I would agree that the impedance determines to a large degree what the potential of the piano is. So does the hammer you start with. At least, it pushes you in a direction.
The partial thing is complicated because it depends where in the piano we are talking about. The 10th partial in the 5th octave is pretty meaningless.
When one does a spectrum analysis it is interesting to note that the partial strength can vary note to note depending on, probably, inherent soundboard resonances, impedance charateristics, or other factors. This is true especially in the lower partials. It is relatively easy to influence the development of high partials with needling or polishing the crown of the hammer. Lacquer works on the crown as well but I consider that something undesirable as it will also tend to overdevelop the high partials on a soft blow--something that is a bit bassackwards, IMO. What is also interesting to note is that the relative strength of the partials may or may not change as you go through the dynamic range (on a single note for example). That seems to be related to the specific characteristics of the hammer.
For example, today I worked on a Steinway AIII and a Steinway B (newish) for a new customer who owns both. The new Steinway B has a set of semi bulky Steinway hammers, lacquer of course. The AIII has a new action which I installed with a set of Ronsen Weickert Special Felt Low Profile hammers (my design with help from Jack Brand and Ray). It's a fairly lightweight hammer, much in keeping with the original, cold pressed, of course. There are some other features as well which I won't get into now. What is interesting is that when you put the Spectrum analysis on it you find that the New Steinway maintains a fairly consistent relationship between the partials as you climb the dynamic ladder. The AIII, on the other hand, shows greater development in the upper partials as you move from p to ff. In other words, the partial balance remains the same on the new B, on the AIII it changes. It may be interesting to note that the customer in conversation before I revealed this finding to him expressed that while he very much liked the B and the tone that it produced he found himself gravitating to the AIII in large part because he felt that it had a broader color pallette. I'll let you draw your own conclusions, I have (had) already drawn mine. The differences in the hammers are fairly obvious in terms of tension, spring-like qualities, mass, as well as felt type (read quality), and, of course, the presence of lacquer and its impact on overall flexibility.
I do think that different hammers respond differently and that it has to do with the reactivity of the felt, i.e. the amount of stored tension. A hammer that has little tension, less spring like quality will not respond in the same way as one that does thus in the process of voicing your procedures and goals are different. In one case you are relaxing the spring, in the other case you are creating an artificial spring by manipulating a density gradient. In the former, the felt when needled away from the crown reacts at the crown. The degree to which it reacts is a function of tension and also the makeup of the felt itself (combination of different fiber lengths perhaps). In the later case you have to do more needling nearer to the crown (or directly into the crown) because there is no stored tension to release or use. Thus, the two hammers will have different spring rates, the rate at which the hammer stiffens when subjected to compressive force. That combined with the differences in mass, shape, etc, mean that the spectral development will also vary. The pianos will develop a different relationship between volume and partial development.
With respect to Steinway hammers responding to shoulder needling I think you are basically correct. A light application of lacquer will simply stiffen the fibers and with it the spring. The hammer is stiffer but the full range of it's compression is not yet altered. Needling in the shoulder still relaxes the spring. As you add more lacquer you begin to bind everything together and to add density which, in effect, begins to limit the range of compression of the spring. It bottoms out earlier. That might be desirable if you are after power. But it can't help but have an effect on the spring-like quality of the hammer that contributes to how the partials will develop through the dynamic range.
No time to proofread so forgive any typos. There is, of course, more to the story which I hope to present at WestPacIV (Structural Voicing).
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David Love RPT
www.davidlovepianos.com davidlovepianos@comcast.net 415 407 8320
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Original Message:
Sent: 01-09-2014 23:03
From: Fred Sturm
Subject: Voicing for partial development
I have never thought of impedance as a separate issue and in those terms (while voicing) - but perhaps I should. My own approach has always been to "see what the piano is capable of" and adapt the voicing level, including the "overall partial balance" (average tone color) and the "partial development curve" (degree to which the tone changes to having more higher partials on heavier blows, and how fast that occurs) to the potential of the piano. But I guess that is really saying the same thing, as it is precisely the same as adaptation to different impedance systems when you come down to it, at least in large part. The impedance determines to a large degree what the "potential of the piano" is.
