[CAUT] Tenor thonk

[Alan McCoy]

Thanks Ron, Ron and Ed,

These are some ideas I will pursue. Yesterday I clipped on a couple vise
grips to the lower tenor bridge pins.  It made a small but noticeable change
in the right direction. Ron O. is right that the high bass bridge is part of
the problem - too boomy. Ron N gives me the idea to take the scale data and
see if adding some wrapped strings in the low tenor might be helpful. In
listening to the area it's the lowest 3-5 notes of the tenor that are most
thonky. I'll put the info into Tremaine's program and see if that sheds some
light on the subject. Adding the vise grips removes some of the thonk but
doesn't add any "boom" to match the bass. I'll try a dowel to see if that
tones down the bass a bit.

I appreciate your thoughts.

Alan


-- Alan McCoy, RPT
Eastern Washington University
amccoy at mail.ewu.edu
509-359-4627


> From: Overs Pianos <sec at overspianos.com.au>
> Reply-To: "College and University Technicians <caut at ptg.org>" <caut at ptg.org>
> Date: Tue, 29 Aug 2006 07:47:06 +1000
> To: "College and University Technicians <caut at ptg.org>" <caut at ptg.org>
> Subject: Re: [CAUT] Tenor thonk
> 
> 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
> _______________________
> 
> Web http://overspianos.com.au
> mailto:ron at overspianos.com.au
> _______________________