<!doctype html public "-//W3C//DTD W3 HTML//EN"> <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=iso-8859-1"> <meta name=ProgId content=Word.Document> <meta name=Generator content="Microsoft Word 10"> <meta name=Originator content="Microsoft Word 10"> <link rel=File-List href="cid:filelist.xml@01C51148.22DAA880"> <title>re: Killer Octave & Pitch Raise</title> <o:SmartTagType = namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="City"/> <o:SmartTagType = namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="place"/> <o:SmartTagType = namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="time"/> <o:SmartTagType = namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="date"/> <o:SmartTagType = namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="PersonName"/>  <style>  </style>  </head> <body lang=EN-US link=blue vlink=purple = style='tab-interval:.5in'> <div class=Section1> I should have said stiffness in the = panel versus stiffness in the assembly. = I mean that in terms of acoustic properties. <o:p></o:p> <o:p> </o:p> <div> David Love <st1:PersonName>davidlovepianos@comcast.net</f= ont></st1:PersonName> = <o:p></o:p> </div> -----Original = Message----- From: = pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org] On Behalf Of David Love Sent: = <st1:date Month="2" Day="12" Year="2005">Saturday, February 12, = 2005</st1:date> <st1:time Hour="20" Minute="35">8:35 PM</st1:time> To: = <st1:PersonName>'Pianotech'</= st1:PersonName> Subject: More CC vs RC = questions was RE: Killer Octave & Pitch Raise <o:p> </o:p> Another very = basic question about these design elements: Is there a difference between tension in the panel and stiffness of the panel? I mean that in terms = of the physical properties of the panel. Intuitively, it seems that the CC board would be under greater = tension owing to the crowing process. = While the same amount of stiffness might be achieved by how the board is loaded = and the amount of bearing, does tension (whatever that is) play a role in tonal = output?<o:p></o:p> <o:p> </o:p>= Another question = is this: A CC board, as = we’ve discussed, runs a greater risk of compression set and cellular wood = damage due to the fact that it bears some of the load that is born by the ribs to a greater degree in a RC board. = Do I have that right? If that’s = the case, how do we know that it isn’t the fact that the panel bears more of = the load that contributes to the tonal output. While the ribs may bear the load and spare the panel to some = degree, is there not a tonal price to be paid for that. Which isn’t to say that an RC board can’t be made to = sound acceptable or good, they obviously can, but will it sound different by = virtue of the type of crowning and what is that difference, if any? I think that’s an important question. = <o:p></o:p> <o:p> </o:p>= <div> David Love <st1:PersonName>davidlovepianos@comcast.net</f= ont></st1:PersonName> = <o:p></o:p> </div> -----Original = Message----- From: = pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org] On Behalf Of Overs Pianos Sent: = <st1:date Month="2" Day="12" Year="2005">Saturday, February 12, = 2005</st1:date> <st1:time Hour="18" Minute="45">6:45 PM</st1:time> To: Pianotech Subject: re: Killer = Octave & Pitch Raise<o:p></o:p> <o:p> </o:p> <div> At 1:54 AM +0100 <st1:date = Month="12" Day="2" Year="2005">12/2/05</st1:date>, Richard Brekne = wrote:<o:p></o:p> </div> <blockquote style='margin-top:5.0pt;margin-bottom:5.0pt' type=cite = cite> <o:p> </o:p> </blockquote> <blockquote style='margin-top:5.0pt;margin-bottom:5.0pt' type=cite = cite> Udo Steingræber and I got into a = conversation about this in = <st1:City><st1:place>Helsinki</st1:place></st1:City> a couple years back on the only opportunity I've had to sit and chat with him.  It was part of a discussion where he was explaining why he = felt compression soundboards were the way to go.<o:p></o:p> </blockquote> <div> <o:p> </o:p> </div> <div> You've mentioned this before on the list, but = the question I asked at the time of your original post, "has Udo done = any modelling experiments with both types of construction?" remains unanswered. Would you ask Udo this question, since you have already = established a relationship with him?