<html> <body> Del, <x-tab>        </x-tab>Thank you! Those answers serve to solidify a great deal of my ideas about soundboards in general. I was hoping I was on the right track. I guess I'm getting there a little bit at a time. Best, Greg At 09:34 PM 5/9/2003, you wrote: <blockquote type=cite class=cite cite>  ----- Original Message ----- From: "Greg Newell" <<a= href="mailto:gnewell@ameritech.net">gnewell@ameritech.net</a>><= br> To: "Pianotech" <<a href="mailto:pianotech@ptg.org">pianotech@ptg.org</a>><br= > 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 th= e motion of the bridge and the 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 carefully placed cutoff bar. Energy is being traded back and forth and is essentially being wasted. Going back to my analogy of the piano soundboard functioning somewhat like loudspeaker driver: the soundboard functions best when it is appropriately sized for the frequency range through which it is expected to function. If it is too small it is great for sustain but will not be able to develope the desired power. If it is too large, however, both sustain and power suffer. Sustain because energy is being wasted in the excess soundboard area and power because acoustical energy is being traded back and forth between the various resonant areas and is 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 did try to make them somewhat more massive but over time have found that this is not really necessary. I don't have any formula for this, I just 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 (<a href="http://www.grisoft.com/"= eudora="autourl">http://www.grisoft.com</a>). Version: 6.0.474 / Virus Database: 272 - Release Date: 4/18/2003</blockquote> <x-sigsep></x-sigsep> Greg Newell Greg's piano Forté <a href="mailto:gnewell@ameritech.net"= eudora="autourl">mailto:gnewell@ameritech.net</a></body> </html>