Posts tagged tri-chord
Over the last few years, I decided to run a few ultra-marathons (marathons run on trails in the forest). And I must go on record by saying that maintaining fitness is much easier than trying to get in shape to begin with. It was an arduous journey trying to get ready for my first event. But when our bodies are used to a certain routine over time, it becomes the new normal. In essence, we train in order to raise the bar for a new level of expectation.
You wouldn’t think it, but pianos can be in shape or out of shape. Pianos can go out of shape mechanically in the way that they play but can also get out of shape in the strings which determines intonation or pitch. Today I’d like to take a brief look at a bit more of a structural and mathematical concept of tuning and pitch. Before we do, we need to examine how and why pianos go out of tune and when you understand why they go out of tune, there is greater understanding with regards to getting them in shape and maintaining tuning stability.
Pictured above are the 3 types of strings on any piano. When you depress a key on the piano, it activates a hammer that strikes the strings. Depending on the zone (high or low), there are different types of strings. The largest bass notes are called mono-chords and only have one string per note. The double stringed notes are called bi-chord where the hammer strikes two notes simultaneously. And then for the top 2/3rds of the piano, a set of 3 strings (tri-chord) are struck simultaneously by one hammer. As seen on the chalkboard, there are 88 keys on the piano. When we separate the notes by type, we see that there are approximately 227 wires (which vary depending on the design of the piano). Multiply this total by the tension from each string (approximately 160lbs per string) and this gives the grand total of 36,320 pounds of string tension pulling on any piano! Note: the string tensions vary from maker to maker, model to model but also within one piano, the string tensions vary considerably. These are simply averages to grasp the concept of how much tension is pulling on the frame. Conservatively, the piano has 18 tons of tension (36,000 pounds) pulling simultaneously and that number can reach almost 30 tons of string tension for larger concert grands.
The wires then pull with an incredible force or tension. The cast iron frame (pictured in gold) together with the structural beams resist this tension. It’s a constant tug-of-war. The strings pull while the cast frame resists. Slight variations in this tension result in change of pitch and an out of tune piano. The question then is: what factors change the pitch of a piano?
There are 3 main elements which affect tuning stability:
1. New strings and windings
2. Tuning pin torque
3. Soundboard environmental changes
1. When it comes to change in tension, strings when installed at the factory will stretch. You wouldn’t think it but new strings have considerable stretch in the steel. The windings, knots and coils will also tighten and stabilize. This only applies to brand new pianos. There is a finite amount of stretch that will happen with new strings and within the first few tunings this will no longer be an issue. There is wisdom in tuning new pianos more frequently until the strings feel like they’ve settled.
2. The tuning pins are the adjustable “pegs” that technicians loosen or tighten with a tuning hammer. They are friction fit into the pinblock ~ usually a multi-laminated plank of wood. Interestingly, in England, they refer to the pinblock as the “wrest-plank”. The word “wrest” (similar to wrestling or wrench) denotes forcibly to pull or in this case, to turn the “wrest pins” (or tuning pins) inserted into the wrest-plank. Because the tuning pins are friction fit into the pinblock, they must have the correct amount of torque (the measurement of how tight fitting the pins are). Too tight and the pins becomes too difficult for a technician to adjust. Too loose and the tension of the string pulls on the pin resulting in loss of pitch. Tuning pin torque then is a significant factor that affects tuning stability.
3. Probably the greatest factor affecting pitch, however is the soundboard. The soundboard affects the tuning stability insofar as the strings cross over the bridge which is connected to the soundboard. In the picture you can see the strings cross over the bridge (adhered to the soundboard). Not only are the strings pulling end to end, but there is something called down-bearing where the strings are pushing down on this bridge. Since the soundboard is comprised of wood, it is subject to environmental conditions. Seasonally as the soundboard absorbs or dispels humidity, the soundboard will arc or flatten slightly resulting in pressure on the strings. Pianos can even go up in pitch if the arc puts considerable pressure on the strings.
All three of these factors contribute to slight deviation in pitch. When the steel strings are new, they stretch and become slack and need to be re-tuned. Tuning pins can move slightly and gradually turn out of position. The soundboard arcs more and then less depending on environmental conditions.
