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Great results not following the impedance theory.

  • 1.  Great results not following the impedance theory.

    Posted 12-01-2021 21:43
    I post this NOT to be snarky or as a calling out of others, but to further the conversation for positive advancement. I was concerned about some of the past postings regarding impedance mismatching. Since my theories are somewhat opposite in nature, as mine is empirically based rather than theoretical based. My theory was to make a soundboard as light in weight as is structurally possible, and to apply a light downbearing load so that less energy is wasted getting the mass to move. Essentially energy efficiency.
    Attached is a link to a video i just posted on my youtube channel of a pianist coming to my shop and playing on a Baldwin SD6 i just rebuilt. The soundboard is 5lbs lighter than the original was. The hammers i used are Renner Blue Points. So if there was going to be an impedance concern, this was it.

    There was no soundboard impedance issues perceived whatsoever by me or the pianist. No barking, loud, or obnoxious wolf tones. No under power or over power. By going "light in weight" only resulted in a fully responsive, singing, and full dynamic range piano.
    So what better test than asking a competent pianist to put the piano through the lightest and heaviest pieces in the repertoire?
    And getting real time feedback?  Besides its always interesting and educational the dialog that can happen between Pianist and Technician
    Anyways, I hope you'all enjoy the video.
    -chris
    https://www.youtube.com/watch?v=QFC7pOCDWho

    ------------------------------
    Chernobieff Piano Restorations
    "Where Tone is Key"
    chernobieffpiano.com
    grandpianoman@protonmail.com
    Lenoir City, TN
    865-986-7720
    ------------------------------


  • 2.  RE: Great results not following the impedance theory.

    Member
    Posted 12-02-2021 10:13
    Chris,

    Excellent voicing on this Baldwin, nice work!

    Ian

    ------------------------------
    Ian Graham
    Piano Technician
    Instrument and Clock Restoration
    www.igraham.ca
    ------------------------------



  • 3.  RE: Great results not following the impedance theory.

    Member
    Posted 12-02-2021 12:47
    I totally agree with you.
    Energy is conserved. One of the first laws of physics.
    If you can't account for where the energy goes when applied to a system, it needs more work.
    Energy is lost through friction in the action. It is lost when the action can't accelerate the hammers to full velocity because of too much mass.
    If the board has too much strength,,, it wants to vibrate up easier than it wants to compress. I see this as restricting the energy of the vibration on one side of the sine wave. The amplitude will be higher on the upswing and less in compression because the board is to it's stress threshold on the compression.
    Dale Erwin and Bob Davis used to tell me it didn't matter what hammer you used,,, some just take more work to get them where you want them.
    Bob, before his class at a convention,, took a hammer that was looked like it was from C6 and put it on G4. He voiced it and it sounded better than the rest of them. When he pulled the action out after talking about the aspects of voicing,,, people went WOW.
    He had the famous hammer flex-o-meter. To me,, so much energy is lost in improper voiced pianos and hammers that don't have bounce. The exchange of energy from the hammer to the wire is one of the most important in the piano.
    Having a board that moves free with minimal loading is one that will last longer, IMO

    ------------------------------
    Keith Roberts
    owner
    Hathaway Pines CA
    209-770-4312
    ------------------------------



  • 4.  RE: Great results not following the impedance theory.

    Registered Piano Technician
    Posted 12-02-2021 13:53

    Ok but that just begs the question. If it doesn't matter what hammer you use and it's just a matter of how much work you have to do then what are you accomplishing with the work you have to do? The answer is to get the hammer to comply with the belly you're dealing with. That's exactly what impedance matching means. 



    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320
    ------------------------------



  • 5.  RE: Great results not following the impedance theory.

    Registered Piano Technician
    Posted 12-02-2021 13:58

    Further. The fact that a C6 hammer sounded better than the heavier G4 hammer supports my thesis. The lighter hammer (and it probably differed dimensionally as well, i.e., the thickness of the felt) in this case was a better match. 

    The hammer definitely matters both in terms of weight and other performance criteria. 



    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320
    ------------------------------



  • 6.  RE: Great results not following the impedance theory.

    Registered Piano Technician
    Posted 12-02-2021 17:23

    Keith wrote:

    "Having a board that moves free with minimal loading is one that will last longer, IMO"

    I can't speak to whether not will last longer but a board that moves too freely will likely sound percussive with inadequate sustain. Impedance means, in our case, the rate of energy transfer. If the energy transfers too quickly we have percussive power with inadequate sustain. If it transfers too slowly we have inadequate power with longer sustain.  A banjo head is a freely moving "soundboard". 

    We don't want a free moving soundboard, one that's "unimpeded", we want one in which energy transfer is controlled so that we have adequate percussive power along with adequate sustain.  Tastes may vary as to where on that continuum things fall but that's the goal. 

    A light soundboard (stiffness and/or mass) tends to move more freely, if you will, so that if you use, say, a high mass hammer you will tend to have an attack which is too percussive although the percussive quality may be somewhat dull. If you soften a high mass hammer in order to filter out some energy then you will tend to filter out high partials due to the increased dwell time of the hammer on the string so you tend to get a dull "whump". Where was that in evidence? On Steinway pianos during a period when they had very high mass and soft hammers. 

    Where this becomes even more in evidence is when rehammering over an old and tired soundboard that had, as in the case of older Steinways, a very light and relatively soft hammer. If your new hammer goes to something high mass or overly stiff (or both) you will be moving in exactly the opposite direction than the board requires due to its changing impedance. Of course you can voice it down to affect the stiffness and thereby reduce the amount of energy transferred, but you can't do much to change the mass other than remove material in which case you probably should have started with something lighter and softer to begin with. 

    There is no getting around the impedance matching model. It is an inherent quality of the beast. 



    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320
    ------------------------------



  • 7.  RE: Great results not following the impedance theory.

    Posted 12-02-2021 19:06
    David,
    I'm not questioning the impedance theory, i'm questioning its value for the piano technician. I see its value in electrical circuits and wires selection, but not the piano. An electrician can measure directly with meters. What such device for piano technicians? I, like i am sure others, have used the identical hammer on every known piano with great results ( from spinets to a 9 foot). In my case, i have put the same set of Ronsens (for years) on every rebuild. Ronsens even made a Yamaha C7 sound better. Only recently have i used another hammer, and that was just to get a different sound for variety sake, and and at clients request. For me then, the different hammers offer a different tone color to suit ones tastes.
    In the recent example from the videos of the old Baldwin Soundboard versus the new Soundboard with a weight difference of 5 lbs., (which you have said in the past is a whole lot) the same size and weight of hammers were used in each. Certainly, if an impedance theory is of any importance to a piano technician, you should be able to calculate in advance that removing 5 lbs of mass from the soundboard would have a certain result, yes? Please share.
    In this case, as i see it, when someone talks about the impedance theory and then uses their ear and experience to select the "appropriate hammer",  then that defeats the purpose of needing to quote a theory. Because in the end its your ear that decides.

