Lachenal Duet Concertina Reeds




This project grew out of a discussion on  Tasmanian player and enthusiast David Hornett happened to mention his plan to measure up reeds from Lachenal duet concertina No 3316.  Sensing an adventure, I offered to help organise and present the measurement data.  It proved somewhat of a learning curve for both of us, and you can follow that journey here.  I then felt we should have a place to preserve the final outcomes, hence this article.

Before we get into the measurements and analysis proper, some background...

Why is David doing this?

Why my curiosity re reeds?  Well ... I ordered a Suttner 2 years ago and am still waiting, figured they can't be too hard to make.  I mean Jeffries was a tinker, and every man and his dog who worked at Wheatstone's seems to have at some stage taken up the trade, and then there was Stanley and his clock springs: so I figured I'd make four, C/G. D/G ... get the drift?

Anyway, then the learning curve began!! I am now amazed that, with basically nothing, no background and rather primitive working conditions, ears for tuners and candles for mid winter light, our ancestors knocked out such good instruments ... absolutely amazing.  Anyway I have got to the position of reed making.

Now I did a bit of reading (reeding?) on concertina net and came across the comments about special hard 'Swedish steel'', "master reed makers", particularly "Honking" (I assume not some sort of cabaled concertina coding referencing a courtship ritual) and the such like -- all supposedly only known to Jeffries who pretty well remains unknown to anyone ... I mean did that jaunty little fellow in the hat really make concertinas, or did he assemble components made by others in their misery to gain a buck? 

So I figured I'd find an old Jeffries, fix it and learn a bit along the way. Now the Jeffries I found needed a few reeds made, (in fact it needed everything, so I pretty well made most of a new Jeffries in my workshop dungeon under the house, while the wife terrified her peace of mind watching Midsomer Murders above).  So, I purchased the Lachenal duet for which you now have the readout (on ebay. The Duet girls seem to be the poor siblings of their very sexy folksy, angly brothers); stole some of the reeds (the ones missing from your chart) filed them down and put them into the Jeffries -- I absolutely defy anyone to tell the difference, and those reeds are not Swedish steel and I am not a master reed maker! 
At about this point I measured all the duet reeds and sent the measurements off to Terry McGee. AND then I experimented and put a few Lachenal reeds directly into the Jeffries instrument. They can be picked as different, but just! (My wife, Masters in Music, master of most instruments and a wonderful ear player tells me: "There is no difference, I can't hear it anyway, people get a bit too obsessional about their instruments, they sound like concertinas to me.) They 'Honk' but are not as strong, exactly why the difference I am not sure and have been to lazy to follow through: but they are a little shorter than the Jeffries and have therefore a slightly different taper. One day I will compare the two: but I am absolutely certain it has nothing to do with 'special Swedish steel' because the reeds I replaced in the Jeffries were: one brass and one german silver, (and the top 'E' which was entirely missing, shoe and all) and they sounded in the box just like Jeffries reeds but softer.
So now, thanks to your insistence, Terry, I am embarking on a full set of concertina reeds, using your chart as a guide, and using 5 different thicknesses of blue tempered steel (rather than two like the Lachenal).  In CNC'd shoes which are fractionally longer and wider than Lachenal reeds for the same note, and with parallel sides like the broad reeded Jones (1880), one of which I have, and which, according to Malcolm Clapp, is the loudest Jones he has ever heard.
Below are the end actions assembled for the Tassie Tiger concertinas (blue gum, leaves, Tassie eagle, devils and tigers with the Tasmanian map thrown in too) I am making (I am NOT making them to sell, just one for each of the kids and the wife when I pass the mortal coil - Oh, what a legacy!?).

 And the revived Jeffries with its nice new Kangaroo skin bellows....

(Purchased this Jeffries some years back. It came from the Peace Hospice, London. The Lady had included a note to say it was turned into them after being found on the banks of the Thames, completely waterlogged in its leather case, and no one had approached the police to claim it. Animal glue and water don't go well together, it literally came as bits in its leather case.
This last picture is of the reeds from the Lachenal Duet. The reed closest to the needle point micrometer is the odd one out in the set -- longer reed, narrower shoe, slightly different taper: I would put what money I have on it being a Jeffries reed.

And the instrument?

