Pianotech

Expand all | Collapse all

Weight of Soundboard Assembly

  • 1.  Weight of Soundboard Assembly

    Registered Piano Technician
    Posted 26 days ago

    I believe I've seen reference to this before.

    I'm interested in what a Steinway B sound board assembly might weigh.

    Would some of those out there who build bellys be able to provide this info?

    Weight of panel with ribs?

    Weight of panel with ribs and bridges?

    I've never weighed them but I do notice after I'm done some feel heavier than others

    I'd like to start keeping track

    Thank you list

    Fenton Murray, RPT


    Sent from my iPhone


  • 2.  RE: Weight of Soundboard Assembly

    Registered Piano Technician
    Posted 26 days ago
    Typical and original S&SB S/B assemblies, without bridges, weigh approx. 17 lbs. give or take. Large "A" boards are similar. Bridges add about 6 lbs. more. Variations in weight from one old board to another (which aren't dramatic) are due to overall panel thickness, degree of edges thinning, and rib dimensions.

    A S&S "D" board without bridges can weigh as much as 25 lbs.

    These structures are relatively lightweight, and independent of attachment to the rim and beam foundations, could never withstand the force of downbearing.





  • 3.  RE: Weight of Soundboard Assembly

    Registered Piano Technician
    Posted 26 days ago
    Meant to add that heavier assemblies, such as found on old M&H boards (more sq. footage, more ribs for a given piano length, thicker rib endings at the central and longest ribs, and extra heavy bridges along with massive rim and beam foundation) resist the string impulses and are considered high (or higher) impedance systems. Overdone, such systems encourage longer sustain (not necessarily very audible), but at the expense of power output, especially "in your face" power.

    Too much downbearing on any system increases impedance (resistance to string impulses), the negative effect sometimes referred to as "choking the tone." Force loading (bearing) and mass loading (amount of wood in the entire system inc. rim and beams) both affect impedance in a primary sense, yet differently regarding filtering of the harmonic spectrum.





  • 4.  RE: Weight of Soundboard Assembly

    Registered Piano Technician
    Posted 25 days ago
    Thank you Nick!
    Great helpful info.
    I weighed my ton of bricks today and it tipped the scales at 16.3 pounds.
    Nice!
    with the base cut off shortening the four longest ribs there's likely the other .7
    that in the elimination  of the coupling device on the three long ribs, which I could still easily add back to the assembly
    this is a maple bar that couples three ribs
    would you comment on its function ?mass loading or simply coupling the ribs to help them share the load?
    incidentally I have choked the tone before, I used to add a degree and a half of down bearing which I got from somebody way before the Internet
    now I'm in the neighborhood of a third of a degree to 1° in the treble.
    this of course requires more exact woodworking on the bridge top
    thanks again Nick
    Fenton

    ------------------------------
    S. Fenton Murray
    Royal Oaks CA

    S. Fenton
    ------------------------------



  • 5.  RE: Weight of Soundboard Assembly

    Registered Piano Technician
    Posted 25 days ago
    You're welcome, Fenton.

    Are you saying that your S&S B has a cutoff bar? Original Bs do not.

    As to the bar connecting the longest three ribs (five ribs on later models), it is called a pulsator bar (PB), but only heaven knows why. I  have heard some interesting speculations as to the existence of a mechanical pulsating effect Re vibrations running down the rib length, reaching the PB, and then crossing laterally to connected ribs. It is unclear (to me, anyway) as to what the desired tonal output is supposed to be. Maybe there is something to this.

    It's been awhile since I read Steinway's patent for the PB, but I recall that its function is to buckle together the stepped-down ribs in the upper bass area. The purpose of this is to encourage those ribs to sort of move as one, and remain "in line", with climate changes which tend to either bend the ribs or relax them. The overall effect of the stepped-down ribs and pulsator bar buckling is to raise the bass corner of the board in a kind of cupola or vaulting effect as the board crowns in ambient conditions. This cupola effect is also realized at all pared down rib ends. I believe that earlier Young Chang grands copied this system. If not YC, then some other Asian import.

