Ric, To be sure there are many factors that probably play in to this but how long is the backscale length? Is it short and trapping the bass bridge? I'd sure think that a thick board in the bass region would also produce a too stiff assembly. How much downbearing is there? Too much in the bass could choke the sound I should think. Can you tell if the board is tapered or not? If so, where? As a possible solution short of a new board could you rout a channel in it to make it more flexible? Are you rebuilding this or just looking for reasons that it is the way it is? Greg Newell Greg's Piano Forté www.gregspianoforte.com 216-226-3791 (office) 216-470-8634 (mobile) -----Original Message----- From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of Richard Brekne Sent: Sunday, December 09, 2007 12:43 AM To: pianotech at ptg.org Subject: Lack of low frequency response Thanks Roger. Wide and tall... pointing in the direction of too stiff ?... I wonder how much compression there was in these boards ?. Please read a couple of my other replies... and let me have some further thoughts. In the mean time I'm going to take a couple measurements on the nearest Zimmerman upright I can find :).... rib dimensions and soundboard thickness.. But what grain directions and what that forces in terms of rib length.. ?. What about the idea that the middle part of the soundboard could be not stiff enough, causing the panel to break up into many small <<tweeters>> as it were... preventing the panel from vibrating as a whole ? Cheers RicB Hi Ric, The few Zimmerman's I have seen, the ribs seem way too wide and tall, This may account for part of it. Lot's of other scaling issues, around the tenor break. Maybe the thinking was big crowned ribs, no problems with flat boards??????? Just a guess. Regards Roger.
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