Pianotech

Recently I saw a posting about a piano having two unisons on the tenor end of the long bridge, with no hammers to strike them. That makes me wonder, as one who doesn’t have much physics background, nor piano design experience, could that be a simple solution to the thunking tone of most low tenor (typically, the lowest 2 unisons.) Is that the design intention?

And this leads to another question: what methods are out there to determine, if one would be adding mass to the bridge to overcome the tonal problems there, to figure out just how much mass to add? For example, if I’m attaching a vise grip to the bridge pin to test any tonal improvements, that’s only one weight, which may be too much to effect a good change. I’m wondering how to test different weights coupled to the bridge without damaging the bridge or soundboard?

I appreciate any replies.

Joe Wiencek

<I'm wondering how to test different weights coupled to the bridge without damaging the bridge or soundboard?

Simply screw different configurations of brass weights to the bridge at current soundboard button locations. It takes a fair amount of time to test the various possible permutations, but that's how you do it...seat of the pants...mess around and see what it does. You need to make up a selection of different brass weights to test. I have a test set of 50- 200g. I have 1-1/4" brass round stock, I get from Mcmasterr-carr. Band saw and drill it to make the weights. Also, you need a selection of screw lengths, as the different mass loads will have different heights, and need different length screws. I use Robertson square drive screws from Mcfeeleys. Drywall screws will work, but they tend to sheer too easily. I never use them for this task, or for bridge attachment.

For the quick and dirty test with the vise grips, get a set of really small vise grips to set along the bridge at various locations, on the back pins. I got my tiny set at Loews for really cheap a while ago. They are not useful tools for using as a vise grip, but for this application, just right. 

I have done a fair amount of this type of experimentation, and it is quite educational. I usually do not end up adding weights to the bass end, as I don't like the way it damps the sound. Low tenor sometimes works for me. I did have one grand where the low tenor improvement was so much better than the non weighted condition, that the damping, though there, was less objectionable than the non-weighted version.

But...there is no way around the down side of weighting, which is damping. The weights add mass, which lowers the local resonant frequency. This lowering of the resonant frequency is often helpful. However, the mass, as well as lowering RF, also, dampens to some degree... You pays your nickel and takes your pick...

   




------------------------------
Jim Ialeggio
grandpianosolutions.com
Shirley, MA
978 425-9026
------------------------------

Original Message:
Sent: 09-16-2018 00:44
From: Joe Wiencek
Subject: End of the long bridge

Recently I saw a posting about a piano having two unisons on the tenor end of the long bridge, with no hammers to strike them. That makes me wonder, as one who doesn't have much physics background, nor piano design experience, could that be a simple solution to the thunking tone of most low tenor (typically, the lowest 2 unisons.) Is that the design intention?

And this leads to another question: what methods are out there to determine, if one would be adding mass to the bridge to overcome the tonal problems there, to figure out just how much mass to add? For example, if I'm attaching a vise grip to the bridge pin to test any tonal improvements, that's only one weight, which may be too much to effect a good change. I'm wondering how to test different weights coupled to the bridge without damaging the bridge or soundboard?

I appreciate any replies.

Joe Wiencek

Original Message------

<I'm wondering how to test different weights coupled to the bridge without damaging the bridge or soundboard?

Simply screw different configurations of brass weights to the bridge at current soundboard button locations. It takes a fair amount of time to test the various possible permutations, but that's how you do it...seat of the pants...mess around and see what it does. You need to make up a selection of different brass weights to test. I have a test set of 50- 200g. I have 1-1/4" brass round stock, I get from Mcmasterr-carr. Band saw and drill it to make the weights. Also, you need a selection of screw lengths, as the different mass loads will have different heights, and need different length screws. I use Robertson square drive screws from Mcfeeleys. Drywall screws will work, but they tend to sheer too easily. I never use them for this task, or for bridge attachment.

For the quick and dirty test with the vise grips, get a set of really small vise grips to set along the bridge at various locations, on the back pins. I got my tiny set at Loews for really cheap a while ago. They are not useful tools for using as a vise grip, but for this application, just right. 

I have done a fair amount of this type of experimentation, and it is quite educational. I usually do not end up adding weights to the bass end, as I don't like the way it damps the sound. Low tenor sometimes works for me. I did have one grand where the low tenor improvement was so much better than the non weighted condition, that the damping, though there, was less objectionable than the non-weighted version.

But...there is no way around the down side of weighting, which is damping. The weights add mass, which lowers the local resonant frequency. This lowering of the resonant frequency is often helpful. However, the mass, as well as lowering RF, also, dampens to some degree... You pays your nickel and takes your pick...

