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I'm trying to understand what it is that makes a piano to feel 'light' and 'heavy' and, consequently, how to approach the digital vs acoustic action comparison. I used to think it was all about the weight, but after reading this:
http://www.pianofinders.com/educational/touchweight.htm
I decided to do an experiment - to measure the very 'light' action on my Technics PR170, a top-of-the-line 1996(!) instrument. The numbers came out thus:
Downweight - 69.5 (heavy)
Upweight - 36.5 (normal/heavy)
Sum - 106 (heavy)
Difference - 33 (normal)

If it were a regular piano the, according to the link above, it would be diagnosed with heavy hammers as its main issue. However, the action is so light that I easily depress neighboring keys in case of any mis-hit. It's very hard to be precise on this piano. Secondarily, the keys seem to 'bounce' up rather than return steadily like a nice grand, but that's probably due to the implementation of this (non-hammer-action) weighted keyboard.

So, could someone with technical knowledge of the subject chime in with an explanation of this phenomenon - why does a very heavy keyboard feel very light, and how can one compare a top digital (e.g. a Kawai CA 95) to a decent upright (e.g. a Yamaha U1) objectively?

I'll take a tiny swing at that question.

Digital keyboards don't have any mass, they have resistance. Trying to compare the measurements, as if they were a piano, will not work. Apples/Oranges, ok? Old square grands would often have carefully weighted keyboards, where the keys would be 'balanced', yet would not play well. Why? Because some keys were 14-inches long with no leads, and others were nearly 3-ft. long with 7 or 8 leads! Even though the keys were balanced for downweight, getting the long keys with multiple leads moving made for clunky feeling and badly performing actions. Inertia and mass. It's more than just downweight when the fingers are playing.

Pianos are moving the keys (...with lead), whippens, hammers, dampers (more lead), and the resistance of the springs in uprights and the repetition-lever spring in the grand. A lot of material, a lot of weight; it is more than a question of leverage and balance, you have to overcome the sheer existance and mass of the moving parts. Inertia; getting the bits in motion, too.

Your keyboards, digital that is, try to find the right balance of resistance to simulate the feel of the weight/mass and 'touch' of the piano. That's why your numbers make it appear that the touch is 'heavy' in numbers, but light in feeling. No mass. Just the spring or whatever resistance the digital action is designed for. It can't really simulate the 'feel' of getting a piano action's mass in motion. OK?

I cannot offer you a way to compare any digital to a piano for touch. I would not even try! Unless...you want to talk about a Yamaha GranTouch which uses a grand piano action as the 'trigger' for the keyboard. ;>)

This is why new approaches to the question of geometry and intertia in the action are so interesting and fascinating to the piano techies.

Search John Rhodes, and weightbench, for another 'take' on how actions should be measured for inertia and 'touch'. The topic has been discussed several times.

Hope that helps!
Sincerely,
I remain,
Yr. humble and ob't svt.,

Digitals have come a long way since your Technics DP. The high-end DPs from Roland and Kawai now feel close enough to an acoustic grand in key action that most pianists would have no difficulty switching back and forth. Not only are their key weights of standard downweight (around 50g at middle C - I measured my Roland V-Piano at exactly that), they are graded (heavier in the bottom notes and lighter in the top ones, just like in acoustics) and they also have simulated let-off/escapement feel, the 'notch-like' resistance you feel when the key is partially depressed which, IMO, is important for anyone intending to play on acoustics as well as their own DP: it allows for extra control at ppp and gives the action that extra authentic feel and 'weightiness'. Yamaha Clavinovas, strangely, do not have the let-off feel and their key action is unrealistically smooth all the way down. Maybe Yamaha want customers to buy their very expensive AvantGrands or the new NU1 to get better key action.....

One of the difficulties in getting a handle on this is that the current "standard" way of measuring key resistance is partly voodoo physics. Static measurements tell you what is happening when nothing is happening. Dynamic response doesn't necessarily track with static parameters.

If you want a professional opinion of a piano's action, ask a professional.

I don't give a rat's a** of any measurement of a piano ... I play it for myself and make my own opinion.

If the original poster is not qualified to make an opinion, he or she should hire someone who plays for a living to offer an opinion.

Wow, Dave. That's a pretty harsh response. Not to mention completely unhelpful to the original poster, who simply requested technical information on piano actions so he can better understand how digital and acoustic pianos compare. By the way, he did ask for expert advice ... from people who actually understand how actions work and can offer something beyond a personal assessment of a specific piano.

Agreed.