<o:p></o:p> </div> <div> <o:p> </o:p> </div> <div> I have done modelling with both types of = construction. I have built full size models and tested them on the bench. For those = who might be interested to see an image of our experimental setup, go to our = second web page on my I-rib development.<o:p></o:p> </div> <div> <o:p> </o:p> </div> <div> http://overspianos.com.au/iribbd2.html<o:p></o= :p> </div> <div> <o:p> </o:p> </div> <div> Regardless of the sound board construction = method chosen, the maximum stress on the sound board assembly will be directly = under the bridges, if the ribs are of a uniform cross-sectional area. When RC construction is employed, the depth of the ribs under the bridges can be increased to reduce the stress point under the bridge. Our I-ribs are = flat on the bottom flange and crowned on the top flange, so they will be = relatively stronger in the middle where they are deeper (standard solid RC ribs can = be profiled in the same way). Rib feathering allows for all boards to be appropriately weakened at the edges where there is less stress, to allow = for greater sound board activity. Our I-ribs are tapered also in the width = of the bottom flange (we call this secondary feathering), which allows us to = further vary the strength of the rib along its length, creating a sound board = which deflects more uniformly under the downbearing load. The same result can = be achieved with a solid RC rib, by varying depth along its length. Terry = Farrell has shown some excellent images of RC ribs which had significantly = greater depth in their mid sections. Would you like to post a couple of links, = Terry, to show the troops what you and others are doing? Varying the strength = of the ribs along their length is, I believe, the way forward in sound board = design. I can't imagine how similar rib strength variation could be achieved with = a CC board, unless the builder is prepared to forgo crowning in the proximity = of the bridges, since a deeper CC rib will prevent the re-hydrated panel from = forcing the board into a crown.<o:p></o:p> </div> <div> <o:p> </o:p> </div> <blockquote style='margin-top:5.0pt;margin-bottom:5.0pt' type=cite = cite> He mentioned something about the so called K = point (I think this is a Klaus Fenner coined term), which as I understood it was = that point on the soundboard where crown from both along the grain and cross = the grain intersect and is at its highest point. This area is exactly (and = always) in the area typically refered to by american techs as the <<killer octave>> area, and of course varies somewhat from piano to = piano.<o:p></o:p> </blockquote> <div> <o:p> </o:p> </div> <div> The highest point of the sound board, from = the instruments I have measured, is somewhat further down the long bridge = towards the middle of the board.<o:p></o:p> </div> <div> <o:p> </o:p> </div> <div> The killer octave, for most 'conventional' = designs, is the grossly overloaded part of the sound board. They also are often = overloaded directly under the bridges. Try placing a 150 mm steel rule under the = bridge, almost anywhere, on the underside of the panel of any CC boarded piano. = The rule almost always will rock, which indicates that the crown has = reversed directly under the bridges. I have observed this many times, even with = pianos which were under one year old. Quite a number of the new grand pianos = exhibited at last year's Adelaide piano technicians convention had reverse crown = directly under the bridges. And this observation was not limited just to the = lower priced pianos either (the = checking with rule was done late in the night to avoid upsetting various = exhibitors - some examples already had 'nicely developed' killer octave zones - Ron N = was party to these observations = also).<o:p></o:p> </div> <div> <o:p> </o:p> </div> <blockquote style='margin-top:5.0pt;margin-bottom:5.0pt' type=cite = cite>  It is then  also the exact point = then that is most vunerable to failures.<o:p></o:p> </blockquote> <div> <o:p> </o:p> </div> <div> How do you arrive at this conclusion? The = only part of any sound board which is prone to failure would seem to be those areas = that are under-engineered and overloaded.<o:p></o:p> </div> <div> <o:p> </o:p> </div> <blockquote style='margin-top:5.0pt;margin-bottom:5.0pt' type=cite = cite> Udo was of the position that along the grain = crowning was every bit as important as cross grain = crown.