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Retuning, Setting Reeds, And Warbling Reeds

Tuning Reeds

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#1 Paul_Hardy

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Posted 28 November 2014 - 05:40 PM

I've been learning about tuning reeds, by embarking on retuning a brass-reeded Lachenal tutor to concert pitch from old philharmonic pitch. I bought it as a wreck some years ago and have been restoring it intermittently - see  lachenal_52313.html. I realise that retuning is hard, and tedious, and I'm likely to make mistakes, but I'd prefer to make mistakes on this instrument which will never be a great one. A famous physicist once said that an expert is someone who has made all the possible mistakes in their subject!

 

I've done a first pass on all the reeds, and now doing a second pass. It's all going reasonably well, except that I have three reeds which are within four cents of true pitch when blown gently, but when the pressure is increased slightly, they warble and go sharp. There was another like that, but by repeatedly tweaking the setting of the reed in the frame I managed to make it OK. However the remaining three (low Ds and B on RHS) are resisting my efforts.

 

So, does anybody have any hints for how to correct that scenario? I've already tried cleaning the edge of the reed and the frame. Note that this happens when the reed is in an external tuning jig, as well as when re-inserted into the instrument, so it's nothing to do with the fit of the frame in the wood slot.

 

It is of course quite possible that in my learning, I've manage to file the reed to a strange cross-section, so if nobody can suggest a solution, I could send the reeds off to Concertina Spares to be replaced or fixed, but I'd like to understand the cause of the problem and see if I can fix it myself if someone can suggest an approach.

 

In general, are there any hints on setting of reeds beyond the description in Dave Elliot's Concertina Maintenance Manual?

 

Regards,

 

 



#2 Greg Jowaisas

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Posted 28 November 2014 - 08:04 PM

Paul,

If you have cleared the filing "sludge" from the reeds and checked to make sure the tongues are centered (centering can make quite a difference in volume and performance and perhaps a few cents in pitch) then perhaps the seating of the valves is contributing to the problem?  A valve that catches on a chamber wall and then slides free can change pitch and volume dramatically.  Sometimes a short valve that doesn't quite cover a vent all the way can make a reed sound funny.  And valves that are not centered can affect reed performance and make lots of odd noises.

 

While the above is good advice, in rereading your post it seems you are getting the warble in the tuning jig as well which would negate any effect from a valve.  So I'd check the centering.

 

One of the challenges of tuning is to keep the reed tongue filing even so the thickness or the reed stays uniform across its width.  Perhaps the concertina reed makers who have made hundreds or thousands of reeds can wade in on the effects of uneven filing.  Would the reed actually twist and cause air to dump more quickly as pressure increased and cause the reed to cycle more quickly raising pitch?

 

As a repairman I've had to deal with reeds over thinned by bad or ill advised filing.  Sometimes the results do not sound very pretty.  The overly thinned reeds are prone to drift in pitch with moderate pressure changes.  In most cases they go flat with more pressure.

 

I'm not sure if I've had a reed "warble" but I've had to change lots of valves that "gurgled", "popped", "hummed", and yes, "warbled".

 

Best,

 

Greg

 

BTW I DID notice some warbling in tuning tonight.  These were late model Wheatstone reeds in aluminum shoes (Always more of a problem to securely fit in the reed holder).  When I adjusted the tuning jig's reed holder properly the warbling stopped.


Edited by Greg Jowaisas, 28 November 2014 - 10:29 PM.


#3 d.elliott

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Posted 01 December 2014 - 11:40 AM

This is often the result of a filing burr down the flank of the reed, de-burr the reed tongue flanks, and check the reed frame vents for any nodules of white oxidisation salts .



#4 Dana Johnson

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Posted 01 December 2014 - 02:35 PM

I find when low to upper mid range reeds go sharp on increased volume, often it is because the reed is swinging far enough to start hitting something either in the reed window or on the reed that wasn't touched at lower amplitudes. This goes back to Dave's post.
Low and mid range reeds tend to flatten under high pressure, stronger reeds and well centered ones are least affected. I have found that above a certain pitch, increased pressure has the opposite effect even when the reeds are good. ( poorly centered reeds still go flat.)
When reeds are filed so that one side is thinner, the reed will actually swing in an elipse or a sideways arc. Unbalanced filing at the tip has less effect unless the tip is only a one or two thousandths thick where removal of a half thousandth on one side can cut the reed thickness proportionally in half, , but farther down it becomes more important. Rarely is it enough to cause the reed to hit the sides, but it can effectively de center a well centered reed while it is in motion.
This could make a reed unstable to tune, but isn't likely to cause your problem. Crap at the root of the reed ( rust, corrosion , bits of filings from tuning, etc) often effectively shortens the reed at increased volume for an increase of pitch.

#5 Paul_Hardy

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Posted 01 December 2014 - 02:38 PM

Thank you both for your responses. I have now managed to get all the reeds speaking OK-ish, and I'm sure Dave is correct that the cause was filing burr material on the side of the reeds. I'd come to this conclusion yesterday, because although I previously said: "Note that this happens when the reed is in an external tuning jig, as well as when re-inserted into the instrument, so it's nothing to do with the fit of the frame in the wood slot.", In fact I noticed that if I didn't push the reed shoe firmly home in the slot in the tuning jig, then it didn't warble, so the slight squeezing of the reed frame was sufficient to narrow the gap and trigger the warble.

 

I'd already tried cleaning the edge of the reed and the frame, but did it a little more assertively and managed to get it speaking better, although I suspect that two of these reeds are very snug in their frames,

 

I now need to play the instrument a while to get it running smoothly, but I do feel that it is now workable again and in concert pitch.

 

Thanks again.







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