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High powered sealed sub + room eq.

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  • #46
    Thanks for the information guys!


    • #47
      Originally posted by camplo View Post
      ... The average playback level in a club is 116db. Though I know and entertain the philosophy, there are other philosophies that suggest something like 86-87db to be the best mix volume. ...
      Note that dBFS, deci-Bell Full Scale, is commonly used in reference to signal level in the digital domain. Per SMPTE RP155 standard, 0_dBFS in the digital domain corresponds to +24_dBu signal level in the analog domain and +20_dB on a VU meter, and -20_dBFS is an alignment level in the digital domain which corresponds to +4_dBu analog signal level which corresponds to 0_dB on the VU meter. For easier reading in this post below, I take the liberty of converting everything to dBFS. (for Europeans reading this, the EBU R86 has analog signal levels 6_dB lower than SMPTE levels for same digital signal levels, uses -18_dBFS digital alignment level to correspond to 0_dBu analog signal level, and with 0_dBFS corresponding to +18_dBu).

      Monitor level used during mastering...

      In the early 1970s, optimizing for high quality relative to that era, using all analog signal chain and using multitrack magnetic tape as the recording medium and using vinyl LP record pressings as the primary retail distribution medium, the subject matter expert Ioan Allen of Dolby Labs recommended a mastering monitor level of 86_dB at -20_dBFS summed with uncorrelated phase, 10*log(x), at the listening position as propagated from a stereo pair of monitors, which is 83_dB at -20_dBFS at the listening position from each of the two monitors measured individually. That included consideration of s/n ratio of the recording and playback signal chain on high quality gear, the dynamic range and saturation characteristics of magnetic tape, and dynamic range limitations of vinyl LP playback, etc.

      Note that with spherical propagation from a point source there is -6_dB change in SPL with each doubling of distance from the point source, -20*log(x), so for example the SPL at 4 meters distance is -12_dB relative to a reference level at 1 meter distance.

      In the mid-2000s Dolby Labs issued a white paper on mastering music on 5.1 multichannel digital recordings. That whitepaper also included recommendations for conventional 2.0 channel recordings. In that, regardless the number of monitors, Dolby Labs recommended an uncorrelated sum of 85_dB at -20_dBFS at the listening position, which is 82_dB at -20_dBFS at the listening position from each of two monitors measured individually. They further recommended that the loudspeakers should be capable of providing linear behavior to at least +3_dB headroom above 0_dBFS, and the amplifiers and upstream analog signal chain including the analog portion of the DA converters should be capable of providing linear behavior to at least +6_dB headroom above 0_dBFS.

      Note that in theory a peak centered between 0_dBFS samples at a frequency that is onehalf of the sample rate would slightly exceed +4_dB above 0_dBFS, however for good quality results it is necessary to low pass filter the audio to place coherent audio well below the noisefloor at a frequency that is half of the sample rate, and practicable low pass filters have a corner further below that, so a maximum peak would not likely exceed +3_dB above 0_dBFS. Only the tweeter would experience that higher peak at the upper end of its passband on very brief crests. Any electronics upstream of the tweeter would need to swing that voltage unclipped for best quality.

      For mastering high quality music, Bob Katz echos Ioan Allen's 1970s recommendations mentioned above, and that is "K20" on Katz's scale, 86_dB at -20_dBFS at the listening position, summed uncorrelated. For pop-music and film soundtracks, Katz recommends "K14", 86_dB at -14_dBFS. K14 requires more dynamic range compression than K20, as maximum crests in K14 are 6_dB lower than the maximum crests in K20.
      Last edited by JRT; 03-03-2019, 09:21 AM.
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