<o:p></o:p> </blockquote> <div> <o:p> </o:p> </div> <div> I would have expected this point to be a = 'position', rather than a 'conclusion'. Crowning along the grain is something that = will occur naturally in any sound board once it is fitted to the case, = whether CC or RC crowning is used. However, the resultant crown along the grain won't = really help a sound board to better withstand the downbearing forces. While it = might appear to be beneficial, the span along the long bridge relative the = section sizes of the materials used, will make it impossible for it to be of any serious assistance.<o:p></o:p> </div> <div> <o:p> </o:p> </div> <blockquote style='margin-top:5.0pt;margin-bottom:5.0pt' type=cite = cite>   Something to do with along the grain compression due to downbearing having a stablizing effect on cross grain = crown and strength.<o:p></o:p> </blockquote> <div> <o:p> </o:p> </div> <div> I doubt it. Very slight soundboard = compression will result along the grain as the downbearing is applied, especially since = the bridge is located above the 'mounting-plane' of the inner rim, but it = won't help or hinder the net ability of a sound board to resist sinking. = Furthermore, it would be very difficult to build a sound board with compression = crowning along the long grain, since the bridge would need to be dried before = gluing it to the panel, and there would be insufficient shrinkage of the bridge, = along its length, to achieve an alleged worthwhile crown along the = grain.<o:p></o:p> </div> <div> <o:p> </o:p> </div> <div> The ability of a sound board to support = downbearing is related primarily to the ability of each rib/board segment's ability to = support the load to which it is subjected.<o:p></o:p> </div> <div> <o:p> </o:p> </div> <div> This, I think, ties in with Ron N's reply to = Terry Farrell's original post;<o:p></o:p> </div> <div> <o:p> </o:p> </div> <div> At = 6:41 AM -0600 12/2/05, Ron Nossaman wrote:<o:p></o:p> </div> <blockquote style='margin-top:5.0pt;margin-bottom:5.0pt' type=cite = cite> <![if !supportLineBreakNewLine]> <![endif]><o:p></o:p> At = 5:22 PM -0500 11/2/05, Terry wrote:<o:p></o:p> <blockquote style='margin-top:5.0pt;margin-bottom:5.0pt' type=cite = cite> When I raise the pitch of a = piano, typically I find that I need to pull an area of the treble, commonly = around the sixth octave or so, a bit extra so that area does not end up flat when = the pitch raise is completed. I use typical pitch raise overpulls - 20% in = bass, 25% in tenor and 33% or so in treble - but that one octave or so in the = treble needs to go a little further - maybe 35 or 38%. I find this to be true = on most pianos.<o:p></o:p> </blockquote> <blockquote style='margin-top:5.0pt;margin-bottom:5.0pt' type=cite = cite>  <o:p></o:p> </blockquote> <blockquote style='margin-top:5.0pt;margin-bottom:5.0pt' type=cite = cite> My understanding is that = one factor that may conspire to produce a killer octave (low volume and/or short = sustain) in a piano is the fact that the killer octave area is also the area the long bridge is curved most - rather than having = the downbearing supported in part by a straight (or nearly so) bridge (like = in the tenor), the curved part of the long bridge in the killer octave area is = more prone to rolling - I know, not rolling - actually soundboard deformation = - but I'm trying to point out that it can rotate in this area more easily than = other areas.<o:p></o:p> </blockquote> <blockquote style='margin-top:5.0pt;margin-bottom:5.0pt' type=cite = cite>  <o:p></o:p> </blockquote> <blockquote style='margin-top:5.0pt;margin-bottom:5.0pt' type=cite = cite> My question is - might = these two phenomena be related? Is the killer octave area more prone to going = flat because the bridge is rotating (I suppose in part due to soundboard not = having enough support in that area)?<o:p></o:p> </blockquote> <blockquote style='margin-top:5.0pt;margin-bottom:5.0pt' type=cite = cite>  <o:p></o:p> </blockquote> <blockquote style='margin-top:5.0pt;margin-bottom:5.0pt' type=cite = cite> Thanks for any = thoughts.