SpectraFoo Rad 3 f17 Release Notes

This release is being made freely available to all registered users of MLM, SpectraFoo and SpectraFoo Complete, just as all previous updates to the SpectraFoo Range have been. This release contains two primary enhancements. The first enhancement is a compatibility addition. The second enhancement is a feature addition. We recommend that all customers update to this version of the software.

RTAS Support

The first enhancement is a compatibility addition: the TDM version of SpectraFoo now fully supports RTAS. This has two significant benefits for Pro Tools users:

You can now install MLM, SpectraFoo and SpectraFoo Complete for use with Pro Tools LE and Pro Tools Free.
You can now install or update MLM, SpectraFoo and SpectraFoo Complete for use with Pro Tools 5.1 and take advantage of RTAS instantiation in Pro Tools 5.1 to use SpectraFoo Metering without using any DSP. When used in this mode there may be signal routing limitations.

The TDM updater will automatically replace the Plug-in with the updated Universal/RTAS version of the SpectraFoo plug. This version of the plug supports Merle ("Classic") DSPs, MIX DSPs, and RTAS.

K-System Support

The second (and most significant) enhancement is the addition of full, elegant support for the K-System metering system as defined by Bob Katz. For a detailed description of the Metering System and its motivations, please see Bob's Paper "An Integrated Approach to Metering, Monitoring, and Leveling Practices" that appeared in the AES Journal. You may be able to find other relevant (and not-so relevant to the K-System but interesting and useful) information at his website <http://www.digido.com/> .

While SpectraFoo provided all of the components to implement the spirit of the K-System, it was not elegant. There are four issues that needed to be addressed in order to implement support for the K-System:

Native support for dbFS referenced K-20, K-14, and K-12 scales needed to be added. This is required to allow consistent representation of the 0 dB mark, which is important to the standard. In addition, the standard sets out tick positions and labels. The K-scales implemented by this version of 'Foo meet the specification.
The specification defines hard transitions in the color of the RMS level bar. SpectraFoo only supported soft transitions. The color transition mode is now a user selectable option in the Meter Options control window. The K-System presets included with this release automatically set the option to use hard transitions.
The specification is based upon the AES-17 standard for metering practices. In this standard the reference level used for calibrating a meter is directly related to the reading on the meter when the reference signal placed into the meter. What this means is the specification defines that a Peak Reading Meter will read 0dBFS when a 0dBFS amplitude sine wave is placed upon its input. It also defines that an RMS reading meter will also read 0 dBFS when it is fed the same sine wave signal. SpectraFoo has always used the same scale for both Peak and RMS. This means that the RMS level for the sine wave described above will be -3.01 dBFS. SpectraFoo's RMS level reads 3.01 dB low when compared to AES-17 calibrated meters. This is essentially a "po-tay-toe" vs. "po-tah-toe" issue, as long as the definition is well understood by the user of the meter. However, this issue has caused confusion in comparing studio calibrations and makes it impossible to fully calibrate SpectraFoo to the K-System since the K-System simultaneously specifies both peak and RMS calibration. In order to allow a full implementation of the K-System (and, additionally, full support for AES-17 calibrated RMS metering) we have added a user option to apply the 3.01 dB correction to the RMS levels in the meter. This option is automatically selected by the K-System presets.
The K-System specifies that the monitoring system must be calibrated with pink noise so that 0 dB K is set to 83 dBC SPL. SpectraFoo Complete provides a highly accurate wideband pink-noise source via the integrated Signal Generator. This source may be used for monitor system calibration. Previous versions of SpectraFoo Complete allowed the user to set the output level of the Pink Noise via its peak amplitude. The K-System specifies the level of the calibration signal in dBFS RMS. We have added a RMS checkbox to the signal generator to allow you to set the pink noise amplitude in dBFS RMS. We have also included 3 new signal generator parameter files to allow easy monitoring system calibration for K-20, K-14 and K-12.

All the issues have been resolved in cooperation with Bob Katz. We have included K-20, K-14, and K-12 presets for the meters and K-20, K-14, and K-12 signal generator presets for calibration. The K-meter options may be used independently of each other to build other meters that are not fully K-System compliant by may still be useful and interesting in other contexts.

A configuration tip: In the meter options window: you can click on the numerical readouts to "popup" a text-entry box. This allows you set the parameter value precisely. We will be propagating this interface feature (or a similar implementation) to all of the controls in the various instruments in SpectraFoo in a future release of the Software. You can use this feature to create derivative slow forms of the K-meters for calibration. You would want to set the VU settling time from .600 s to 6 s for a slow, long term average.

If you calibrate your monitor system according to the K-System recommendations, you can configure SpectraFoo's global level calibration to provide SPL readouts using the SpectraFoo scale. To do this use the SPL reference offset, e.g. for K-20, -20dBFS RMS Pink = 83dB SPL, so 0dBFS RMS Pink = 103dB SPL. In the global level calibration (Menu Path: Analyzer->Level Calibration...) make 0 dBFS = 103 dBu and then ignore the dBu -- the reading is SPL when you configure a meter with the SpectraFoo scale and select the AES-17 compatibility mode (use the Meter Options).

NOTE: If you install this update using the updater your signal generator parameter files get moved to the Metric Halo Moved Items folder. Depending on your Mac system prefs, the Standard File dialog stays "stuck" to the folder, even after it has moved. So, when you go to open the file, it shows you the old files, which are, of course, the same as the new files minus the K-System files. After you mess around enough, you wind up resetting the Mac OS internal preference and you start seeing the proper folder in the Standard File Dialog. Make sure you navigate to the correct folder or open the file by double-clicking in the Finder.

Metric Halo would like to extend Special Thanks to Bob Katz for reviewing this implementation of his specification.

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SpectraFoo is a trademark of Metric Halo Distribution. Pro Tools, TDM and RTAS are trademarks of Digidesign, a division of Avid, Inc.