    -chris

    ------------------------------
    Chernobieff Piano Restorations
    "Where Tone is Key"
    chernobieffpiano.com
    grandpianoman@protonmail.com
    Lenoir City, TN
    865-986-7720
    ------------------------------



  • 8.  RE: Great results not following the impedance theory.

    Registered Piano Technician
    Posted 12-02-2021 22:54
    Chris

    It's called a paradigm. I don't use impedance formulas for calculating anything. But make no mistake, the rate of energy transfer in pianos is a reality that we contend with one way or the other. Whether it's voicing, hammer selection or soundboard and scale design, the target of establishing a balance between power and sustain is an impedance issue.

    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320
    ------------------------------



  • 9.  RE: Great results not following the impedance theory.

    Posted 12-02-2021 23:25
    Two cents is'n't a pair of dime.

    -chris

    ------------------------------
    Chernobieff Piano Restorations
    "Where Tone is Key"
    chernobieffpiano.com
    grandpianoman@protonmail.com
    Lenoir City, TN
    865-986-7720
    ------------------------------



  • 10.  RE: Great results not following the impedance theory.

    Registered Piano Technician
    Posted 12-02-2021 13:49
    Without knowing the before and after dimensions (panel thickness and rib dimensions: length, width and depth and include crown and downbearing settings) it's hard to make any comment. How do we know the assembly wasn't overbuilt to start?

    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320
    ------------------------------



  • 11.  RE: Great results not following the impedance theory.

    Posted 12-02-2021 14:16
    Ian,
    Why thank you for the unexpected compliment.  These were Renner Blue Points and i voiced them this way. Bass section I applied B-72 (1 pass for bichords, 2 passes unichords about a 1-16 mixture), top 6 notes also received B-72.  The rest i applied All fabric softener (2 passes with a mist sprayer) to the shoulders which opens up the sustain. (I covered the tips with 1/4" masking tape). All of these procdures are not Renner approved. But the velvety sound is a plus. I then finished of with 150 to V-shape (Darrel Fandrich called it Viper voicing) then 600 to smooth and 1500 to slighty brighten  any softies that appeared.

    Keith,
    Funny you mentioned Erwin. He's really intrigued with my concept of making boards lighter also. He just texted me the other day, and said he had removed 2 lbs off of a Steinway O. I can't wait to hear any feedback from him.

    David,
    That's my point, most are overbuilt. Especially so with off brands. For the most part Steinways are the lightest because of the diaphragmatic, but it could be done better.
    I did a 20 video series of the Baldwin rebuild. Go to playlist and look for Baldwin Restoration on my channel. One video, i have the old board and the new board side by side. 5 lbs hardly make a visible notice. It's subtle.

    -chris

    ------------------------------
    Chernobieff Piano Restorations
    "Where Tone is Key"
    chernobieffpiano.com
    grandpianoman@protonmail.com
    Lenoir City, TN
    865-986-7720
    ------------------------------



  • 12.  RE: Great results not following the impedance theory.

    Registered Piano Technician
    Posted 12-02-2021 14:59

    Without the actual dimensions looking at pictures on the video is really not sufficient information to make any assessment about how stiff the board is. Nor is the fact that this one happens to be over built any indication that the impedance matching "model" breaks down.

    In the simplest terms all it means is that lighter assemblies (both mass and stiffness) need less to drive them and heavier assemblies need more.  That manifests itself in lighter or heavier or softer or harder hammers.  I'm not sure what's so hard to accept about that. It seems pretty basic. The original Steinway hammers on relatively light assemblies with low tension scales were light and relatively soft, appropriately. Bosendorfer Imperial hammers with much beefier assemblies with high tension scales need more massive and stiffer hammers. If you switched those hammers around you would not like the result, at least I wouldn't.

    Whether you happen to find an assembly that is too stiff or had too much mass or both doesn't really address the issue as stated in your subject line. 



    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320
    ------------------------------



  • 13.  RE: Great results not following the impedance theory.

    Member
    Posted 12-03-2021 11:01
    Chris,, yeah Dale had me build his soundboard press, it was about the first thing I did in his shop. He had a dished caul that used go-bars. A hydraulic one on a base the firedept could use to break in doors. The pressure tubes that were mounted on 2 x 10s were too short to span the dished caul. I cut the caul down, shortened the all thread rod to fit and plumbed individual valves so you could set up and pressure each rib separately. Then I built a heavy simple base for it. I think he had pressing a board down to an hour. 
    I got to listen to a few boards. Getting a board to boom took a week or two of curing. He had one Steinway B in the final room and it had an ethereal sound that made my eyes water. Literally.  My bench was in that room and people would stop and play a few notes,,,,, it was like they were stunned. One person said it made his mouth water.
    Dale commented on the old boards he took apart and how on the bass end, the short sort of corner board was a wide grained cruddy piece of wood. I believe you can actually separate the sound board from the rim along that board and free up the sound. About the last time I saw a board,, he had put a cruddy piece of wood there.
    It's all good in practice but it will never work in theory.

    ------------------------------
    Keith Roberts
    owner
    Hathaway Pines CA
    209-770-4312
    ------------------------------



  • 14.  RE: Great results not following the impedance theory.

    Posted 12-03-2021 20:26
    Keith,
    Thank You for some of the inside stories.
    -chris

    ------------------------------
    Chernobieff Piano Restorations
    "Where Tone is Key"
    chernobieffpiano.com
    grandpianoman@protonmail.com
    Lenoir City, TN
    865-986-7720
    ------------------------------



  • 15.  RE: Great results not following the impedance theory.

    Posted 12-04-2021 14:54
    Chris, 

    Intentional or not, throwing out a term, any term, without clearly defining that term, sporting a negative connotation, is a "dog whistle".  Dog whistles elicit emotional responses but communicate nothing...by design. Dog whistles are only useful for someone wanting to create division, and seek advantage. They do not communicate actionable information.
      
    Since I am fairly certain you did not intend this post to be a dog whistle, it behooves you to define, what it is, you are not following. We need a clear definition from you, as to what exactly the "impedance model" is, in your mind. Since the term and context is yours, you need to describe what is is you are not following. I have no idea what you are referring to precisely.

    WIth a clear definition from you, maybe we can arrive at a shared definition. Then, there will be room for communication and for folks to consider thinking differently, about how they approach this whole topic.

    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
    ------------------------------



  • 16.  RE: Great results not following the impedance theory.

