Specifications

However, sometimes program material consists of dynamically louder and quieter parts. If the

limiting parameters were set for the quiet passages, when the louder parts occur the artifacts

mentioned previously will become very apparent. PSP Xenon Leveller applies a relatively con-

stant, slow-changing gain reduction to loud passages before the limiting is applied. This is par-

ticularly useful for loudness maximization applications, in which the goal is to make each part

of the song sound as loud as possible. For traditional limiting of short peaks without clipping,

the leveller can be turned off (leveller knob all the way up) thereby preserving the original mac-

rodynamics of the program.

Metering in PSP Xenon

By default, PSP Xenon shows the peak level of the input and output signal as well as the gain

reduction applied. The peak meters have falloff time of 8dB/sec. To allow for consistent loud-

ness control, we built the K-System mastering metering system into PSP Xenon. The K-Sys-

tem metering measures both average RMS and peak levels. Three different K-System scales

(K-12, K-14, K-20) are available. The scales differ by the amount of headroom and were care-

fully chosen to help engineers produce masters having consistent loudness and a crest factor

optimized for the specific audio being mastered. K-12 is designed for mastering audio for

broadcasting purposes, K-14 is intended for typical CD production, and K-20 is optimized for

movie production.

K-System metering is not only a metering system. It is the first integrated metering and monit-

oring system. To achieve the goal of standardizing studio loudness levels it includes guidelines

for calibrating speakers levels using a pink noise generator and an SPL meter. To facilitate this,

PSP Xenon includes band-limited pink noise generator which produces pink noise at the RMS

level appropriate for the given K-System scale, thereby making speaker calibration much easi-

er and faster.

Explaining every detail of the K-System metering and monitoring system is beyond the scope

of this manual. For further information please visit the site of the designer of the K-System,

Bob Katz, at his Digital Domain site: http://digido.com .

Metering a digital sample’s value is often not the safest way to measure peak audio level. The

reconstruction filter in the end-listener digital-to-analog converter might create inter-sample

peaks that exceed the analog level corresponding to 0dBFS. This overshoot and ringing is

known as the Gibb’s Effect. Many cheap analog circuits don't have enough headroom to

handle such levels and get non-linear. As a result of the nonlinearity the distortion is intro-

duced. For this reason, PSP Xenon includes the oversampled (reconstruction) metering op-

tion. In this mode the meters attempt to estimate the actual level that comes out of the convert-

er, allowing the engineer to lower the level of the digital audio so that distortion is not intro-

duced in the converter. And as noted in the Approach to Limiting section above, the envelope

detector can itself be oversampled to automatically protect against intersample peaks.

Requantizing

The limiter is usually the last stage of a mastering processing chain. If no processing will be

done after this stage one might need to requantize the resulting audio to the bit-depth required

by the storage media being used—for example, if the audio is to be rendered to CD, you may

need to requantize the audio to 16-bit. PSP Xenon includes a built-in requantizer designed for

PSP Xenon Operation Manual