---------------------- multipart/mixed attachment --=====================_25959187==.ALT Del, Thank you! Those answers serve to solidify a great deal of my=20 ideas about soundboards in general. I was hoping I was on the right track.= =20 I guess I'm getting there a little bit at a time. Best, Greg At 09:34 PM 5/9/2003, you wrote: > >----- Original Message ----- >From: "Greg Newell" <<mailto:gnewell@ameritech.net>gnewell@ameritech.net> >To: "Pianotech" <<mailto:pianotech@ptg.org>pianotech@ptg.org> >Sent: May 09, 2003 3:46 PM >Subject: Re: Modal Analysis > > >Del, > I wonder if you might help me understand this. You say, "And a >good example of why soundboard cutoff bars can (should) be used to some >advantage." In the views I saw on the web page there seemed to be quite a >bit of movement in the area normally eliminated by a cutoff bar. > >Yes, and it is exactly out of phase with the motion of the bridge and the= =20 >area of the soundboard surrounding the bridge. > > > >---------------------------- >If there >is that much movement is that not contributing to what we hear rather than >detracting from it? As I type and look back at the pictures in another >window I'm tempted to rationalize that while one part of the board, >specifically that part in question, is on the down part of a wave the rest >of the board is up and visa versa. Is this what you wish to eliminate with >the cutoff bar so that the board acts as a whole instead of in separate >parts? It would be interesting to see what the board would do using this >modal analysis with a cutoff bar installed. >Yes, this is what I am trying to eliminate with the addition of a=20 >carefully placed cutoff bar. Energy is being traded back and forth and is= =20 >essentially being wasted. Going back to my analogy of the piano soundboard= =20 >functioning somewhat like loudspeaker driver: the soundboard functions=20 >best when it is appropriately sized for the frequency range through which= =20 >it is expected to function. If it is too small it is great for sustain but= =20 >will not be able to develope the desired power. If it is too large,=20 >however, both sustain and power suffer. Sustain because energy is being=20 >wasted in the excess soundboard area and power because acoustical energy=20 >is being traded back and forth between the various resonant areas and is=20 >effectively cancelled out. > > > >---------------------------- > This brings me to another question. In all of the examples I've >seen of pictures with cutoff bars installed, all seem to be a great deal >smaller in size than the corresponding inner rim section they are >replacing. I understand that they are epoxied into the existing inner rim >and doweled as well. I further understand, I think, that the cutoff bar is >attached to any support beams over which it passes. Do the combinations of >these items make it unnecessary that it be of similar dimension as the >inner rim? > >Yes. That and the fact that they are generally rather short. Early on we=20 >did try to make them somewhat more massive but over time have found that=20 >this is not really necessary. I don't have any formula for this, I just=20 >look at the thing and decide. If it is quite a long cutoff I'll make it= taller. > >Del > >--- > >Checked by AVG anti-virus system (http://www.grisoft.com). >Version: 6.0.474 / Virus Database: 272 - Release Date: 4/18/2003 Greg Newell Greg's piano Fort=E9 mailto:gnewell@ameritech.net=20 --=====================_25959187==.ALT An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/cf/ac/b2/45/attachment.htm --=====================_25959187==.ALT-- ---------------------- multipart/mixed attachment --- Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.474 / Virus Database: 272 - Release Date: 4/18/2003 ---------------------- multipart/mixed attachment--
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