A good customer with a blues label phoned me yesterday saying that the manufactured CDs were back from the plant and that they sound a little ‘smaller’ than the final approval reference I gave him. He was posting a copy which should arrive today: in the mean time I’ve burnt myself a reference from the original project and plan to null-test the two and see what happens. What degree of nulling should I be seeing if all is well? – I’m thinking 90dB+.
You need to have 100% null! It’s either an exact copy or it’s defective. Now you may have to line up the audio underneath the other as there may be a tiny tiny offset time-wise, but once you have it aligned to the sample you should hear and measure NOTHING.
If you do have a complete null but the pressing seems a bit smaller, then welcome to the world of audio voodoo. At that point I suggest you copy the pressing into your system and cut a copy of it on the same writer that made your ref, then do a comparison. If they match sonically at that point then you can safely say that the plant introduced a bit more “jitter” or whatever other voodoo you wish to ascribe. This is not unusual. It can be an audio illusion or reality, it’s hard to say at that point and you would be in for months of rigorous and hard-to-do blind tests to prove your point. But at that point I would suggest you may need a better D to A converter or CD player because the playback equipment is supposed to correct these issues.
Not to say that I don’t also hear some issues like these, but at this point, the issues are so small with the gear that I have that I just shrug it off and move on to more important things (once the null test was passed). I do find that I can often cut a REF that sounds better than a plant pressing, but by such a small margin that only the pickiest or most nerdy clients ever hear or care about the difference.