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Reed Generated Vibrations Path Of Travel Through A Concertina.

Reeds Vibrations Materials End plates Direction

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#1 4to5to6

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Posted 18 October 2016 - 04:20 AM

A discussion on the defining Wheatstone's golden age resulted in discussions on materials, end plate design, fret work etc. and I started thinking about how the vibrations travel through a concertina...

I thought it would be more appropriate to pick it up here...

I don't really understand how the ends affect the sound as it's a total mystery how the reed generated air vibrations even travels through a concertina. For example, with two sets of reeds on an English, why are there reed pan chambers only on the outside of the pan? Wouldn't this chamber only be active on press when the air inside the bellows flows through the inside reed, pulsates or cuts up the air flow causing a tone, goes through the valve then into the chamber and finally out through the open pad hole and out the fret work. But what about on pull when the air flows inward? Does the sound still go outward? Probably a dumb question but it appears it does and so a total mystery to me! I've always wanted to make some models to experiment with how the sound travels through then start doing experiments with chamber sizes, pad hole sizes, reed scaling, etc... even how the thickness of valve material affects the tone. I've asked this a few times with conflicting answers.

Maybe someone could explain it quickly and especially the affects of different valve thicknesses and stiffnesses.

Why are shallow reed pans louder? What about mahogany reed pans? And this is all apart from the different types of reed material which radically affects the tone.

It would be awesome to be able to go back 90 years and pick the brains of one of Wheatstone's master builders. Wouldn't that be something?!!

#2 Chris Ghent

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Posted 18 October 2016 - 06:14 AM

It is always tempting to imagine the sound follows the air path through the concertina..! But obviously it doesn't.

 

There is a lot of stuff around your questions in the archives but it is hard to find because it is not typically reflected in the thread name. Writers to look for include Dana Johnson and Tom Tonon; both will no doubt chime in if this thread gets legs. In the meantime more general reading might help you focus your questions, for example, the chambers are in fact generally referred to as being on the inside of the reedpan, and the reeds in them are active on the draw.

 

Here is an approach to some of your questions, though I am hesitant to make categorical statements as my experience has been the more definitive the statement of concertina law the less true it turns out to be. All this is just my opinion.

 

Valves; thicker and stiffer are not completely the same but if you accept the intention in choosing a thicker valve is to make it stiffer, a stiffer valve will take more effort to shift out of the air stream, and it will shift the tone, probably by removing higher partials. It will drop the pitch more also. Another factor is the material used, it can make a difference to the absorption of partials. So why not use  very light valves? Because they can be influenced by wind "currents" and will couple with the movements of the reed beside them and create strange effects in the sound of the reed. Valves are problematic, you (I) want them to get out of the way easily and quickly but return with force and stay shut. Competing demands unlikely to be found in one material!

 

I suspect a smaller chamber volume  means less force needed to create temporary compression/vacuum in the chamber meaning more energy to open the reed further and quicker. I look forward to feedback from Dana and Tom on that one!

 

I have not made a mahogany pan but the padboards I have made using mahogany absorbed rather than reflected more high partials.

 

Reeds materials affect tone only through their stiffness. A stiffer reed (ie. brass) cannot open as far so will not be traveling as fast, creating fewer higher partials, leading to a sweeter sound and creating less volume because that is related to the amount of air passed in each cycle. Clearances are also important in tone and I have never seen a very close fitted brass reed (though they probably exist). Wider clearances, while inefficient, create a more pleasant sound, and if all brass reeds were fitted with wide clearances they would all have a sweet sound but it would be misleading to think it intrinsic to the material used other than the affect of the stiffness.

 

Good luck with testing materials. I have done some of this and it is extremely time consuming. It is difficult to confine your test to just one factor.


Edited by Chris Ghent, 18 October 2016 - 06:20 AM.


#3 wayman

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Posted 18 October 2016 - 06:58 AM

I've recently made a Bb/F anglo [1] which is intentionally modular so that in time, I can make alternate fretworks and ends [2] to experiment with the resulting sound and performance. As a busy post-graduate I'm not sure when I'll have the opportunity to make alternate parts, but in theory as I've already got the files it's just a matter of finding the time and materials. I hope to experiment with ...

 

different kinds of wood

different kinds of metal

different thickness

different open-ness of design

whether the material of the end frames contribute meaningfully to sound difference separately from the ends themselves

 

Someday. And someday sooner I'll throw together a page about its design and construction and record and post some videos!

Will

 

[1] (... about which more later, someday, when I have a chance to write this up properly! but in short, newly-designed and built 39-button anglo using 1926 Aeola reeds plus a few from a ~1900 Lachenal baritone anglo)

[2] (theoretically reedpans too, though that was never the design)



#4 Patrick McMahon

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Posted 18 October 2016 - 10:29 AM

I'm not claiming that I know, but I'm offering what I think is probably the answer to the question about the chambers operating on both squeeze and draw.