    Photos are of a S&S B. Ambient shop conditions are dry, and the board has been kept dry, but even so extra cupping (rib bending) at the upper bass corner is noticeable. The PB is not to be confused with a cutoff bar as it does nothing to limit the length of the longest ribs.

    Your downbearing comment (choking effect) suggests a much broader discussion, but many new and vintage grands (such as Steinway) do apply an average of 1.5 degree of dry bearing (or variations on that main theme) with excellent success. In the strung piano, and on a suitably flexible board, the measurable bearing would typically net 1 to 3/4 or even 1/2 of a degree. Soundboards, as springs, are supposed to be compressed so as to introduce strain energy into the system, later to be tapped by the mechanical vibration of a pulsating string.

    A very celebrated European grand piano maker applies considerably more than the average 1.5 degrees and these pianos sound wonderful.






  • 6.  RE: Weight of Soundboard Assembly

    Registered Piano Technician
    Posted 25 days ago
    Yes Nick,
    I added a cut off bar
    Which shortened 456 and seven Bringing them down to somewhere around 35 1/2 to 37 1/2 inches
    As to measuring down bearing before stringing
    The amount of preloading affects all measurements
    I wedge the board down quite a bit at the struts before I pull my string and measure down Bearing
    😊

    Sent from my iPhone




  • 7.  RE: Weight of Soundboard Assembly

    Registered Piano Technician
    Posted 25 days ago
    Did not see a photo attached

    Sent from my iPhone




  • 8.  RE: Weight of Soundboard Assembly

    Registered Piano Technician
    Posted 25 days ago
    I see the photo now, thank you Nick.

    ------------------------------
    S. Fenton Murray
    Royal Oaks CA

    S. Fenton
    ------------------------------



  • 9.  RE: Weight of Soundboard Assembly

    Posted 25 days ago
    The problem with copying the original Steinway board is that no two boards are alike. Some are well made, some are horrible. Most are too heavy, even when they were diaphragmatic, the weight was reduced incorrectly especially from the top treble.
    The rib scales are always uneven and to copy those dimensions is a missed opportunity for improved soundboard performance. Ribs add stiffness to the panel and thus a stiffness curve is created. Smoothing out these curves has been beneficial.

    The cut off bar in most cases is a bad idea. What's the point of getting a bigger piano if you just reduce the size of the board? The chladni tests I have done show that acoustically, that area is important.  Further tests show that there really isn't much downward force in that corner anyway.  Based on the many boards i have studied that were over 50 years old with still plenty of crown, i'm content with the longest rib being 45". Over that, I may add a cut off bar, but it would be a small one. Also adding a cut off bar and determining its size or location willy nilly is not a good engineering approach because by altering 3 ribs you also change the whole stiffness curve of the entire scale, which should be based on smoothness/evenness so that a collective strength is built into the structure.  Also when you change a ribs length, you also change the position of the driving point, which should be lined up under the bridge. Location of Driving points are critical towards making a board better than the original because massed produced instruments skip that important step. After becoming aware of driving points I found three pianos so far that had them aligned- Richard Gertz MH, an early Weber, and a Stieff upright. Once the driving points of the ribs are aligned ( by adjusting the scalloping length and thickness), the panel too has to be adjusted because once the panel is glued on, it will alter the locations. This is the real reason to change the thickness of the panel in all the key areas, otherwise its a guess. After all of these procedures are done, I have removed only the unnecessary parts of the soundboard and left the structural integrity in tact. My boards usually come out at five pounds lighter.

    -chris





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



  • 10.  RE: Weight of Soundboard Assembly

    Registered Piano Technician
    Posted 25 days ago
    ( by adjusting the scalloping length and thickness)  Interesting. Math? 


  • 11.  RE: Weight of Soundboard Assembly

    Posted 24 days ago
    Paul,
    Math wouldn't help in this case. What I do is deflect the rib at the bridge location and measure the deflection of both ends until they are the same.
    -chris

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



  • 12.  RE: Weight of Soundboard Assembly

    Registered Piano Technician
    Posted 24 days ago
    Empirically. Yeah, thanks!