    Registered Piano Technician
    Posted 12-04-2021 23:10
    I stumbled upon another scientific acoustics journal, the Journal of Sound and Vibration, they don't seem too interested in pianos but there are a couple of papers that might be relevant here:
    https://www.sciencedirect.com/science/article/abs/pii/S0022460X13002472
    https://www.sciencedirect.com/science/article/abs/pii/S0022460X12007936

    ------------------------------
    Steven Rosenthal
    Honolulu HI
    808-521-7129
    ------------------------------



  • 17.  RE: Great results not following the impedance theory.

    Registered Piano Technician
    Posted 12-05-2021 12:55
    I subscribed to the Journal of Sound and Vibration until it stopped publishing. These articles on mode density are great. But they are now behind a paywall. Perhaps PTG should get them in our library.

    ------------------------------
    Edward McMorrow
    Edmonds WA
    425-299-3431
    ------------------------------



  • 18.  RE: Great results not following the impedance theory.

    Posted 12-05-2021 17:34
    Well Jim,
    The definition is on the internet.
    Webster: Impedance- the ratio of the pressure to the volume displacement at a given surface in a sound-transmitting medium. There are quire a few videos of electricians measuring it on electrical circuits with meters.
    My post, was a claim, because no one has fully explained how you use the impedance theory in practice making soundboards or matching hammers to them.
    Other techs have said i'll have impedance problems when reducing soundboard weight without offering proof as to why they say that.
    So i have asked " how do you measure the  impedance of a soundboard? And the Hammer? And use that info to predict an impedance issue?

    So instead of espousing a theory, to force a curious person down a theory hole. How about a real conversation about techniques that are actually used in practice to fix or prevent soundboard/hammer matching issues. 
    There was discussions in the past about mass loading, then there is also riblets. But these are "after the fact" fixes.( I've left out the music wire choices because riblets, mass weights on bridges, and vice grips on bridge pins indicate a soundboard problem). I think, the problem is the design, and that a good working soundboard will accept ANY hammer.  My claim is that a soundboard made correctly via "light in weight" and an "even rib scale" will address the tonal focal problems. That is what my last soundboard and hammer choice showed.
    I used Renner Blue points on an Baldwin SD6 with a light weight board, and the same hammer on both a Baldwin R and M&H A, with lightweight boards. All were beautifully balanced across the scale. None have riblets, mass loading, and with original scales used.
    I was told the removal  of 5lbs of weight would cause impedance problems. It didn't and hasn't.
    -chris

    ------------------------------
    Chernobieff Piano Restorations
    "Where Tone is Key"
    chernobieffpiano.com
    grandpianoman@protonmail.com
    Lenoir City, TN
    865-986-7720
    ------------------------------



  • 19.  RE: Great results not following the impedance theory.

    Registered Piano Technician
    Posted 12-06-2021 21:40
    This is like having a geology discussion with someone who thinks the earth is only 6000 years old.

    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320
    ------------------------------



  • 20.  RE: Great results not following the impedance theory.

    Posted 12-06-2021 23:00
    Well let's be clear, Chris is, in fact, is the only one who really knows how old the world is...every one else is either a scoffer or a pretender.

    I envy that level of certainty about everything.

    Interesting thing is, that he doesn't realize, that if you want someone to consider your point of view, hitting folks in the head, doesn't tend to convince folks of anything. Well...it does convince them of one thing...that would be to avoid conversing with you. If you want someone to listen to what you may have to say, and consider your thoughts, it works way better, if it is stated with some modicum of positivity and camaraderie...some shared experience.

    The negativity that accompanies all his declarations of truth, is simply not an effective way to get his point across. 


    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
    ------------------------------



  • 21.  RE: Great results not following the impedance theory.

    Posted 12-07-2021 11:36

    Dr.'s David and Jim,
    I'm just asking a piano related question. Not to question your Psychology degrees, but your evaluations are quite far off.
    My question is "How is an Impedance formula used in Piano Technology?" 

    I don't remove weight for its own sake off my boards, as David has falsely implied. I have removed 5lbs through engineering refinements that were made possible because existing designs are basically overbuilt. In all the other branches of acoustic musical instrument making, that's pretty much what everyone else is doing too.

    Its bad design that can add excess weight and create tonal irregularities. I've addressed those issues by applying what I've learned from the previous boards, and not making the same errors on the next board.

    How does the impedance  formula solve those problems? Like I have already stated, an electrician has a meter and can measure it immediately and make a determination as to transistor and wire choices.  There's no such tool for hammer/ string/soundboard mating.

    The title of the thread was chosen to emphasis the value of empirical methods.

    Thanks,

    -chris



    ------------------------------
    Chernobieff Piano Restorations
    "Where Tone is Key"
    chernobieffpiano.com
    grandpianoman@protonmail.com
    Lenoir City, TN
    865-986-7720
    ------------------------------



  • 22.  RE: Great results not following the impedance theory.

    Registered Piano Technician
    Posted 12-07-2021 13:32

    I do have degree in psychology actually. Focus on cognitive psychology and the psychology of perception (that's why I have to make my living as a piano tech). But it does have interesting applications in our trade. However, I did stop short of my doctorate so calling me Dr. would be inappropriate.

    Impedance is a fact that is indisputable in soundboard performance. Whether or not we use impedance formulas is beside the point. We respond to impedance characteristics of the board in several different ways from assessing a design and comparing percussive power to sustain or voicing or changing hammers. In soundboard design I don't use impedance formulas. There are other formulas, for example load bearing, that allow us to quantify changes in a way that directly affects impedance. The assessment we make especially along the power/sustain continuum is an evaluation of impedance in which both mass and stiffness play a role though stiffness is probably more the issue there. Mass loading, btw, something you mentioned, is often to compensate for something that is too stiff in order to slow the  board down. Mass is not a substitute for stiffness. Riblets are designed to add stiffness with minimal mass. Most boards that get compromised do so because they lose stiffness and thereby the impedance is lowered and they become more percussive with shorter sustain. It is natural then to assume, or at least question, whether removing 5lbs of material might compromise the board's stiffness. 

    I questioned what you expressed originally as a standard procedure of removing 5 lbs of material from the board as potentially problematic. On Steinway pianos, which I rarely find overbuilt, removing nearly a third of the weight would be worrisome. I've asked you several times to give me the details for example changes in panel thinning or changes in ribs dimensions to account for those changes, exactly where you removed materiel from and the before and after dimensions so that I can make some quantitative assessment of what it is that you're doing. So far you've not responded with any real data so as far as I'm concerned you're just blowing smoke. 