The speed of sound in air is about 700 mph, or somewhere vaguely near 1000 kph. 

So if you have air travelling through the reed at less than that speed, then the sound will go both ways every time.

 

It's like if you stand in a doorway and shout. Even if there's a hurricane blowing through the door, you will still be heard both sides of it.

So the chamber affects the sound just the same, whichever way the air is passing.



#5 4to5to6

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Posted 18 October 2016 - 01:18 PM

It's hard for me to visualize how the sound is "amplified" in a concertina. The reed itself doesn't significantly make any sound I've often read, it generates a frequency by cutting (starting and stopping) the air column travelling through the shoe as the tongue swings back and forth through the gap like a pendulum. I can visualize that this how the sound starts but not how it is amplified or resonates through the concertina. Sucking or blowing through a reed removed from the instrument makes very little sound. Maybe the reed shoe just has to be attached to something solid with mass to cut the air column cleanly. I am guessing.

I can visualize the sound generation and amplification in a clarinet, trumpet, flute (the hardest one) and even a lot easier in a harmonica.

I just can't see how the chambers affect the tone in a concertina especially when the sound is the same on both draw and push while the chambers are on only one side.

Edited by 4to5to6, 18 October 2016 - 01:27 PM.


#6 Patrick McMahon

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Posted 19 October 2016 - 09:04 AM

I think when you have an enclosed space, the sound waves are bouncing around inside it, and come into contact with each other. 

On the ocean, when two waves merge at just the right moment, it can massively increase the amplitude. That's resonance.

In a chamber with walls, there's a lot of opportunities for that to happen, especially if all the sounds are created at the same frequency. 

So the chamber essentially is helping the waves to work together, rather than individually.

 

Accordions have a chamber, and have valves, but the tone is different. Old accordions have leather valves like old concertinas, but they sound different. So if you want to explain tone, I think you have to look at the differences between the two. I don't think it's much to do with valves. It's how the reeds are set into the wood. Accordion reeds are connected by wax, concertinas reeds are jammed in tight. 

That seems to make a big difference, because accordion reeds waxed into a concertina sound much more like accordions. 

Maybe the vibrations from the reeds are fed back into the reed, via the wood. Or maybe the wood vibrates in sympathy, and gives out sound, like a guitar top. Or maybe a bit of both is going on.



#7 Jeff Loen

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Posted 19 October 2016 - 09:07 PM

Patrick, I think you are on the right track.  When a note is played, the interaction with nearby materials and the air chamber can lead to three possible outcomes; subtraction, no change, or addition.  Simple physics.  In the better instruments, I think that things are designed so that frequencies add, giving louder, deeper sound.

 

Advances in understanding string instruments began to be made 40-50 years ago when resonance modes were measured and adjusted for the best response for the central register of the instrument (ie center two strings of the violin).  Basic modes that were found to be important for the violin are air resonance frequency and a number of wood resonance frequencies.  This is a good place to start with the concertina, since we are also hearing air and wood resonances.

 

I think that we're nowhere nearing understanding how resonance of materials and air volumes affects concertinas.  Systematic work like that described by wayman is needed.



#8 4to5to6

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Posted 20 October 2016 - 12:55 AM

Thanks. Along the line of your thoughts... I wonder if tuning a concertina to A440 down from A453 messes everything up? In the old days, they fined tuned everything by ear to the old pitch... chambers, hole sizes, pad opening, even voicing of the reeds.

Edited by 4to5to6, 20 October 2016 - 12:57 AM.


#9 Geoff Wooff

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Posted 20 October 2016 - 04:23 AM

Having brought down a lot of  old concertinas  from 452  to 440hz. many years ago  when my hearing was much  more  acute,  I  never detected  much in the way of tonal  changes.   Losing  a sweet temperament during the process  will have  more effect  than  a small change in pitch  might have on chamber shape/size.

 

Much of the  vent hole    and chamber depth  sizings  appear to be  an attempt to arrive at an overall balance  of sound output  and attack.  To find points of reference  without recourse  to  measuring equipment  tends to be difficult  but one point I constantly notice  is that the C,  two octaves above  middle C,  is  always the loudest  note  on an  English...  what accoustic reason  there is for this I am not sure.

 

 

Changing  the end plates,  material  and amount/ size of  piercings  does have a very marked effect  on the sound  output. My loudest  EC has the exact  same internals   as those found on  the Dot and Comma  models .  The  resulting difference between the two model's volume  is  huge.

