A hard rim or (case) offers the board to vibrate more stablely and then contribute to the focused,pure and solid sound. While a piano soundboard vibrates,there is more or less unstable vibration(whick is called "chaos" vibration),as well as very stable vibration(named vibration modes). "Chaos" vibration could be easily understood if we think about a piano string with fluse beat.We all know that fause beat usually comes from bad string temination,such as loosed bridge pins,bad-knotched bridge cap,etc'.the fause beat is a good sample of unstable vibration(chaos). The maple rim can restrict the chaos vibration of the board the then allowe the board vibrate more stable,more solid and,then creats a pure, focused piano sound. That's my understanding of a solid piano case. Baoli --- Tony Caught <caute@optusnet.com.au> wrote: > Hi Gordon, > > I try to look at this another way, I know that what > you are saying seems to > be the general consensus but. > > The original vibrations come from the strings, these > vibrations are > transmitted along the bridge to other strings > causing them to vibrate in > sympathy with the original strings and at the same > time, to the soundboard. > Now the soundboard is vibrating in a very complex > manner. It must be to > allow machines like Tunelab to pick up all the > harmonics of a particular > note when other notes are sounding as well. > > Now all these frequencies travel at different wave > lengths and if they are > reflected back from the rim out of phase then they > would cancel out the > frequency coming from the string. > > Thus, IF the rim is reflecting the vibrations back > into the soundboard the > resultant sound will vary in accordance to the pitch > of the notes and key in > which they are played. I would prefer a sound that > comes from the strings > without any rim echo. > > The firmer the rim or the edging of the soundboard > the better but my > thoughts are this. If the rim is solid and rigid > then the soundboard will > be held in a more exacting position. If it is solid > it will also not > vibrate. Yes it will transmit the sound but it will > not vibrate as the > soundboard does, thus the vibrations stop at that > point. > > Possibly in the ideal piano the rim should be rigid > and solid, the > soundboard attached only by the ribs with the boards > thickness varying from > 1/4" in the bass to 1/2" in the treble with possibly > the ribs becoming > closer as they progress to wards the treble. This > way the rim cannot > possibly reflect the vibrations back and the board > would be totally reliant > on the strings for the sound generation. > > When the sound or vibrations are leaked to the case > whether this is via the > rim or the pressure bar or the iron frame the energy > is taken away from the > soundboard to the detriment of the tonal qualities > of the piano. > > A solid rim is ideal for holding the soundboard and > thus the bridges > attached to the soundboard in an exact position. If > the soundboard is > attached only via the ribs less restrictions are > there to allow the > soundboard to vibrate freely. If soundboard is > vibrating freely then there > is less energy lost. If the soundboard has more > energy then the sustain will > be longer, the volume louder and the tone more > harmonically rich. > > Some manufacturers are heading this way but at a > slow pace. But as you have > heard from Ron Overs and Del Fandrich and and first > you have to prove you > are right over 50 years to be accepted. There are > many other aspects of > construction to be considered, maybe if this thread > carries on they also can > be explored. > > Now, what do you think. Lets see if we can build on > this concept or should > it be cast aside. > > Regards > > > Tony Caught > caute@optusnet.com.au > > > > ----- Original Message ----- > From: "gordon stelter" <lclgcnp@yahoo.com> > To: "Pianotech" <pianotech@ptg.org> > Sent: Monday, September 16, 2002 6:26 PM > Subject: Re: Piano Sound: was something else > > > > > --- Tony Caught <caute@optusnet.com.au> wrote: > > > So you says that a rim reflects or has to > reflect ?. And why should it. > ? > > > > > Well, it WILL reflect some vibration back, > regardless. The stiffer, > denser, and more rigid the rim is, the more > vibrations will be relected back > into the board. What is not reflected will be > tranmitted to the case/rim, > and either carried back to the board somewhere else > or dissipated as heat in > the rim wood fibers. I think it is optimal that this > vibration be dissipated > by heat in the lampshades and curtains of the room > the piano sits in, not > the piano itself. In other words, as much of the > pianist's finger pressure > as possible should be converted to sound and LEAVE > the piano, before being > absorbed by soft materials. I believe the softer > case woods in many modern > pianos, > Asian or otherwise, largely contributes to their > relatively impotent tone > when compared to high quality pianos from 100 years > ago!!! > That said, the relationship between stiffness > and density will play a > vital role in the piano's tonal "personality". Some > pianos ( Boesendorfer, > old Chickerings, Emersons, etc. ) use spruce for > case and beams, so that > some of the energy transmitted to them will still be > converted to audible > resonance. Spruce, while light, is still considered > a "hardwood" as the > fibers between the rfesonant vacuous cells are > tightly compacted. So it has > both high transmittal and resonant properties. But > not the best reflective > properties when used in a case application, as it is > not dense enough, > overall, to make extremely rigid structures. > At the other extreme are old Knabes, which > have the most "rock hard" > rims (and cases) I have ever seen! In these pianos a > fast, loud, rather hard > tone is emitted, as vibrations are quickly kicked > back to the board, which > is held very rigidly by massive rock maple cases. I > have seen many 100 year > old Knabes > with excellent crown. It should also be noted that > these boards have a > heavy coat of finish, usually shellac, which is > extremely stiff ( and > brittle ) when fully cured. This brittleness surely > aids vibrations as they > travel across the face of the board. ( But I use 2 > part "conversion" > varnish, as it also has this property but is more > impervious to humidity, > and is inedible to the house crickets that live > here. "Down side" is that it > emits formaldehyde fumes like crazy for several > months as it cures. ) > On many old pianos the cases were also > veneered with rosewood or > ebony. This was not just cosmetic, as these very > dense woods transmited > vibrations around the case to where they could be > re-absorbed by the board. > The builders new this. > > > Gordon Stelter > > > _______________________________________________ > pianotech list info: https://www.moypiano.com/resources/#archives __________________________________________________ Do you Yahoo!? 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