This is a multi-part message in MIME format. ---------------------- multipart/alternative attachment ----- Original Message -----=20 From: Erwinspiano@AOL.COM=20 To: pianotech@ptg.org=20 Sent: December 30, 2001 7:34 PM Subject: Re: Piano Rims ./soundboard stiffness .=20 Del writes=20 >=20 > >Typically the loss of sustain time due to a low-mass,=20 > >low-stiffness rim is countered by making the soundboard thicker = and the=20 ribs=20 > >a bit stiffer. (Though ribs don't really have much effect on tone = > >performance through the last couple of octaves in the treble.)=20 Phil Ford=20 > Why do you say that? Should the ribs be removed in=20 > this area? What then? Make the board a little=20 > thicker?=20 With the bridge so close to the belly rail the stiffness of the = soundboard=20 panel has much more effect on the soundboard system impedance than = do the=20 ribs.=20 Del=20 =20 Hi Del=20 That being the case why is the more modern/recent technique of = using a spruce rib preferred in the capo treble areas as opposed to the = lighter weight sugar pine version which was original equipment? Also = if it is true that the ribs don't effect impedance as much as the board = stiffness does then why so much weakness in the killer regions or is = that the point where the rib stiffness/impedance really comes into play? = My thinking is that right around note c- 6 must be crucial cross over = point. It's clear from the diagram you posted that in radial version = boards the soundboard grain and ribs don't cross at right angles in the = upper trebles creating greater stiffness and the shorter grain angles in = front of the bridge at the belly do as well (due to the non traditional = panel grain orientation off the belly rail ). I think I'm starting to = get it=20 If the ribs have little to do with stiffness/impedance and tone = production up high it would seem that all this stiffening shouldn't be = needed. However the feedback is that the sustain is so much better in = this radial board indicating that a lot of extra stiffness is needed = from the board and the rib to get the improved sustain characteristics. = Am I missing something?=20 My experience is that too much stiffness can make the board a = little stingy in the trebles including the killer region. I find that I = personally like the sound from retaining the sugar pine configuration in = the capo areas but crowning them from roughly a 50 ft radius graduated = up to about a 25 ft. On the last rib. This obviously adds some stiffness = the flat ribs lacked and it seems to have a good tonal balance between = attack/power and sustain/power balance but doesn't make it to tight = sounding. I hate subjective terms=20 The on going question is how stiff is stiff enough?=20 My qustions/comments are in relation to reproducing original = designs and not really to redesigns all though I'm sure the principles = are similar and applicable.=20 I love this stuff.=20 Best-------------------------------- Dale Erwin Personally, I'm not convinced there is much difference in performance in = the top octave or two that can be attributed to the use of spruce ribs = vs. sugar pine ribs. I even tried maple ribs up there once--not much = difference I could attribute to those either. There are so many = variables involved in the process and the structure it's impossible for = me to tell what to attribute to what. I've not ever heard of any = controlled tests done to confirm just what changes in performance there = might be. The traditional piano (with its compression-crowned soundboard) depends = at least as much on the internal compression of the wood in the = soundboard panel (and the stress interaction this creates with the ribs) = for its overall stiffness than it does on the ribs per se. With = conventional soundboard design the region around C6 is a particularly = difficult area for this. Yes, I think got it. I should probably have said something like, "With = the bridge so close to the belly rail the stiffness of the soundboard = panel has much more effect on the soundboard system impedance than do = the ribs in a soundboard assembly of conventional design." You might = also note in my drawing that the ribs are a bit closer together than is = common. Del ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/33/6a/a7/cc/attachment.htm ---------------------- multipart/alternative attachment--
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