The original poster gave a list of weights for actions and while that might be of some benefit to the techs who work on pianos, for those of us who play, those numbers are completely meaningless. What we are interested in is how the piano plays\responds. I've played brand new concert Steinway pianos that had feather light response. That's great for a performance, but I wouldn't want that for a practice piano. I didn't measure the weight ... and if I had and stated that weight, it wouldn't have made any discernible difference, what mattered was how I felt it responded (to me).

We can discuss this issue 'objectively' but it still comes down to the personal preference of the player - subjectively.

My N3, a hybrid, has a 'touch sensitivity' control. Now it doesn't physically change the action in any way shape or form, but it still feels like the action has changed. The action really feels as though it has gotten heavier ... or lighter.

I wouldn't be surprised if the same effect exists in pure acoustic pianos where one piano will seem lighter or quicker in response than another piano but the actual measurable weight might be exactly the same and it's other components or properties of the action that lead us to make a statement that this piano is lighter or heavier than another when in fact it isn't. My point, it comes down to the user interface, if you will, and not the actual measured 'numbers'.

Of course, I could be wrong.

None of what you've said in your second response addresses the harshness of tone you had in your first post, although this one has toned down quite a bit. Bad day perhaps?

All of which does not address the issue of the inappropriate tone of your initial post. It's how you say things that make the difference.

If the various measurments like downweight made no difference(not saying these are the only important factors), then the piano makers are wasting a lot of time trying to calibrate these precisely on their pianos.

I will apologize for the inappropriate tone of my first post in this thread. I apologize.

I stand by everything else I wrote though. One plays the piano and makes an opinion. I have never taken a measurement of the weight needed to depress a key ... and neither should you. It's meaningless.

If a measurement is needed for a technician, fine. I will never make a judgement about any piano by specs. You play them and you make your up your own mind.

Responding to two quotes by two different people. . .



This is absolutely correct.



Unfortunately, this is true to a large extent. The measurements that are used have little (I won't say absolutely nothing) to do with how the piano actually feels to play. That is why we still get pianos from the same factory that are engineered and produced in the same way and individual units feel different from one another. This may be more true with some factories than others, but it is presently universally true of production from all factories as far as I know.

Reasons for this may be in an upcoming Journal article. . .

I happen to agree with this.

In everyday life one has to make a decision who to listen to:

Technician or customer?

In a perfect world there is no conflict - quite the opposite.

Norbert

Hello folks. First of all, thanks to everyone for pointing out to Dave that his original post was basically a flame. I was ready to fire off a flame back, especially since he had no basis for judging my experience or lack thereof, but decided to cool down for a couple of days instead. I'm glad to see that the discussion has righted itself. Second, I decided to clarify why the downweights actually mattered to me beyond the perception of piano's action.

The best I understand after doing some research, the piano action depends on both the physical action, and its ability to generate volume (which is what the digital pianos allow one to control).

Adjusting the volume response does cause one to hit the key harder; however, there are two problems with that, potentially:
1. Being rusty, I'll sometimes accidentally mis-hit neighboring keys; if they are soft, they will also generate sound, which will make me sound even worse than I already am. On an acoustic, they never release the hammer.
2. A piano action is a type of weight training machine. The more inertia the keys have, the stronger the fingers become. So in theory, one would want to practice on a stiff piano (not so stiff as to get Carpal tunnel syndrome!) If a key is light, adjusting its velocity-to-volume response may not cause it to build stronger muscles, at least not in the same way as moving a heavier piano's key.

So what I'm trying to understand is to what extent it is truly heavier to move a counterbalanced acoustic piano key with leads than a light (non-counterbalanced) digital key without lead, assuming their static downweight is equal. The best I can come up with is that the digital will reset faster after the hammer departs, because it's lighter, but until the hammer departs (while the downweight measurement holds), the two keys should take the same amount of effort.

The reason I'm interested in this level of detail is that, this side of a $20000 grand piano, I rather prefer the Kawai CA 95 action to that on most uprights, but I'm worried that my daughter may not learn proper technique practicing on it. In other words, I am not upgrading just for myself, and cannot go on my preference alone. My daughter's teacher, a very proper classical musician, demands an acoustic, even a cheap one, but definitely a heavy-action unit. However, she has not played any of the top-of-the-line recent digitals. If I go against her advice and with my preference (and also with the preference of many people on this forum), I had better be very sure of what I'm doing. For Dave specifically, I have also had an input from a conservatory-educated friend advising me to go with a top-of-the-line digital; and another piece of advice, from a former internationally known concert pianist, to get as good an acoustic as I could afford. In other words, no consensus.

