Button stroke vs clear sounding notes

[fred v]

I am moving this from another thread as it needs it's own thread.

 

I would like to hear some comments about how high do the pads have to go to get a clear tone. When I made my button covers I played every note and looked at how much stroke was needed. I found that most notes had about double the needed stroke. That is a huge waste of motion for fast playing. I spent quite some time bending levers to get the action all at the same height; then made my plates to the thickness that allowed just enough stroke to sound right. My buttons stick up about .12" above the plate. It looks like Alex did similar with the Muller instruments.

[Alan Day]

If of course the button is too high the the button pillar comes out of the pilot hole and the button jams up, or wears the sides of the hole away and eventually may need bushing.

Button height adjustment can usually done by increasing, or decreasing the pad height. Bending the levers sounds a bit drastic to me unless they are clearly wrong.

Sliding across the base notes on a run are easier if the buttons are lower.

Al

[alex_holden]

If you measure the distance from the centre of the pad to the action pivot, and divide that by the distance from the pivot to the centre of the button, that gives you your action lift ratio. Subtract the height of a released button from its height when it is fully pressed to get the button travel distance. Multiply the action lift ratio by the button travel distance to find the pad lift height.

 

My instruments have a lift ratio of 2. I try hard to design the action such that every button has the same ratio, but occasionally it's necessary to move the pivot slightly further towards the pad, lowering the ratio a little. If you move the pivot too far, it will feel and sound different from its neighbouring buttons.

 

Most of the instruments I've built have a button travel of 3mm (about the same as your 0.12"), giving a pad lift height of 6mm. A few of them have a 2mm travel/4mm lift instead. I find that the 3mm/6mm setup gives a slightly louder and brighter sound, whereas the 2mm/4mm feels very slightly quicker and less effort to play.

 

I've used what I call "low buttons", i.e. buttons that stop flush with the end plate, on three Müller-style Englishes and two duets. It doesn't suit everyone, but all of the customers I've built them for have been very enthusiastic and have told me their playing has benefitted from switching to low buttons.

Edited January 17 by alex_holden

[Łukasz Martynowicz]

My big box has what Alex called „low buttons” in the post above, with 3mm travel, 2:1 lift ratio and the lowest spring tension that still keeps the pads closed on the normal force push. They also have different costruction, with different button-lever interface and no button post. The result is silky smooth, absurdly responsive action, that was however absolute nightmare to set up properly. I can’t really imagine how lowering button travel would result in any significant speed increase if you lift your fingers way above the endplate when playing faster, centimeters above... What influences speed way more, is spring tension. You want buttons to resist your movement as little as possible, and it doesn’t really matter, if you play on 3mm travel concertina, or 6mm travel CBA. 

 

Personally, I’m a sworn advocate of low buttons and it’s of no surprise to me, that Alex’s clients were enthusiastic about them. They allow for very natural slides and finger substitutions, and because you rest your fingertip on large area when the button is fully depressed, 6mm buttons feel more like 15mm buttons on a CBA. The ease of slides also means, that when lifting a finger you’re already moving it sideways to the next note. Sinking flush means, that your fingertips are travel stops, so there is no need for felt dumpeners below the button, no bottoming noise and when playing fast your fingertips bounce back off the endplate, conserving energy. Normal non-flush buttons made my fingertips hurt after long practice session, low buttons never did. I can’t really think of any downside of this solution, except for increased wear of the endplate. Fingernails longer than 0mm will scratch the coating no matter what.

[Chris Ghent]

Buttons only need to be pushed to the bottom of the travel.  I suspect those liking flush low travel limits are pushing harder than that. I find when you push harder and further than needed you lose feel of how little the finger needs to move to release the button and it takes longer. 
 

My ratios are about 2:1 and the travel distance (this really helps with speed) is 2.75. When the ratio is 2:1 you need to watch out the top of the arm does not hit the underside of the action box. Thinner felt layers in the pad will help that. 

Edited January 17 by Chris Ghent

[Łukasz Martynowicz]

30 minutes ago, Chris Ghent said:

Buttons only need to be pushed to the bottom of the travel.  I suspect those liking flush low travel limits are pushing harder than that. I find when you push harder and further than needed you lose feel of how little the finger needs to move to release the button and it takes longer. 

