Violin Forum/Message Board

[jethro]

I test plyed my just finnished #2 son about 2 weeks ago. Played fine but way loud and proj. at bridge too high... all most didn't have enough bridge blank. Removed FB, planed about 1 mm off bridge end of neck and
tapered back the other way to zero. Also took a little off of underside of FS since it got a little thicker towards the bridge anyway.
All back together now and bridge height looks more nominal.
I have tried the first 2 bridges I cut and just lowered the top edge and
re-thicknessed the from the heart upward to what looked reasonable.
However..... Since when I cut these before the modification, I had to leave
the feet and ankles as long as possible to have enough bridge material.
So the current bridge now has relatively long ankles and shorter top
section (above the heart) .
I have noticed that when I play it - especially on D and A but also on
G and E--- when I bow VERY gentely wit allmost no pressure the strings
WANT to play a very high harmonic- not the string fund. pitch. If I push
down a little harder the pressure seems to override thesuper high part
and I get some fundimental. But still eeven then I can hear the higher
harmonics making the notes sound really "dirty" - or some kind of unpleasany quality. It didn't do this before I modified the neck and FB.

I am thinking this is a bridge problem- like the bridge frequency is way high and so it is supressing the fundimentals and increaseing the
gain (electrical word !) of the really high frequencys . ( when I play A
string lightly I get A5 as output)

Could this be the situation of having legs too long and rejion above heart
too short ? If I cut a new bridge I NOW would cut the feet upward untill
I was allmost out of foot and then trim the upper down to give proper
string clearance. (before I sanded the feet bottoms - removing as little as possible and then cut the top of the feet downward to to meet.- lleaving long ankles.

Any thoughts? should I just do a new bridge and see what happens ?????

Tim

[KenN]

I had the same thing with my number one where it would jump an octave if I played with low pressure. It's not playable right now, so I can't do anything with it. Haven't figured out what causes that. Is it normal? I know woodwinds with conical bores (oboes, saxophones etc) will do that. The 2nd frequency is mode is larger and overrides when the volume goes down. I even checked a guitar once on a fft program and it said the high E string was a B! For some reason the fifth was stronger.
High frequency harshness sounds like it could be a bridge thing. It's my understanding that the bridge is the equivilent of a frequency cutoff. Much is known about woodwind frequency cutoff, the hole size, thickness and spacing determine that, and there are formulas and everything.
I've never seen any formulas for bridges! Play it on a computer analysis progam and see where the frequencies roll off. They should start dropping off at 3000-5000 or so. Put another bridge on and check it too. Thin one of them down and try it again. Keep trying until the problem is gone. Tell us what worked.

[jethro]

High Ken and all.... Just wrote a lengthly explanation but Wonderfull
Netzero decided to disconnect me about 10 secconds before I hit "submit"
so you get the short version !!!!!

I tried about 5 bridges-all different. No change.
Noticed earlier sound post rotated when being set.
Maybe post not making full contact across it's end surfaces.
Made new post - used new method to cut end angles to more closely match plate inclines. Put in new post- restrung--- slapped on a random junk bridge....... Problem about 95 % gone the first draw of bow.
I think It will subside more in the next few days as dampness of post
evaporates and conforms more from pressure.

Ken --- maybe this will fix your problem too !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Is there a precice way to make sure post ends are EXACTLY conforming
to plate surface contours ????????

I will tell you how I did it tomorrow. (NZ will cut me off if I type more! )

Tim

[KenN]

That could be it. I need to play around with the neck and fingerbord first, but I did have the soundpost in very loose. It was about 4 mm to the center from the end of the bridge. Maybe the octave jump is a symptom of a bad soundpost.

[Jack H.]

Jethro,
The finger board projection should be 27 mm at the mensur ( run a straight edge down the middle of the fingerboard overhanging the mensur adn then another ruler upwards from the table at the mensur. you should be reading 27mm, anything else will have an adverse effect on the sound of the instrument.
A bridge should be between 31 and 33 mm high. with proper string height. Maximum wood should be removed off the bottom of the feet before fitting so as not to leave the ankles too long. The only removal of the wood at the ankles should be to even out the thickness, not to remove a lot of the wood if it was left before fitting. On a new instrument I leave the bridge a little thick, 4.2-4.5mm at the feet adn 1.3 at the top.
it is always easier to remove a bit here and there to fine tune it than it is to cut a new bridge.

the problems you are experiencing could be from the long ankles and the small space above the heart, or it could be many other things as a recent post about an 8 year old violin shows...
hard to tell untill you do everythign to the proper measurements to help figure it all out. I have no idea about the fundamentals of the bridge frequency. them words sound too new fangled for me.

Get the measurements right for the fb projection and then cut a nice new good qulity bridge adn let us know what happens.

[Jack H.]

[Michael Darnton]

Jethro, your lack of precision in regards to describing the neck set is a clue that the neck set is still not right.

[jessupe goldastini]

jethro

1. buy a neck jig...this will help with achiving proper angle everytime, which will translate to a "rutine" when setting the bridge up...

dual tone, harmonic waiver, enharmonic disruption are usually caused by a sound post not in well, either location, contact or grain direction....

the right foot of the bridge will marry with the soundpost and thus the plates....when the string vibrates it will start the left foot pumping up and down on the plate, thus making the sound we hear, when other tones are heard besides the string it is generally caused by bad contact somewhere and thus allowing for "bounce back" or cross vibration which will deaden sound or "add" another undesired tone ie. you hear the string being played and the post "buzzing" like a "reed" against one of the plates, as they sound together they create a waiver as generally they are not harmonically sync'd....ie. for example, sound an A string and then add 1 5/8 step above that, gennerally not a pleasant sound,

i have named this acoustical phenomonon..."mousefarting"

[jethro]

JackH. ---- Yes the first post was crap I think !
I marked the post location on front and back plates. I put a steel
combination square/protractor tangent to the marked spots and read
off angles for the top and bottom (assuming the outside of plates are
paralell to insides) I got about 97 degrees. I then cut a block on the bandsaw at this angle and glued on sandpaper. Used this to establish
correct angle on ends of post. Gradualy nibbled it back about .010 in
with this sanding block till it was about in the middle of the foot. It felt
way better -I could tell - when I set it. I think It's pretty close on the contours..... probably better than I could see through the end hole-
(which seems like I couldn't doo very precicely...) The octive problem
was way better but not completely gone. I then cut a new bridge from scratch. I think the rest of the octive problem MAY subside. I do notice
a slight resistance as I bow .. like the tone doesn't come out quite free
enough yet. The ankles are pretty thick yet. I will be making small
bridge adjustments to see if the resistance problem improves. After I put the new post in I just throw on an old bridge to see what happened.
I knew I was going to make a new one the next day anyway!

AFTER the neck adjustment my bridge is about 33-34 mm high at it's peak.

Michael : I think I have some kind of problem that I am somehow
getting my necks a little too steep. I have to carefully examine this
when I fit the next neck !!!!!!!!!!!!!

Does the exterior angle measurement/ sanding block technique sound precice enough ?
I don't have confidence in my ability to see the angles when the post is in
place.......

Will give updates as I adjust and test !

Thanks for the help Yall !

Tim