P.S. I have many secondary reasons to buy a digital, the biggest of which is that the only room I have to place a piano is my sunroom; it gets very hot during the day, colder at night, and gets tons of UV through my old single-pane windows. A real wood piano, especially a nice instrument, will be hurting in that environment.

The digital action is only one draw back, what about the dynamics you get from a real action and pedaling you get with an acoustic you wont get with a digital?

If she is going to be a real accomplished pianist, I would agree with the teacher.

Maybe start with a quality upright, so if the sun room takes its toll you are not out too much. In a few years if she is still playing then consider the grand.

Three years ago, I'd have agreed with you - I'd never touched a digital till then (but have played on lots of awful acoustics as well as a few good ones).

Since then, I've realised that top-end digitals are often better than poor-quality verticals, especially if poorly maintained. The digital I've now got is better in every way than the little Yamaha vertical that I learnt on as a child, and far better than many of the acoustics I've had to put up with over the years. For a start, it's got much better tonal and dynamic range, as well as pedal effects, with three pedals; and its key action is close enough to that of good grands that I never have any difficulty switching back and forth between it and concert grands. (The Yamaha vertical had just a practice/soft pedal and a sustain pedal, and its tone was tinny and strident from p to ff: pp wasn't possible. And its action was far too light, and its keys prone to sticking).

But a good quality upright is certainly better than all but the top-flight digitals in terms of developing good piano technique and tonal and dynamic control, especially if playing classical music.

Its seems you answered your own question.

rimorob,

This may seem off topic, but it's really up to your budget and your daughter's practice habits. Digital piano manufacturers have developed beyond entry level uprights and certainly most cheap pianos found on the used market.

A good, mid-quality upright, new or used (and spending the necessary recommended maintenance on precise regulation) offers a better platform for learning than even the best DP's. DP's offer advantages that no acoustic has.

If the only thing she ever practices one is a DP or single below average piano, she will have great difficulty transitioning to the great variety of pianos. If she regularly practices on a top DP + plays other acoustic pianos on an occasional basis, she will be better prepared. A nice acoustic piano is even better preparation.

Too light of an action certainly presents problems, but I see a misplaced emphasis on heavier actions. Better preparation is to play on different pianos. Top pianists don't spend their time practicing on sub-par pianos, always preparing for that rainy day. They play on the best pianos they can as often as they can.

The current weakness of top digitals is in 2 areas: the influence of pedals (on sound and action) and the limits of speakers in sound reproduction. These become important in developing technique, but they can certainly come in later years. And for an experience pianist, they are easy to overcome when using a DP.

Having a quality acoustic piano become most important when trying to develop from an intermediate to advanced repertoire. That phase in learning shows the limitations of a DP, not minor action differences.

So if a good DP helps develop interest and practice habits, supplement that with visits to other pianos and start saving for that $20k grand or whatever acoustic piano that gets her excited.

Sam,

Your response is precisely on topic. As far as I can tell and experience, the main differences between my top choices, Kawai CA 95 and a Yamaha U3 (used) are roughly these:
1. On Kawai, a digital, the action doesn't change when the damper piano is pressed. It ought to get lighter on an upright, though I haven't paid this any attention in the past.
2. Kawai may not do as good a job with overtones, although a) they have seemingly addressed this problem somehow and b) feeding everything through soundboard helps.
3. Most DPs don't offer the feedback of an acoustic body. Again, the CA95 soundboard does a great job here
4. The CA95 has the sostenuto peda, and I think U3 actually does too, but most under-4K uprights don't. I'm not quite at a level where I need it (probaby ABRSM 6 equivalent), and my daughter will go many years before she overtakes me.
5. Kawai has a seemingly softer keyboard, though I intend to spend another hour or two playing both side by side. My impression at a store that the CA 95's keyboard felt more like a nearby Kawai grand (50K) than like that of any of the uprights in that huge store. I've played a good dozen to get an idea of the range. And, as I've said in another post, there's the problem of climate control with the acoustic, which I'm not sure I can adequately solve in my house.
6. Kawai sound is different. I can't tell whether it sounds more like a grand, or is simply missing overtones. My lack of experience on top-end instruments limits me here.

I feel that this choice should be easier. Five years ago I would have bought an acoustic without hesitation, but now it's too close to call.

If I were considering buying a piano for my daughter given what I already know, I'd give serious thought to the NU1 by Yamaha. She'd have a real upright action married to an instrument that never needs to be tuned or have the hammers needled after several years of intensive playing.

She could practice on her piano at the same time I'm practicing on my piano ... in the same room. Just a thought. :-)