theodoropoulos
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angle in bridge for intonation control
can any luthier tell me if must i place the bridge in an angle with the centerline of the sound board(or the glue line in other words) and not
perpendicular to it.just look in a les paul and notice the angle i mean..
They do it here to control the intonation,something in ouds cannot be afforded with mechanical tuners.So would this angle help??
[img]http://images.google.gr/imgres?imgurl=http://www.philbrodieband.com/1968GibsonLesPaulCustom01vb.jpg&imgrefurl=http://www.philbrodieband.com/1
968GibsonLesPaulCustom.htm&usg=__NLaVLEktFSfkjnFfHn22shb4SPE=&h=750&w=562&sz=120&hl=el&start=57&sig2=SW4e_YkCJH_9n8GhwTofQ
g&tbnid=FgiHjKoGrOCWYM:&tbnh=141&tbnw=106&prev=/images%3Fq%3Dles%2Bpaul%2Bgibson%26gbv%3D2%26ndsp%3D21%26hl%3Del%26sa%3DN%26start%3D42
&ei=V7okS4mjMKOTjAfmnIDZBw[/img]
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theodoropoulos
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this is the foto...
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Dr. Oud
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the oud has no frets, guitars do, and steel strings need intonation correction due to the higher mass difference of the strings. Intonation on the oud
is done by the position of your finger on the fingeboard. Bridge angle is not an issue.
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oudmaker
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Richard
Manol made it on a sligth angle. And Hadi have critised him doing so to me. I do it on my ouds !! ??
Dincer
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theodoropoulos
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Dr oud i guess you are wrong,and let me explain.There are no frets BUT imagine that there were.The first fret for example of the first string and
the first of the bass string should be exactly at the same position.Well if the bridge has no angle those first frets have a difference in position
and you can hear it by ear,if you want to be EXACT in tune.Otherwise you hear microtunings
i dont know if i am understood. that i mean with intonation...
as far as steel strings you say oud has difference in string masses and that is an issue..
mr Dincer how is that angle you make?In guitar with about the same scale with ouds the angle is about 4 degrees...
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jdowning
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Interesting that in many of the surviving lutes of the 16th to 18th C the front edge of the bridge is not at a right angle to the sound board centre
line but slopes upwards (towards the nut) at the bass side so that the bass strings are slightly shorter than the trebles.
This shortening effect is achieved either by making the bridge wider at the bass side than at the treble (the bottom of the bridge being set at a
right angle to the sound board centre line) or by setting the bridge at an angle to the centre line (or a combination of both).
I have checked my museum drawings of lutes and measured the angle of the front edge of the bridge relative to centre line for either alternative which
range between 1 degree of angle to 3 degrees - the latter being more common on Baroque lutes and with extended neck 'arch lutes' - with up to 14
courses.
The shortening effect can also be achieved on wide fingerboard, multi course (8 to 10) lutes, due to the bridge being centred on the sound board and
the slope of the edge of the fingerboard resulting in the treble top string being longer than the sixth or seventh courses. On a lute, further
adjustment may also be provided by setting the frets at a slight angle (the frets on a lute are made of gut tied on so can be easily shifted around
for fine tuning if necessary).
With modern overspun basses (a type of string that did not come into general use until later in the 18th C) any intonation problem should be
significantly less than for a lute (or oud) strung with plain silk or gut strings so I wonder if Dincer - in setting a bridge at an angle - is harking
back to a more ancient oud building tradition from a time prior to, say, the mid 18th C when the oud would also have been strung with plain gut or
silk strings?
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oudmaker
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I move the bridge 1 mm towards the nut at the location where 6th string hole is. I do it also to give some comfort to the left hand on the upper part
of the fingerboard. Any comments ???
