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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:
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.



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.

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