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hi, kieth,
yes, it was covered extensively in many threads over the past couple of years, but the quick lowdown is that we determined, after much refinement of the regulation until it was as perfect as possible, and measuring crown and downbearing, etc etc all the things you do when the tone isn't right, and having one tech voice it to perfection only to have the tone fall apart again the next day.....

that the hammers are the cause of the poor tonal quality in the fifth octave, which has been very resistant to both conventional and creative solutions.

we've established that the desired tone is inherent in the piano, that it is not a design problem, as killer octave problems frequently are. so, after conferring with many experts, all came to the same conclusion--the hammers were either not of the usual quality, were defective in some way, or received some sort of treatment prior to delivery that didn't agree with them. we'll never know for certain.

a new set of hammers should do the trick, in any event. keep your fingers crossed for me.

What you are calling “personality” I am calling “voice.” The voice of the piano starts with the stringing scale and works out. The design of the soundboard assembly should be chosen to match the string scale philosophy. A high-tension scale will require a somewhat stiffer soundboard assembly than would be appropriate for a low-tension scale. Different scaling philosophies will have different voices.

The final step in the process is to select a hammer that is appropriate for the string scale, soundboard assembly, rim, etc. A high-tension scale will require a harder, more massive hammer. This same hammer would overpower a low-tension scale and you would be constantly trying to voice it down — usually by needling. A more resilient, less massive hammer that would work well with a lower tension scale would wash out if used with a higher tension scale. You would be constantly be trying to voice it up — usually by soaking it with some hardening solution.

Hammers will only take so much voicing either way. Over needling them will ultimately cause them to go completely dead. They lose all resiliency (of which they had precious little to begin with). They will end up “soft” but with little “bounce.” Over hardening them will ultimately cause them to lose all resiliency. They end up like little rocks. They can still be needled down some to make them “softer” but nothing can be done to restore their resiliency, their “bounce.”

The hammer must match the character of the piano and its scaling before the voicing process begins. The idea of voicing is to improve that match, not to make an inappropriate hammer match whatever scale it finds itself on. The voicer can only do so much.

The tendency over the past several decades — for production and cost reasons — has been toward harder and denser hammers leaving it to the voicer to bring them down to more-or-less suit whatever scale they happen to end up on. And many factory voicers have done a masterful job of this. But it has come at the expense of depth of tone, what I call “dynamics.”

The idea is that the range between pianissimo and forte should be covered by both a volume control and a tone control. The actual wave envelope should change. There should be more emphasis on the fundamental and the first few harmonics at pianissimo with more of the higher harmonics coming in at forte. In other words, the voice of the piano should change along with the volume. This character is sadly lacking in many modern pianos.

Del

thanks again for such a crystalline explanation.

now, based on what you just wrote, it is too tempting to ask you your opinion of my situation.

i take it from the above that you probably wouldn't care for most hot pressed hammers.

what is your opinion of the most appropriate hammer for a grotrian grand? i don't know if it is a higher or lower tension instrument. i do agree with you about the lack of color and what is being lost through the overuse of hot-pressed hammers.

i don't know yet which make of hammer is going to arrive for my grotrian. what would you recommend for that string scale?

You are right -- I don't much care for hot-pressed hammers. I've been preaching on this subject for a couple of decades now and maybe, just maybe, it's finally having some effect. Abel is pressing much cooler now and I've heard Renner might be doing so Real Soon Now.

Sorry, I don't know enough about Grotrian's scaling or soundboard structure to give you anything resembling sage advice. Other than to discuss the issue with your technician before the new hammers go on.

I would guess that Grotrian uses Renner hammers (but that is only a guess, it could be Abel). Both Renner and Abel make a variety of hammers and there should be something in there that is appropriate for your piano.

Del

Hi Del,
Also thanks for sharing such interesting information. You've got me curious now, what is so bad about hot pressed hammers? .

Come to think of it, I saw a picture of the S&S hammer press in a magazine article once. It has some kind of heating or cooling arrangement to the metal forms of the press.

Dan

If Steinway is using heat at all it can't be much. They actually start out pressing a pretty good hammer. It's not until they start saturating them with hardening solutions that they run into trouble.

Excessive heat — there is no absolute here, but in my experience ‘excessive’ means anything much over 120° to 130° — resets the wool fibers. This in much the same way as heat and moisture reset the wool fibers when a wool suit is pressed. When hammer felt is pressed into a caul it is seriously bent. The fibers on the outside of the felt strip are stretched and those on the inside are compressed. To keep the outside of the felt strip from literally breaking open the felt is saturated with moisture to make it more flexible. Combining this moisture saturation with heat resets the wool fiber resulting in a hard and dense hammer with little resiliency.

Felt breakage is not much of a problem with hammers of more moderate mass and density but hammer mass and density is an absolute necessity if one is going to end up with the loudest and most powerful piano on the block.

The primary function of the heat, by the way, has nothing to do with bending the felt. It is necessary to cure the thermal-setting adhesives used to bond the felt to the wood molding quickly and reliably. Thermal-setting adhesives usually kick over at about 170° F or so. Felt is a pretty good insulator so the side cauls must be some above this to get the glue-line up to the requisite temperature. The hammer maker walks a fine line between keeping the side cauls hot enough to set the adhesive quickly and burning the felt.

