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I was recording the sound made by the indicators (turn signals) in my car. I figured this wouldn't be too hard. The sound is loud enough to be heard travelling up the motorway so I used my OKMII binaurals to capture this, with the engine off for a decent signal to noise ratio.

I got a noisy recording - so I tried it again with all the mics I could get hold of -

OKMII, Sony ECM719 and MS957, and Sennheiser MKH30/40

http://freesound.iua.upf.edu/packsViewSingle.php?id=1499

It was kind of surprising to me that I needed to go to the MKH30/40 to get a decent signal to noise ratio on this everyday sound. Okay, so it's not a controlled test - apart from the OKMs which were about 60cm from the sound source I set the others up between the seats about 90cm away. It brought it home to me that the OKMs are more for urban field recording that usage inside buildings. I wish there was a quieter version of binaural mics, there's a lot of places you can go with OKMs you can't with the MKH rig!

Thanks for posting this. What recorder was used? The MKH pair is clearly the winner of the bunch as far as noise goes, but I wonder how much of that may have been your preamp. Although the self-noise of the MKH is legendarily low, your results with the other mics are much noiser than I'd expect. MKH's have very high output compared with the other three mics you used, and so they don't require you to use as much gain on your preamp; lower output mics expose not only their own self-noise, but that of the preamp stage as well.
Anyway, just a thought.

mab

did you use the soundmans with the little preamp they supply (at least in the 'luxury' edition)? I've found that the soundman has WAY too much bass -as you can hear on the recording- and their preamp has a bit of rolloff...

I still have to experiment with it though.. Still haven't done a-b tests between with and without the little preamp.

- bram

Bram,
It's not really a preamp, but a battery box that feeds the mics 6 volts instead of 3v or so of plugin-power. I think it's supposed to increase tolerance to high sound pressures (distortion). In my experience it does not increase gain.
I shlould also warn people that the 'little box' than came with my OKM produces unpredictable noises, as the battery moves a bit around the compartment. Tried to fix this with small pieces of paper, only with moderate success...

my 2 cents

I used a Sony MZ-NH-700 HiMD recorder, which I measured the input stage noise at -116dBu unweighted.

It was hard to win the specs of the OKMIIK from Soundman's site but it has a sensitivity of about half the MKHs at 11mV/Pa @ 1kHz and a self-noise of -61dB ref 1PA (=94dB SPL)
At 1Pa the output would be -37dBu so the mic noise floor is -98dBu, and the HiMD should not significantly affect that.

http://www.soundman.de/englisch/techdata_okm_eng.htm

I used a battery box which is a 9V battery with two 6k8 tail resistors to power the mics for the OKM, as the HiMD does not provide anough PiP current to get the mic within its voltage spec

The Sennheisers were powered using a battery box of 6x8.4V nicads. Apart from the OKMs, which were used in my ears from the drivers position, all the other mics were set up in the middle of the car directly between the front seats and raised to the height of the seat back (about shoulder level when seated)

I was disappointed in the noise level of the OKMs - that's what I was first going to use for this sound until I heard the recording. But it does explain why I have always failed to capture the 'sound' inside cathedrals etc with this mic - the noise has always dominated.

The Sennheisers also sound a lot closer to what I heard, but I guess recording inside such a confined space is always going to be a bit hit and miss.