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alex_holden

Making Quieter Reeds for a Drone Button

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I'm looking for a way to make a particular pair of reeds sound quieter than the rest of the instrument without otherwise compromising their performance. It is for a low D drone on an anglo.

 

On a previous instrument I made the drone reeds and chamber in the same way as I would a standard bass note, and the note sounds fine when played intermittently, but if you hold it down constantly through a tune it sounds too prominent. Ideally I would like to make it quieter than the other notes on the instrument without compromising on efficiency (if you're holding it down constantly you don't want it to use a vast amount of air), pitch stability, or speed (the speed is important because the startup time is noticeable as a 'hiccup' when you reverse the bellows direction).

 

I tried modifying it after construction by putting a choke across the pad hole. The effect was to give the note a muffled tone, slowed down the response a bit, limited its maximum volume, and most problematically it caused lots of pitch flattening as you increased the bellows pressure into normal playing range. Not really satisfactory. I also tried stuffing foam inside the chamber with similar/worse results.

 

A couple of options I have been considering trying are: 1. Alter the proportions of the reed tongue, i.e. keep it the same length but reduce the width so the area of the vent slot is smaller. 2. Put the reeds at the end of a convoluted chamber, so the air path zig-zags back and forth before it exits the pad hole. My hypothesis is that 1 will reduce the amplitude of the air pulses produced by the reed, and 2 will absorb higher frequencies and mellow the tone. I'm unsure about possible negative side effects.

 

Any other thoughts before I start experimenting?

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2 sounds very similar to the cassotto system used on some piano accordions.  In those the addition convolutions are usually limited to one change of direction.  Emmanuel Pariselle  uses a double length reed chamber on the bass reeds of his diatonic accordion design.  In this case it allows the bank of bass reeds to be folded over and lie on top of the smaller reeds in order to save space, but it does have a beneficial effect on the bass sound, and I think actually improves the reed response. 

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How did you effect the 'choke', Alex ? was it something solid ? I don't know if you have come across  'Mull'...it is a bookbinding material ? it's like a 'sized' or starched open(ish) weave, cotton gauze - typically what old books had down the spine.  It's value is that is quite stiff.  Stiff enough to 'fix' across the chamber or the 'inside' of the sound hole. 

 

It might be worth considering - I can let you have some if you want to try it.  

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1 hour ago, Theo said:

2 sounds very similar to the cassotto system used on some piano accordions.  In those the addition convolutions are usually limited to one change of direction.  Emmanuel Pariselle  uses a double length reed chamber on the bass reeds of his diatonic accordion design.  In this case it allows the bank of bass reeds to be folded over and lie on top of the smaller reeds in order to save space, but it does have a beneficial effect on the bass sound, and I think actually improves the reed response. 

 

Thanks, that's an interesting reference. I'm planning to stick with a single layer flat reed pan rather than tacking on a double decker chamber. Given the pan layout I'm starting with I can see a fairly easy way to construct a Z shaped air path (it would take up the width of 3 chambers). With that arrangement I could probably make two of the dividers adjustable to tune the length of the air path to some extent. I can see a different possible arrangement that would allow for an approximately L shaped path, but it would be slightly trickier to construct and the length wouldn't be adjustable.

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56 minutes ago, Sprunghub said:

How did you effect the 'choke', Alex ? was it something solid ? I don't know if you have come across  'Mull'...it is a bookbinding material ? it's like a 'sized' or starched open(ish) weave, cotton gauze - typically what old books had down the spine.  It's value is that is quite stiff.  Stiff enough to 'fix' across the chamber or the 'inside' of the sound hole. 

 

It might be worth considering - I can let you have some if you want to try it.  

 

Thanks. It was an adjustable metal plate. I think what I learned from that experiment though is that choking a loud reed isn't a good way to make it quieter because of the pitch instability caused.

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56 minutes ago, alex_holden said:

 

 I can see a different possible arrangement that would allow for an approximately L shaped path, but it would be slightly trickier to construct and the length wouldn't be adjustable.