   




------------------------------
Jim Ialeggio
grandpianosolutions.com
Shirley, MA
978 425-9026
------------------------------

Leaving the eloquent scientific explanations aside. From a practical point of view, what i look for is whether or not the bridge ends over a rib or in the field. 
I always liked the continuous bridge to solve this issue. Riblets are also very handy at times. I'm fortunate that I usually have access to soundboards after removal. Then making small changes to the rib structure and then making sure the tenor bridge lands over a rib usually does it.
Good question Joe,
-chris

------------------------------
I don't always play the piano, but when i do, I prefer my own.
chernobieffpiano.com
grandpianoman@protonmail.com
865-986-7720
------------------------------

Original Message:
Sent: 09-16-2018 12:35
From: Roger Gable
Subject: End of the long bridge

Joe,

The extra length of the tenor end of the main bridge is to extend the stiffness beyond the usual final note at the tenor break. Mass and stiffness determine the resonant frequency. The soundboard resonant frequency needs to be higher than the frequency of the associated string. If not, this low "mismatch" of impedance provides a quick pathway for those low frequencies to enter the soundboard, which manifests as a thud. Adding weight will suppress the the rapid transfer of the low frequencies – keeping them trapped in the string -- while encouraging the development of higher frequencies in the string because the heavier weighted termination at the bridge reflects the higher frequencies back into the string. The added weight process tends to turn the tonal envelope upside down with too much high and not enough mid and lower frequencies entering the soundboard. Sometimes though, you get it just right.

 

Jim,

Your statement, "The weights add mass, which lowers the local resonant frequency", can be misleading. Certainly, weight, by itself, has a lower resonant frequency. Imagine tossing a bowling ball back a forth between your hands verses a tennis ball. The bowling ball is going to resist your ability to toss them rapidly between your hands, hence a lower resonant frequency. But added weight to a unchanging stiffness system of the board and bridge will react to the various frequencies in the string as a higher impedance unit. Carry the thought to the extreme. Imagine a bridge made of solid cast iron. You now have a system with high mass and high stiffness. Such a scenario would resist the transfer of low frequencies and favor the high frequency transfer to the soundboard.

Roger

Original Message------

<I'm wondering how to test different weights coupled to the bridge without damaging the bridge or soundboard?

Simply screw different configurations of brass weights to the bridge at current soundboard button locations. It takes a fair amount of time to test the various possible permutations, but that's how you do it...seat of the pants...mess around and see what it does. You need to make up a selection of different brass weights to test. I have a test set of 50- 200g. I have 1-1/4" brass round stock, I get from Mcmasterr-carr. Band saw and drill it to make the weights. Also, you need a selection of screw lengths, as the different mass loads will have different heights, and need different length screws. I use Robertson square drive screws from Mcfeeleys. Drywall screws will work, but they tend to sheer too easily. I never use them for this task, or for bridge attachment.

For the quick and dirty test with the vise grips, get a set of really small vise grips to set along the bridge at various locations, on the back pins. I got my tiny set at Loews for really cheap a while ago. They are not useful tools for using as a vise grip, but for this application, just right.

I have done a fair amount of this type of experimentation, and it is quite educational. I usually do not end up adding weights to the bass end, as I don't like the way it damps the sound. Low tenor sometimes works for me. I did have one grand where the low tenor improvement was so much better than the non weighted condition, that the damping, though there, was less objectionable than the non-weighted version.

But...there is no way around the down side of weighting, which is damping. The weights add mass, which lowers the local resonant frequency. This lowering of the resonant frequency is often helpful. However, the mass, as well as lowering RF, also, dampens to some degree... You pays your nickel and takes your pick...






------------------------------
Jim Ialeggio
grandpianosolutions.com
Shirley, MA
978 425-9026
------------------------------

Roger...you are right on the complexity and my incompleteness of the physical explanation.  The bottom line is that the work to be done is empirical, as per the specific piano. The explanations, frankly, can make this seem harder than it is. Listening to the results of experimentation and proceeding with what works best, or least, what works less bad, does the trick.



------------------------------
Jim Ialeggio
grandpianosolutions.com
Shirley, MA
978 425-9026
------------------------------

Original Message:
Sent: 09-16-2018 12:35
From: Roger Gable
Subject: End of the long bridge

Joe,

The extra length of the tenor end of the main bridge is to extend the stiffness beyond the usual final note at the tenor break. Mass and stiffness determine the resonant frequency. The soundboard resonant frequency needs to be higher than the frequency of the associated string. If not, this low "mismatch" of impedance provides a quick pathway for those low frequencies to enter the soundboard, which manifests as a thud. Adding weight will suppress the the rapid transfer of the low frequencies – keeping them trapped in the string -- while encouraging the development of higher frequencies in the string because the heavier weighted termination at the bridge reflects the higher frequencies back into the string. The added weight process tends to turn the tonal envelope upside down with too much high and not enough mid and lower frequencies entering the soundboard. Sometimes though, you get it just right.

