From: Martyn Hodgson <[email protected]> To: Martin Shepherd <[email protected]> Sent: Friday, 1 August 2014, 10:40 Subject: Re: [LUTE] Re: Lute Bridge vs Guitar Bridge Functioning Dear Martin, Thanks for this. I mentioned string slide in the context of modern guitar bridges with a straight top to the saddle (ie no notches). The notches on the nut of a lute (and modern guitar) avoid the problem of such slide (provided they're not made too wide of course). As you'll know, citterns (like some modern guitars) do generally have a 'zero' fret just before the nut but since the maximum amplitude of the pluck is at closer to the bridge end the displacement (slide) at the nut is minimal. regards Martyn __________________________________________________________________
From: Martin Shepherd <[email protected]> To: Martyn Hodgson <[email protected]> Sent: Friday, 1 August 2014, 8:11 Subject: Re: [LUTE] Re: Lute Bridge vs Guitar Bridge Functioning Dear Martyn, Thanks for this clear explanation. It seems there must be a tradeoff between bridge height and mass, in the sense that a higher bridge would presumably increase the volume of sound but the greater mass would decrease it. I've often wondered about the issue of bridge flexibility, entertaining suspicions that a bridge which is too stiff may have a damping effect, but this is only intuitive. I'm interested that you raise the issue of string slide - it occurs to me that this can't happen at the nut on a lute because of the extreme angle of the pegbox, but could happen on baroque guitar/vihuela nuts and theorbo lower nuts? Best wishes, Martin On 01/08/2014 08:29, Martyn Hodgson wrote: > In fact both lute and guitar bridges function in the same way. In > short, a horizontal force (imposed by the string) is momentarily > increased when the string is displaced (plucked); this in turn > increases the turning moment of the bridge (ie force x height of string > above belly at take-off point) which in turn causes the belly to > vibrate with mostly a wave action (tho' some vertical pumping action > too) and thus amplifying the sound by varying the air pressure within > the soundbox. Whether the vibrating string leads from a loop (lute) or > from over a saddle (later guitars) is immaterial - it is the height of > the string at take-off which is relevant. Vibration patterns have, in > fact, been studied: eg the Galpin Society Journal (Hellwig I recall) > which contains relevant papers. > Differences in timbre between instruments may well be due to many other > factors rather than the way the physics of the bridge works, including: > mass of bridge (size and density), surface area of base of bridge, > stiffness of bridge, barring, internal shape of soundbox and its > volume, etc. > An illustrative example: many years ago I made a 5 course guitar after > Sellas and fitted an ebony bridge (thinking the original had one). The > sound was quiet and muffled (tho' with considerable sustain). I had a > rethink and after further investigation decided to remove it and fit a > fruitwood (actually pear) black stained bridge to precisely the same > design: the resulting sound was considerably freer and increased the > output ie volume. In fact the much greater mass of the ebony bridge was > acting as a considerable dampener requiring more of the vibrational > energy of the string to set it in motion than that of the fruitwood > bridge which had a mass less than half that of the ebony. On the other > hand, the ebony bridge's greater mass meant that it had more inertia > and thus continued to oscillate for longer than the fruitwood bridge - > thus giving the greater (if much quieter) sustain. > MH > PS Incidentally, drilling the string holes low down on a modern guitar > bridge does not increase the string tension/force and hence the turning > moment of the string at the bridge (and it could not be otherwise, > since for a given string the pitch is simply a function of transverse > force/string tension) but does increase the resultant vector > downbearing on the saddle which avoids excessive frictional string > slide (and hence loss of energy ie output) across the saddle. The > discrete loop take-off point used on lutes and early guitars avoids > this problem. > __________________________________________________________________ > > -- To get on or off this list see list information at http://www.cs.dartmouth.edu/~wbc/lute-admin/index.html
