MH BB Pinblock

[Ed Sutton]

I suppose a fairly authoritative test could be done, thus:
Start with a piano with full fit pinblock. Record and measure the sound of 
the piano in some controlled manner.
Use a Bolduc cutting wheel to disconnect the stretcher from the pinblock. 
Nothing else has been changed.
Repeat the controlled recording and compare with the first recording.
Never mind hypotheses, just see if the sound is changed by cutting the 
stretcher loose.
This would not be very difficult to do with a piano that was in the shop for 
rebuilding.
Ed Sutton


----- Original Message ----- 
From: "Ron Nossaman" <rnossaman at cox.net>
To: "Pianotech List" <pianotech at ptg.org>
Sent: Saturday, August 02, 2008 4:02 PM
Subject: Re: MH BB Pinblock


>
>>   I think there is some acoustical loss in an unattached block, simply 
>> because there is vertical movement in it that is not as well resisted by 
>> the mass of the case.  The difference in stiffness between a block that 
>> is doweled in and one that is not is profound.
>
> Is it? Unfortunately, I'm a couple of days past being able to directly 
> test this with the piano I'm currently working on, but I think it's worth 
> looking at. A dial indicator, set up under the stretcher and pinblock 
> (plate firmly screwed to it) will tell you pretty easily. How much 
> deflection with your weight on just the stretcher, and your weight on just 
> the plate/block assembly? I think you'll find the stretcher to be 
> considerably, possibly profoundly less rigid.
>
>
>>The sound transmission is also noticeably different if you tap the 
>>undowelled block then clamp it to the stretcher and tap it again.
>
> It also is when you tap the undowelled block, and the same block with just 
> a clamp attached without the stretcher because you've lowered the resonant 
> frequency and raised the impedance of the thing with the mass of the 
> clamp. You can observe the same thing by tapping the belly rail when a 
> soundboard is out.
>
> Ron N
>
>