The reeds come from a Lachenal Crane "Triumph" Duet concertina No 3316, believed to be from around 1913.  You can see the endplates to the right.

David adds, for this documentation project:

Reeds exhibiting the slightest possibility of tuning file marks, tip or root, were discarded.  The instrument was in an old tuning, approximating 63 cents sharp of A 440.

[Note: A440 + 63 cents = A456.3Hz - about as high as "Old Philharmonic Pitch" ever went.]

So, with all that out of the way, let's get into some measurements.....

Reed length

We look first at the lengths of the reeds, or more precisely, the lengths of the slots the reeds operate in.  It's much easier to measure the slots than the reeds, and quite good enough for our purposes (there is only a tiny clearance between the tip of the reed and the end of the slot).

We can see, depending on how you interpret a few intermediate lengths, that there are about 10 reed lengths employed, although most of the reeds fall into 7 categories.  I've put in a trend line (thin blue) to illustrate the general slope followed.


I've also illustrated what the slope (thin orange trend line) would be if the reeds followed the theoretical lengths, i.e. doubling in length each time you go down an octave.  As you can see, the bass reeds would be much longer (and therefore harder to fit into the instrument) and the treble reeds much shorter (and therefore quieter and less responsive).  


But having stepped away from theoretical scaling, the laws of physics demand we make adjustments elsewhere.  We should keep a lookout for where these compensations are made as we go through the other parameters of the reeds.

Reed shoe thickness

While we're on the topic of the reed shoes, we also looked at the shoe thickness.  A confusing picture emerged:

It's very hard to see any pattern emerging.  David's feeling is: "seems to be a product of uneven rolling, uneven pressing and varied sheets of metal stamped".  


Probably good to keep in mind that the nominal thickness is probably 2.08mm, 14 gauge.


Reed Widths

Now we move on to reed widths.  The blue columns indicate the reed width at their tips; the orange at the base.



Once again, we find they are not incrementally scaled, but in about 5 tiers, for practical reasons.  Note that over half the reeds are in the middle tier.  Reed width is not something that needs to be scaled incrementally, but some tweaking is clearly called for over the range. 

Reed Thickness

On to reed thickness, and, firstly, the general overview:



Treble reeds on the bottom right, bass reeds upper left.  Heels at the back right, tips at the front left.  Note, I've duplicated the heel measurement to illustrate the stock thickness under the clamp.

  • We can see that most of the reeds are made from thinner stock, around 0.48mm, with the lower bass reeds cut from 0.82mm stock.

  • All reeds are thinned, compared to the starting stock.  It is perhaps surprising that thinner stock isn't used as the starting point for treble reeds to save the need for so much profiling.  

  • Treble reeds are thinned most of the way, and are thinner at their tips than anywhere else, sharpening their pitch.

  • Midrange reeds use tip mass to slow them down, lowering the pitch.

  • Bass reeds make use of their thicker stock primarily by using it for increased tip mass.

There's probably more we could deduce from this graph, but it might be more easily seen on one of our alternative thickness graphs.

Reed Thickness, continued....

The 3D Overview is fun, but it's hard to appreciate all it's trying to tell us.  So let's look at the simpler 2D version...




 Some observations:

  • the navy trace is the heel, the section of reed under the clamp.  Confirms just two thicknesses of stock used in this instrument.

  • the G#4 reed is missing, hence the hole in the data at that point.

  • you'll see I've provided trend lines for the other data (thin lines) to alert us to where the maker was forced or happened to deviate from the trend.

  • the middle of the reeds and the quarter-point nearer the heel (green and yellow respectively) vary least across the range.  The variation is from about +50% in the bass to around -30% in the treble, a total of 80%.  That's small when we consider the frequency range is about 700%.

  • the roots of the reeds also vary to about the same extent (the orange trend line is parallel to the green and yellow), but are all slightly thicker, as they transition up towards the heels.

  • the middle, quarter and, to a slightly lesser extent, the root form the belly of the reed - the section over which it bends.

  • the big determinant in this system is the tip of the reeds, in aqua.  It varies from bass to treble over a 10:1 ratio, or 1000% - more than the ratio of frequencies.  So the tips of the reeds are doing most of the heavy lifting.  They are at full thickness in the bass, where their weight is needed to pull the reeds down to pitch (remember that the reeds didn't vary in length to the full extent science would have liked).  And they are ground right down to next-to-nothing in the treble, where the reeds have been made longer than ideal, in order to meet other practical requirements.

