SW heresy?

[Richard Brekne]

Sarah Fox wrote:

> Hi all,
>  
> ...
> I was advised off list that I shouldn't force the hammers to 
> artificially conform to a standardized Stanwood curve but to simply 
> even out the jags to make the action smooth from bottom to top.  
> There's something to be said for this idea.

Sure there is... its easier, and it provides the most important aspect 
of Stanwoods whole philosophy IMHO... even strike weights.  No hops or 
jumps. The entire remaining bulk of why to choose any particular Strike 
Weight curve remains largely a subjective matter still up for discussion 
in most regards. But I dont personally see any real room for argument as 
to whether or not evening out Strike Weights has a very benificial 
effect on the touch of the action.

>  
> But as I got to thinking about the SW curves, I was wondering, where 
> do they REALLY come from?


As far as I know these are the result of two things basically.  First... 
Stannwood simply took measurements from a few thousand pianos in order 
to gather enough data by which to arrive at some basic statisical 
quantities like <<average>> <<mean>> and the like for use in 
establishing tendancies.   Then two... they are the natural result of 
how he implements his SW or balance weight formula.  Remember there are 
a few givens in that formula when solving for SWs.  You have to settle 
on a BW,  WW, KR, and SWR.  The only things left are FW and SW.  The 
curve you select for one of these affects the shape of the curve for the 
other of course... and if you dink around with a spread sheet I have 
that Mark and I (mostly Mark) worked on a while back, you can see this 
in action.  In the end tho... Stanwoods particular curve shape is 
somewhat a subjective choice me thinks... tho he may say different.  He 
can and from time to time does provide custom curves for given 
situations that are not quite this same shape. Steinways own default 
curve is somewhat flatter btw.


> Contrast this function with other functions that might actually relate 
> to optimal hammer mass:  String length and mass both decrease with the 
> note number, with a function that is concave upwards.  Note frequency 
> increases with a function that is concave upwards.  Note period 
> (inverse of frequency) increases with a function that is concave 
> upwards.  The Stanwood curve seems rather meaningless with regard to 
> any of these functions.  For instance, it might be good to match 
> hammer mass to string mass by some proportion.  Right?  As the scale 
> goes up, string length and mass approach an asymptote of zero.  
> Therefore, shouldn't hammer mass approach an asymptote of zero?  
> Instead, the curve starts taking a dive in the treble.  If the scale 
> went up well past 88, hammer mass would eventually crash to zero.  
> Because these curves do not have the same form, the relationship 
> between hammer and string mass is anything but constant.  That doesn't 
> make sense.

To my knowledge no one has actually approached hammer weighting this 
way, at least not from a mathmatical models point of veiw.  I wouldnt be 
suprised  tho that Steinway has rather fallen into their selected curve 
shape from a trial and error perspective.... listening to different 
configurations over time.  The issue of hammer weight has been discussed 
and debated for a very long time.  Tho many insist that it is the actual 
weight/mass of the hammer head itself that is important, and that the SW 
is a meaningless quantity with regards to piano sound. Some also claim 
that the addition of lead is a big no no exactly because of the effect 
lead mass has on the sound and because of how it displaces the center of 
gravity for the leaded hammer.  The effect of lead in a hammer on sound 
is a claim I personally find difficult to swallow... but  who knows ?



>  
> So is this something that is the way it is just because of tradition 
> -- because the cauls are built that way, and that's what ya' get?

It seems reasonable to assume that the chosen manufactured shape of a 
set of hammers would directly affect the basic shape of the curve.  
Cutting of hammer sets into individual hammers no doubt accounts for 
some of the spikes... as does variations in wood density... and probably 
a lot of other things I havent really thought about.

>  
> Now that I look at my linear SW curve (with jags), I'm wondering if 
> this isn't REALLY a closer match to something meaningful (like string 
> mass) than the idealized Stanwood curves.  Any thoughts, y'all?


I think Sarah, that the most important thing here is that the SW curve 
you select remains very evenly graduated, is within reason with respect 
to what kind of mass levels you need in the keys to counter balance for 
your desired BW and given SWR (Balance Weight Ratio).

>  
> Peace,
> Sarah
>  

Cheers
RicB