Do tracks have to be specially mastered for transfer to vinyl? If so then what are the frequencies in the spectrum to pay special attention to? I had four tracks transferred to vinyl and told the pressing plant to do any necessary EQ'ing required. I got the test pressings back and found them to be very harsh in the upper frequencies when compared to my CD master. Should I get my tracks professionally mastered for vinyl next time?
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Technical Editor Hugh Robjohns replies: Mastering for vinyl is, like all mastering, a combination of art and science which takes a lot of experience to do well. If your budget allows, I would certainly recommend going to a mastering/cutting house with a proven track record in vinyl production.
I can, however, suggest a couple of issues to consider when preparing material for vinyl. Wide stereo width at low frequencies causes vertical movement in the groove and can result in the needle skipping or the record being unplayable. So it's a good idea to reduce the width of low frequencies to close to mono. Avoid stereo flangers on bass guitars or stereo chorus effects on keyboard bass lines, for example!
Another important point is that the record groove is not cut with a flat frequency response. In sounds generally, there is far more bass energy than high-frequency energy, and to optimise the signal-to-noise ratio of a record, as well as to maximise the amount of time a side can play for, the cutting signal is processed with a large amount of pre-emphasis. In other words, the low frequencies are reduced and high frequencies increased on cutting, and the RIAA (Recording Industry Association of America) standardised EQ curve used in the phono preamp (see diagram) restores the bass and reduces the treble, achieving a flat overall frequency response on replay.
What this means in practice is that if there is a lot of high-frequency energy in the original recording (as there tends to be in dance music, for example), the record cutter protection limiters can be activated, and this can often result in the kind of harsh sound you have referred to. A good mastering engineer will optimise the EQ, high-frequency compression/limiting and overall levels to keep the sound the way you want it while maximising the level of the cut.
Without the training and experience to know how much EQ and dynamic control is required, it's very hard to second-guess this kind of thing when mixing your track at home. So, yes, I would head to a professional mastering engineer with a proven track record. When looking for someone suitable, ask to hear examples (off vinyl, naturally) of material similar to your own music that he or she has cut.