anyone use them and if so do you think it helps sound as it does for violin and cello?
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anyone use them and if so do you think it helps sound as it does for violin and cello?
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No, a soundpost does not make bowed instruments louder. because it ties the belly and the back together they vibrate in the same direction, there is no "pumping" of air in/out with the back moving the same direction as the belly.
Instead it does 2 things
1: the soundpost braces the trebble side of the belly/soundboard so that it can be thinner and move more. The bass bar on the bass side of the belly is just like a brace on an acoustic guitar soundboard, strengthens it so it can be thinner. without a soundpost a violin/viola/cello/bass is at risk of the string/bridge pressure deforming the belly over time.
2: it acts as a fulcrum. bowed instruments only vibrate the string sideways as the bow drags across the string, the elevated bridge acts as a lever to change that side-to-side string vibration to an up/down vibration on the bass side of the belly with the soundpost acting as the fulcrum.
This is getting tooooo complicated - I always thought "the fulcum" was that complete chunk you finally got coughed up when you inhaled while eating toast !!!! Am I right??? AmI right????
;-) ;-) - I need emoticons!!!
Hi jawbone, It was too complicated before the explanations.
Here's the simple bottom line:
If the string vibrations are continuous [as in a bowed instrument] then the soundpost plays an important role in producing sound.
If the string vibrations are instantaneous [plucked as in a guitar] the soundpost has a dampening effect on sound.
Simple example: plucked notes on a violin produce a lower volume.....remove the sound post and the volume is increased markedly.
Cheers Taff
This sounds very convincing, Taffy, and I'm sure you're right in theory. In practice it seems to be more complicated though and there seem to be other factors than continuous vs. instantaneous vibrations playing into this: I installed a soundpost in my 8 string mandolin and it not only considerably helped with sustain but also with volume. But in my 3 and 4 string guitars I could not replicate that effect. Quite the contrary, the effect was detrimental to sustain and volume. How can this be explained? String vibration is instantaneous on both guitars and mandolin and both have square cigar box bodies, but only in the mandolin the sound post helps... And also: If this is just about continuous vs. instantaneous vibration, why do some archtop guitars have soundposts? Just to support the top?
Hi Hans, as mentioned earlier it is a very complicated subject, and sound physics at this level is not my thing.
Just to clarify, I do not build violins, but have tried to learn as much as I can over the years about it, to help me with repairs and the set up of orchestral stringed instruments.
I try to answer questions on here from my experiences in building and repair, and not google someone else's answers. Having said that I have a crap memory and have refreshed my thoughts prior to responding at times either from my many reference books or, yes, google. Where would we be without google.
So you can see I'm not an expert so I try/have to keep things simple.
To answer your question why you got a better response from your mandolin, for me ,is only guesswork as I don't have the mandolin to evaluate. But this is what comes to mind from my experience.
What I have found in the past with guitars that have a too flexible a top, is that they lack volume and tone. For example if a brace breaks or becomes unglued from the inside of the top. When I reglue or repair the braces, this stiffens the top and it will react better to string vibrations and brings about better volume and a more defined tone. So..........
It could be that with 8 strings on a top that may have been underbraced you may have been getting less than optimum output. By fitting the post you stiffened up the top to get the result as per the guitar story above.
With the 3-4 stringers, they may have been working efficiently to start with and fitting the post had a dampening effect on the top. Three strings trying to move the top and back is a big ask, you have 8 strings doing that job on the mandolin.
Re soundposts in guitars. My dozen's of luthiery books make no mention of them. However I did find some info that suggested to me that they may be there for support or to control the top to limit feedback, by some makers.
As a matter of interest I have posts in the full resonator guitars I build, but I don't call them soundposts as their job is for support.
Just my thoughts. Taff
Thanks, Taff!
That is very likely the explanation. There is some bracing in my mandolin, but probably not enough for the pressure of eight strings - I'm learning a lot here!
Taff nailed it. it adds support, so a too-soft soundboard gets better, and already firm enough one gets too stiff.
Thanx Taff - I was just joking - sometimes it just jumps out - sometimes words just strike me funny - today it was "fulcrum" - probably the same reason that in my shop when I talk to myself I use cartoon voices - makes me seem more interesting !!! If I didn't have my cartoon voices the only person I may talk to is my wife, and she is tired of listening !!!
I need emoticons !!!
I don't know, either, but many of us have sound posts like those in Korrigan's pic built into all or most of our gits. Most of us have a stomach muting the back, also. Maybe I'll try some over-the shoulder, behind-the neck git playin' for comparison. Jimi did it, Stevie did it, Robert Cray does it...you know, a lot of players have done it. Perhaps there is a clue to tonal improvement in there! We'll see.
You can get around the stomach muting with a resonator back, like some banjos have... but you probably knew that, Grandpa..
My vote for acoustic / mechanical amplification is still some sort of stroh / grammaphone type deal...
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