[CAUT] Tenor thonk

[Overs Pianos]

Hello Alan and all,

>I'm working over a Chickering grand, about a 6 footer or a shade longer. The
>bass on this piano reminds me of a M&H BB, big and boomy. Running a
>chromatic scale up from the bass there is an obvious transition problem when
>you get to the tenor.

Yep, the chromatic-run test is the one which shows up a problem.

>  It is kind of a nasal "thonk." Funny thing is though
>when you run the chromatic scale down the tenor and into the bass, the
>transition doesn't sound as obviously poor. Tenor sounds reasonably decent -
>not big and boomy, but not thin either, fairly round but just doesn't
>project or have the swell like the bass. I have done all I think possible
>with hammer voicing to even it out. I'm thinking it is a board/bridge/string
>issue of mass (too much or too little?). Or impedance? Or, ??? Short of
>board re-design, anyone have any suggestions for improving this transition?
>
>It is in a lively classroom. It is not used for performance, but is used for
>chamber practice and such. Not the highest priority situation, so re-design
>is not an option. But it is a decent piano and worth keeping around.

 From what you describe it might be a case of too little weight in the 
low tenor, combined with too much board activity at the high end of 
the bass bridge. The treble bridge will be a lot lower in height than 
the bass bridge, so there's often a weight difference which can 
easily be addressed by adding a brass weight or two to the soundboard 
buttons, as Ed suggested.

As Ron N mentioned, the scale is an area which may provide some 
enlightenment also. You can add weights on top of sound board buttons 
by using longer screws with the same diameter and thread pitch. This 
will allow you to add quite a bit of weight if necessary. From what 
you describe it sounds as if the high end of the bass bridge might be 
placed too far out from the perimeter of the board. This is a common 
problem and it often results in a 'boomy' high end of the bass. One 
trick which may help you is to place a dowel between a back beam and 
the sound board, placing it at a strategic distance to reduce 
soundboard activity some, but not too much. I've done this several 
times to help a cross-over which is uneven. It becomes a piano with a 
sound-post but it works.

Another 'suck it and see' test you can perform is tapping the bridges 
at the cross over, listening to the characteristic thump of the sound 
board at each end of the two bridges. In pianos which have a good 
crossover, the thump characteristics of the bridge ends will sound 
very similar. When the cross is ordinary you'll often hear a thump 
which is much darker on one of the bridge ends (usually it will be 
the bass). When a piano is strung, I perform this relative-thump test 
by placing a clean piece of cotton cloth on the bridge to avoid 
touching the strings. This test will still give you an indication, 
even though the piano is strung.

When rebuilding pianos. when the piano is stripped we habitually tap 
the board at the bridge ends in an attempt to determine if the 
soundboard activity levels match. For many pianos, we've tapered the 
board at various places, added weight and extended the foot of the 
bridges as necessary, to modify the soundboard activity levels before 
re-assembly.

Its always easier to make fundamental changes when a piano is 
stripped, rather than applying the limited options available once the 
piano is re-assembled. When you strike a piano that's together its 
harder, but its nonetheless surprising what can be achieved. Fixing 
scale problems will require a tear-down, but sound board activity 
problems can often be helped with judicious use of weights and 
hardwood dowels.

What I find staggering is how some manufacturers can build the same 
instrument for decade after decade without asking the question of 
what makes a certain instrument sound the way it does. Many of the 
problems we hear must have been in the original piano at day one.

Designing a new model is such an exciting time, with the opportunity 
at hand to make a real difference. I have received my first 
commission to design a new piano for another manufacturer. The piano 
in question is a 131 cm upright. The current piano made by this 
manufacturer has so many problems it will need a totally new scale, 
plate and sound board. This is a new challenge for me since I have a 
133 cm design exercise which I did back in 1996. Some of my tone 
building ideas have evolved since then, but a lot of the design 
remains valid. I'm currently laying up the sound board area, scaling, 
back scale and note spacing. Since I have decided not to manufacture 
any upright pianos myself, all of my design ideas from  the 1996 
concept can be incorporated into the new 131 design.

I expect to be building the prototype by December. The manufacturer 
is sending me a semi-built shell, without a sound board or plate. 
I'll build the protoype into the existing case to save the cost of 
re-tooling for the case.

Regards,
Ron O.
-- 
OVERS PIANOS - SYDNEY
    Grand Piano Manufacturers
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Web http://overspianos.com.au
mailto:ron at overspianos.com.au
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