  • 13.  RE: Weight of Soundboard Assembly

    Registered Piano Technician
    Posted 24 days ago
    Chris wrote:

    "People seem to ignore the fact that to get something heavier to move requires more energy.  So if you input the same energy into a lighter board it will sustain longer because it took less of that energy to get the board moving and the rest of that input energy goes toward sustain."

    Hmmm.  Not sure about that and not sure how you isolate mass from stiffness or ignore the impedance model.  How long a board sustains has to do with how much energy is transferred to the assembly from the vibrating string versus how much is deflected back to the string and how quickly energy dissipates from the assembly.  The ease with which the board moves (soundboard velocity) has much to do with how loud the attack is and is related to how much and how quickly the energy transfers.  Once the energy from the string has transferred there is no more sustain.

    A higher rate of transfer means higher velocity of the board (louder) initially but the energy will dissipate more quickly (shorter sustain).  Mass and stiffness both contribute to impedance characteristics.

    As the illustration shows, left side is lower impedance, energy transfers quickly, soundboard velocity is greater (amplitude is greater), volume at attack is greater, string dissipates more energy more quickly, sustain is shorter.

    Right side shows higher impedance, energy transfers more slowly, soundboard velocity is less (amplitude is less), volume at attack is less, string dissipates energy more slowly, sustain is longer.

    Isn't that pretty basic?



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



  • 14.  RE: Weight of Soundboard Assembly

    Registered Piano Technician
    Posted 24 days ago
    David has this exactly right. Any "debate" as to the existence and / or operation of impedance (high or low or usefully balanced) in a piano soundboard is pointless. There can be no opinion on the matter.

    Ref. http://whyyouhearwhatyouhear.com/chapterfiles/chpt19/other/JAS002128.pdf
    by giordno

    and
    http://www.speech.kth.se/music/5_lectures/introd/introd.html#sound
    intro and section by H. Conklin

    ------------------------------
    Nick Gravagne, RPT
    Mechanical Engineering
    Nick Gravagne Products
    Strawberry, AZ 85544
    gravagnegang@att.net
    928-476-4143
    ------------------------------



  • 15.  RE: Weight of Soundboard Assembly

    Registered Piano Technician
    Posted 23 days ago

    I'm in a room full of experts looking for small takeaways.
    Thank you Jim perimeter cauls that are confined to the glue joint.
    Terry, are you saying you don't worry about the small portion of the rib within the notch?
    Either on side or bottom,
    Sides are tough to nail without shimmimg.
    And you certainly wouldn't want the ribs too tall, erring on the side of safety will be just the opposite with a small gap.
    Questions to the List,

    Other than looking at the physical size of a bridge or rib there's no way to know the mass of that soundboard system without weighing it?
    Is the impedance of the system affected by the amount of down bearing?
    So, can we find this "usefully balanced system"
    On An already created structurally sound soundboard system by applying the appropriate down bearing?

    Sent from my iPhone





  • 16.  RE: Weight of Soundboard Assembly

    Posted 23 days ago
    Fenton M. asked: "Terry, are you saying you don't worry about the small portion of the rib within the notch?
    Either on side or bottom,
    Sides are tough to nail without shimmimg.
    And you certainly wouldn't want the ribs too tall, erring on the side of safety will be just the opposite with a small gap."

    Correct. I do make sure the notch is deep enough for the rib end, but otherwise fit is not an issue. In my book - especially in the tenor & bass area - the main reason for a rib to extend all the way into the rim is to discourage the panel from cracking near the rim in an area where the panel grain direction is near parallel (or tangential) to the rim.


    ------------------------------
    Terry Farrell
    Farrell Piano Service, Inc.
    Brandon, Florida
    terry@farrellpiano.com
    813-684-3505
    ------------------------------



  • 17.  RE: Weight of Soundboard Assembly

    Registered Piano Technician
    Posted 23 days ago
    Hi Fenton, hope you're doing well.