 

I wasn't recommending the L shaped path for your application,  just explaining the thinking behind Emmanuel's design.  I suspect that the shape of the path matters less than its length and volume.  The effect on the sound seems to me to be to filter out some of the higher frequencies, but not to reduce the volume of the lowest pitch.   That might do what you need if it is the higher frequencies that are the more intrusive part of the drone sound.

 

I wonder if a narrower reed tongue might be counter productive?   I'm thinking of G Jones who made a selling point of his "broad reeds", but most Jones concertinas I've come across have a softer sound than similar Lachenals with relatively narrow reeds.

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Thicker, softer valves?  Eva foam on the chamber wall(s)?

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3 minutes ago, Greg Jowaisas said:

Thicker, softer valves?  Eva foam on the chamber wall(s)?

 

Thanks. I did experiment with the valves a bit on the previous one. Gluing them down part way had some muffling effect but I didn't like the result and returned them to normal. There wasn't enough space to try lining the walls on that one, but it could be worth experimenting with in the future. Maybe cover them with chamois: Using foam inside an instrument makes me a little nervous because some types break down and crumble over time.

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44 minutes ago, Theo said:

I wonder if a narrower reed tongue might be counter productive?   I'm thinking of G Jones who made a selling point of his "broad reeds", but most Jones concertinas I've come across have a softer sound than similar Lachenals with relatively narrow reeds.

 

Yes, I don't know what causes the Jones softness and if it is a difference in the volume or only the tone. I think I'll have to make two reed assemblies with different proportions for comparison.

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Restrictions on a reed generally aren’t good for either sound or response.  A reed used as a drone can afford a bit less responsiveness, but you still want a good tone from it.  
   There is a good bit of latitude in designing reeds of a given pitch.  The set of baritone Wheatstone reeds I have are a bit larger than their equivalents from the Wheatstone McCann duet I based my reeds on originally.  Linota reeds are wider but not quite as long.  A few possible ways you could deal with this are:  
    Keep reed profile an length the same but narrower.  (As mentioned earlier). That gets you a reed that still behaves like your set, but just can’t affect as much air.  The stuff I’ve read on reed organs says that narrower reeds have weaker higher overtones, which could be helpful to keep a drone from walking over reeds an octave higher.  
   You can also reduce the center area of your reed to make it weaker in the more or less neutral area which will mean it will reach it’s max swing at a lower pressure than it’s mates for a lower volume.  Stronger reeds have higher maximum volume because they require higher pressure to increase their swing.  
   Related to this is to substantially increase the reed’s draft angle which allows it to dump air before it has swung very much.  The low D is normally long enough not to require more than a few degrees draft because it clears the window before it has swung very far.  This sort of pulls the rug out from under the reed.  You might use a small ball end mill to cut a wide groove down the center of the backside of the window leaving only maybe half the shoe thickness left for the window.    Years ago, Marcus did something similar to his hybrid reeds with a v shaped cutter ( I think he asked for this from the manufacturer) in order to approximate the concertina reed geometry.  It certainly didn’t hurt them, but I don’t know if they are still done like that.  It was 25 years ago.
    A shorter weighted reed can reduce the volume as well, but gives poorer response than a reed long enough not to need the extra weight at the tip.  This may not be an Important issue with a drone.  
overly weak or weighted reeds are more susceptible to blowing flat under pressure, but you should be able to manage fine for a low D drone.  You can be quite a few cents off and still be only a couple hz off, with barely noticeable beating against any melody note more than a perfectly tuned note would create.  You can always tune the drones a few cents sharp at low pressure so they will come on pitch at a bit higher pressure, yet not be too flat at full volume.

Good luck.  I’m glad someone has thought to pay attention to this.  I’ve only seen restrictive measures so far.

Dana

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11 hours ago, Dana Johnson said:

Good luck.  I’m glad someone has thought to pay attention to this.  I’ve only seen restrictive measures so far.

 

Thanks for your response Dana. I have been thinking about the tradeoffs involved in shortening the reed or keeping it the same length. I wonder if the ratio of length to width was too high, the tongue would be prone to developing a twisting/sideways movement and clipping the sides of the frame. I don't want to make it too slow to start because of the break in the drone sound when you reverse the bellows, but I suspect an extra long (bent or convoluted) reed chamber would help with that.

