<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META http-equiv=Content-Type content="text/html; = charset=iso-8859-1"> <META content="MSHTML 6.00.2800.1106" name=GENERATOR> <STYLE></STYLE> </HEAD> <BODY> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>----- Original Message ----- </FONT> <DIV><FONT size=2>From: "Greg Newell" <</FONT><A href="mailto:gnewell@ameritech.net"><FONT color=#000000 size=2>gnewell@ameritech.net</FONT></A><FONT = size=2>></FONT></DIV> <DIV><FONT size=2>To: "Pianotech" <</FONT><A href="mailto:pianotech@ptg.org"><FONT color=#000000 size=2>pianotech@ptg.org</FONT></A><FONT size=2>></FONT></DIV> <DIV><FONT size=2>Sent: May 09, 2003 3:46 PM</FONT></DIV> <DIV><FONT size=2>Subject: Re: Modal Analysis</FONT></DIV></DIV> <DIV><BR><FONT size=2></FONT></DIV> <DIV><BR><FONT = size=2>Del,<BR>         I wonder if you might help me understand this. You say, "And a <BR>good = example of why soundboard cutoff bars can (should) be used to some <BR>advantage." = In the views I saw on the web page there seemed to be quite a <BR>bit of = movement in the area normally eliminated by a cutoff bar. </FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT color=#000080 size=2>Yes, and it is exactly out of phase = with the motion of the bridge and the area of the soundboard surrounding the bridge.</FONT></DIV> <DIV><FONT color=#000080 size=2></FONT> </DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>----------------------------</FONT></DIV> <DIV><FONT size=2>If there <BR>is that much movement is that not = contributing to what we hear rather than <BR>detracting from it? As I type and look back = at the pictures in another <BR>window I'm tempted to rationalize that while one = part of the board, <BR>specifically that part in question, is on the down part = of a wave the rest <BR>of the board is up and visa versa. Is this what you wish to = eliminate with <BR>the cutoff bar so that the board acts as a whole = instead of in separate <BR>parts? It would be interesting to see what the board = would do using this <BR>modal analysis with a cutoff bar = installed.<BR></FONT></DIV> <DIV><FONT size=2><FONT color=#000080>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.</FONT></DIV></FONT> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>----------------------------</FONT></DIV> <DIV><FONT size=2>         = This brings me to another question. In all of the examples I've <BR>seen of pictures = with cutoff bars installed, all seem to be a great deal <BR>smaller in size = than the corresponding inner rim section they are <BR>replacing. I understand = that they are epoxied into the existing inner rim <BR>and doweled as well. I = further understand, I think, that the cutoff bar is <BR>attached to any support = beams over which it passes. Do the combinations of <BR>these items make it = unnecessary that it be of similar dimension as the <BR>inner = rim?<BR><BR></FONT><FONT size=2><FONT color=#000080>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.</FONT></FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2><FONT color=#000080>Del</FONT> </DIV></FONT></BODY></HTML>