 

Jim,

Your statement, "The weights add mass, which lowers the local resonant frequency", can be misleading. Certainly, weight, by itself, has a lower resonant frequency. Imagine tossing a bowling ball back a forth between your hands verses a tennis ball. The bowling ball is going to resist your ability to toss them rapidly between your hands, hence a lower resonant frequency. But added weight to a unchanging stiffness system of the board and bridge will react to the various frequencies in the string as a higher impedance unit. Carry the thought to the extreme. Imagine a bridge made of solid cast iron. You now have a system with high mass and high stiffness. Such a scenario would resist the transfer of low frequencies and favor the high frequency transfer to the soundboard.

Roger

Original Message------

<I'm wondering how to test different weights coupled to the bridge without damaging the bridge or soundboard?

Simply screw different configurations of brass weights to the bridge at current soundboard button locations. It takes a fair amount of time to test the various possible permutations, but that's how you do it...seat of the pants...mess around and see what it does. You need to make up a selection of different brass weights to test. I have a test set of 50- 200g. I have 1-1/4" brass round stock, I get from Mcmasterr-carr. Band saw and drill it to make the weights. Also, you need a selection of screw lengths, as the different mass loads will have different heights, and need different length screws. I use Robertson square drive screws from Mcfeeleys. Drywall screws will work, but they tend to sheer too easily. I never use them for this task, or for bridge attachment.

For the quick and dirty test with the vise grips, get a set of really small vise grips to set along the bridge at various locations, on the back pins. I got my tiny set at Loews for really cheap a while ago. They are not useful tools for using as a vise grip, but for this application, just right.

I have done a fair amount of this type of experimentation, and it is quite educational. I usually do not end up adding weights to the bass end, as I don't like the way it damps the sound. Low tenor sometimes works for me. I did have one grand where the low tenor improvement was so much better than the non weighted condition, that the damping, though there, was less objectionable than the non-weighted version.

But...there is no way around the down side of weighting, which is damping. The weights add mass, which lowers the local resonant frequency. This lowering of the resonant frequency is often helpful. However, the mass, as well as lowering RF, also, dampens to some degree... You pays your nickel and takes your pick...






------------------------------
Jim Ialeggio
grandpianosolutions.com
Shirley, MA
978 425-9026
------------------------------

What kind of piano? I'd be interested to see pictures of what they did.  How are the unisons damped?

Might be that the added unisons serve to stiffen the soundboard past the last speaking unison through the application of downbearing on what amounts to a bridge extension.  

I don't find that mass loading the end of the bridge works that well.  I've tried it countless times and have always ended up removing them.  Not even sure they are less bad than just doing nothing.  It does quiet the end of the bridge effect but adding mass is not the same as adding stiffness.  Added mass tends to create a somewhat thin and nasally tone.  Adding a slightly longer bridge extension is a better idea if you anticipate a problem and if you are able to do that during a rebuild.  Same is true at the top of the bass bridge.

------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
------------------------------

Original Message:
Sent: 09-16-2018 00:44
From: Joe Wiencek
Subject: End of the long bridge

Recently I saw a posting about a piano having two unisons on the tenor end of the long bridge, with no hammers to strike them. That makes me wonder, as one who doesn't have much physics background, nor piano design experience, could that be a simple solution to the thunking tone of most low tenor (typically, the lowest 2 unisons.) Is that the design intention?

And this leads to another question: what methods are out there to determine, if one would be adding mass to the bridge to overcome the tonal problems there, to figure out just how much mass to add? For example, if I'm attaching a vise grip to the bridge pin to test any tonal improvements, that's only one weight, which may be too much to effect a good change. I'm wondering how to test different weights coupled to the bridge without damaging the bridge or soundboard?

I appreciate any replies.

Joe Wiencek

Original Message------

Recently I saw a posting about a piano having two unisons on the tenor end of the long bridge, with no hammers to strike them. That makes me wonder, as one who doesn’t have much physics background, nor piano design experience, could that be a simple solution to the thunking tone of most low tenor (typically, the lowest 2 unisons.) Is that the design intention?

And this leads to another question: what methods are out there to determine, if one would be adding mass to the bridge to overcome the tonal problems there, to figure out just how much mass to add? For example, if I’m attaching a vise grip to the bridge pin to test any tonal improvements, that’s only one weight, which may be too much to effect a good change. I’m wondering how to test different weights coupled to the bridge without damaging the bridge or soundboard?

I appreciate any replies.

Joe Wiencek