-27 threaded stands; AT8134 windscreen; protective carrying case

BP4073 SPECIFICATIONS
ELEMENT Externally polarized (DC bias) capacitor
POLAR PATTERN Line + gradient
FREQUENCY RESPONSE 20-20,000 Hz
LOW FREQUENCY ROLL-OFF 80 Hz, 12 dB/octave
OPEN CIRCUIT SENSITIVITY -29 dB (35.5 mV) re 1V at 1 Pa
IMPEDANCE 50 ohms
MAXIMUM INPUT SOUND LEVEL 141 dB SPL, 1 kHz at 1% T.H.D.;
151 dB SPL, with 10 dB pad (nominal)
NOISE 13 dB SPL
DYNAMIC RANGE (typical) 128 dB, 1 kHz at Max SPL
SIGNAL-TO-NOISE RATIO 81 dB, 1 kHz at 1 Pa
PHANTOM POWER REQUIREMENTS 48V DC, 4.8 mA typical
SWITCHES Flat, roll-off; 10 dB pad (nominal)
WEIGHT 99 g (3.5 oz)
DIMENSIONS 233.0 mm (9.17") long,
21.0 mm (0.83") maximum body diameter
OUTPUT CONNECTOR Integral 3-pin XLRM-type
ACCESSORIES FURNISHED AT8405a stand clamp for 5/8"-27 threaded stands; 5/8"-27 to 3/8"-16 threaded adapter; AT8144 windscreen; two O-Rings; protective carrying case

Those two polar patterns are pretty close - the reason the AT4073 looks lopside is they graphed 6 frequencies, putting the lower three on the left side of the graph and the higher three on the right so the graph didn't get so muddied up. For the complete pattern, take the left side and flip it to superimpose its mirror-image over the right and vice-versa.

In terms of the numbers, the only really signifigant differences on the BP version are its 15dB higher maximum SPL, the 6dB lower sensitivity, and the lower shelving point of its HPF.

Hey Steve, would say that with 6 dB lower sensitivity and only 1 dB better S/N ratio that the new mic effectively has more noise (to achieve the same signal), or is that already factored in? I don't really know what "1 kHz at 1 Pa" means.

The mic's internal noise, its EIN, is the equivalent to the signal that would be produced by exposing the mic to a 1 kHz tone @ 13dB SPL were there no internal noise. The mic also achieves its rated output when exposed to a 1kHz tone at volume that generates 1 Pascal of overpressure, about 94 dB SPL. Thus at rated output the signal+noise to noise ratio is 94 - 13, or 81dB. The dynamic range is the Maximum SPL, 141dB, minus the EIN, 13dB, or 128dB SPL and describes the range between the softest sound the mic can detect and loudest it can handle without distortion. The older mic has 1 dB more internal noise, hardly noticable.