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I'm looking into a handheld for the sole purpose of recording those quick one-off ambiences: a subway station late at night, wind whistling in a stairwell of somewhere you're visiting when you don't have your full kit - you know the drill.
Out of the obvious H4N, PCM-D50, PCM-M10 etc. which onboard mics are the best at recording (sometimes quiet) ambiences? Any less popular recorders I should look at?
I carry a Zoom H2 with me all the time, just in case something interesting happens. I am thinking about changing to either the Zoom H2N or a Marantz PMD620. At work I use the Marantz PMD661, as the built-in mics are surprisingly good.
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Since you asked for quiet and less popular recorders, I'd also look at the Sony PCM D1 or the Nagra SD.
I haven't tried the Nagra, but there's a good review of it here. I have the PCM D1 and it has very little self noise. I use it to record room tone all the time. Both are pricey, but low noise preamps are expensive to manufacture, especially in a small hand held package.
Although something like a subway station will probably have a high enough noise floor that you can get away with a less expensive hand held like the PCM D50; which is the best recorder in its class imho. Hopefully Sony will revamp its hand-helds soon; they're about due for something new.
If you're looking for good on-board mics and don't necessarily need external connections, the PCM-D50 is most usually recommended.
I've the PMD-661 and the on-boards are fine for capturing reasonably loud town/city ambiences. But, if you're looking to capture something as nuanced and dynamic as wind, then perhaps the D50 (or equivalent) is your best option.
I own a Zoom H2 and for quiet ambiences I wouldn't say it had one of the quietest sets of internal mics. It's perfectly good for those off spur of the moment times when you want to capture something interesting, as long as its reasonably loud enough! As previously mentioned, the D50 is often recommended and if your budget stretches to one I'd go for it.
I think its about time Sony updated their D50 with something new (and even better) so I'm waiting a little longer until I take the plunge in upgrading ;)
EDIT: Just added an ambience recorded with my H2 to the SSD Soundcloud group if you want to listen.
What kind of Mic does the Nagra have? It looks like a mono. Recently I used a friend's zoom h4n and found it to he very good. It has stereo xy Mic with 90 and 120° angles width and 2 xlr-phono combo inputs with phantom power. I used a sennheiser 416 shotgun with a rycote shield to record vehicle sounds and simultaneously used inbuilt mics for ambiences. Plan to buy it now as renting mic is cheap but not the recorder.