In any case, I do think Forss' thoughts on specifying partials that should be heard in every note, and his advice that we should not voice so as to remove those higher partials (8th, 9th and 10th) that give brilliance to piano tone are well taken (and, practically speaking, it means treading very carefully in the crown area). It is a good idea to have some guideposts rather than the notion of some version of "beautiful tone color" that we are trying to achieve, especially when dealing with performance instruments. The concert technician (which really includes all CAUTs) needs to be particularly aware of the need to bring out upper partials on all notes, and needs to develop techniques of voicing that "avoid killing them," something that is fairly easy to do. It is quite a bit harder to preserve the ability to produce the higher partials, while at the same time creating a more mellow pp to mp sound.
With respect to different techniques for different hammers, I am more struck by the overall consistency of the type of pattern to be applied than by the differences. In most cases it is more a matter of doing more or less of the same procedure than it is one of a different procedure. There are some exceptions, as, for instance, some hammers can be easily "needled up" (made more brilliant) by deep insertions of a particular sort, while on others this has little effect.
Interestingly, I have found that lacquered hammers respond to deep shoulder needling in a way that is analogous to "hard-pressed" hammers - if they haven't been over-lacquered. By "over-lacquered" I mean hammers where deep insertion of a needle meets great resistance and leaves a hole, to put it in practical terms. Sometimes it can be impossible to insert a needle 10 mm into a shoulder, in an extreme case. In hammers lacquered so that a three needle tool can be inserted with a normal amount of pressure10 mm into shoulders, and when withdrawn the hole has at least partially closed up, I find that normal techniques for hard-pressed hammers do, indeed have an effect that is quite helpful, both in bringing down excess harshness and in developing more range of tone color. It is particularly useful in a piano that has been played quite a while and has become overly harsh (also due to filing and exposing denser felt). I guess I heard someone say once that he had done that successfully, and decided to try it again myself (earlier experiments had seemed to confirm the generally accepted opinion that shoulder needling had no effect). I have done this to a few of my concert instruments with good success. If there is too much lacquer, you need to wash some out first. (Again, confirmed by experiment).
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Fred Sturm
University of New Mexico
fssturm@unm.edu
http://fredsturm.net
"When I smell a flower, I don't think about how it was cultivated. I like to listen to music the same way." -Federico Mompou
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Original Message:
Sent: 01-08-2014 23:49
From: David Love
Subject: Voicing for partial development
Everything interacts, including the impedance of the piano. The relationship between attack and sustain will be determined in part by the impedance charateristics. For example, a low impedance system with a heavy and relatively hard hammer will require some heavy needling to get the hammer to absorb unwanted energy that would not do well in the low impedance system. That needling (plus the mass of the hammer) impacts partial development. In order to bring the low impedance system under control, in this case, you will sacrifice or at least change the partial balance that you might other wise want. Similarly on a high impedance system with a light, soft hammer you will have to harden the hammer to get more energy to the soundboard. In doing so you will boost the high partial development because of the combination of hard and light. You won't be able to avoid that or at least a movement in that direction. Everything interacts and must be considered as a whole, both selection of hammer and what needling or hardening the hammer does. That may well be driven by the impedance characteristics of the piano.
BTW not all hammers fall into the realm of "standard products". The Renner/Abel products can be quite different in terms of internal tension, density, type of felt, mass, shape (profile). Hammers with more tension will react differently to voicing (say shoulder needling) than hammers with less tension or no tension. For example a lacquered Steinway style hammer doesn't react much at all to shoulder needling. Differences between so-called hard pressed hammers can also be quite significant and the reactivity of each can be different enough to alter voicing strategies.
A lot to get into here but that's the gist. Voicing starts with hammer selection and ends with needles or lacquer as the case may be. The resulting partial development will be largely a consequence of the need to control how the soundboard system is driven through the sought after dynamic range. The goals of hammer characteristics, impedance matching, dynamic range, and partial development and balance are all inextricably linked.
I would not put partial balance at the top of the list. It is no less important than controlling the dynamic range or the relationship between the attack and the sustain phase of the tonal envelope. While the final decision remains an aesthetic judgment, and those judgments may vary for a number of legitimate reasons, all things must be taken into consideration in establishing the piano's "voice".
My opinion of course.
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David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
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