 

There's also the possibility of altering the shape of the set or rounding off the bottom corners of the tongue for a mellower tone (and maybe a slight volume reduction?) at the cost of some loss in efficiency.

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I don't know how to do it, but I know it can be done. When I was playing English seriously Colin Dipper built me a special instrument with two two-note drones. One was D3 - D4 for Scottish tunes and one was G3 - D4 for Northumbrian. The levers had catches so they stayed open without being touched. It worked very well. They were much quieter than ordinary reeds but unfortunately I don't know how that was achieved. I seem to recall them being overall smaller than standard reeds, but that's all. I certainly don't recall any chokes or baffles. I don't recall anything special about the chambers either.

 

LJ

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I would try fitting brass reed tongues. if the tongue fit is good, then response is not too badly affected, or you could try tempering back the existing reed tongues to soften them around the belly of the reed, obviously they will drop in pitch but should be able to be brought back to where you need them.

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2 hours ago, Little John said:

I don't know how to do it, but I know it can be done. When I was playing English seriously Colin Dipper built me a special instrument with two two-note drones. One was D3 - D4 for Scottish tunes and one was G3 - D4 for Northumbrian. The levers had catches so they stayed open without being touched. It worked very well. They were much quieter than ordinary reeds but unfortunately I don't know how that was achieved. I seem to recall them being overall smaller than standard reeds, but that's all. I certainly don't recall any chokes or baffles. I don't recall anything special about the chambers either.

 

Thanks, that's useful to know.

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1 hour ago, d.elliott said:

I would try fitting brass reed tongues. if the tongue fit is good, then response is not too badly affected, or you could try tempering back the existing reed tongues to soften them around the belly of the reed, obviously they will drop in pitch but should be able to be brought back to where you need them.

 

Thanks Dave.

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Perhaps mounting;placing the reeds in the interior of  the reed pan?  

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25 minutes ago, Greg Jowaisas said:

Perhaps mounting;placing the reeds in the interior of  the reed pan?  

 

From experience with the instruments I've built that have inner chambers, that wouldn't give me the effect I'm looking for here. It changes the tone slightly but doesn't noticeably reduce the volume.

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16 hours ago, alex_holden said:

I wonder if the ratio of length to width was too high, the tongue would be prone to developing a twisting/sideways movement and clipping the sides of the frame. I don't want to make it too slow to start because of the break in the drone sound when you reverse the bellows, but I suspect an extra long (bent or convoluted) reed chamber would help with that.

I don’t think making the reed a bit narrower will cause you much trouble unless you start approaching a width that is similar to the thickness.  ( square cross section ) Reeds that are too wide can push up the natural twisting mode into the frequency range of the fundamental and cause problems.  WithIn the normal proportion range that mode is a good bit lower in frequency.  I don’t remember what the proportion was where that could begin to happen.  Haven’t thought about it for 20 years really, but it looked like you only might get close to it in high reeds which are short for pitch, but wider to keep their volume up.  Low reeds are always too long to come anywhere near that ratio.  
    The low D in my old duet was in the range where the chambers were getting longer than the reeds.  By the time you got to the low G it was half again as long as the reed shoe.  It will better support the low fundamental..  those chambers were also deeper.  The layout was similar to Englishes that have the shorter and longer reeds mostly on opposite quadrants of the reed pan.  This meant by mounting one side of the reed pan deeper in the bellows frame than the other, but keeping the tops of the chamber walls level, the low reed chambers could have more depth while the higher ones were allowed to be shallow.  Again, this allowed for a solid fundamental.  
   Rounding the reed edges does make the reed closure less abrupt and reduces harshness, but as long as the final clearance is good, I don’t think it will badly affect efficiency.  More clearance has a similar effect, but does lower the efficiency / response.

   In my early days, I tried making a reed that was mounted over a window in .025” shim steel that was then mounted over a full length window in a reed testing setup.  I was surprised that it was much quieter than when a normal reed /reed shoe was mounted in the same place.  I may try this experiment ( milling out the backside of the window ) on one of my lo D reed shoes and compare the results with the same reed in the same instrument.  I’ll let you know.

Dana

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