Making Sense of Cents
Pitch is not simply some arbitrary sound but rather, it has evolved into more concrete, measurable and universal terms. A440 is the global standard. A is the note (just above middle C) and 440 is the frequency or speed of that wave measured in Hertz (named after Heinrich Rudolf Hertz accredited for conclusively proving electro-magnetic frequency waves). When it comes to piano tuning, while you can measure Hertz, you can also define pitch in degrees called cents. As seen in the picture, each semi-tone has 100 degrees or cents. A full tone then has 200 cents. What this means is that there are 100 increments or degrees of pitch from one note to the next neighbouring note. So in discussing pitch, being a math and facts guy, I like to know how many cents the piano is out of tune. A piano that is wildly out of tune will be 40 cents flat (pianos usually go flat rather than sharp). So 40 out of 100 cents, if a semi-tone is 100 cents, that piano has fallen in pitch 40% of a semi-tone! Pianos that are tuned regularly might only go out 1-3 cents (out of a total 100). Often, pianos might go out of tune 5-15 cents in a year. What does this depend on? The 3 factors we looked at above. If your piano has gotten over “new string” settling when the piano is first purchased, then that leaves tuning pin torque and soundboard fluctuation as main factors determining pitch or intonation. The pinblock and soundboard will change with humidity. Pianos LOVE stable environments. Baseboard heaters, fireplaces, direct sunlight, drafts… even excessive fish tanks, plants all have bearing on humidity in the room which affects the soundboard which in turn affects the tuning. Change in ambient temperature (and subsequent humidity) within the house but also seasonally will make micro-changes in strings which also create difference in pitch.
Getting Your Piano in Shape
There’s a saying about piano tuning “You can’t tune a piano unless it’s in tune”. Paradoxical? It sounds that way unless you understand the sentiment. The farther out of shape your piano is, the more the tug-of-war will happen. The strings get pulled into shape, the piano tries to pull back to its known comfort zone. If a piano is 40 degrees out of pitch and you raise it to concert A440, guess what ~ your piano will not be at A440. Why? Because the tug-of-war is happening. The soundboard is adjusting to a new level of fitness. The subsequent outcome is that most pianos will pull back ~ sometimes up to 1/3 of the raise in pitch. So let’s take that example of 40 cents. One third of 40 is roughly 13. After tuning to A440 once, the piano will respond by possibly dipping down as much as 13 cents. Most technicians compensate and tune a little sharper knowing that this pull-back is going to happen. And so here’s the part that technicians CAN’T control. They can’t control the adjustment of the piano and the subsequent pull-back in 225 strings. Those strings will pull back at varying rates and thus, one tuning will never do the job getting a piano into shape that is vastly out of tune. The only way to do that is to tune again. You can really only tune a piano when it’s in tune ~ meaning that unless it’s close to pitch, you will never be able to get an exact stable tuning the first time. It is better to keep a piano consistently in tune than to let it drop significantly and try and pull it back into shape.
I’ve heard from many people over the years. “The piano doesn’t need tuning because I don’t play it that often”. While it can be true that a pianist who plays with incredible force can knock a piano out of tune, it is most likely the least contributing factor to making a piano go out of tune. Regardless of whether you touch a note on the piano or not, there is 18 tons of string tension pulling every day, 365 days per year. If a piano is prone to going out of pitch 4 cents per year, it might be out 8 cents in 2 years, 12 cents in 3 years and so forth. And pianos are funny that way. I’ve witnessed pianos that go out 12 cents in one year while others go out 2 cents in 8 years. But in closing, I will state 2 truths:
1. The farther out of shape the piano is, the harder it is to get it back into shape. And it may require more than one corrective tuning
2. Environmental stability is everything
Pianos are introverts. Hah… they like dark shady places where the sun doesn’t shine and no one rocks the environmental boat. The only problem is, we want pianos to be social and live in the center of our lives and enjoy the music with the sunshine. We need to maintain pianos if we want them to sound pure, beautiful and harmonious. I’m a firm believer in the fact that we are the recipients of the music from our pianos. If we train our ears with a consistently out of tune piano, that sound becomes the new normal. With an in tune piano, we communicate proper pitch every time we play. In closing, the message is simple: Regular maintenance is so much better for the piano than letting it drop in pitch for years at a time. Tune at least once per year and you will keep everything from sliding drastically out of alignment. Tune more than that if your ears demand it. And if you haven’t tuned for quite some time, do yourself a favour and get your piano tuned. Nothing is more satisfying than playing a piano that truly sings and really, pianos only sing when they are in tune and each note is in unison. Your piano may have gone down in pitch to such a degree that it might require more than one tune up session but as an old technician friend of mine used to tell me, “The difficult we can do. The impossible may take some time” 😀
For a name of a piano technician in your area, please visit our more than 800 technicians listed with Piano Price Point: HERE
Today’s topic is piano dampers. When your finger depresses a key on the piano, the string vibrates allowing us to hear the wonderful tone of the piano. But what happens when we lift that same key? The key returns to its upright position and the tone stops resonating. Why? The piano mechanism called the dampers simply press felt blocks on the vibrating strings to terminate the singing tone.
