Pianotech

In a recent discussion in Pianotech on the new Renner KMD device, (Re: KMD Renner Key Measuring Device Comparison to tradional (sic) method) the discussion of methods and spreadsheets came up with respect to the process of establishing proper touchweight specs. Please refer to that discussion for context. 

I decided to share my touchweight spreadsheet that can be used to achieve proper and targeted levels of inertia as well as creating both smooth FW and SW curves from sample data.  The process as outlined is designed to produce a SW curve that matches the existing action ratio using a preset FW and a BW target to assure that inertia is properly controlled.  It is accepted science that the primary driver of inertia is the relationship between the SW and the AR and this method is designed to establish that relationship.  Of course, different situations may call for different approaches, but the method is easily modified to use for any situation, from simply replacing a set of hammerheads to changing all the parts in an action.  Your own tastes, or your customer's, may call for different targets but the system allows for easy modification to accommodate those differences.  It's really quite simple and a study of the attached Excel spreadsheet will show just how it's done. 

While the attachment is protected (meaning you can't change cell information) you can study it and duplicate if it if you wish. If you don't know how to do that and would like to purchase the spreadsheet along with some guidance from me on how to use it, contact me privately.  There is a fee, quite reasonable, that accounts for the work in preparing it and any guidance I'm able to offer.  

I've used this or something like this for several decades but have now simplified the method to make it easier to use.  Feel free to ask questions here in this forum.

The touchweight arena seems to be one that has been couched in secrecy and magic and plagued by various, sometimes cumbersome practices often requiring multiple measurements of levers, inputs and outputs, or the weight of several individual components, or charting SW curves manually, with people often disagreeing on just how those measurements should be taken. This simplifies the process considerably. 

Good night and good luck.   

NB: I had planned to present and explain this in a journal article and still might do that but still working on it.  Maybe this precludes it.  Thanks Scott Cole for your patience. 

PS (Edit): My apologies if people are reading this as my disparaging of any other methods.  That's not my intent.  My intent is to offer a simplified and alternative method for determining these relationships and values, that's all.  I trust people will continue to use the methods and practices that work for them and that they are most comfortable with.  

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David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
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Attachment(s)

Touchweight Calculation Sheet for Distribution PTG attach...xlsx   79 KB 1 version

This discussion is getting away from KMD evaluation. However I would like to comment on David Love's lovely excel program.  I'm compelled to overlay onto his strike weight graph my reference scales as qualified by decades of empirical studies of pianos from the late romantic era to present day and published in the March 2000 PTJournal.  It's not at all to say anyone should conform their SW scales to the reference scale standards.  They simply offer a frame of reference.  Without them its hard to look at a graph and draw any particular conclusion about weight quality. In my judgement I feel his particular example is just fine for typical home or studio use.   Too light for concert halls. As for expected inertial/dynamic playing quality, I would rate his design in this particular example as on the light side of medium at C4.  I come to this conclusion by referring to my empirically derived touch design selection guide as published in the October 2023 PTJournal and updated in the EuroPiano Journal #1 2024  https://www.stanwoodpiano.com/Europiano_2024_03_Stanwood.pdf

  Attached is Love's strike weight chart with reference scale overlay. 

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David Stanwood
stanwoodpiano.com
stanwood@tiac.net
508-693-1583
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Attachment(s)

LoveSW-StanwoodOverlay.pdf   1.08 MB 1 version

Thank you double DD's. DL, I did manage to create your spreadsheet from the Reno Class but can use this one for comparison.

Oops!  I thought we were still on KMD subject line.   David S

Yes, this is a departure from the KMD thread though the KMD is very useful for this method.

Keep in mind, this example isn't a "design" or recommendation, it's just a sampling from a set of hammers bored and tapered out of the box for purposes of illustration of how to use the spreadsheet. I think it was a set of Premium Blue hammers Gr4 with a modest taper. 

Of course, choices can be made about the SW curve levels for whatever the purpose. It might be noted, however, that early 20th century Steinway Ds that played concert halls, including concerto work, had pretty light hammers on them, and accompanying low ARs, as did Horowitz's piano.  I would probably argue that a concert grand doesn't necessarily needs concert level hammers as indicated in your charts.  It might, but it might not.  Much depends on the SB impedance characteristics, those can vary.   

However, it might be noted that my SW zones are a little different than yours, as is my FW maximum chart.  They are mostly just a reference point.  In fact, on the SW curves I don't necessarily target that particular shape.  Some sets come out of the box with a much more straight-line curve (no, that's not a contradiction in terms) and in that case I don't necessarily alter that just to achieve a theoretical shape. That being said, tonal considerations, as well as the graduated inertia levels, are not unimportant in that choice.

On the FW max, we start at about the same place but I have boosted the upper end maximum by a fair amount and, arguably, the FW max at the upper end of the piano is less important.  Won't go into the why of that now but I can if people are interested in my thoughts on the matter.

Thanks for weighing in and appreciate the complements on the chart.  I hope folks will find it useful for their own purposes.  

DL, I just looked at your posted spreadsheet and it give a nice simplified perspective.

Several people have PM'd me with questions so I have produced this set of FAQs. See attachment.  

Attachment(s)

FAQs Touchweight Spreadsheet.pdf   34 KB 1 version