Interesting testing Gianni, thanks a lot.
Bob Cain did a computation for the mic2496 more
than a year ago which concludes, "the pre
equivalent noise (due to their EIN related back
through the [MKH-40's mic's sensitivity of
25mV/Pa]) would be 12 dBA for the mic2496." The
mic2496's mic pre came out considerably nosier
than the MP2. I'm wondering if there is
consistency between Bob's computation and your
findings. When you write:
>Thus, to evaluate the real mics noise I used the Mic2496 digitally
>connected to the PDAudio system based on an old iPaq (the MT2496
>could be used for digital recording as well) or the MOTU.
are you using the Mic2496's A-D mic pre circuit
to compare the mics? If so, shouldn't there be
masking of the noise produced by the NT1-A if
Bob's value is right? If not, perhaps you're
using another pre circuit to come up with the
absolute mic self noise rankings?
re:
> "the Mic2496 offers greater gain and less noise than the MT2496.."
Is it possible that the "digital boost" in the
MT2496's menu setting is the "Hi Setting" to
obtain the higher ~55dB gain? If you did use the
higher gain setting and you are getting a similar
equivalent 12db(A) self noise equivalent for the
Mic2496's mic pre, it seems pretty clear that the
MT2496's TRS mic pre is not as suitable as other
pres we have become accustomed to for nature
ambient recording in quiet settings.
I also find it surprising that the MOTU's pre
noise performance would be only a 6-7dB
improvement over the Mic2496. Thanks again, Rob D.
=3D =3D =3D =3D
At 9:28 PM +0200 10/18/05, Gianni Pavan wrote:
>Hi all,
> I tried to figure out how different mics could behave with the
>MT2496 and the Mic2496 while recording in a quiet environment. My
>target was to understand more of the relationships among sensitivity,
>self noise and mic preamplifier noise.
>
>Here the equipment I used:
>
>MAUDIO MT2496 --> 2GBCF
>CoreSound Mic2496 --SPDIF--> MAUDIO MT2496 --> 2GB CF
>CoreSound Mic2496 --TosLink--> CoreSound PDAudio CF --> iPaq 3870 --> 2GB =
CF
>MOTU Traveler --> FireWire --> Laptop
>
>Microphones:
>
>SONY ECM957 (stereo)
>AKG SE300+CK98 (short shotgun)
>AKG 451EB+CK8 (short shotgun bought 15 years ago)
>Sennheiser K6+ME66 (short shotgun bought 10 years ago)
>Rode NT1A
>Telinga EM23
>
>I used 96K and 24 bits; due to time constraints I did not test all
>combinations and permutations; after few tests I focused on comparing
>the Rode NT1 / EM23 / AKG SE300 and the MT2496 vs the Mic2496.
>
>I worked in a very quiet room at night. A piezo beeper at 3m distance
>in front of the mics was recorded to roughly calibrate levels in post
>processing (it makes "bips" and not noise). The Mic2496 was set for
>max gain to get the "bips" at about -15 dB with the loudest mics; the
>MT2496 was set to High gain position and Max level position (I
>avoided to use the digital boost available in the menu' Settings).
>
>The most interesting results I got are that the Mic2496 offers
>greater gain and less noise than the MT2496.
>By recording with the Rode I got 16 dB more on the "bips" and 8 dB
>less noise with the Mic2496 than with the MT2496.
>I got the same numbers by recording with the AKG SE300+CK98 (same
>sensitivity as the Rode).
>
>It is now interesting to look at the numbers with a different perspective:
>
>The MT2496 noise masks the noise differences of all the mics I
>tested!! A Rode NT1, the quietest mic, appears as noisy as the AKG
>SE300 and the SONY MS957, that are the noisiest mic!
>
>Thus, to evaluate the real mics noise I used the Mic2496 digitally
>connected to the PDAudio system based on an old iPaq (the MT2496
>could be used for digital recording as well) or the MOTU.
>After adjusting the "bips" levels in post processing (normalization)
>I can compile the following list of microphones ordered according to
>their noise floor (electronic hiss, above 1 kHz), or, to be more
>correct, to the Signal to Noise ratio they can offer if connected to
>a quiet preamplifier (I don't consider here the directional
>characteristics nor the tonal quality nor frequency response):
>
>Rode NT1 (the quietest)
>Telinga EM23
>Sennheiser K6+ME66
>AKG 451EB+CK8
>AKG SE300+CK98
>SONY MS957
>
>The disappointing result here is that the AKG SE300+CK98 has a noise
>floor 15-16 dB higher than the Rode NT1A noise floor (they have the
>same sensitivity and thus the noise floor comparison has not been
>affected by the normalization) but its noise was completely masked by
>the MT2496 noise and low gain.
>
>The EM23 is 4-5dB more sensitive than the Rode but after
>normalization it is 7-8dB noisier.
>The least sensitive microphone is the SONY MS957: 15dB less than the
>Rode; after normalization it is 17-18dB noisier than the Rode and
>only 2-3 dB noisier than the AKG SE300. In the SONY the R channel is
>noisier than the L; the L is flat but the R increases at high
>frequency up to 6dB more.
>
>These results are the combination of self-noise and sensitivity on a
>specific preamplifier whose noise floor is lower than the self-noise
>of the microphones, but of course the quietest microphone could have
>been affected in some way by the preamplifier noise. Also, the least
>sensitive microphones (the SONY) could have been affected by the
>preamplifier noise pumped up in the post-processing amplification.
>
>The results on the Rode and AKG have been also confirmed by
>connecting them to the MOTU Traveler: the Rode noise was 15 dB lower
>the AKG, but the test was disturbed by the fan of the laptop.
>
>The comparison among the Mic2496 and the MOTU is interesting too, but
>not definitive because of the fan of the laptop.
>The MOTU was set to 48dB gain for both the Rode and the AKG. By
>comparing the Rode recording, the bips were 12 dB higher on the MOTU
>than on the Mic2496, and the noise was 6-7dB higher on the MOTU than
>on the Mic2496. Thus the MOTU allowed a Signal to Noise Ratio 5-6dB
>better than the Mic2496.
>
>I hope these preliminary information are useful to understand a bit
>more how different combinations of hardware behave and may fit
>different requirements.
>
>Sooner or later I hope to be able to repeat the tests with more
>accuracy and more devices to compare,
>Gianni
>--------------------------------------------------------------
>Gianni Pavan
>Email
>Centro Interdisciplinare di Bioacustica e Ricerche Ambientali
>Universita' degli Studi di Pavia
>Via Taramelli 24, 27100 PAVIA, ITALIA
>Tel=A0 +39-0382-987874
>Fax +39-02-700-32921
>Web http://www.unipv.it/cibra
>
>
>
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