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Re: [ARSCLIST] Software for Mac
At 02:09 PM 2008-10-15, Robert Cham wrote:
That's great! A typo in a message about typos.
Yes I meant 24 bit 96 KHz. The reason that I wonder if it is good
enough is that research was done in the late '70s or early '80s that
showed that the average Joe could discern information over 20 dB
down into the noise on an analog recording. No, I don't have the
citations anymore.
This is the localization information that tells you about the
acoustic properties of the hall and even can help one discern depth
in a two track recording played on a good reproduction system. All
of this falls below 1 bit on a CD, and is the reason that they sound so "flat".
All of the above is only true if a coincident micing system is used,
or at least well placed spaced omnis. What I refer to as
multi-track mono (many mics close to instruments) does not capture
any of this information. Some of the tapes that I have to transfer
are of this quality. I hope to make data discs on DVD at at least
24 / 96, for use when the playback technology catches up with
analog. Thus I wonder if 24 /96 is good enough to capture all of
the information on the tapes.
Hello, Bob,
I suspect that the current crop of commonly available 24-bit
converters are close to adequate, and the 24-bit spec, if fully
implemented should be more than adequate resolution and dynamic range.
The Benchmark ADC1USB delivers an unweighted broadband S/N ratio of 119 dB.
The RME Multiface II that I use (8 channels both ways for about 75%
of the 2-channel one-way Benchmark price) provides an unweighted S/N
ratio of 107.5 dB.
If we look at the specs for a Studer A80 with DIN (Butterfly) heads,
we see a record-play S/N ratio, unweighted referenced to the 3%
Distortion point of 70 dB. So, even the RME Multiface (which isn't a
Benchmark) is spec'd as having 37 dB more dynamic range.
The maximum dynamic range of 24 bits is about 144 dB, as compared to
the 16 bits of the CD at 96 dB.
If we look at room background noise and peak levels, I suspect that
the limiting factor would be the room background noise in most
two-mic recordings, but it also depends on the ensemble. An
interesting noise dose test can be found here:
www.rcm.ac.uk/cache/fl0003528.pdf
with some in-orchestra peaks at 138 dB(c), but these would be reduced
substantially at the presumed single-pair mic location, based on
inverse square law falloff.
I don't think there are (m)any concert halls with a wideband
(C-weighted) noise floor of 20 dB SPL (though A-weighted there may be
a good number--I didn't check my concert hall books).
Perhaps the way to look at this is to look at each band rather than a
broadband number and if we go back to the Benchmark unit, across the
board, in a 32K B-H FFT, the noise floor is shown at about -148 dBFS.
THe RME doesn't look that good...but nothing is above -110 dB. There
are some hum harmonics that approach -110 dB, but that could be
external wiring as I didn't remove the external wiring. RMS noise is
-90 (far noisier than the spec, so I suspect it's wiring).
Anyway, when the machines are powered up, this degrades substantially
-- more than 20 dB.
Cheers,
Richard
Richard L. Hess email: richard@xxxxxxxxxxxxxxx
Aurora, Ontario, Canada (905) 713 6733 1-877-TAPE-FIX
Detailed contact information: http://www.richardhess.com/tape/contact.htm
Quality tape transfers -- even from hard-to-play tapes.