 

Well, no. Flush buttons should best be viewed as completely different keyboard design, not simply shorter buttons. The experience and techniques on both types differ greatly. The simplest example - slide. On protruding keyboard, with 6mm diameter buttons, you have to overcome a dent in your fingertip from pressing the first button, the valley between buttons, both adding greatly to the friction of the move, especially with flat top buttons, and only then you arrive at the rise of the second button. On a flush keyboard, there is only the rise of the second button, no fingertip dent and no valley. On my Hayden I can perform slides in any direction, including those up a row, against the anatomic limitations of our fingers. Another example is finger substitution - you basically just put the second finger down beside the first while shifting fingers slightly. On protruding buttons you have to place your second finger slightly overlapping the first one and then quickly "skip" fingers, because you can't easily slide the second finger into position. 

[Chris Ghent]

Very different playing styles Lukasz. I use the style you describe on my B/C accordion.  

[Łukasz Martynowicz]

39 minutes ago, Chris Ghent said:

Very different playing styles Lukasz. I use the style you describe on my B/C accordion.  

Exactly. Flush buttons „accordinify” the experience without the need for larger button diameter, and that is in my opinion a very good thing. I play some tunes that would be way, way harder to play with classic, protruding buttons.

[Steve Schulteis]

How does hole/pad diameter affect the required vertical clearance?

[alex_holden]

14 hours ago, Łukasz Martynowicz said:

I can’t really imagine how lowering button travel would result in any significant speed increase if you lift your fingers way above the endplate when playing faster, centimeters above...

 

Having played two of my instruments side by side set up to 2mm and 3mm travel, the shorter one did feel a little quicker and less effort though. Regardless of how far your fingers move in total, the active part of the movement is 33% shorter. I've also played vintage instruments set up with a lower action ratio and much longer button travel (5 or 6mm), and they felt quite sluggish and hard work in comparison.

 

I agree that light springs are good, up to a point. If they are too weak the pads don't close quite as snappily particularly when the bellows are pressurised. I test this by assembling the instrument without reed pans and tapping rapidly on the buttons while squeezing the bellows: I like to hear all the pads close with a percussive 'pop' sound rather than a soft 'pfft'.

[Steve Schulteis]

HansQ, I'm well aware of the construction characteristics you mentioned. What I'm asking is if anyone has experimented with how the hole and pad diameter interact with the shift in tone that Alex described when adjusting pad height. Is it the same effect? Does increasing the hole size allow a lower pad height with the same tone, up to a point?

[Łukasz Martynowicz]

That’s why I wrote „lowest tension that still keeps the pads closed under normal push force”. I can get away with lower tension, because my lever-button joint being completely unrestricted does not add to action resistance, and large bellows cross section lowers the pressure. 
 

About „higher tension makes closing of the pads faster”. That is true, but at the same time it increases necessary muscle tension and fatigue, resulting in slower play. For me, buttons should resist only so much, that you can „prime” the note. After switching to my big box I had quite long adjustment period, because Elise has 3x higher button force and I was constantly triggering notes too early. I’m also the „lifting finger to play” kind of player, so buttons should activate on simply releasing the extension muscles of the fingers. 
 

Regarding pad lift, diameter, airflow and sound projection. This is tricky and gets even trickier for lower reeds, especially on „singing accompaniment”, lower volume instruments. Action chamber height affects tibre and volume, so there may be limitations in how high your lift can be, padhole aperture affects both volume and pitch stability, and you have to balance relative volume of low, mid and high reeds. As a result, it’s a puzzle of compromises, and action’s speed is just one of the possible goals here.

[Łukasz Martynowicz]

8 minutes ago, Steve Schulteis said:

HansQ, I'm well aware of the construction characteristics you mentioned. What I'm asking is if anyone has experimented with how the hole and pad diameter interact with the shift in tone that Alex described when adjusting pad height. Is it the same effect? Does increasing the hole size allow a lower pad height with the same tone, up to a point?