 

Most of the  Duets I have encountered  have  less  piercings  in the fretwork  of the left hand  end , as if the designers  meant to  utilise  this  to    calm  the output  of  a chordal accompaniment  to a right  side  melody.  Unfortunately  this  is not  feasible  on an EC, though  you do see  many where the amount of fretwork over the  lower  note  holes  is  reduced  considerably.  The canted ( angled)  reedpan  goes a long way  to  balancing  the  output and  tone  through the range  and these later  instruments  tend to have   more evenly  pierced  fretting  as a result

 

Sorry for stating he obvious  here.

 


Edited by Geoff Wooff, 20 October 2016 - 04:44 AM.


#10 Chris Ghent

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Posted 20 October 2016 - 03:38 PM

In the old days, they fined tuned everything by ear to the old pitch... chambers, hole sizes, pad opening, even voicing of the reeds.


What is the evidence for this? I'm not sure exactly what you mean by voicing the reeds but the adjustment of the other things in your list is driven by response and tone rather than tuning.

#11 Theo

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Posted 20 October 2016 - 04:44 PM

Thanks. Along the line of your thoughts... I wonder if tuning a concertina to A440 down from A453 messes everything up? In the old days, they fined tuned everything by ear to the old pitch... chambers, hole sizes, pad opening, even voicing of the reeds.


"The old pitch"? There is no one old pitch. Some Wheatstone catalogues offered three or four different pitches. In my collection I have a Lachenal with two sets of reed pans. Neither is in modern pitch.

Edited by Theo, 20 October 2016 - 04:45 PM.


#12 4to5to6

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Posted 20 October 2016 - 05:23 PM

Chris, The evidence for this is that they didn't have harmonic and frequency spectrum analyzers, electronic tuners, etc. to see what was going on.  The y used their ears.  Don't take me wrong... I was complimenting their ability.  I am simply wondering if by lowering the pitch to A440 we are throwing everything out of wack... All those things they tweaked by ear...  Is it possible the tone and the response is thrown off by lowering the pitch of each reed.  Just throwing it out there.  I may be totally wrong.

 

Theo, I agree, just as there was no thread standard for the end bolts, there was also no standard for the overall pitch of the instrument.  I understand they have tested tuning forks found in old opera houses and they have been all over the map as far as pitch.

 

This all aside, Back on topic...

 

I still can't understand why you blow on a reed with your mouth and there is very little sound and yet put it into a concertina and it is LOUD.  I understand there is almost no vibrations in the reed shoe so it's not like a guitar top.  The air is chopped up by a pendulum swinging through an air gap.  How is the sound amplified and what is the path of this sound and why are there chambers for only the draw reeds (yet the same tone on push)???

 

What am I missing here?


Edited by 4to5to6, 20 October 2016 - 05:24 PM.


#13 David Hornett

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Posted 20 October 2016 - 10:18 PM

Soft lips give a soft sound, but is that not the way it should always be?

 

David



#14 4to5to6

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Posted 21 October 2016 - 12:20 AM

Soft lips give a soft sound, but is that not the way it should always be?
 
David


:) Good one! :)

#15 Chris Ghent

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Posted 21 October 2016 - 02:05 AM

Chris, The evidence for this is that they didn't have harmonic and frequency spectrum analyzers, electronic tuners, etc. to see what was going on.  The y used their ears.  Don't take me wrong... I was complimenting their ability.  I am simply wondering if by lowering the pitch to A440 we are throwing everything out of wack... All those things they tweaked by ear...  Is it possible the tone and the response is thrown off by lowering the pitch of each reed.  Just throwing it out there.  I may be totally wrong.

 

I still can't understand why you blow on a reed with your mouth and there is very little sound and yet put it into a concertina and it is LOUD.  I understand there is almost no vibrations in the reed shoe so it's not like a guitar top.  The air is chopped up by a pendulum swinging through an air gap.  How is the sound amplified and what is the path of this sound and why are there chambers for only the draw reeds (yet the same tone on push)???

 

What am I missing here?

I know they did not have the aids we have but they had skill and knowledge. Nothing we don't have today but a tuner is quicker and more consistent. They had tuning forks and notes could be compared and equalised by listening to the beat. This skill is not lost, piano tuners do it this way. Also consider the possibility most concertinas were not perfectly in tune. If you listen to earlier concertina recordings you can often hear dubious notes.

 

I don't think the situation when changing pitch is like flutes. When older flutes are tuned to a modern pitch by extending the head slide they often upset the relationship between the notes. With concertinas, when you shift the pitch, it is moving a max of about a semitone. This is not a significant shift when you consider any particular reedframe in a concertina already stretches across several semitones, and in Jeffries concertinas they will stretch across up to 6 semitones.  And chamber sizes are often dictated by the frame size. This is why they look "tuned", because they follow the frame size, which follows the pitch. The response may change ever so slightly when the reed is reprofiled, for better or worse.

