The Dorrough 21B Vertical Analog Loudness Meter with Percent Modulation is a straight line version of Dorrough's standard 40 series loudness monitor. The 21B requires rack mounting and needs an external power supply. It also comes in a handy vertical orientation.
Like the 40B, the 21B measures Relative Loudness to Peak Modulation. The meters are calibrated in percent modulation, referenced at 100%. Access phase correlation, peak hold, sum/diff, and reference mode allowing 0 reference setting to 0.1 dB accuracy, directly or with the optional remote control.
- Actual Energy Display
- Dorrough Loudness Meters display actual energy content of the program material, regardless of frequency, while still indicating the peak amplitude of the complex audio signal. This feature allows all program material to be adjusted for equal perceived loudness while protecting the peak of the waveform.
- Peak and Average Level Metering
- The 21B, like all Dorrough loudness meters, simultaneously displays peak and average, in this model in a straight-line scale display calibrated in percent modulation, referenced at 100%. The relative difference, in dB, between these two ballistics is derived from the integration time of the persistence scale.
- Right and Left Inputs for Stereo Mixing
- With one instrument, the operator can easily see the stereo mix and avoid classic in-phase/out-of-phase problems as well as center channel buildup causing a mix to seem louder. This is especially important in preparing stereo program material for broadcast, while still being able to maintain monaural compatibility.