Boombastix wrote:selig wrote: ↑07 Aug 2018
There ARE good reasons IMO to leave some headroom when exporting a mix for mastering - not sure how any of this is a “myth” unless one believes it somehow sounds better with more headroom than less (it doesn’t).
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Back in the days when we put final mixes on DAT we had to avoid harsh digital distortion when recording to DAT tape. So mastering guys said, leave xx dB of head room, but it was mainly to avoid over-driving the DAT tape into digital clipping/distortion. 6dB was the "safe" standard often used.
But nowadays:
My understanding is that mastering studios have quality equipment and the can change the volume in the digital domain to whatever you they want before they apply EQ and so on. For a finished track (digital) that will be converted to analog signal by the user/listener, you may want a small head room for inter sample peaks (ISP), so a -1.5 to -2dB peak can be smart. -2dB is about 0.22V below 0dB just in case the DA converters are of low quality and cannot convert ISP above 0dB. MP3 conversion also needs some head room, about the same. Am I missing something?
In either case, if you mix your master to 24-bit, the noise floor is so low that some head room won't matter, it will sound the same after mastering. I would just keep a 1.5 to 2dB head room as a standard, pre-master mix, or finished master.
My experience:
Going back further in time, mixing to analog meant you CAN go over 0 dB since headroom was built into the metering system. But when moving to digital, there was no built in headroom with the metering system, and we had to totally re-think levels.
Besides the headroom issue, moving from analog to digital meant we were exclusively using peak metering to set mix levels. With analog, we had peak LEDs on some meters to show peaks, but metering was largely VU based.
This move from analog to digital necessitated the workflow change of building in our own headroom when mixing to digital sources. At that early point, it had little to do with mastering engineers IIRC, though I’m sure they were seeing the same thing we were seeing. It was simply obvious we needed keep the concept of headroom from the analog world as we moved into the digital world.
16 bit DAT mixing had it’s own issues, one being the analog stage of cheeper DAT recorders potentially distorting BEFORE the signals even reached digital clipping. In the digital domain, all clipping is pretty much the same - 16 bit clipping is no different from 24 bit clipping. This had nothing to do with “overdriving the DAT tape into clipping/distortion, since tape doesn’t distort digital signals! It’s the A/D we’re talking about here, same as with any digital recording medium from tape to optical disc to magnetic or solid state disc.
Finally, there’s a difference between a pre-master mix and a final master, with regards to headroom. The topic here pertains to pre-master levels, so I’ll stick to that. With 16 bit sources one could argue the need to “kiss the reds” to retain dynamic range. But as you note, with 24 bit systems, there’s no need to do so.
And as I’ve mentioned elsewhere, in some cases your mix levels are not 100% repeatable from pass to pass, considering random elements such as algorithmic reverbs and non-synced LFO FX. The levels may not vary by much from pass to pass, but if you’re trying to avoid all clipping while mixing to 24 bit, and we’re talking about pre-master levels, there’s no advantage to spending the extra time (and risk of clipping) to push for that extra dB or two.
I instead just relax and enjoy mixing, and am happy when my levels are anywhere above -6 dBFS but below -2 to -3 dBFS. Which happens to be where my mastering engineer still requests my mix levels to sit, FWIW.
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