Dincer
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oudmaker
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I forgut to add that my string length is allways 585mm
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oudmaker
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I forgot to add that my string length is always 585mm
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Dr. Oud
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Quote: Originally posted by theodoropoulos  | | Dr oud i guess you are wrong,and let me explain.There are no frets BUT imagine that there were.The first fret for example of the first string and
the first of the bass string should be exactly at the same position.Well if the bridge has no angle those first frets have a difference in position
and you can hear it by ear,if you want to be EXACT in tune....... |
I believe that your finger position will compensate with instructions from your ear for the intonation difference. I don't believe that you can place
every finger in exactly the same distance from the bridge, unless you are a robot 
. Your ear will tell your brain to place your finger where to go. Frets, being fixed, cannot make this adjustment.
Lutes are fretted so the position of the notes across the strings is fixed. Adjustment for one string would cause another to be out of tune, no?
BTW, I have seen one Roufan Nahat oud wih an angled bridge, all the rest are perpendicular.
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jdowning
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For those interested, the attached sketches illustrate the three possible alternatives for angling early lute bridges as described in my previous
post. These may be as shown or combined to produce a slight shortening of the 7th course relative to the first course of between 1 to 2 mm for a
renaissance lute and up to 4mm for a Baroque lute.
Example A shows the angle produced by making the bridge wider at the bass side than the treble by between 1 to 2 mm typically. The bottom edge of the
bridge is set square to the sound board centreline.
Example B shows a bridge of equal width tilted at an angle typically from 2 to 3 degrees giving a relative shortening the 7th course of between 2 to 4
mm. The shortening of the courses that are not stopped on the fingerboard (8 to 13) is of no consequence as those strings are only played 'open'.
Example C is again found on 13 course Baroque lutes where the bridge is centralised and the treble side of the fingerboard is sloped whereas the bass
side is vertical. The bridge is set square to the centreline of the sound board. This arrangement results in the 7th course being shorter than the
1st course by typically between 2 to 4 mm.
Shown here for completeness as it is not an historical possibility for an oud.
Note that not all surviving lutes from the 16th and 17th C have angled bridges. Whether or not they ever did is difficult to determine as most have
been subject to bridge repair or replacement at some period (or worse, modern 'restoration')
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theodoropoulos
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MR Jdowning and mr Dincer we have a problem as i can see .In the photo i sent the angle which is created makes the bass strings LONGER than the
trembles.The schetch MR Jdowning send shows the opposite.The bass stings are shorter.Also mr Dincer from what you say i can understand the the same
happens...
what is the right finally??shorten the bass strings lenght or shorthen??
besides look at this mathematical formula
String frequency equation
The equation for the fundamental frequency of an ideal taut string is:
f = √(TL/m)/2L
where
f is the frequency in Hertz (Hz)
T is the string tension in Newtons (N)
L is the length of the string in meters (m)
m is the mass of the string in kilograms (kg)
√(TL/m) is the square root of T times L divided by m (it is the square root of what is in the parentheses but not including the 2L)
so if we increase the mass of the string what happens to the L??
THE LINK
http://www.school-for-champions.com/science/sound_string_equation.h...
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jdowning
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I interpreted the guitar photo as having a bridge canted - on the bass side - towards the nut!
No matter. The 'Mersenne' string formula applies to a 'perfect' string - but no strings are perfect - particularly bass strings and more particularly
bass strings made from gut or silk. Thicker bass strings must be made more elastic by the way they are constructed in order to sound good. This was
achieved for the early gut/silk strings by their twisted, sometimes rope like construction or by winding a wrapping of silk (or gut?) around a thinner
core - a bit like the modern, metal over-spun strings now in general use.
Also string tension is not usually constant from treble to bass but reduces towards the bass side for both ancient and modern strings.
The proportional reduction in length for the bass string that Dincer refers to is only about 1 mm if I understand him correctly - for modern metal
overspun string applications. For the early gut strung lute, this is a little greater at up to 4 mm. - all very small length reductions where string
length of the top course may be between 585 mm (Dincer's ouds) to say 600 mm up to 900mm for an early lute
I don't know if this reduction in length of a lute bass string was for intonation correction or not (but I suspect that it was) - I am just reporting
my observations on some of the surviving lutes.
