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Geoff Wooff

Straight or Tapered reed tongues ?

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Posted (edited)

Following  Stephen Chambers'  comment  regarding  concertina reeds  having  tapered  tongues,  on the  recent  Lachenal  reed shoe  thread,  which  made  me  think    ' do  all  concertina reeds  have  tapered tongues /slots  ?    My  memory  is  that this is  not  always the  case.

 

At the moment  I  have only  two  concertinas,  but  a  tin of  old/  spare reeds   by  various  makers   proved all to have  tapered  tongues,  however , of  my  two  instruments  one  has  parallel  tongued  reeds.  Both  are Wheatstones ,  the  parallel  reed  model, a  raised metal  ended  treble  English,  dates from  about 1898, it  has  a lovely  full tone , of  bell like quality.   The other  is  a 1927  Aeola  with  tapered  reeds , very well balanced  throughout  its  4 octave range  and  a  good strong tone    with   wooden   ends.

 

To  my ear  the  tone  of  these  two concertinas  differ  considerably,  although they are  not  at  all  the same  model   but,  I  have  encountered  several   very similar    to  the 1898, but dating from  20+  years  later,  that  do  not  have  that same  tone  quality.  Condition is  a big   factor  but  just  how  much  difference  could  be  attributable  to  this  one  detail ?

 

Measuring the  tapered reeds:  the  smaller  ones  appear to  be  .005" (.127mm)  narrower  at the tips, the  mid sizes  perhaps  .008"(.2mm)  and the  biggest  taper  by  as much as .011"(.28mm).  Not a great  amount of taper  but  fairly  constant  throughout the range.

 

An old   accordion reed bank    I  inspected  this morning  shows   parallel  tongued  reeds    on the lower notes and tapered  tongues  for  the  higher  notes, so I see the  possiblility  of  using  width  to help  achieve  pitch  .

 

Any thoughts ?

 

 

  Do modern makers  use  tapered or  straight  reeds  ?

 

 

Edited by Geoff Wooff

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On my current instruments I progressively vary them from parallel on the lowest notes to about 0.8 degrees on the highest. A taper makes it easier to get a good fit, but I feel that if you taper the low reeds you have to use a less optimal profile (thicker at the tip). I don't have a clear idea what effect it has on the tone but I know it is only one of many variables.

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Some (excellent) modern makers use parallel reeds but this may be related to methods of construction rather than tone or response. Some time ago I measured the difference in surface area of a parallel reed compared with a typical tapered reed, can’t remember the pitch, and the parallel was 3% larger. Not enough to make a signal difference, I thought. It does mean a low reed can be a little less thick at the tip but so what? Of course, it will need to also be thinner in the belly.  A high reed will need to be thinner at the tip, mmm, could be meaningful. For the same degree of taper in the reed window relief the tapered reed will lose pressure earlier. Also could be meaningful?

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1 hour ago, Geoff Wooff said:

An old   accordion reed bank    I  inspected  this morning  shows   parallel  tongued  reeds    on the lower notes and tapered  tongues  for  the  higher  notes, so I see the  possiblility  of  using  width  to help  achieve  pitch  .

 

My two Jeffries (nw sold) both had tapered reeds with .010 difference in width from base to tip regardless of length, which gives a nice scale for percentage of taper relative to length / pitch.  My Wheatstone duet and some other Wheatstones I have checked had parallel reeds, but they made so many kinds of reeds, I am not surprised by your tapered Aeola reeds.  
   One thing that needs to be taken into account, is that tapering a reed is a close equivalent to a reed profile that is thicker toward the root.  If you simply increase the width of a parallel reed, you just make it a stronger spring, but don’t change its pitch.  If you only increase the width towards the root, you add greater stiffness overall, but without the compensating mass at the tip, so all else being equal, the pitch will be higher.  Because  Increasing thickness increases stiffness faster than increasing width does since more material is farther from the center of bending,  it isn’t strictly identical to changing the reed profile.  What I think is important, is that tapering a reed allows you to have higher reeds being longer than they would be if they had been parallel at the same pitch and overall stiffness.  Since large lower reeds are generally louder than small reeds, having longer and hence larger high reeds could help with balance.  This isn’t too much of an issue for instruments with the range of a c/g Anglo or a 48 button treble, but on a duet or even something like a 56 button tenor treble, the difference in size between low and high is more extreme and you start to see efforts to decrease the output of the lower reeds.

   I have been fitting reeds for a long time, and find no need to adjust the fit with anything but a rather large file.  It is pretty easy to hold a large file straight and I found it took very little time to get a feel for how much bite the file is taking.  Adjustments of .0001 inch are normal.  Using the taper to fit the reed does work well, but I don’t think that was the reason it entered reed design.
   Tone of different reeds in different concertinas is a tough nut to crack.  Different models can have construction details and materials differences that can dominate the sound, so it may be hard to pin the tone on the reeds alone.  But, in reed organ literature,  longer narrow reeds are said to be less bright than wider reeds.  Wheatstone made a type of reed where the side edges were rounded, and were advertised as a better class of reeds.  Those kinds of changes can be tied to the reeds more easily.  Same for short scale vs long scale reeds.  Just because tapered reeds are a combination of narrow and wide, I wouldn’t be surprised if they tended toward  brightness. From looking at reed waveforms, I’ve seen the higher pitches having more Sinusoidal  wave forms, and perhaps they benefit from the extra brightness.  Since this is so prevalent in the accordion industry, it would be interesting yo hear their take on it.

Dana
   

 

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34 minutes ago, Chris Ghent said:

For the same degree of taper in the reed window relief the tapered reed will lose pressure earlier. Also could be meaningful?

This is an interesting effect of tapered windows, and perhaps might be assisting in response?

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1 hour ago, Chris Ghent said:

Some (excellent) modern makers use parallel reeds but this may be related to methods of construction rather than tone or response. Some time ago I measured the difference in surface area of a parallel reed compared with a typical tapered reed, can’t remember the pitch, and the parallel was 3% larger. Not enough to make a signal difference, I thought. It does mean a low reed can be a little less thick at the tip but so what? Of course, it will need to also be thinner in the belly.  A high reed will need to be thinner at the tip, mmm, could be meaningful. For the same degree of taper in the reed window relief the tapered reed will lose pressure earlier. Also could be meaningful?

 

Hi Chris. My hypothesis (which could certainly be wrong) is that if you make the tip of a bass reed thicker, it will need to travel further on the downward half of the cycle before it dumps enough of the air pulse for it to start back up again. That might mean it takes slightly longer to reach full amplitude, and could contribute to increased pitch bending. At the high end, tapering them means the tip doesn't need to be quite as ridiculously thin as it would if it were parallel.

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