No downbearing ? REVISITED

[Ron Nossaman]

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>>As has been explained, downbearing is to compress the board to raise it's=
=20
>>impedance to meet the requirements of the string scale. It isn't to=20
>>enhance the coupling between the string and the bridge surface. The=20
>>bridge pins do that quite nicely.
>
>What you appear to be saying is that, no matter whether there is positive,=
=20
>zero, or negative angle at the front "bearing point edge"(Wapin),  the=20
>transmission of energy from string to bridge to board is unaffected.

I have no idea what the Wapin patent says, nor particularly care in this=20
discussion. What I said, and what I meant is that bridge pins installed in=
=20
a conventional manner will clamp the string to the bridge top quite=20
adequately without positive downbearing. I did not say "unaffected", as=20
there may well be some measurable differences.


>Do you think there might be any difference in vibrational mode and=20
>transmission performance  between a string which, due to positive=20
>downbearing, terminates in both the semi-vertical pin plane, as well as=20
>the horizontal "bearing point edge" plane verses a string which, due to=20
>negative front bearing, has minimal or no contact with the horizontal=20
>"bearing point edge"?  Actually, with regard to Negative front bearing,=20
>another question might be about the difference in impact between the=20
>Potential Phase, where the direction of the force upon the pin is upward,=
=20
>not down, and the  Equalizing Phase, where the string has begun to ride up=
=20
>the bridge pin, reducing the upward force, but, at the same time,=20
>eliminating contact with the "bearing point edge".

Beats me, but I don't see any possibility of a string riding up a bridge=20
pin unless the pin is near vertical, and the bearing is negative. Bridge=20
pins set at a 20=B0 slant, with a 10=B0 offset angle will hold a string to a=
=20
bridge top even with some negative bearing.


>>There is no magic energy transfer inherent in the bridge to string=20
>>interface that the bridge pins don't adequately supply.
>
>Can I take this to mean then that, apart from the impedance-producing=20
>function of downbearing, a string could traverse the bridge at some=20
>distance above its surface, coupled by the bridge pins, without adversely=
=20
>impacting upon the transmission of vibrational energy to the board?

Not with conventional bridge pinning. Please clarify.


>>I have used a Lowell gauge for many years.  My Lowell gauge has gotten me=
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>>in deep s.... with a few manufacturers and dealers over the years.=20
>>Without it, I would probably never been aware enough to even raise these=
=20
>>questions in the first place, so, go blame Tom.  The fact is however,=20
>>that the gauge, when used as directed in the instructions, does not give=
=20
>>an entirely accurate image of the configuration. The ideas I have about=20
>>this are either already a part of common wisdom, or not.  I'll save them=
=20
>>for a different forum, unless they prove to be entirely relevant.

Considering the difficulty in getting to what you're asking, and presuming=
=20
you are asking within this framework of ideas you have, I'd say that=20
without giving us some idea of what you're thinking, you won't get an=20
answer you're looking for except by accident. What doesn't the gage tell=20
you that you need to know? Maybe we can help clarify.


>>Even then, the numbers obtained are meaningful only in the context of=20
>>remaining soundboard crown,
>
>I'm not sure I see why things become so relative?  If I am measuring zero=
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>or negative downbearing, I don't see that it matters whether I have crown=
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>or no crown for the purpose of examining the coupling mechanics.  Again, I=
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>am not addressing the question of the proper amount of downbearing for a=20
>given impedance result for a given board, except and unless you were able=
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>to answer a previous question, which was, how local the impedance=20
>function, or, how large an area of non-compression (zero/neg) would you=20
>have to have before you would expect to perceive tonal degradation?

Ah, I think I begin to understand. Things are so relative because we are=20
working within a rather complicated system of interactions, rather than a=20
series of discrete conditions easily isolated from the rest for study. A=20
fine and well crowned soundboard with no bearing on it will probably sound=
=20
pretty thin and awful. That's not because of the string to bridge=20
interface. It's because of the lack of bearing in a board that is capable=20
of carrying it. Compress that board, raise it's impedance, and the tone=20
will improve - but not because of the string to bridge interface, but=20
rather the improved impedance match. A flat board with a lot of bearing may=
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still sound just fine, because even though there is no measurable crown, it=
=20
is still supporting the bearing and providing an adequate impedance match.=
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When you find a flat board with zero or negative bearing, it probably not=20
only sounds terrible, but doesn't have much to offer in increased impedance=
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by adding bearing. Just measuring bearing doesn't tell you half of what you=
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need to know to evaluate the system or it's potential.



>>>Are there any builders or rebuilders out there who would, with no=20
>>>hesitation, put out a product which had zero or negative downbearing?
>Ron N
>>With an existing soundboard, no.
>
>Okay.  This addresses the reality.
>
>>  With a soundboard I had (successfully) designed to work with zero or=20
>> negative bearing, of course.
>
>This is theoretical.

No, it isn't. It's directly to the point of the question, because if the=20
soundboard wasn't designed for zero to negative bearing, I surely wouldn't=
=20
accept anyone's assurances that zero to negative bearing measured in the=20
piano wasn't a problem.

Ron N

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