Thank you, Alexander, for your long explanation. No arguments here. I thought my puzzle was already solved: direction of plucking influences the start of the sound (attack), hence the marked difference in sound between parallel and perpendicular plucking. The article about technical aspects of the guitar and its tone production kindly brought to our attention by someone else on this list (I forgot who! shame on me) said it quite clearly, too.
David ----- Original Message ----- From: "Alexander Batov" <[EMAIL PROTECTED]> To: <lute@cs.dartmouth.edu> Cc: "LGS-Europe" <[EMAIL PROTECTED]> Sent: Sunday, September 03, 2006 9:13 PM Subject: Re: [LUTE] Re: strings: direction of vibration? > ... after the 'waves of vibration' seem to have subsided ... > > On Saturday, August 26, 2006 8:06 PM David van Ooijen wrote: > >>> Beliefs and convictions ...? Just down to earth physics. > >> ... In my simplified way of looking at the physics' >> world I should think the sound board must vibrate as much as possibe. Up >> and >> down that is. So if we give up and down energy to the string, the string >> will impart that to the sound board. > > In a very simplified way indeed! The only situation that I can think of > when soundboards would really 'obey' us is when they are blown with a > hammer. Otherwise, they've got the mind of their own. > > It may seem paradoxical to you but the very idea of the lute soundboard > construction that it has had evolved to is to minimize such up and down > movements, or at least bring them under control. And for a good reason! > > A typical lute soundboard has a fairly developed transverse barring > structure in front of the bridge and a really clever one behind it, sort > of combination of transverse (j-bar) and 'mixed' (two to four fan bars) > variety. The first of the main transverse bars is set close to the front > of bridge and thus, quite effectively, helps to suppress its side to side > and up and down movements. Fan-bars on the treble end of the bridge act a > step further to stiffening the soundboard in this area and blocking such > movements even more - not for the detriment but the most optimum way of > energy transmission from vibrating string to the soundboard. > > As somebody have already noted earlier, the purpose for the nut and the > bridge is to provide a firm 'resting' or 'nodal' points for a string to > vibrate: the disturbance caused by plucking of the string spreads along > it, reflects from the 'nodal' points at the bridge and nut and forms a > standing wave of vibration. The nut, by default, is a fairly steady > 'nodal' point; the bridge is a point of compromise. It can't be as steady > as the nut (there'll be no sound transmission to the soundboard) but if > it's too limply the vibrating string would start to 'carry it along', in > up and down movements. This may give a louder initial attack to the sound > but it will start dying out rather quickly: the standing wave of vibrating > string will simply dissipate from the lack of a firm 'nodal' point. This > sort of phenomena can be observed on lutes with over-thinned soundboards > or too lightly constructed barring or both. The sound, of the first string > in particular, is rather 'rough', distorted, lacking clarity, not 'defined > in pitch'; the basses are boomy but lacking sustain. > > There is a very clever phrase describing how soundboard parameters affect > the sound (don't remember where I came across this expression and who said > it but it sits in my memory ever since): "Both stiffness and mass impede > the sound, but mass impedes treble more than bass and stiffness impedes > bass more than treble". This is exactly what barring arrangement in the > bridge area of the lute does: fan-bars stiffen the soundboard at the > treble end of the bridge and suppress its up and down movement (by saving > the energy of vibrating string and, at the same time, optimising its > transmission to the soundboard); while the j-bar curving around the bass > end of the bridge gives it more freedom to vibrate in all planes. Such > soundboard / bridge structure as well as its behaviour is further > exemplified by the very idea of resting the little finger either on the > soundboard, in close vicinity of or on the bridge itself. If only the > mechanism of sound production 'relied', to some notable degree, on up and > down movements of the bridge, they would inevitably be blocked by even the > lightest pressure (which would also act as a "mass" in the quotation > above). As for the rocking movements of the bridge though, they largely > remain unaffected even with the little finger rested firmly on it - for > the bridge is a 'nodal' point after all. > > It may well be that this particular barring structure was developed as a > result of trial and error approach at utilising the maximum amount of > vibrating energy from thick gut basses but in the later period (late > 17th - early 18th century), with a possible use of open-wound (demi-file) > or even close-wound bass strings began to be replaced with fan-barring > type of arrangement (I mean in the area below the bridge). Anyway, this is > just a thought ... > > --- > > The baroque guitar soundboard (if constructed in the authentic way, with > just two bars, one above and one below the sound hole) has a noticeably > larger degree of flexibility in the transverse direction (i.e. across the > grain). The nearest transverse bar is much farther than that in the lute; > no j-bar and fan-bars either. So its bridge's side to side and up and down > movements are certainly less constricted than in case with the lute > soundboard. The only way to control the soundboard (and bridge) behaviour > here is mainly through appropriate thicknessing of it. Sufficient amount > of rigidity which would in this case be associated with the presence of a > fair amount of soundboard wood seems to be as a good idea: original > soundboards of baroque guitars which have survived untouched by later > conversions (not many of those unfortunately) are c.3.0mm plus in some > areas. > > And just the last bit: I'm currently restoring a rare mid-18th century > guitar which is attributed to Francisco Sanguino (perhaps even one of the > earliest surviving guitars of this maker, there are six - seven of them in > all). The soundboard and the bridge of this instrument have truly > remarkable 'record' of wear marks on them from which one can almost > re-construct the way it was played: > > With the palm of the right hand perpendicular to the strings, little and > very much possibly ring finger both resting on the bridge, alternating > strokes with i and m fingers, perhaps with nails (two really deep > elongated marks are just next to the edge of the bridge) > > Was this their ideal type of stroke for an optimum sound? With a possible > original string length c.71cm and frighteningly close spacing in-between > individual strings in courses ... quite possibly so! > >> That's where a bridge on which the >> strings rests (guitar) comes into play: a string 'bouning' on a bridge >> will >> give more energy to the sound board than a string 'sliding' on that >> bridge >> . > > I just want to repeat again that there is no principal difference between > the classical / romantic guitar and the lute type of bridge here. And if > strings, as you say, start either 'bouncing' or 'sliding' or both on the > bridge (or rather saddle) then it would be better to take the instrument > to a local maker to fix. > >> But what do I know about physics? Perhaps a plucked string will very >> quickly >> vibrate in all directions alike, so it doesn't matter in what direction >> we >> pluck it initially? Or perhaps the sound board wants to flex in all >> directions, not just up and down? So hence my question. > > I don't know very much either, hence so many words ... > > Alexander Batov > To get on or off this list see list information at http://www.cs.dartmouth.edu/~wbc/lute-admin/index.html