Another complicating factor - as far as early lute is concerned (that might also apply to early fretted ouds) is that the fret diameters may be
graduated - thicker at the nut end, thinner at the bridge end (typically 0.9 mm diameter to 0.6 mm diameter).
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jdowning
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As the relative shortening of the bass string relative to treble (1 to 4 mm) has very little impact on the fundamental vibrating frequency of the bass
strings I wonder if a more significant effect of canting the bridge is to introduce an asymmetric stress loading of the sound board to improve
response?
I don't know the answer just curious.
At the other extreme here is a well known example of an early metal strung instrument from the early 17th C where the bass strings are increased
significantly in length relative to the trebles either to improve bass string performance or to increase the relative pitch of the trebles.
This is the Orpharion by Francis Palmer 1617 housed in the Nationalmuseet, Copenhagen, Denmark catalogue CL139. Detailed drawings and a report on the
instrument are available for free download from the museum website.
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theodoropoulos
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well in this instrument we see that frets are also canted to follow the bridge's angle.in other words multi scale fretboard..this is something
different.We talk about something else.in our issue the scale is the same but the lenght of each strings varies alwaysm a little.as i can see we
cannot find an answer.....
as far as the respone you say how do you connect the increase of stress by reducing the string's lenght??i believe the opposite happens.And if that
happens it does not improve responce....i think...violins have more thickness under bass area to improve it.By increasing tense only i dont think this
could pass to the soundboard with greater responce....
i think we got out of our issue..But i see in this lat photo the angle of the bridge is similar to my guitar,different from the scetches.....I am
completely confused......finally what is the correct and why>???????
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Sazi
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Hi Theodoropoulos, I understand your confusion! but I can see that there is a common thread among the majority of instruments with significantly
canted bridges, and that is they are metal strung, if you look at nylon string acoustic guitars, they don't have this compensation as it is really not
necessary, and so should not be necessary on oud ...
maybe...
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theodoropoulos
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| Quote: |
if you look at nylon string acoustic guitars, they don't have this compensation as it is really not necessary, and so should not be necessary on oud
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ΙΝ oud there not only nylon strings.....so ,what's going on?
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norumba
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Its not a matter of metal strings or not, but string thickness/tension, pitch and scale length. Of course you can compensate via fingering with
the left hand, but that's no reason to discount or blow off having an oud with good intonation; if the intonation is set well, the whole instrument
just rings and resonates so much better.
Check your harmonic at where the neck joins the body versus the stopped note at the same location, see if its accurate. If there are any problems,
it's usually that the bass strings might be a little sharp on the stopped note.
Nice advantage of the floating bridge/Iraqi design is you can adjust this , at least somewhat, so I angle my bridge ever so slightly downward
(towards the string tie block) on the bass side to help; it's still not perfect, but its closer than running the bridge perfectly straight across.
Not all ouds may have this issue, depending on their tuning. But for my 7 course oud, running C to f, it's basic sense that the low C wont play in
tune if the intonation is set accurately for the upper courses. But that's generally the widest range you'll find on ouds these days, so other
tunings probably don't need that adjustment.
with the seeming increase in popularity of 7 course floating bridge designs these days, i encourage makers on this forum to may be give a little
thought to this issue 
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theodoropoulos
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| Quote: |
so I angle my bridge ever so slightly downward (towards the string tie block) on the bass side to help
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I think we discussed it before,i agree with you.The photo of the guitar in the beginnig of the thread shows it.But could Mr Dincer tell us why he
angles the bridge opposite from what we agree for?In other words if the bass lenght shortens of gets longer...AND WHY??a mathematical formula could
help...just connecting frequency,tension,lenght and mass of the string..
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jdowning
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You might find some information leading to answers in this paper " A Primer on the History and Technology of Strings" by Eph. Segerman, N.R.I. at
http://www.nrinstruments.demon.co.uk/StrPrim.html
Segerman - a pioneer in the research, technology and manufacture of historical instrument strings - discusses the theory and technology of the various
types of strings - including metal and compound, overspun strings - and the factors that lead to variances from the standard Mersenne-Taylor formula
for calculating the fundamental vibrating frequency of a string.
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