    The impedance *is* affected by downbearing.  Since stiffness is a factor in the impedance characteristics and since increasing compression on the soundboard "spring" (which is a non-linear spring) does stiffen the assembly, more downbearing does raise the impedance level.  The question is how much downbearing is required to adequately stiffen the assembly the desired amount, since compression of the spring is, ultimately, a factor in determining just how stiff the assembly needs to be

    Interestingly, we tend to calculate the rib scale based on load bearing principles not on impedance characteristics, but they are not unrelated.  If we were to build the board such that it achieved the requisite stiffness, say, without any downbearing what would we get?  One thing we would not get is the dynamics of how the board responds when the spring is compressed, or loaded, creating some potential energy in the system.  The board is ready to spring: strings pushing the board down and the board pushing back up with the forces necessarily equal.  That would be, presumably, a much different response than a board which is made with some higher level of load bearing capacity (stiffer) but then with zero downbearing.  Of course, if there's no downbearing load put on the board it sort of defeats the purpose of building the board based on load bearing principles.

    This gets to the question of why do we set downbearing, what is its purpose?  I would say that the purpose are mainly two fold: First, to compress the board to its requisite stiffness for the purpose of controlling impedance. Second to introduce potential energy into the system.  Downbearing as a necessity for coupling the strings to the bridge, as is often cited, seems to be not that necessary owing to the bridge pin array which accomplishes that coupling whether there is downbearing or not.

    Can there be too much downbearing such that the board is "over-compressed" and lacks freedom of mobility?  It seems to me that is possible and could be one reason that some pianos sound "choked".  Interestingly, some years ago some folks were advocating rescaling in a manner that basically just increased the string diameters and thereby the overall tension.  Given the same downbearing settings that would increase pressure on the board, flatten out the assembly somewhat more and possibly put the downward force from the strings out of balance with the upward force of the soundboard.  Not literally, because the forces are necessarily equal, but in terms of how the board is able to respond with inputs of energy.  Think of it like we might think about the spring in a piano hammer.  There is some ideal in which the spring can respond in both directions (left illustration).  If we have a soundboard that is too stiff either by compression or by design, we have something like the hammer pictured in the center.  Sadly, we can't needle soundboards (or lacquer them--at least not to increase stiffness).  If we have something like the picture on the right, then the spring is a bit flabby, the impedance characteristics in the soundboard will be too low with the resulting tonal response.  While the design plays a critical role in determining the final characteristics of the spring, downbearing also plays a role.  In our case, with a soundboard assembly, we are starting with something more akin to the hammer pictured on the right and achieving the requisite stiffness as pictured on the left by the downbearing.  In other words we are compressing the spring to both achieve the level of stiffness we want and to load the spring with potential energy.  Of course with a hammer there are some differences. We can't load the spring with downbearing and must achieve the desired stiffness through other means.  But that's another story.

    From the article Voicing: Methods and Ideas by David Love, copyright, all rights reserved.  Please don't use without permission.


    (BTW I do try and fit the rib ends exactly the height of the notch so that the rib end is glued solidly to the bottom of the notch.  I don't worry too much about a perfect fit on the sides of the rib in those notches.)

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



  • 18.  RE: Weight of Soundboard Assembly

    Member
    Posted 23 days ago
    David Love <This gets to the question of why do we set downbearing, what is its purpose?

    I've done practically a 180 on this point. I no longer am thinking of these systems exclusively as two opposing springs, according to the impedance model David has described. Yes the system has impedance, and yes the string system and board system are in opposition. But what the impedance is contributing, to the tonal performance, is not necessarily been proven. Actually, experiment by Dain and Paullelo suggest that a much higher involvement in efficiency of terminations, as opposed to the usual horribly inefficient bridge pin setup, has much to do with what sound comes out of a belly.