To understand a bit more about dampers, we brought in Marc Venet from world renowned felt maker Laoureux in France!
But before we delve into piano dampers, we need to take a brief look at the piano strings. On any modern piano there are usually 3 sets of strings: tri-chord, bi-chord and mono-chord. The prefixes of tri- bi- and mono- give away the fact that there are notes on the piano that contain 3, 2 and 1 string. This is significant because as we’ll soon hear, damping 3 strings at a time is very different than damping 1 string. The largest strings on the piano are the bass strings. They are copper-wound strings and produce the lowest notes of the piano where you can actually see the vibration of the string. Conversly, as you move higher in the piano, the frequency of the waveform gets faster and we can’t see the vibration. Piano strings can be called “sinusoidal” from where we get the root “sine” wave. The purpose of the damper then is to stop the wave and subsequently, the sound. The damping techniques and felt types are really different to mute different thicknesses of strings and their varying degrees of energy.
Without further adieu, and knowing a bit more of the background of dampers, let’s talk to Marc Venet from Laoureux.
Glen Barkman: The history of Laoureux, it’s been going a long time and is one of the largest piano felt makers in the world. Can you tell us a brief history of the company and how you got involved?
Marc Venet: Laoureux was founded in 1923 by Mr. Laoureux and after 3 generations of Laoureux’ leading the company until 1976, it wasn’t doing well financially. It was purchased by SCAPA group who bought the company in order to build a conglomerate in European felt business (Naish felts, Royal Georges felt, Laoureux, etc.)
My father was hired at this time in order to restore the profitability of the company Laoureux, which he succeeded to do above their expectations and quite possibly be the reason why Laoureux is now the only felt maker from this group that survived and producing today. The choice he made was to concentrate on high quality, hand made felts and avoid mass market felts like those found in the automotive industry, for example, which have bigger profits, yes but also involve big risks and large turnovers. It was a good choice. My father finally bought the company in 1988 and I joined the company in 1998.
GB: There are 3 types of strings and yet 4 types of dampers (mono,bi,tri and treble), can you tell us how each of those work?
MV: The shape and the types of dampers depend on the string they are supposed to damp.
A – The “Mono” or “One string” looks like a square with a V shape inside in order to envelop the large string on bass section of the piano.
B – The “Bi” or the “Two strings” looks like a V shape in order to get inside the space between the two strings on the tenor section of the piano.
C – The “Tri” or “Tri strings” looks the same as the “two strings” wedge shape but contains a split in the middle to act as a double wedge. These are for the lowest plain wire strings.
D – the “Flat damper” looks like a cushion of low density felt and are used for the highest notes on the piano.
For all dampers the target is to damp the sound, that means that they are in charge of absorbing the vibrations of the strings. Those vibrations are in fact frequencies like sinusoid signals (pictured above). The bass notes have low frequencies which mean long and spaced sinusoidal waves, and on the contrary, the treble or high notes have high frequencies which mean shorts but repeated sinusoidal waves.
Of course, for playing the piano, it is interesting to have more or less the same time to dampen the sounds when you release the keys, wherever you play on the keyboard (bass, tenor, or treble) and yet the frequencies and subsequent energies are quite different. For achieving that, we use different dampers with different properties adapted for the frequency of the sound. On the treble section, frequencies increase drastically when you play more to the extreme treble section. So for this section, even if there are 3 strings for each note, we have to change the method of damping from the double wedge to the flat block dampers.
