Lack of low frequency response

[Richard Brekne]

Hi Frank.

Yes. I think the basic question I'm asking  is... can a lack of cross 
grain stiffness at some point create a situation where the difference 
between cross grain and along the grain stiffness becomes large enough 
that the soundboards ability to vibrate well at lower (large) modes 
becomes inhibited.  One of the points in the Five lectures is that cross 
grain stiffness is needed to equalize stiffness in both directions 
exactly because of the need to get the total vibrational area of the 
soundboard vibrating.

I'm downstringing to do a couple things over/better on the instrument I 
am working on... so I can try spreading sand or glitter on the panel and 
hit the mid-low tenor area of the long bridge to see where it gathers. 

Aside from the specific job I'm on... this is really interesting as it 
touches on why older pianos sometimes start developing this kind of 
sound.. why some new ones seem to have it built it... and suggests a 
possibility of dealing with the symptom without removing the 
soundboard.  It also adds argumentation on both sides of the CC and RC&S 
discussion.  And on top of that it starts clearing up (in my mind at 
anyrate) some of what possible reasons designers have had through the 
years in selection of grain orientation and rib patterns along with rib 
orientation relative to the grain.

So... do you think then if one goes too far (as you put it) in reducing 
stiffness in the area of the soundboard at question here can cause this 
kind of thinning / nasalness of the sound ?  And if so, does the idea 
that the lack of cross grain stiffness being enough relative to along 
the grain stiffness fit in here ?

Thanks for your thoughts

Richard Brekne



    ---- Richard Brekne <ricb at pianostemmer.no> wrote:
     > I'm wondering if a nasal sound... with little or no apparent low end
     > response can have to do with LACKof stiffness in the fat part of the
     > soundboard... i.e. in that section that is somewhat front of the
    long
     > bridge and bass bridge.... low tenor area. I know this seems to go
     > contrary to the usual conclusions we'd jump at.... but it
    connects with
     > aging soundboards and why they start sounding thin and nasal...

    I can't find the exact posting, but earlier in the thread it was
    suggested that the soundboard might divide into many small
    "tweeters" and thereby inhibit the full vibration of the soundboard,
    as a "woofer."  Forgive me if my memory has misconstrued the intent
    of the statement.  I have seen studies of soundboard vibration where
    black glitter is sprinkle over the entire surface of the
    soundboard.  As different frequencies are introduced at different
    locations along the bridge, the glitter moves to define nodal lines
    on the surface of the board.  The patterns came out differently for
    different frequencies.  It seems to me that these nodal divisions of
    the board do not inhibit the fundamental frequency, but work
    concurrently with it, in much the same way as a sounding string has
    a complex envelop of multiple partials at multiple frequency.

    Regarding reduction of stiffness in the bass region of the board, I
    believe you can go too far in that direction.  I am reminded of a
    piano that makes much ado about its reverse crown and floating
    soundboard in the bass.  To me it sounds much like an old upright
    where the bass bridge has come unglued from the apron.

    Frank Emerson