Lack of low frequency response

[Greg Newell]

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.