    My observations lead me to define downbearing, almost entirely, as something we have to do because the bridge termination is such a poor structural system. DB is required, in my current take, because the pin terminations cannot retain their peak functionality for any length of time in a negative situation. Positive DB simply provides safety, so DB does not go negative, and yank on the pins.  Plenty of evidence, over the last few years, with folks building zero DB and rib-less systems, prove empirically, that the common impedance model, while describing a real physical effect, is not entirely describing what is happening in the complex piano board system, or does not describe what the interaction between efficient terminations and board system overall impedance actually is.

    While its dangerous to go to the other extreme, and say impedance is not important at all...this would be foolish. But given attention to termination efficiency, pivot terminations, duplex involvement, the levels of impedance we have learned to assume, I think are not as absolute as they may sound. My observations, the last couple of years, in new as well as old boards, is get the DB off the board, to the degree that will not challenge the functionality of the horrible bridge pin termination system, and pay a lot off attention to the conditions that front bridge pin experiences.

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



  • 19.  RE: Weight of Soundboard Assembly

    Registered Piano Technician
    Posted 23 days ago
    All assemblies will have impedance characteristics no matter how you build it or how you set up the downbearing.  It's inherent in the system.  No question there are some different models being made.  I've heard assemblies that were on the stiff side, presumably needing less downbearing to stiffen them and some of them did have less (some didn't).  I wasn't thrilled with the result either way.  But I can't say it was wrong, just didn't appeal to me.

    I've also heard many pianos that had sections of the scale with negative bearing.  I can't say I was pointed to that because of audible termination issues or that I'm even convinced that it necessarily creates termination issues, I suppose, depending on where in the scale it falls.

    There are some very reputable builders who after setting up the piano go through and  tweak the bearing in order to balance the impedance levels (in layman's terms balance the attack and sustain phase of the tonal envelope).  Their claim to be able to accomplish that successfully.  I always do the same thing once the piano is strung, stable, terminations cleaned up, preliminary voicing procedures gone through.  Often I do that initially just to correct minor discrepancies in the residual bearing but I'm also paying attention, especially in the treble, to how that section balances (attack v sustain) to see if i can improve it.  These are pretty subtle changes and clearly won't compensate for a poorly executed set-up.  The lower part of the piano seems less sensitive to changes in bearing.

    The other issue, however, is just as important, in my opinion; loading the soundboard with potential energy.  Now any amount of downbearing will do that but the question is how much is too much and how much is too little or does it matter at all.  I think it does.

    Having heard lots of different designs (and redesigns) over the last 40 years I can say there are clear differences but also a limit to the range of what is acceptable.  I think there is a kind of "sweet spot" where the board not only has impedance balance (attack/sustain) but also has a certainly "liveliness" for lack of a better word.  I can't help but think that liveliness is related to the potential energy in the loaded system combined with the freedom with which the board is able to move in both directions (up and down).  The best pianos get that balance just right.  Lesser pianos don't.

    I can't claim to be able to clearly quantify that.

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



  • 20.  RE: Weight of Soundboard Assembly

    Registered Piano Technician
    Posted 22 days ago
    On a related subject one of the things that I would like to see explored is whether phase cancellation is an inherent problem in piano soundboards.  This speaks somewhat to Chris's comment about the cut-off bar and whether it's necessary or why you would put one in at all (spoiler alert--many manufacturers do and did install cut-off bars routinely).  Phase cancellation is a phenomenon where multiple sound waves of the same frequency are operating out of phase with each other and when that happens the frequencies are diminished, or, if the are operating 180 degrees opposite each other they are lost completely.  It's a problem frequently encountered in the recording industry.

    Looking at various simulations of soundboard response like this one (there are some others including by Bernard Stopper posted some years ago) one wonders whether the natural properties of the SB create some sort of phase cancellations, what the effect of that is on what we hear, is it something that can be addressed, say, by some alternate form of rib design or structure, or even if it's a desirable thing to try and address.  Beyond my pay grade to be able to answer those questions.

    https://www.youtube.com/watch?v=qv3yeoklu3Q&feature=youtu.be

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



  • 21.  RE: Weight of Soundboard Assembly

    Posted 20 days ago
    I suspect the main purpose of downbearing is to increase the sustain time in a soundboard. If it behaves like the weighted lath strip i have that is. It then utilizes the energy its given efficiently.