  • The three-quarter point (in brown) also comes into play, but not to such a degree - around 500% to put a number on it.  Not only is it transitional between middle and tip, it also changes role as we go up the scale.  In the bass reeds, it joins the tip as being part of the weighting system.  In the treble reeds, it becomes part of the bending system.

  • When we compare the thick aqua data trace with its thin trend line, we spot an area of divergence which will repay closer attention.  We can see that the reeds from F3 to A3 would probably have preferred to be made from the thicker stock (or stock of an intermediate thickness).  When you interpose a compromise in a musical system, you have to compensate somewhere else.  We might have thought the logical place to compromise for lack of tip thickness would have been at the three-quarter point, but the brown trace remains on trend in that area.  But check out the orange root trace - it dips dramatically to save the day.  The reed-tuner, finding that the reeds are too sharp has flattened them by filing down the root more.  Can't increase weight?  Increase flexibility.  (Heh heh, I might have been tempted to reach for the soldering iron...)

Reed thickness, some more....


There's always another way to look at things, of course, and reeds are no exception.  If we look down the other axis in our 3D Overview, we get an impression of how each reed is profiled.  Of course, with so many reeds, that can get a bit busy, but even so, we can make out a few interesting points:



It's easy to see, on the left, that we have two stock thicknesses, plunging downward then into the bellied region, and then radiating out from the middles to the tips either upwards, if we're looking at a bass reed, downward for a treble reed, or somewhere in between for the midrange reeds.  Perhaps, I'd hope to see a more even spread in the radiation?  We do have to remember that this work is being carried out by human beings, not robots.  And probably outworkers with less than remarkable facilities at that.  And we've already discussed that the decision to use only two stock thicknesses means that some fudging is going to be needed in the bellies department.


We do see a few reeds which look a little suspicious - eg the two shades of blue at the top of the root column.  They appear to reach their minimum thickness over at middle, while most of the reeds have bottomed out by the first quarter.  I suspect they are the two Eb3 reeds - if you look back at the other 2D view, you'll see there are some shenanigans going on there at Eb3.


Getting it all together

It struck me that it would be instructive to be able to view the reed thickness, width and length all on one graph, as these all contribute to the reed's tuning.  Width and length are not incremental in the concertina - they are, for practical reasons, varied in tiers.  But thickness is infinitely variable (within the limits of stock thickness!) and so it must fall to thickness to make up for the rigidities of the other two parameters.  So we should be particularly interested in what happens to thickness at the changeover points in the lengths and widths.  


Trying to display so much data on one graph presents problems, so this attempt simply assigns fake values to width and length.  But it does enable us to see where the changes are happening, which is our main aim. Keep in mind these are not to scale; indeed I've managed their values to maximise clarity.  It's their location and direction that we're interested in.



You'll see the new information as the two lowest traces on the graph above.  Sure enough, looking up from any of these changes we can usually see sudden jerks in one or more of the thickness curves, as the reed tuner deftly swerves to avoid an oncoming tuning issue.  The laws of physics seem still to be working....


Note though, the biggest cat among the pigeons still remains the sudden 41% reduction in stock thickness, which we dealt with earlier.  Had the concertina continued to exist, it would have been interesting to compare the sounds of the two reeds on each side of that change.  It's a big change to ask the reed tuner to deal with.



That's probably enough rabbiting on by me.  By now, you'll be becoming aware of the dangers to mental health posed by excessive indulgence in forensic organology.


We do have to keep in mind that this is one set of reeds for one make and one type of concertina made on one day by one man in a hurry.  We shouldn't view it as indicative of the broad range of concertinas out there.  It may well be, but we can't tell from here.


It would be great to have a "bank" of this kind of information, covering at least the major makers and models, and ideally covering their best periods.  (Their worst might be more fun!)  I'm happy to help anyone who has or could take a set of data to present it visually.  Even a partial data set is better than none.


A reminder that if you want to follow the full journey, including comments by many more knowledgeable than we, you can find it here.



Thanks to David Hornett, for putting so much effort into the measurements.  And to those on who put up with us!

Back to McGee-flutes Index page...

Created: 19 June 2014