    I have no doubt that some assemblies are overbuilt but until I see the data I have no way to assess what you're doing.  I don't need your baseless snark or self congratulations, just the facts sir, just the facts. 



    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320
    ------------------------------



  • 23.  RE: Great results not following the impedance theory.

    Posted 12-07-2021 14:56
    David,
    A misrepresentation again.
    First, i only have to prove my results to my clients, not you.
    Second, i have presented oodles of data, here and elsewhere. I have published many rib scales, and discussed how i arrived at them and what i was after. I have also made hundreds of videos of many of my procedures. Further supported with the observable conclusions of comparing weights of before and after soundboards on a digital scale. Also on several videos.
    So its not that i have refused to post facts, its that all along the way you have dismissed those facts. 
    Steinways, are light boards, but they are laid out incorrectly in my opinion. They weaken too much where it needs to be the strongest. I can usually remove a 1/2 to 1 pound off, and rearrange the parts slightly to work better and be more durable.

    -chris

    ------------------------------
    Chernobieff Piano Restorations
    "Where Tone is Key"
    chernobieffpiano.com
    grandpianoman@protonmail.com
    Lenoir City, TN
    865-986-7720
    ------------------------------



  • 24.  RE: Great results not following the impedance theory.

    Posted 12-07-2021 20:32

    Chris <The title of the thread was chosen to emphasize  the value of empirical methods.

    Well... it didn't work.  Your title and presentation  achieved  the opposite of your supposed intent.  

    This thread  supposedly isn't about  impedance, but that's all we are discussing. We could have discussed various empirical methods that you are discovering for yourself, but we are not. Instead, fueled by the title and your presentation, we are not discussing impedance, which, of course, we are discussing , even though this tread is not about it. We are not discussing impedance, by discussing impedance. The whole thing is rather absurd.

    How about just telling us what you did empirically?

    There is no conflict between understanding a complex system theoretically, and understanding a complex system in a hands on, holistic, concrete , empirical way.  Some brains can utilize theoretical and abstract concepts, and some brains get tripped up in the abstract. There is no  conflict between these two approaches. They are in fact complementary. Each approach can inform the other. 

    To some brains , like mine, theoretical concepts and terminology are an impediment to understanding the complexity of the structure as a whole. This is not because there is no theory that explains it, but because my brain cannot process the sheer complexity in an abstract way.  Instead I, and it looks like you, understand the complex system,  in a more holistic, hands-on, real-time, visual, empirical way.  I actually get slowed down and confused by the theoretical, but I can understand it, if I can touch or see it.

    That does not mean theoretical abstraction is incorrect. It means some brains can work better from the abstract to the concrete, and other brains can work better from the concrete to the abstract. Both can master the system in their own way.

    You are having trouble seeing that your way of thinking is not the only way it is possible for a human brain to grasp the system we are working on.  Or said another way...there is no "one true way", Grasshopper, they are all complimentary.



    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
    ------------------------------



  • 25.  RE: Great results not following the impedance theory.

    Posted 12-07-2021 21:56
    Jim,
    I agree with most of what you said,but, i did explain what i do empirically in the first opening post. 

    I removed 5 lbs of weight off of the Baldwin SD6 soundboard. Here is some other changes, although you have heard them from me before. I redesigned the rib scale for evenness, scalloped them differently, so they place the bridge in the center of amplitude, and tapered the panel so that its synchronized with the scalloping. 
    With the last few boards, i began to notice that when the excess weight was removed, the well known impedance problems were going away. No vice grips on bridge pins or brass weights needed to fix annoying loud notes. No riblets needed either. I wasn't concerned at all about hammer weight (not enough or too much from an energy input point of view) as i have been using the same hammers on the last 10 pianos, regardless of size of piano. Before i started being concerned about the weight of the board, the final outcome was unpredictable, with riblets often being needed to blend the notes.

    2 videos aligning the Center of Amplitude 
    https://www.youtube.com/watch?v=b7PUihwYMOY
    https://www.youtube.com/watch?v=54MUvzuiquU

    Performance on the Baldwin when delivered
    https://www.youtube.com/watch?v=Mmnd5fpC3Hw

    -chris









    ------------------------------
    Chernobieff Piano Restorations
    "Where Tone is Key"
    chernobieffpiano.com
    grandpianoman@protonmail.com
    Lenoir City, TN
    865-986-7720
    ------------------------------



  • 26.  RE: Great results not following the impedance theory.

    Posted 12-07-2021 22:32
    OK....now we're getting somewhere. A couple of questions:

    On the scalloping,  are you reducing the thickness of the thinned portion of the rib to center the amplitude?  Are the indicators located at the point where the scallop becomes full dimension height?

    How are you determining where to thin the panel to match the rib scalloping?

    Clamping the test rib effects the deflection of the rib big time. How are you clamping the rib so that you are not influencing artificially the clamp stress, in a way it will not be influenced when glued in to the rim?

    Are you aware of the interesting work Craig Hair and Richard Blais are doing in their re-crown conservation work?  They feel there is decent evidence to suggest vintage board makers were in fact tuning their ribs, but tuning them so that the bridge is located on an anti-node, which generally is not centered on the span. Beveling of the rim or only beveling certain parts of the rim, also effect the center of amplitude and other nodal behavior of the rib.

    Craig Hair Richard Blais Wave motion of a piano rib  3 videos

    Note that in your centering the amplitude, mass loads are used as a diagnostic. There are other ways to use mass loads as a laser like diagnostic.  Many boards exist that don't need to be torn out, especially given the scarcity of fine old growth spruce. Using diagnostic tools, without bias as to what constitutes a true blue piano board , can return those  boards and their excellent aged wood to excellent musical service.   




    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
    ------------------------------



  • 27.  RE: Great results not following the impedance theory.

    Posted 12-07-2021 23:46
    Jim,
    Please remember that this is still experimental and i am exploring and trying different methods.
    On the scalloping I'll remove any material on the long side to match the deflection on the short side from the bridge location. The short side, i always make the scalloping the same length and match the long sides deflection  to it. If a piano has 4" scalloping i'll keep it, or if it has 6" scalloping i'll keep it. Its the long side i manipulate. Dial location is set equidistant. Good question on the jig setup, which shows you have tried this before. I was having that problem with clamps, but the square hole/wedge setup works fine. 
    I found that there is an interesting natural layout of the rib structure, kind of a natural twist involved that is somewhat synchronized with the curve of the bridge. Up in the treble the long side is on the curve side. Then there always a symmetrical rib ( I call the pivot rib) then the long side switches to the spine side for the rest. Don't know if it means anything though. Just an observation.

    What Craig was doing was not exactly the same.  In my view, the bridge location is a driving point, which has a different function than nodes and anti nodes. I want the driving point to be where the board has maximum movement for energy distribution.  An anti node is more of a little boost for the radiated energy. So i don't think  Craigs experiment is valid.

    So far, on panel thicknessing i have been using pairs of dial indicators on each rib location, and placing weight on the bridge  to check deflections. Then plane and sand to get the long side to move like the short side. So for this method, the corner area that others remove with cut off bars have been a valuable area for equalizing and centering the bridge. I'll probably post a video in the future on the panel thicknessing when i'm satisfied i have a  procedure i'll stick with.

    -chris



    ------------------------------
    Chernobieff Piano Restorations
    "Where Tone is Key"
    chernobieffpiano.com
    grandpianoman@protonmail.com
    Lenoir City, TN
    865-986-7720
    ------------------------------



  • 28.  RE: Great results not following the impedance theory.

    Posted 12-08-2021 09:25
    I get that these are in-process experimental techniques...so are many of my posts, like the titanium bridge pins. I'm still not sure whether that was something I will do again. At first, after doing a whole spec piano belly with them, I thought...no. But then, after letting it sit and ignoring it for about 4 months, I went back to tune it up to sell it, and by golly that small previously horrible piano sounds damn good...I need to get some other tech ears to see what they think...but yeah...its an in process thing...proceed at your own risk.

    So, in adjusting the rib, are you extending the long side scallop when you fine tune the balanced amplitude, or do you retain the long side scallop length and remove other material.  The reason I ask this, is that in a previous experiment I tried, extending the long side scallop was a real bad thing to do. One needs to make sure there is sufficient connection to the rim, otherwise the near-rim conditions will board bypass the entire rib structure in the main field of the panel.

    Dials set equidistant relative to what?...the clamp points?

    Re Craig and Richards experiment:

    the anti node is the point of maximum amplitude and excursion. I think you may be mis-understanding what they are proposing. In all their re-crown projects, the bridge is off what would be considered the crest of the crown(crest is not necessarily or usually centered).The crest of the crown is controlled by the rim being beveled or flat, or a combination of the two. Reason being that the crest of the crown, in accordance with their tests, is the location that is less compliant and most resistant to load. Bridges are set slightly off to the side of the crest. Their view is that the loudest area of the piano soundboard is not at the crest, but slightly off to the side.

    I think this challenges the mental concept that many of us may have, that the board is a simple diaphragm, pulsing in simple opposition to simple transverse string movement. And I think any of the scientific demonstration of SB nodes has shown this...it is not a simple up and down thing at the bridge.

    This, by the way, agrees to some degree, with my own diagnostic explorations. In experimenting with mass loads, in existing or old boards, the location right smack under the bridge is not usually the ideal location for the mass. Slightly off to one side by just a couple of inches, and wolf tones open up in the treble. Its really quite amazing. As well, in trying to address unwanted resonances, which a wolf tone is, the way to defeat a resonance is to impose an asymmetrical force to the system. So, the intellectual bias, that middle of the system is best, which we probably all assume, at least at first, is something that has to be tested and challenged, and experimented with.

    I know you and probably all techs are of the belief that mass loads are the work of the devil....but sorry...biases and beliefs die hard. One needs to see what benefits a laser guided, asymmetrical, rib applied mass load, has to offer our imperfect constructions. Especially what it has to offer in the existing imperfect boards we face every single day, day in and day out, on the job, and in the concert hall.


    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
    ------------------------------



  • 29.  RE: Great results not following the impedance theory.

    Registered Piano Technician
    Posted 12-08-2021 21:40

    I can appreciate the posting of experiments and explorations, it's how we improve. But the data is important. What I'd like to hear in this discussion is: this is where I began (all rib dimensions and details) and these are the changes i made (new rib dimensions etc). This resulted in a change in weight of X…  

    Changing the scallop simply will not result in 5lbs of reduction. Wood doesn't weigh that much. So what I want to know is where you started and where you ended up. Otherwise It's impossible to determine what actually changed and whether that change was warranted. That you liked the sound when you were done is not meaningful data.

    I agree that some pianos might be overbuilt and that rib scales can often be improved. But I don't agree that most assemblies are overbuilt, certainly not with Steinways (the bulk of my experience). 

    i also strongly disagree that "any hammer will work". Scale tensions dictate the strength of the assembly and that often affects hammer choice. I think that is without question. The so called "impedance model" is one that is used to determine the best hammer fit for a given assembly.  That is often and empirical decision, i.e., this hammer is too aggressive or this hammer is jnadequate to deliver what I need and voicing will not get me to where I want.

    For pianos with similar scaling and therefore similar assemblies with respect to support, one would expect that hammer choices would be similar. Whether you go with a Renner Blue Point or Ronsen Wurzen the requirements are all within reach by normal voicing. But where the scaling and soundboard structures vary from low tension and light to high tension and heavy you would expect, and you would be right, that the hammer requirements would be somewhat different. Similarly, on older, compromised soundboards that are still functional you might expect that there might be a hammer that would be more or less suitable.  

    My goal with hammer selection, and this is where most of us fall and was the impetus for discussing the "impedance model" in the first place, we are not redesigning a soundboard. Instead we are developing a sense of best fit for a particular piano and that is a critical skill. That choice, IMO, is largely driven by the impedance characteristics of the existing assembly.  

    How light or how heavy to design a new assembly is almost a separate discussion. Many new "redesigns" I've seen are, in my opinion, too heavy, or more apt, too stiff. That creates its own set of issues that can also affect hammer choice. But impedance, which I define as the resistance to the rate of energy transfer, is an inherent characteristic of pianos and is something we deal with knowingly or not. 



    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320
    ------------------------------



  • 30.  RE: Great results not following the impedance theory.

    Posted 12-09-2021 16:12
    As requested.

    "I can appreciate the posting of experiments and explorations, it's how we improve. But the data is important. What I'd like to hear in this discussion is: this is where I began (all rib dimensions and details) and these are the changes i made (new rib dimensions etc). This resulted in a change in weight of X…

    Changing the scallop simply will not result in 5lbs of reduction. Wood doesn't weigh that much. So what I want to know is where you started and where you ended up. Otherwise It's impossible to determine what actually changed and whether that change was warranted. That you liked the sound when you were done is not meaningful data.

    I agree that some pianos might be overbuilt and that rib scales can often be improved. But I don't agree that most assemblies are overbuilt, certainly not with Steinways (the bulk of my experience). "

    The original rib scale 

    Modified rib scale

    The before and after weights:
    Original board  25.3Lbs.
    New Board  20 lbs

    Panel:
    Original panel thickness was 10mm throughout with Sitka Spruce
    The new thickness started at 9.5mm and is tapered on the appropriate areas of the board. Swiss Spruce.


    Ribs:
    Ribs are spruce on original
    New ribs are Eastern White Pine

    I even used a heavier thicker bridge cap than the original.

    With the combination of the engineering process and careful wood selection, weight was reduced 5 lbs.

    I also only put on it, a light downbearing load. A very healthy crown still present after stringing and tuning stability.

    -chris

    Video of the weight comparison:
    https://www.youtube.com/watch?v=d9W0ZCt6id8&t=106s








    ------------------------------
    Chernobieff Piano Restorations
    "Where Tone is Key"
    chernobieffpiano.com
    grandpianoman@protonmail.com
    Lenoir City, TN
    865-986-7720
    ------------------------------



  • 31.  RE: Great results not following the impedance theory.

    Posted 12-09-2021 18:32
    What was the load?  I have been backing my loads way down as well.

    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
    ------------------------------



  • 32.  RE: Great results not following the impedance theory.

    Posted 12-09-2021 19:00
    Guesstimate is about 500 lbs. I pretty much follow the Baldwin Accu-just  procedure. .5 degree at tenor up to 1 degree at treble, .5 to zero at bass. Let it self load.
    It was a little ordeal to use that procedure without accu- just pins but its creatively do-able. It just takes me 3 times as long to string a piano is all. 
    -chris

    ------------------------------
    Chernobieff Piano Restorations
    "Where Tone is Key"
    chernobieffpiano.com
    grandpianoman@protonmail.com
    Lenoir City, TN
    865-986-7720
    ------------------------------



  • 33.  RE: Great results not following the impedance theory.

    Registered Piano Technician
    Posted 12-10-2021 00:19
    Thank you Chris. I look forward to examining this more closely over the weekend.

    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320
    ------------------------------



  • 34.  RE: Great results not following the impedance theory.

    Posted 12-17-2021 11:34
    The weekend analysis?

    ------------------------------
    Chernobieff Piano Restorations
    "Where Tone is Key"
    chernobieffpiano.com
    grandpianoman@protonmail.com
    Lenoir City, TN
    865-986-7720
    ------------------------------



  • 35.  RE: Great results not following the impedance theory.

    Registered Piano Technician
    Posted 12-20-2021 14:47
    Chris

    Running your data but I need the rib lengths.  Do you have that?

    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320
    ------------------------------



  • 36.  RE: Great results not following the impedance theory.

    Registered Piano Technician
    Posted 12-20-2021 15:18
    Chris

    Could you also clarify your loading targets?  You mentioned 1/2 degree as a target. Is that residual bearing or is that your preload starting point?

    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320
    ------------------------------



  • 37.  RE: Great results not following the impedance theory.

    Posted 12-20-2021 15:43
      |   view attached
    Here are the lengths. Load target is a guesstimate of about 500lbs. I don't pre-load, but set downbearing as i string. I aim for half a degree and am happy with 1 degree up in the treble. Usually the bass is one quarter of a degree and is set last.
    -chris

    ------------------------------
    Chernobieff Piano Restorations
    "Where Tone is Key"
    chernobieffpiano.com
    grandpianoman@protonmail.com
    Lenoir City, TN
    865-986-7720
    ------------------------------



  • 38.  RE: Great results not following the impedance theory.

    Registered Piano Technician
    Posted 12-20-2021 18:50
    So the residual load is ~.5 degrees at full tension?  That would make sense at about 500 lbs. understood there's some variation across the scale.

    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320
    ------------------------------



  • 39.  RE: Great results not following the impedance theory.

    Registered Piano Technician
    Posted 12-21-2021 18:55
    Chris

    Lengthy post below but necessary for comparison.  Additional comments at the end.

    So below is my analysis. I have the original, your redo and mine below that. We're not too far apart.  The original rib scale on this piano I agree was not very balanced and a bit overbuilt.  

    For the sake of consistency I've taken 493 lbs of residual load, i.e. after the piano is strung and pulled to tension.  For the purposes of this experiment I distributed the load on 17 ribs evenly at 29 lbs per rib.  Not going to get into a discussion on this right now but for the sake of illustration that's how I did it.  I used a crown radius  of 18M (59'))

    Original design:

    Rib # Design Load Carrying Capacity Working length  L (in) Intermediate length Width  W (in) Target Height  Volume H (in) length/height MOI MOI (in) Z Modulus
    1     29 91.0 635 25 317.5 25.7 1.01 19.6 19.4 0.77 32 16 0.038 0.100
    2     29 66.1 838 33 419.1 25.9 1.02 19.1 25.2 0.75 44 15 0.036 0.096
    3     29 83.3 991 39 495.3 25.7 1.01 23.4 36.2 0.92 42 27 0.066 0.142
    4     29 83.5 1054 41.5 527.05 25.7 1.01 24.1 39.8 0.95 44 30 0.072 0.152
    5     29 84.1 1067 42 533.4 26.2 1.03 24.1 41.1 0.95 44 31 0.074 0.155
    6     29 71.4 1118 44 558.8 25.9 1.02 22.9 40.4 0.90 49 26 0.062 0.138
    7     29 78.6 1143 45 571.5 25.7 1.01 24.4 43.6 0.96 47 31 0.074 0.155
    8     29 75.3 1118 44 558.8 26.2 1.03 23.4 41.7 0.92 48 28 0.067 0.145
    9     29 77.0 1003 39.5 501.65 25.7 1.01 22.6 35.5 0.89 44 25 0.059 0.133
    10     29 83.0 940 37 469.9 25.9 1.02 22.6 33.6 0.89 42 25 0.060 0.135
    11     29 99.0 787 31 393.7 25.9 1.02 22.6 28.1 0.89 35 25 0.060 0.135
    12     29 107.5 711 28 355.6 25.4 1.00 22.6 24.9 0.89 31 24 0.059 0.132
    13     29 97.9 668 26.3 334.01 24.4 0.96 21.3 21.2 0.84 31 20 0.047 0.113
    14     29 91.3 579 22.8 289.56 22.9 0.90 19.8 16.0 0.78 29 15 0.036 0.091
    15     29 74.0 490 19.3 245.11 22.6 0.89 16.5 11.2 0.65 30 8 0.020 0.063
    16     29 92.0 432 17 215.9 22.6 0.89 17.3 10.3 0.68 25 10 0.023 0.069
    17     29 95.3 351 13.8 175.26 22.9 0.90 15.7 7.7 0.62 22 7 0.018 0.058
                                     
