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From: Rob on 27 Dec 2009 00:48 On 26/12/2009 12:51, Rowland McDonnell wrote: > > It is a technical error, these days, to mix the typical audio recording > in a fashion optimized for vinyl discs, In what way is audio recording optimised for vinyl? Do you mean mixing, or some form of filter? I only ask as someone interested in recording *from* vinyl, and asithappens, listening to LPs. Rob
From: J. J. Lodder on 28 Dec 2009 04:29 Rob <patchoulianREMOVE(a)gmail.com> wrote: > On 26/12/2009 12:51, Rowland McDonnell wrote: > > > > > It is a technical error, these days, to mix the typical audio recording > > in a fashion optimized for vinyl discs, > > In what way is audio recording optimised for vinyl? Do you mean mixing, > or some form of filter? I only ask as someone interested in recording > *from* vinyl, and asithappens, listening to LPs. A better way to put it would be that the audio signal to be put on disk is constrained by the limitations of vinyl and PU elements. Jan
From: J. J. Lodder on 28 Dec 2009 04:29 Adrian Tuddenham <adrian(a)poppyrecords.invalid.invalid> wrote: > J. J. Lodder <nospam(a)de-ster.demon.nl> wrote: > > > Adrian Tuddenham <adrian(a)poppyrecords.invalid.invalid> wrote: > > > > > J. J. Lodder <nospam(a)de-ster.demon.nl> wrote: > > > > > > > Rowland McDonnell <real-address-in-sig(a)flur.bltigibbet.invalid> wrote: > > > > > > > > A listen to a classic Decca recording will show the fallacy of all > > > > > those assumptions. > > > > > > > > Try feeding the signals through a low-pass filter, > > > > and see how much S-component you've got left. > > > > But you cleary never tried it. > > > > The pick up elements of those days > > > > just can't handle the large vertical amplitudes. > > > > > > > > BTW, you can even see it with a magifying glass. > > > > The long wavelength wiggles are purely horizontal, > > > > > > During the era of changeover from mono to stereo when both types of > > > record were on sale, Decca produced two completely independent mixes for > > > the two issues. > > > > Yes. Why wouldn't they? > > Some record companies just combined the two channels, with or without > filtering, to produce their mono versions, it was a lot cheaper and > less time-consuming. The proportion of reverberation has to be > different wth mono and that can't be properly controlled by just > knocking the 'S' signal out of a stereo recording, which was why Decca > took the extra trouble to get it right. It was said at the time that there was a difference of philosophy between Decca and Philips. (aka Phonogram) Decca wanted to produce real HiFi, on the best of equipment. Philips wanted to make it sound as well as still possible on the crummy mass market stuff they produced. > > > The limitation on the vertical channel with a grooved medium was more > > > due to the slew rate than to pure amplitude, so it was the high > > > frequencies that were badly affected. The other reasons you give for > > > central bass were more-or-less correct for commercial pop records, but > > > they didn't apply to good quality orchestral recordings. > > > > Disagree. Large low frequency vertical amplitude is a problem. > > See for example > > <http://www.gzcd.cz/en/vinyl/customer-area/production-materials/master-f > > or-vinyl/> points 4 and 5 for the same recommendation. > > That refers to extremely high antiphase amplitudes at 20 c/s, which are > rarely found in orchestral or natural instrumental recordings. (Except > organs in reverberant surroundings) As it happens, when I wrote the previous post I was thinking of the 16' pipes going full blast in the War Requiem. > > In extreme cases the needle may even jump. > > The extreme cases are those resulting from high levels of modulation on > pop records combined with poor playback equipment, they almost never > occur in classical orchestral recordings intended for playback on good > equipment. > > > Other problems at the high frequency end are irrelevant for this point. > > High frequencies are the end of the spectrum where the limitations are > imposed by the inherent geometry of the medium, rather than by > deficiencies in the playback equipment. The vinyl is no longer stiff, and understanding what happens in detail becomes very difficult. .. > > > With really good studio monitor speakers and a proper stereo recording, > > > the 'bass' can appear to be be directional, mostly because the harmonics > > > give the position away. > > > > That's what I said already. > > And (also as I said already) > > it's the reason why a single central subwoofer > > with good satellite speakers works nearly as well. > > (with a crossover well below 400 Hz) > > The problem with that setup on real instruments is that the fundamental > and some harmonics may be below the crossover but other harmonics may be > above it. This 'splurges' the image of the instrument across the stereo > stage. Whilst it can work with some instruments, it might not work with > all of them, so it is an unnecessary limitation of the playback system > (unless space or price constraints oblige you to use a poor quality > set-up, where you must accept those restrictions). It will rarely be noticable under home listening conditions. Even under studio conditons you would need a trained ear and to know just what to listen for to notice it. > On one occasion only, I have selected-out the bass and boosted it to > the opposite channel to move the image of a double-bass nearer to the > centre of the stereo stage. It was done because the instrument had > become damaged before the recording session and was not producing its > fundamental properly - also it was partly hidden behind the piano due to > limitations in the recording studio layout. The process had to be done > very cautiously and only at certain key points in the recording; the > amount of boost was never more than 3dB. This was a jazz band session > with only one bass instrument, I would never contemplated doing that to > an orchestral recording. (Before you ask, the CD is not yet on sale > because I am waiting for the band to arrange a second recording session > to complete it - they might have repaired the double-bass by then.) > > The record producer who is aiming for a good realistic stereo result > will not want all the bass instruments confined to the centre of the > stage. It is much better to spread them out into their natural > positions - or, at least, keep them separate so that they don't just > merge into one droning hubbub. With pop records, the wanted effects are > artificial and the producer may choose different techniques for the > reasons you gave earlier. > > > > > > > (Example: The recent Radio 4 broadcast of the BBC Philharmonic > > > Orchestra playing the "Upstairs-Downstairs" theme showed a very clear > > > stereo image with quite noticeably directional bass.) > > > > > > If the bass is mono and pan-potted, it is usually central, but that is > > > not a proper stereo recording. If a variation on the Blumlein shuffler > > > is used to try to bring the bass into the middle of a genuine > > > one-mic-pair stereo recording, the result can be confusing if the > > > fundamental moves but the harmonics stay put. > > > > Then there are -a lot- of non-proper stereo records on the market, > > Yes. It has never been easier to make good recordings - and there have > never been so many bad recordings made and sold to the public. Agreed, Jan
From: Adrian Tuddenham on 28 Dec 2009 05:50 Rob <patchoulianREMOVE(a)gmail.com> wrote: > On 26/12/2009 12:51, Rowland McDonnell wrote: > > > > > It is a technical error, these days, to mix the typical audio recording > > in a fashion optimized for vinyl discs, > > In what way is audio recording optimised for vinyl? Do you mean mixing, > or some form of filter? I only ask as someone interested in recording > *from* vinyl, and asithappens, listening to LPs. Grooved media have a lot of limitations due to the geometry of the system; the cutting was done with a sharp-edged tool, but the playback tool is rounded and cannot follow exactly the same path. This becomes significant when the dimensions of the modulation become comparable with the dimensions of the groove (high frequencies and/or low surface speed at the centre of the disc). Truncated elliptical styli can reduce this effect - but they show-up other problems and are noisier with worn records. At high frequencies, the curvature of the modulation waveform can approach the radius of the stylus tip, so waveform distortion occurs on playback. Although the harmonics from this process are above human hearing, the intermodulation products between two high frequencies will appear well down in the audio band and are particularly unpleasant. This is also reduced with a truncated elliptical stylus. The cutterhead ran on a parallel tracking mechanism. If you use a pivoted playback arm, the angle of the cartridge can only be the same as the cutterhead angle at one point across the disk surface and there will be unwanted frictional drag effects. There are all sorts of geometrical kludges for minimising this effect, but they really only amount to 'polishing a turd'; the correct solution is to use a parallel playback system. With a truncated elliptical stylus, parallel tracking is particularly important. A large angular error can give a comb-filtering effect on the mono signal because the stylus tip is picking up the waveform at two displaced points on the two groove walls - so cancellation occurs. If your interest is in early L.P.s, be aware that some of these were recorded before the RIAA standards - each manufacturer used a different standard and you will need a pre-amp with selectable characteristics to play them properly (I recently got caught out by a 1950s L.P. which was recorded to the FFRR characteristics which Decca had developed for 78s). When selecting a playback characteristic, look at the Matrix marks in the run-out area to see who cut the master, *not* which label it was issued on. A huge amount of information on the correct playback of discs is contained in Chapters 3,4 & 5 of Peter Copeland's book: http://www.bl.uk/reshelp/findhelprestype/sound/anaudio/analoguesoundrest oration.pdf ....this is an absolute 'must read' for anyone who transfers discs to digital and wants to understand what they are doing. The artistic side of disc cutting is another matter again that would best be answered by an enquiry on <rec.audio.pro> (bearing in mind that only a few of the respondents will have been disc recording engineers and actually know what they are talking about - the rest are just guessing or repeating urban myths). There is the further matter of whether the discs were made with a particular playback system in mind. We have already touched on this, but a lot of that information has gone, along with the retirement and demise of a generation of recording engineers. -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk
From: Adrian Tuddenham on 28 Dec 2009 06:07
J. J. Lodder <nospam(a)de-ster.demon.nl> wrote: > Rob <patchoulianREMOVE(a)gmail.com> wrote: > > > On 26/12/2009 12:51, Rowland McDonnell wrote: > > > > > > > > It is a technical error, these days, to mix the typical audio recording > > > in a fashion optimized for vinyl discs, > > > > In what way is audio recording optimised for vinyl? Do you mean mixing, > > or some form of filter? I only ask as someone interested in recording > > *from* vinyl, and asithappens, listening to LPs. > > A better way to put it would be that the audio signal to be put on disk > is constrained by the limitations of vinyl and PU elements. I would have said "constrained by the limitations of groove geometry and the intended playback equipment". The vinyl itself does impose some limitations, but most of the problems would still occur if they had used "Shellac" (slate dust with shellac binder), "Acetate" (cellulose nitrate), gelatine, wax, rubber, chocolate, thermosetting resins, catalytic resins or any of the hundreds of other materials which have been tried over the past century. -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk |