<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:st1="urn:schemas-microsoft-com:office:smarttags" xmlns="http://www.w3.org/TR/REC-html40"> <head> <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=us-ascii"> <meta name=Generator content="Microsoft Word 11 (filtered medium)"> <o:SmartTagType namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="PersonName"/>  <style>  </style>  </head> <body bgcolor=white lang=EN-US link=blue vlink=purple> <div class=Section1> To add to this: When I design a radius rib I take into account length, width, height, grain orientation to come up with a deflection number and load bearing capacity. If the rib is tapered as most are – the values that I calculate seem to me to only apply dead in the middle of the rib at the apex of the radius.<o:p></o:p> Gene<o:p></o:p> <o:p> </o:p> <div> <div class=MsoNormal align=center style='text-align:center'> <hr size=2 width="100%" align=center tabindex=-1> </div> From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org] On Behalf Of Gene Nelson Sent: Thursday, May 24, 2012 8:31 AM To: <st1:PersonName w:st="on">pianotech@ptg.org</st1:PersonName> Subject: Re: [pianotech] David Love--Centering the bridge--wasS&S something er other<o:p></o:p> </div> <o:p> </o:p> <div> Not to split hairs here but I had originally talked about centering the bridge on the ribs, not the board.<o:p></o:p> </div> <div> In my mind the ribs are the restorative force that responds to the displacement caused by hammer/string energy. The board although has stiffness, provides the mass that influences how quickly the restorative force of the ribs can do their job and this influences tone.<o:p></o:p> </div> <div> Regardless of the proximity of bridge to rim with respect to the board, I feel that placing a bridge at the end of a rib where tapering is greatest and scarfing begins changes it's response. <o:p></o:p> </div> <div> <o:p> </o:p> </div> <div> Sent from my iPhone<o:p></o:p> </div> <div> On May 24, 2012, at 7:32 AM, "David Love" <<a href="mailto:davidlovepianos@comcast.net">davidlovepianos@comcast.net</a>> wrote:<o:p></o:p> </div> <blockquote style='margin-top:5.0pt;margin-bottom:5.0pt' type=cite> <div> Let me add re this discussion in terms of better or worse.  We’re all reluctant to get into that, I know, because we don’t want to relegate the discussion to one of simply a matter of personal taste.  But better or worse eventually has to become part of the dialogue if we are making changes.  It isn’t enough, at least not for me, to say, ok, that’s different.  At some point I have to make a judgment about whether I like it better or not if I’m going to keep doing it.  For me, simply different is not an end in itself.  <u5:p></u5:p><o:p></o:p> <u5:p> </u5:p><o:p></o:p> <div> David Love<u5:p></u5:p><o:p></o:p> <a href="http://www.davidlovepianos.com">www.davidlovepianos.com</a><u5:p></u5:p><o:p></o:p> </div> <u5:p> </u5:p><o:p></o:p> <div> <div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'> From: <a href="mailto:pianotech-bounces@ptg.org">pianotech-bounces@ptg.org</a> [mailto:pianotech-bounces@ptg.org] On Behalf Of David Love Sent: Thursday, May 24, 2012 7:22 AM To: <a href="mailto:pianotech@ptg.org">pianotech@ptg.org</a> Subject: Re: [pianotech] David Love--Centering the bridge--was S&S something er other<u5:p></u5:p><o:p></o:p> </div> </div> <u5:p> <o:p></o:p></u5:p> First, I do know better than to argue “better or worse” and that’s not where I was headed.  And you may be right about the issue of proximity to the rim versus centerline location.  However, since this question I asked was prompted by a discussion of how to get the high end of the treble bridge more “centered” as if that was desirable, the question is relevant.  Do a simple experiment, take a tuning fork and strike it and place it in the center of a soundboard (unstrung piano will be easier) and time how long until the sound dissipates.  Then do the same thing and place the fork nearer to the rim.  I think you’ll find that it takes longer but do it for yourself.  The impedance characteristics (the rate of energy transfer) is impacted by the location of the energy input with respect to the rim.   Since a centered bridge is as far from the rim as  possible whatever the width of the piano at that section one has to assume that the energy will flow through the system and dissipate more quickly the more centered the bridge is.  With respect to the high treble where sustain is something that is sought after (by some) seeking to center the bridge may not be desirable and may, in fact, be undesirable.  With respect to the lower end of the piano you certainly want it farther away from the rim for reasons mentioned.  For those who have built transition bridges and located those bridges more toward the center of the piano (as in the old three bridge systems), you know that you can encounter impedance problems unless you add support and structure to the transition bridge and even then there can be problems.  So proximity to the rim certainly can make a difference not just in how sections might blend but in the overall quality of the sound as it is impacted by the differences in impedance.  <u5:p></u5:p><o:p></o:p> <u5:p> </u5:p><o:p></o:p> Since the impedance characteristics impact the relationship between the attack and sustain phases, an important consideration in targeting piano tone, I think it’s worth asking whether or not the location of the bridge on a soundboard makes a difference.  I don’t know how to answer it exactly but then if I did I wouldn’t be posing the question.  There are, will be, other differences to be sure.  A wider soundboard will likely have a different rib scale, for example.  A larger area soundboard will also tend to produce a lower frequency when you pound on it.  Does that lower frequency have an impact on the character of the initial percussive attack?  To my ear it seems to but I can’t be sure that’s that actual source of the difference.  <u5:p></u5:p><o:p></o:p> <u5:p> </u5:p><o:p></o:p> A general philosophy of “make no assumptions” has a benefit in that it challenges us to question the way things were done in the past.  But if one is being faithful to that philosophy, it should also bring into question the practices we find ourselves engaging in by virtue of having challenged those old assumptions in the first place.  <u5:p></u5:p><o:p></o:p> <u5:p> </u5:p><o:p></o:p> David Love<u5:p></u5:p><o:p></o:p> <a href="http://www.davidlovepianos.com">www.davidlovepianos.com</a><u5:p></u5:p><o:p></o:p> <u5:p> </u5:p><o:p></o:p> <div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'> From: <a href="mailto:pianotech-bounces@ptg.org">pianotech-bounces@ptg.org</a> [<a href="mailto:pianotech-bounces@ptg.org">mailto:pianotech-bounces@ptg.org</a>] On Behalf Of <a href="mailto:mike.spalding1@frontier.com">mike.spalding1@frontier.com</a> Sent: Thursday, May 24, 2012 5:01 AM To: <a href="mailto:pianotech@ptg.org">pianotech@ptg.org</a> Subject: Re: [pianotech] David Love--Centering the bridge--was S&S something er other<u5:p></u5:p><o:p></o:p> </div> <u5:p> <o:p></o:p></u5:p> And it may be that bridge location relative to centerline is nowhere near as important as bridge location relative to soundboard edge (and, of course, the stiffness of that edge).  Think of the tonal effect of a bass bridge too close to the rim, or of floating the soundboard at the bass bridge, or a treble bridge too close to the belly rail. <o:p></o:p><u5:p></u5:p> <div> <div> <div> <div class=MsoNormal align=center style='text-align:center'> <hr size=1 width="100%" align=center> </div> From: Ron Nossaman <<a href="mailto:rnossaman@cox.net">rnossaman@cox.net</a>> To: <a href="mailto:pianotech@ptg.org">pianotech@ptg.org</a> Sent: Wednesday, May 23, 2012 11:09 PM Subject: Re: [pianotech] David Love--Centering the bridge--was S&S something er other<u5:p></u5:p><o:p></o:p> </div> On 5/23/2012 9:46 PM, <a href="mailto:mike.spalding1@frontier.com">mike.spalding1@frontier.com</a> wrote: > I like Dale's perception of this question. Different configurations > of bridge relative to centerline may have different tonal > characteristics, but not necessarily better or worse. and other > factors, such as soundboard thinning and rib end scallops, can skew > it one way or the other. Yes, there are way too many variables to start presuming the tonal nuances of centering bridges on ribs with no way to isolate the effect from all the myriad potential causes. From a design standpoint, I do it to what degree I can because that's the point of least compromised response, and I'd like to have some sort of standard as a starting place. By the time you throw in scaling, panel thinning, panel compression levels, rib stiffness and loading, hammer choice and voicing, and the phase of the moon, it will sound how it sounds, and you just can't pick it apart minutely as specific cause and effect details by looking at the complex mix. Ron N<o:p></o:p><u5:p></u5:p> </div> </div> </div> </blockquote> </div> </body> </html>