    I never said impedance doesn't exist. Its not really much different from fluid viscosity except you're dealing with sound waves through a solid.

    I read the Giordano paper and its flaw IMHO is its academic nature. He says its "An Upright piano."  as if all are identical.
    We don't know the brand, panel thickness, rib scale (H,W,L) or wood species. Those will have a significant bearing on the conclusions drawn. Plus he draws his conclusions by comparing to Wogram and Conklin, and again we don't know the data of those pianos either.

    Academic studies aside, My objection to the impedance model is that it doesn't prevent design errors, but tries to correct them after? Yes? At that point your kinda stuck with the design flaws (wrong panel grading, thickness, bad rib scale, bridge mass,etc.) and those related problems.

    Why not just make a board that bypasses those problems to begin with?
    -chris





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



  • 22.  RE: Weight of Soundboard Assembly

    Registered Piano Technician
    Posted 20 days ago

    Well, yes but if downbearing increases sustain it does so by raising the impedance. Impedance just means the rate of energy transfer. Downbearing compresses the soundboard spring, the assembly gets stiffer, the impedance increases and sustain increases.

    The purpose of designing ribscales and factoring in downbearing as a measure of the string load is ultimately to control impedance even though we use things like beam formulas, MOI, spring rates and various other checks and balances, including downbearing settings, as the calculus. Mass obviously plays a role as well but the general principle is light, but not too light, stiff but not too stiff.  The assembly must both be reactive and controlled.

    Finding that balance that translates into something we like probably explains the range of designs that we encounter. I don't know if there's any formula that translates directly to some aesthetic model simply because we can't quantify taste. We recognize when something doesn't work but it's harder to pinpoint a specific tonal outcome from some set of numbers. The reality is that at some point (as Del Fandrich is fond of saying) you have to shoot the designer and build it. You take what you find and build another one tweaking this or that and hope that all other things remain constant. It's a constant process of moving toward some ideal. There are no shortcuts.




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



  • 23.  RE: Weight of Soundboard Assembly

    Registered Piano Technician
    Posted 23 days ago
    Hi Terry,
    I know that fitting the rib do the liner perfectly would be easy money for you you.
    Do you eliminate that step as not necessary, or as an improvement?

    ------------------------------
    S. Fenton Murray
    Royal Oaks CA

    S. Fenton
    ------------------------------



  • 24.  RE: Weight of Soundboard Assembly

    Posted 22 days ago
    Fenton M. asked: "Do you eliminate that step as not necessary, or as an improvement?"

    Not necessary. I have no reason to think such a practice is harmful.

    ------------------------------
    Terry Farrell
    Farrell Piano Service, Inc.
    Brandon, Florida
    terry@farrellpiano.com
    813-684-3505
    ------------------------------



  • 25.  RE: Weight of Soundboard Assembly

    Posted 25 days ago
    Nick G. wrote regarding a piano soundboard: "These structures are relatively lightweight, and independent of attachment to the rim and beam foundations, could never withstand the force of down bearing."

    When you refer to "structures" I presume you are referring to a piano soundboard. I don't understand what you are suggesting that the rim and beam foundation does. I do realize that the soundboard has to set on something - otherwise it will just fall onto the floor! But certainly a soundboard setting unattached (except for gravity) on a large table can have the typical 500 or so pounds of downbearing applied to the bridges and the soundboard won't collapse - or at least is certainly shouldn't. Am I missing something?


    ------------------------------
    Terry Farrell
    Farrell Piano Service, Inc.
    Brandon, Florida
    terry@farrellpiano.com
    813-684-3505
    ------------------------------



  • 26.  RE: Weight of Soundboard Assembly

    Registered Piano Technician
    Posted 24 days ago