GB: Is there a certain density of felt that is ideal for piano dampers?
MV: Yes of course there are optimal densities for dampers. And there are also certain densities depending on the placement inside the piano (density for bass and for treble felt are different). Ideally the density should be as low as possible. You could find on the market bass dampers with densities from 0.23 up to 0.35 and for treble dampers ranging from 0.14 up to 0.25. Physically, density is weight over volume (D = W/V). For the felt manufacturer the challenge is to make low density felt because it has superior damping properties however it is much, much more difficult to produce. In order to be able to cut them with a high degree of precision (1/10 a millimetre) the felt should be perfectly consistent otherwise it is impossible to cut. The challenge is also for piano technicians, it is much easier to work with “hard” dampers when you do not have the correct know-how and experience. A soft felt is difficult to make on several levels: First, achieving the felting process for low density is very difficult, because if you are under the good “felting point” (felting being the intertwining of fibres), the middle of the felt will remain as only wool if it is not felted. And if you are over the optimal felting point you are too hard on the surfaces and soft in the center and thus, the felt is not consistent.
The job consists of making felt the same from top to bottom. This is not easy. It takes much more time, involving more hands-on processes and also involves a lot of waste. That is why it is more expensive than denser felt. Ironically, you pay more even if there is less wool inside because it is much softer but contains greater damping properties.
GB: In the cullinary world, it’s kind of like baking the cake right? Too hot and you burn the outside, too cold an oven and the center doesn’t get cooked. Interesting. Speaking of damping properties, what makes for great dampers? And can you take us through the manufacturing process a little?
MV: Wool is the first and natural technical fiber with a “form memory”. The felt pressed against the strings absorbs string vibration. If you leave the felt released, the impression will erase. This is what makes great dampers. The softer the felt, the better the form memory. Making great felt requires technical know-how but also great raw materials. Normally felt is graded by 2 criteria: the quality of the wool used and the density. We buy the wool taking into consideration the length of the fibers (told in millimetres), diameter of the fibers (told in microns), and ability to felt more or less (the curving of the fibers). Of course the thinner and the longest fibers are much more expensive than the shortest and the biggest fibers.
A – Wool opening and Blending: we make a blend of wool with different single lots in order to have something always the same. With blended wine for example, you assemble different qualities with more or less the same proportions to create consistency. If we were using only one type of wool for each production, we would have different results from one production run to another and so good blending allows consistency in production.
B – Carding: the blend goes into the carding lines in order to create wool layers. With our machines we can adjust the weight by square meters of the layers, and also the fiber direction (crossed or not).
C – Composition: It is a hand made process consisting of assembling and cutting several wool layers depending on the final result we want to achieve. In short, we know the final dimension and density we want. We will use the right weight of wool at the right dimension taking in consideration the shrinking coefficient we will apply.
D – Felting: The transformation between wool to textile. It is a natural process (no chemicals involved) where the fibers are matted together via friction.
E – Fulling: Once we transformed the wool layers to felt, we have to shrink it to it’s final dimension in order to give it it’s right density. This is again a hand-made process, one piece at a time. Dimensions of the felt should be controlled because we need to keep consistency in the shrinking. The right density is obtained when the felt is at the right dimension, not before, not after.
F – Drying. The previous process of felting and fulling require moisture and so the felt must be dried.
G – Pressing: Here we calibrate the thickness of the felt, for example 10.2 mm thick. We use hot presses to achieve this.
H – Finishing: Depending the product we make it goes to the dedicated workshop in order to be cut or assembled to its finished purpose.
GB: Aside from piano felt, what other applications do you make felt for?
MV: There are many many different applications for felt. Felt is used for its natural properties of absorbing, transferring and sealing. Some industrial fields using felts: writing instruments, railway, automotive, nuclear, tools, bakery, design and of course, piano making.
Glen Barkman: Wow that was a fantastic glimpse inside the world of felt making by Laoureux. They are located in Normandy, France and operate in 7,000 m2 facility (about 75,000 ft2 factory). A special thanks to Marc for his expertise and continued dedication in providing the world with quality felt.
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