At 5:03 AM +1100 4/1/10, Paul Jacobson wrote:
>
>
>Hi Rob,
>
>There is definitely a lot of uncertainty basing findings on
>manufacturers spec. The main purpose was to come up with a easy
>reference based on manufacturers specs rather than an absolutely
>accurate account of mic performance. List members are frequently
>referred to the Rane148.html page to "look up the numbers on the
>charts".
>
>On 31/03/2010, at 5:19 PM, Rob Danielson wrote:
>>
>> Rode NT-1A 25 5 -118.83 -128.8 dBu YES, A-weighted
>> Rode NT-2A 16 7 -120.70 -130.7 dBu?? Side by
>> side, the 2A is noisier than the 1A. In practice one could get by
>> with a slightly "noisier" pre, not a "quieter" one and one would not
>> need -130.7 dBu (A weighted).
>
>There is no question that the NT-2A has a higher level of
>self-noise, but based on the published specs if you recorded both
>the NT-1A and NT-2A at identical gain settings on the same recorder
>the recorded mic noise floor of the NT-2A _should_ be lower in terms
>of of dbFS than the recorded noise floor of the NT-1A. I'd be
>interested to see your results of such an unadjusted comparison.
Hi Paul--
Its on the test "to-do" list. I'm not following how rec gain makes a
difference in mic self-noise performance and the resulting recording
if a sufficiently quiet pre is used. Such a pre would be necessary to
compare the self-noise performance of the two mics.
> > were trying to get a input noise measurement for Hi-MD recorders, a
>> few folks independently noted that one could barely detect the input
>> noise of the pre at high gain using an MKH-40. Raimund (and others)
>> measured the Hi-MD recorders at -124dBu (A weighted). For pre
>> transparency with that mic, I'd go with a pre measure EIN of -125dBu
>> or higher, not -122dBu.
>
>I think the HiMD tests done by Richard Mudhar on
>www.wildlife-sound.org might provide an answer to that quandary. The
>test measured the MZ-NH700 with sensitivity set high and gain at 28
>and found the EIN was -116dBu. (see:
><http://www.wildlife-sound.org/equipment/himd/himdmyths_meas.html>http://w=
ww.wildlife-sound.org/equipment/himd/himdmyths_meas.html
>) This was compared with the noise output of the MKH-40 mics, and
>the HiMD noise was found to be 4-5dB lower than the MKH40 above
>1Khz. This level of difference is less than the 6-10dB safety margin
>suggested by Rane and tally's with the observations of audible
>preamp noise you relate. This suggests that either the HiMD preamps
>noise floor increased quite rapidly as gain was lowered from maximum
>or that John Beales original testing (the figures listed on
>Raimund's chart) with RMAA gave a EIN that was inaccurate. As far as
>I'm aware there has been little testing done to check input noise at
>typical recording levels vs full gain. Such tests might explain some
>of the anomalous results we see with lower gain settings.
I routinely used "28" for recording with Hi-MD in the field and most
of the tests I did were at "28." I'm not aware of anyone doing a test
showing Hi-MD input noise increases with gain (that its not
proportional). I'm open to the possibility.
In the example of the mkh40/Hi-MD Rane Table 3 conflict, everyone
seems to agree that there will be a tiny bit of audible input noise
from a Hi-MD pre when a MKH-40 is paired. I recall the debate about
the input noise measurements and waiting for the jury. One day I
noticed that if one accepted -124dBu (A weighted) as correct, it
corresponded very well with results someone produced with the same
model mic on a pre that Raimund has measured as slightly quieter.
I think the Table may become less reliable for input noise ratings
between -124dBu and -118dBu where folks are trying to pair-up
somewhat quiet mics with somewhat quiet pres. The warmth of the
LS-10's input noise showed-up on the radar when the number didn't
jive with field results. I see many uses for a chart that showed the
coloration of mic and pre generated noise for popular gear. We'd have
to raise a good bit money for Eric Benjamin to make the 1/3 otcave
measurements.
If one is trying to minimize noise and using mics with 12dB(A) or
lower self-noise, its very safe to buy a recorder that Raimund has
measured as -127dBu (A-weighted), or better. Rob D.
--
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