The problem is that heat migrates. It goes from the side cauls (where it is wanted) down to the bottom caul (where it is not wanted). At least it didn’t used to be wanted down there. Nowadays it probably is considered desirable because it makes possible the incredible massive and dense hammers we are supposed to be getting used to.

As may be, the process is fast and predictable. The shape is consistent. And hammers with great hardness and more density can be pressed this way. It is then up to the voicer to do his/her best to tame these things down and attempt to make a musical piano in spite of them. Sometimes this works, sometimes not.

I have long maintained that any piano hammer shaped objects that requires 50 or 100 needle strokes to “pre-voice” them are not really piano hammers. I don’t know just what they are but they do not belong on a piano. They should be put in a box and returned to their maker. (If they happen to already be attached to the piano you may need a larger box…)

Del

Hi Del,
I checked the Steinway picture again, it shows two hoses going to the bottom form, and hoses going to the two side forms. Obviously they can be setting any temperature they want. About Abel, it seems like they are enjoying some popularity right now, I wonder if it's because of the softer/cooler hammers, do you know when they started doing this?

I wonder why they use thermal setting glues then, if they cause so many problems? Wouldn't it be easier just to glue them up without all that heat?

Dan

so who makes hammers the way you like them, del?

and aren't there also some other problems with modern hammers, such as bleaching weakening the wool, and the poor quality of wool in the first place (due to environmental pollutants, i understand)?

and--what about the difficulties inherent in the old-style steinway hammer, the fact that once voiced, the job is so ephemeral and quickly breaks down. my impression is to have the optimal sound from your steinway hammers you'd either have to rent out the spare bedroom to the voicer so he could voice for you every day, or else never play your piano.

the hammers that are hardened by compression are at least not so high maintenance once they've been given their voice?

i'm very very far from an expert, but throwing out a few devil's advocacy questions here in order to learn more.

I'd be interested in seeing that picture. At Baldwin I experimented some with cooling the bottom caul with good success. I wonder if that is what they are doing.

No, I don’t know when Abel started cutting back on the temperatures. It’s been a couple of years, though. Yes, I expect it is at least in part why their hammers are becoming somewhat more popular.

Thermal setting adhesives are used because they are fast. Once up to temperature they set up in two or three minutes.

Del

Abel is getting there. Ronsen can make a good hammer when they put their minds to it. Steinway makes a good hammer — then saturates them with something or other to get rid of all that wonderful resiliency.

Good wool is available if the hammer maker is willing to seek it out. And insist on it from the felter. And is willing to pay for it. We are, however, very small users of felt and felt products and don’t exactly control the industry.

Old Steinway hammers (1900s through 1940s) were among the easiest hammers to voice ever made. They were not at all touchy. The bloody things could be warn to nubs and they were still voiceable! That is one of the inherent advantages of a hammer properly matched to the piano from the beginning.

My experience seems to be just the opposite of yours. I find a cold (or warm) pressed hammer of suitable density to be both easier to voice and longer lasting. That is, both the voicing and the physical hammer last longer. The resilient hammer bounces off the string more readily without cutting.

Hard-pressed hammers, on the other hand, are constantly giving trouble. Witness the many Asian pianos that keep the boat payments up to date for all those busy tuner/technicians out there.

Del

Hi Del,
No problem
http://www.sonic.net/howl/ss.jpg
It was an article in technology and innovation, that goes on and on about the 150 year old "mystery" of piano making at S&S. And it highlights the continued i"nnovation" there too

darnit, make that

http://www.sonic.net/~howl/ss.jpg

The only two felt manutacturers that I know of are Bacon Felt and Wurzen. There may be others. As far as I know, Bacon supplies for S&S and Wurzen is used in Europe. Europeans love Wurzen felt and it's used in hot pressed hammers, although as Del said, all hammers makers use some heat to cure the glue. Del, I know you design your pianos with a very flexible soundboard. Most people go the other direction and, as you pointed out, require a harder hammer. Any thoughts on which felt is better?

Actually, there are a number of hammer felt suppliers. When we were doing our hammer making experiments in the late 1980s we had hammer felt from five different felt makers to work with.

I'm no longer convinced it really makes all that much difference. We found more performance differences resulting from how the hammers were made than we did from the different types of felt. As long as the felt had approximately the same mass density, was the same thickness, was cut the same way and pressed the same way hammers made from each type of felt sounded and voiced pretty much the same.

The noticeable differences became obvious when we started playing around with press temperatures, pressures, cycle times, caul shapes, etc.

Del

I guess in the old days, the temperature would have been set by the ideal temperature for spreading hide glue. Once the cauls were one, you would want it to set as fast as possible and still have a good bond. I bet that worked very well for the felt. It would be just hot enough to get those proteins flowing!

For the hide glue to set up the cauls would have to be rather cool. Any heat at all would prevent or, at least significantly retard, the glue's drying time.

ddf

Grotrian (as I recall) has a high-tension scale and typically Renners, though I thought in the last 4-5 years some had Abel as well.