See my post above - there are many parameters affected by padhole diameter and lift, all at once, differently for different pitch ranges.

[fred v]

Thanks for this wonderful discussion. I have noticed that with too little spring pressure that my finger might hit against a button and make a sound not wanted (actually horrible). I too had the problem of dented fingers from mashing the buttons. The lower buttons has totally eliminated the mashing problem and my touch is very much lighter. Maybe that is what I mean by shorter stroke being faster.

[Łukasz Martynowicz]

15 minutes ago, HansQ said:

There are no signs that even the biggest producers experimented with these things since the basic construction has been the same for 150 years. It has been said that George Jones. who also was a producer of organs/harmoniums, made some acoustic experiments.

 

"increasing the hole size"....very hypothetical question...for what reason? ...and mostly it is simply impossible, since the measures are already so compact that available space is filled up.

In my view the extreme compactness of the most common models may be counterproductive and a larger standard size than the ca 6 1/4" would have been advantageous in many ways.

 

Either I don't understand your answer, or you didn't understand the question. You do experiment with those parameters every time you design a new box. Padhole aperture vary within a single instrument for the reasons I mentioned above. Perhaps you're thinking too big? We're talking about just milimeter differences in aperture. In my big box I actually made my bass reeds' holes too small at first, then re-bore them too big, so had to print inserts to reduce them again. I also had to remake some levers and even move one reed further away (which required reshuffling two others), because the lever was to short to lift the now bigger pad high enough to achieve full airflow and sound projection. 

[Steve Schulteis]

3 minutes ago, HansQ said:

"increasing the hole size"....very hypothetical question...for what reason? ...and mostly it is simply impossible, since the measures are already so compact that available space is filled up.

In my view the extreme compactness of the most common models may be counterproductive and a larger standard size than the ca 6 1/4" would have been advantageous in many ways.

 

Not hypothetical at all. Shorter button travel has already been identified as desirable in this thread. If making the holes larger allows shorter pad travel with a similar tone, that in turn allows shorter button travel. Increasing pad size isn't "simply impossible" either, although it may require a larger instrument or some other compromise.

 

Looking around a bit, I rediscovered a relevant blurb at https://www.concertinaconnection.com/concertina reeds.htm:

Quote

The distance of the pad to the hole when opened, which is decided by the amount of key travel, has the same affect on the reed performance as the size of the hole. For instance, if the pad does not lift of far enough the effect is the same as a small air hole.   

 

[Łukasz Martynowicz]

8 hours ago, HansQ said:

Honestly, I actually may have misunderstood the question, and I may have expressed my answer poorly as well. I believed " increasing the hole size" referred to conditions with existing or trad design instruments, and not different constructions or imaginable ones.

Padhole size does not always vary with common instruments as I said before and when it does with "better" instruments the variation/graduation seems not regular. This indicates that the pad hole size is not highly specific or *always* of crucial importance. There seems to be a considerable tolerance for hole variation.  But of course it has great influence on air flow and the evenness of tonal balance when many reeds are sounding together. So when you say: 

Please tell me WHAT the issue was that forced you to make these adjustments? I have an Aeola where one single reed got a much smaller hole than its regular neighbours. The only reason I can think of being that it otherwise would be too loud or being located in the reed pan where it rather shouldnt be. I have to check it closer.

 

There are two main reasons for adjusting padhole size: volume adjustment and pitch stability. The problem starts around F3 and increases significantly below C3, when reed size starts to grow rapidly. Large reeds need a very stable and sufficient airflow, otherwise they will be very prone to pitch bend when overdrawing the bellows. This behaviour can be used deliberately, but above certain level of fragility of pitch it becomes impossible to use those low notes, as their behaviour becomes too erratic. Just few days ago I learned, that some people exploit this trait for bassoon register on accordions, by altering how much this register opens up.

 

Now the flipside is, that the bigger the hole, the louder the sound. My big box is balanced for 80dB, which is low for a concertina (CC Elise peaks at more than 100dB when overdrawn, 90-100dB at normal pressure. So for the lower reeds a balance between stability of tone and volume of the lower reeds had to be established carefully, so they don't overpower everything else (F2 and G2 especially).