<o:p></o:p> </blockquote> <blockquote style='margin-top:5.0pt;margin-bottom:5.0pt' type=cite = cite>  <o:p></o:p> </blockquote> <blockquote style='margin-top:5.0pt;margin-bottom:5.0pt' type=cite = cite> Terry = Farrell<o:p></o:p> </blockquote> </blockquote> <blockquote style='margin-top:5.0pt;margin-bottom:5.0pt' type=cite = cite> <o:p> </o:p> </blockquote> <blockquote style='margin-top:5.0pt;margin-bottom:5.0pt' type=cite = cite> I = think so. The tenor isn't heavily loaded, and the soundboard (usually) supports = it, though it sinks some. The upper treble section is heavily loaded, and = barely sinks at all because the bridge is very close to the belly at the top = end. It's sitting on a brick, essentially. With the top end of the bridge as a = fulcrum, any load put on the treble levers down to the curve in the bridge, where = it loses beam support because of the curve. So the killer octave has to = support not only it's own heavy bearing load, but gets additional load from both = the tenor and treble by virtue of being at the end of two third class levers courtesy of that curve.<o:p></o:p> </blockquote> <div> <o:p> </o:p> </div> <div> Exactly Ron N, and the situation in many = cases is made even worse due to the lack of an appropriate sound board cut-off, in = this area of the board, which causes the ribs to be way too long and way too weak = to withstand the excessive forces under which they = placed.<o:p></o:p> </div> <div> <o:p> </o:p> </div> <blockquote style='margin-top:5.0pt;margin-bottom:5.0pt' type=cite = cite> The  soundboard deflects proportionally more at the curve, and the bridge = rotates with it's center of rotation being a line through somewhere at the top = end, and somewhere in the mid tenor. The part of the bridge furthest away from = this center of rotation is the curve, where the killer octave is. This is = also why it's possible to have both negative crown and negative overall bearing = in the killer octave.<o:p></o:p> </blockquote> <div> <o:p> </o:p> </div> <div> Well put Ron N.<o:p></o:p> </div> <div> <o:p> </o:p> </div> <div> And now, back to Mr Steingræber's = claims.<o:p></o:p> </div> <div> <o:p> </o:p> </div> <blockquote style='margin-top:5.0pt;margin-bottom:5.0pt' type=cite = cite>   He also meant that both these were = needed to produce the kind of acoustical results he wanted from a = soundboard.<o:p></o:p> </blockquote> <div> <o:p> </o:p> </div> <div> Mmm? For those of you who haven't seen a = sound board being glued into a case, the 'free board' doesn't even nearly conform to = the profile of the inner rim. The sound board will always have to be clamped = to the inner rim (which places it under some initial stress - which will occur regardless of the construction methods = used).<o:p></o:p> </div> <div> <o:p> </o:p> </div> <blockquote style='margin-top:5.0pt;margin-bottom:5.0pt' type=cite = cite> I'm under the impression, correct me if I am = wrong, that most of the rib crowned methods extoled on this list do not employ = any purposefull along the grain crowning as part of how the panels are = attached to the rim, and therefor do not have this vunerablity.  It would stand = to reason that they too are not able to create the same acoustical  results.... (whether that is preferable or not is an entirely different subject).<o:p></o:p> </blockquote> <div> <o:p> </o:p> </div> <div> I cannot see how it 'stand[s] to reason' at = all. You seem to be implying that RC sound boards are not able to 'create the = same acoustical results', but I don't see how Udo arrived at this conclusion. = You seem to be implying that the RC school membership don't build crown into = the board along the grain. It can't be avoided once the sound board is = installed, regardless of which construction school you happen to be sitting. But = you seem to go further by implying the crown along the grain is somehow a = critical component of tone building. I am not convinced that it is, but even if = it were, its an unavoidable result with both methods once the panel is fitted to = the case.<o:p></o:p> </div> <div> <o:p> </o:p> </div> <div> I believe the important issue is that the = majority of boards are grossly overload at the second top string = section.<o:p></o:p> </div> <div> <o:p> </o:p> </div> <div> Ron O.<o:p></o:p> </div> <pre style='margin-left:1.0in'><x-sigsep>-- <o:p></o:p></pre> <div> </x-sigsep>OVERS PIANOS - = SYDNEY<o:p></o:p> </div> <div>    Grand Piano = Manufacturers _______________________<o:p></o:p> </div> <div> Web http://overspianos.com.au<o:p></o:p> </div> <div> mailto:ron@overspianos.com.au _______________________<o:p></o:p> </div> </div> </body> </html>