 

A reed frame locked into a good reedpan will be rigid, and not absorb energy from the reed vibrating. Any movement in the frame and the reed will not open as far. A wide opening reed passes more air. Bigger air chunks (not longer) mean volume. Your lips are absorbing a lot of the energy. Not the complete answer, but a factor. You may get more volume if you push it against your teeth. Your soft mouth will still absorb energy. Thank you David.



#16 Greg Jowaisas

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Posted 22 October 2016 - 09:59 AM

Chris, The evidence for this is that they didn't have harmonic and frequency spectrum analyzers, electronic tuners, etc. to see what was going on.  The y used their ears.  Don't take me wrong... I was complimenting their ability.  I am simply wondering if by lowering the pitch to A440 we are throwing everything out of wack... All those things they tweaked by ear...  Is it possible the tone and the response is thrown off by lowering the pitch of each reed.  Just throwing it out there.  I may be totally wrong.

 

Theo, I agree, just as there was no thread standard for the end bolts, there was also no standard for the overall pitch of the instrument.  I understand they have tested tuning forks found in old opera houses and they have been all over the map as far as pitch.

 

This all aside, Back on topic...

 

I still can't understand why you blow on a reed with your mouth and there is very little sound and yet put it into a concertina and it is LOUD.  I understand there is almost no vibrations in the reed shoe so it's not like a guitar top.  The air is chopped up by a pendulum swinging through an air gap.  How is the sound amplified and what is the path of this sound and why are there chambers for only the draw reeds (yet the same tone on push)???

 

What am I missing here?

Try holding the reed assembly tightly between the the index finger and the thumb (approximating the dovetail slot.  Blow into the reed covering the top of the index and thumb with the lips.

The volume is startling.  I've surprised many a young (and old) audience with this demonstration. :o  :rolleyes:

 

My take is the reed movement is responsible for the vibration (cutting the air stream or what have you) but much of the resonance and amplification of sound are a result of the interaction of the surrounding materials.  (In the above instance the cupped hand provides a resonating chamber)  Reflection and absorption of the sound by different materials can influence the sound quality and volume of an instrument.

 

I was able to change a fret work end and action from one Aeola to another with both instruments within a year of each other's manufacture.  The Aeola with significantly more cut out area in the fret work was notably louder.  When this end with the open fret work was put on the more "timid" Aeola it suddenly had a louder, more aggressive sound.  Likewise the originally louder Aeola grew more subdued with the restricted fret work.  It was interesting to note that while the loud Aeola with the more open fret work had a brighter more aggressive sound suited for competition with other instruments in a session, the more restrained Aeola with the restricted fret work had a very balanced refined tone albeit with less volume.

 

Over the years I've had hours and hours of discussion with maker Wally Carroll concerning the where and why concerning a concertina's sound.  Wally can add his own comments but I think we agree that the reed itself is only a part of the sound equation.  (And perhaps a smaller part than we suspect :wacko: )

 

The sound and overtones brass reeds vs. steel reeds generate certainly seem to have differences but as anyone who has substituted a steel reed assembly for a broken brass reed may tell you, soundwise, often it is hard to distinguish the steel reed among the brass ones.  (Response is a different matter)

 

The mystery continues.... :ph34r:

 

Greg


Edited by Greg Jowaisas, 22 October 2016 - 10:03 AM.


#17 David Hornett

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Posted 24 October 2016 - 01:38 AM

Yes, I agree, Greg,. 

 

Further, when one plays an instrument , especially on the left hand notes, it is easy to feel the entire instrument vibrate. Reeds tightly fitting to their board will transmit this vibration better that holding a reed to the lips where there is nothing to vibrate, and as Chris pointed out the reed frame actually moves changing the gap. Vibration = sound, hit with the same force, the bigger the drum the bigger the sound  because the diagram does not lose it energy so easy by connection to the side, it can wobble, vibrate, more grandly than a small drum..

 

I have made reed pans of different materials and tried the same reeds in them, huon pine gives a different sound than king billy pine, and there is a difference in volume too, the king billy, a softer wood appears to have a louder voice, but a warmer sound, compared to the blackwood and huon pine I have tried. And likewise metal ends sound harsher and louder than wooden ends.

 

There are lots of things happening when a reed vibrates, but a lot of the volume has to do with how tightly the reed shoes are held in their slots, and they will most likely not be as firmly held by fleshy fingers to the lip, nor will the flesh transmit the sound nor modify the tone as does wood .

 

Hence my reference to soft lips.

 

Such are my thoughts.

 

David



#18 4to5to6

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Posted 24 October 2016 - 02:27 AM

I read somewhere that you can remove all the reeds, reassemble the instrument, play it, and even with all the reeds removed hear the approximate pitches from the air rushing through the tuned chambers.

Is this true?

If so, wouldn't this indicate that the chambers are finely tuned to the reed's pitch? Original "old pitch"!!!

Is this for tuning reed volumes through resonance?

Or... are the reed chambers sized only to influence the responsiveness?

John





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