Allen and Heath ML3000 VU meters out of calibration

Discussion in 'Sound, Music, and Intercom' started by macwhiz, Feb 7, 2013.

  1. macwhiz

    macwhiz Member

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    So my theater has an Allen and Heath ML3000, and the VU meters are out of calibration in comparison to the LED meters. Is there any fix for calibration?
     
  2. FMEng

    FMEng Well-Known Member Fight Leukemia

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    They are not likely out of calibration, they are just showing different things. The mechanical VU meters have slow ballistics so that they read a quasi-average (RMS) level that more closely represents how loudness is perceived. The LED meters are fast, peak reading meters. Peak audio levels are anywhere from 12 to 20 dB higher than VU level with typical audio that has not been compressed or limited. Consequently, with real audio applied, the LED meters will always read higher than VU meters. If you were to check them using sine wave tone, they would compare quite closely.

    VU meters are the standard for broadcast and, in some cases, recording to get fairly consistent loudness. The LEDs are a good tool for preventing clipping and the resulting distortion. Often, the two are used together as your ML3000 does.

    It is also worth mentioning that there can be LED meters with VU like ballistics, although they would not do that alongside mechanical meters. There are also LED meters that display both VU and peak levels simultaneously. such as the famous Dorrough meters. Those are rare due to their complexity.
     
    chausman, macwhiz, museav and 3 others like this.
  3. macwhiz

    macwhiz Member

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    I didn't think of testing that, I'll check on Saturday or Sunday as we have the big blizzard passing by now
     

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