    Total Load 493 Total Vol 476.1 in^2






    -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

    Chernobieff redesign

    Rib # Design Load Carrying Capacity Working length  L (in) Intermediate length Width  W (in) Target Height  Volume H (in) length/height MOI MOI (in) Z Modulus
    1     29 57.8 635 25 317.5 22.9 0.90 16.5 14.6 0.65 38 9 0.021 0.063
    2     29 58.3 838 33 419.1 24.1 0.95 18.5 22.9 0.73 45 13 0.031 0.084
    3     29 59.0 991 39 495.3 24.6 0.97 20.1 29.9 0.79 49 17 0.040 0.101
    4     29 59.5 1054 41.5 527.05 25.1 0.99 20.6 33.3 0.81 51 18 0.044 0.108
    5     29 62.7 1067 42 533.4 26.2 1.03 20.8 35.5 0.82 51 20 0.047 0.115
    6     29 62.8 1118 44 558.8 26.2 1.03 21.3 38.1 0.84 52 21 0.051 0.121
    7     29 64.3 1143 45 571.5 26.2 1.03 21.8 39.9 0.86 52 23 0.055 0.127
    8     29 65.8 1118 44 558.8 26.2 1.03 21.8 39.0 0.86 51 23 0.055 0.127
    9     29 69.2 1003 39.5 501.65 25.9 1.02 21.3 33.8 0.84 47 21 0.050 0.120
    10     29 69.7 940 37 469.9 25.7 1.01 20.8 30.6 0.82 45 19 0.046 0.113
    11     29 78.5 787 31 393.7 25.4 1.00 20.3 24.8 0.80 39 18 0.043 0.107
    12     29 81.7 711 28 355.6 25.1 0.99 19.8 21.6 0.78 36 16 0.039 0.100
    13     29 81.8 668 26.3 334.01 24.9 0.98 19.3 19.6 0.76 35 15 0.036 0.094
    14     29 85.8 579 22.8 289.56 23.9 0.94 18.8 15.9 0.74 31 13 0.032 0.086
    15     29 93.9 490 19.3 245.11 23.4 0.92 18.3 12.8 0.72 27 12 0.029 0.079
    16     29 99.2 432 17 215.9 22.4 0.88 18.0 10.6 0.71 24 11 0.026 0.074
    17     29 117.4 351 13.8 175.26 22.1 0.87 17.8 8.4 0.70 20 10 0.025 0.071
                                     
    Percentage of original volume
    493 Total  Vol 431.2 in^2 91%






    --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

    Love redesign

    Rib # Design Load Carrying Capacity Working length  L (in) Intermediate length Width  W (in) Target Height  Volume H (in) length/height MOI MOI (in) Z Modulus
    1     29 72.1 635 25 317.5 20.3 0.80 19.6 15.4 0.77 32 13 0.030 0.079
    2     29 70.9 838 33 419.1 24.1 0.95 20.4 25.2 0.81 41 17 0.041 0.103
    3     29 68.3 991 39 495.3 24.6 0.97 21.6 32.2 0.85 46 21 0.050 0.117
    4     29 67.8 1054 41.5 527.05 25.1 0.99 22.0 35.5 0.87 48 22 0.053 0.123
    5     29 68.1 1067 42 533.4 26.2 1.03 21.7 37.0 0.86 49 22 0.054 0.125
    6     29 67.3 1118 44 558.8 26.2 1.03 22.1 39.4 0.87 51 24 0.057 0.130
    7     29 66.6 1143 45 571.5 26.2 1.03 22.2 40.6 0.88 51 24 0.058 0.131
    8     29 67.3 1118 44 558.8 26.2 1.03 22.1 39.4 0.87 51 24 0.057 0.130
    9     29 69.2 1003 39.5 501.65 25.9 1.02 21.3 33.8 0.84 47 21 0.050 0.120
    10     29 70.6 940 37 469.9 25.7 1.01 21.0 30.8 0.83 45 20 0.047 0.115
    11     29 74.6 787 31 393.7 25.4 1.00 19.8 24.2 0.78 40 16 0.040 0.101
    12     29 76.6 711 28 355.6 25.1 0.99 19.2 20.9 0.76 37 15 0.036 0.094
    13     29 78.6 668 26.3 334.01 24.9 0.98 18.9 19.2 0.75 35 14 0.034 0.091
    14     29 81.2 579 22.8 289.56 23.9 0.94 18.3 15.4 0.72 32 12 0.029 0.081
    15     29 85.0 490 19.3 245.11 23.4 0.92 17.4 12.2 0.69 28 10 0.025 0.072
    16     29 87.0 432 17 215.9 22.4 0.88 16.9 9.9 0.67 26 9 0.022 0.065
    17 0 -148 29 95.1 351 13.8 175.26 22.1 0.87 16.0 7.6 0.63 22 8 0.018 0.058
                                     
    Percentage of orig Volume
    Total Load 493 Total Vol 438.8 0.92
    in^2








    ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

    Comments:

    Your reduction removes 9% of the volume of the ribs scale, mine removes 8%.  Our distributions are a bit different.  Compared to yours I've added some stiffness to the bass and taken a bit away from the top treble but these are relatively small differences, as you can see from the dimensions.  The actual volume reduction will be less as a percentage in both cases because this doesn't take into account the scalloping which will be relatively equal in each of our designs.  Also, I would probably reduce the panel thickness to 9mm (and more behind the bass bridge, behind the top of the treble and around the bent side and along the spine).  You mentioned the original was 10mm and that you reduced it to 9.5mm.  Even so I don't see how that change amounts to nearly 5 lbs worth of material.  I'll have to take your word for it.  I used white spruce for this calculation, btw, both ribs and panel.  A 10% reduction in total volume would amount to 1.7 lbs if the original was, as you stated, ~17 lbs.  

    Generally speaking, I am concerned first with load bearing capacity (stiffness) and allow the mass to fall where it does.  I would never approach this in terms of mass first as a guiding principle, which was really my point.  For someone to approach these types of projects with the idea of just reducing mass would, I think,  be a mistake and lead to some not great outcomes--structures which are too lightly constructed and don't have adequate stiffness to control impedance adequately.  I would say your redesign doesn't have that problem and so it's not surprising that you had some flexiblity in terms of hammer choice.  Some assemblies are overbuilt, and this one was, but many are not.  In fact there are some places in this assembly that were underbuilt, rib #6, for example.  That's evident in the Z modulus graphs.   


    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320
    ------------------------------



  • 40.  RE: Great results not following the impedance theory.

    Posted 12-22-2021 00:00
    Thank you for the analysis David.  A couple things back at ya. My first priority is basically the same as yours, not mass reduction. Maybe you misunderstood that!? I want the structure to be as strong or stronger than the original, i just focus on removing the material that doesn't contribute to strength but just adds weight. 5lbs of of weight did come off as seen in the video. Obviously no one can predict the amount by just a spreadsheet either. The factors that contribute are 1) species selection, the EWP i use from PA is very very light and yet very strong. I joke that its balsa wood because its so light. 2) i shape my ribs differently that removes more weight. I remove more material on the long side. The amount is determined by deflection testing. 3) My panels start out as large wedges before the side tapering begins. Most of my tapering is done from the bridge towards the corner of belly rail and spine. The final amount that comes off is really determined by how overbuilt the board was, since that's the floating bar. Not much comes off of Steinways, just some distribution.
    Thanks again.
    -chris

    ------------------------------
    Chernobieff Piano Restorations
    "Where Tone is Key"
    chernobieffpiano.com
    grandpianoman@protonmail.com
    Lenoir City, TN
    865-986-7720
    ------------------------------



  • 41.  RE: Great results not following the impedance theory.

    Posted 12-09-2021 00:46
    Jim,
    I believe my system is in agreement with the Craig experiment. However he's moving the "bridge" around, i pretty much always place the bridge in the original location.  My adjusting of the long side of the ribs aligns the driving point under the bridge, and the rib remains asymmetrical. To put it another way- I'm more concerned about driving point alignment, Craig was observing the nodes/antinodes behaviour.
    I place dial gauges in my jig the same distance( 4") away from the ends. I usually start thinning the thin part of the scallop first, aiming to match the deflection of the short side. Then i'll start removing material along the the whole long side (avoiding going under the bridge) under the bridge. With luck, i have equalized the deflections, and the rib doesn't look any different except upon close inspection. Yes, i start out by matching the original scalloping.
    To Avoid:
    An even long taper because the board will crown weird. 
    When lengthening the scallop, it begins to look uneven and weird.
    Good Luck!
    -chris

    ------------------------------
    Chernobieff Piano Restorations
    "Where Tone is Key"
    chernobieffpiano.com
    grandpianoman@protonmail.com
    Lenoir City, TN
    865-986-7720
    ------------------------------



  • 42.  RE: Great results not following the impedance theory.

    Posted 12-09-2021 13:05
    In case someone wants to disagree that any hammer will work, and bases that on, that an impedance model decides the correct hammer. Please make sense of my current situation which is so common. I just finished a Baldwin 9' Concert Grand and am now starting a 5' Knabe grand.

    Here are the numbers for note number 49:
    Baldwin  AR=5.9,  SW= 8.2, ITF = 221
    Knabe​     AR=5.2   SW= 8.8,  ITF = 202

    Notice that the small grand has the much larger hammers, for the smaller soundboard and lower string tensioned scale.
    I think its reasonable to conclude that both respected builders Baldwin and Knabe disagreed with the hammer matching impedance model.
    -chris




    ------------------------------
    Chernobieff Piano Restorations
    "Where Tone is Key"
    chernobieffpiano.com
    grandpianoman@protonmail.com
    Lenoir City, TN
    865-986-7720
    ------------------------------



  • 43.  RE: Great results not following the impedance theory.

    Posted 12-09-2021 20:11
    Chris <Notice that the small grand has the much larger hammers,

    Also notice that the Knabe has a lower action ratio.  Lower AR, pairs with higher hammer weight. Higher AR, pairs with lower hammer weight. Force of the impact is closer to equivalent between the two.

    <It just takes me 3 times as long to string a piano is all.

    speed is overrated, in my opinion anyway.  We came up with a real nice way to string the capos with a true V bar termination without creating misplaced initial self-machined string grooves.  String, and just put enough tension on the wire, where you start to feel tension as opposed to no tension. That will not mark the capo. String paths are still all over the place, because there is not enough tension to straighten the wire.

    After all the plain wire is on, one section at a time, using two of us, and a shop made string spacer (the supply house one has too wide slots for trebles in my opinion), one person behind the capo, one person at the lever and pins. Place the spaced strings where they belong according to previous marked spacing, behind the capo with the string spacer. The person at the pins, moves the messy front segments around to see where they will end up, and when both look good, raise coils and bring up to tension. Was quite speedy, no misplaced string grooves in the capo, and fairly linear process. Way better than our previous iterations.

    On the other hand, in the speed department, watch a speed stringer string the capo. In order to avoid destroying the capo bar, at that speed, the capo must be a wide radius termination, causing all kinds of sadness down the road, not too far away.

    How did you hit your DB targets without vertical hitches?


    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
    ------------------------------



  • 44.  RE: Great results not following the impedance theory.

    Posted 12-09-2021 21:25
    Jim,
    Then for that same equivalent force, shouldn't the soundboards also be the same equivalent size?
    Yes, we talked about the Capo before. I was inspired by your post and came up with something similar which i shared on the other thread, Nothing fancy just a card with marks on it.
    I basically use a .045 punching when using the string across the bridge for Bridge height. A .060 punching on the Bass bridge.
    To get close.
    Then I use brass shim stock of various thicknesses to adjust the height when stringing.
    -chris



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    Chernobieff Piano Restorations
    "Where Tone is Key"
    chernobieffpiano.com
    grandpianoman@protonmail.com
    Lenoir City, TN
    865-986-7720
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  • 45.  RE: Great results not following the impedance theory.

    Registered Piano Technician
    Posted 12-07-2021 20:56

    Chris

    You brought this up in a forum designed to further discussion, not to promote your business to your clients. You have been asked several times to provide the data to support your claims which you continue to avoid doing. At this point I can only assume either you have no data to support your position or you don't want to provide it for some reason. That's fine but at least be honest about it. At this point I'm done with this "discussion".  



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    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320
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  • 46.  RE: Great results not following the impedance theory.

    Registered Piano Technician
    Posted 12-05-2021 13:43
    Keith wrote:

    "Dale commented on the old boards he took apart and how on the bass end, the short sort of corner board was a wide grained cruddy piece of wood. I believe you can actually separate the sound board from the rim along that board and free up the sound. About the last time I saw a board,, he had put a cruddy piece of wood there.  It's all good in practice but it will never work in theory."



    Actually it works quite well in theory (and in practice).  One of the reasons that the bass end of the piano is less often compromised in older soundboards when the upper part of the piano has deteriorated due to loss of stiffness is that the bass end is designed to be more flexible to accommodate the frequency requirements of that end of the scale in the first place.  Thus the aggressive panel thinning that often takes place behind the bass bridge.  Since one isn't concerned with stiffness in the bass, wide grain is just fine. Cutting away the board from the rim in the bass (called a bass float) has been common practice from some builders for 150 years.  Of course it's not quite that simple, you can't simply cut the soundboard away without supporting the free edge of the panel and that's often done by adding a thin cross grain lamination.  A bass float can be quite helpful on smaller pianos to give a better bass response.

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    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320
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