Great thread, interresting read! Another approach is to let the reed find it's optimal arch by the acctual airstream/pressure it self ... and not by tools which with untrained hands easily can overdo and overstress the reed, applying to much force at single points along the reed ... causing micro twists and flaws in the curve In short ... start with a curve/arch close to flat ... then (in the same way Arzajac described when he playes the reed directly on the single reedplate) quite forcefully playing the reed' OB/OD until you run out of air ... do the whole plate and repeat a couple of times. This will guide the reed to find the natural/optimal arch ... which acctually, like we all agree upon (?) is closer to flat ... Then, in further work on the reed, like gapping perhaps, it could be a good idea not to obstruct this delicate curve you have obtained, meaning, work only on the reed's first third along it's length
Read more about it: (It's not like it's my finding) http://www.harmonicaspace.com/harmonica-forum/maintenance-repair-customization/reed-arcing
Last Edited by S-harp on Jan 26, 2016 5:02 PM
STME58, could you adjust the size of the last image you linked? It's making it so I have to side scroll to reed (oops, read) everything.
Andrew, I once wrote a letter to the guys who make that liquid metal stuff. I wondered if they could make something reed sized. It seems to me there are at least three things that affect how long a reed swings after you stop applying force- loss to air resistance, loss to resistance in the reed itself (including wave interference with itself?), and loss at the point where the rivet, reed and reed plate meet. I was curious to see what would happen if you had a springier material...
Of course, they have to do all sorts of special temperature controlled cooling with this, so machining reeds out of it probably wouldn't be practical even if they were interested.
-Warning, mostly off topic-
And I stumbled on this and it made me think of this thread. I can't imagine how you could apply this to a reed, although I imagine some of the same principle applies when you are cupping and cutting off the flow of air out of the harp (and maybe it has something to do, in it's own way with choking reeds?)
The liquidmetal looks interesting in that it has no grain structure. A lot of materials science is about the grain structure in metals, how it forms and how it resists or facilitates deformation. I am disappointed the did not include high carbon steel in the bounce test. I would expect a bearing to bounce high off a high carbon steel plat than a titanium or stainless one. High carbon steel would make great harmonica reeds, for the short time before it rusted.
Nate - re springiness - how about trying something really properly springy like spring steel? If springiness were a factor I would have thought that phosphor bronze (I think I've got some of those - Suzuki?) would be far superior to brass.
That video is amazing BTW, almost unbelievable. Is it real do you think? Maybe it would be too springy - the note never shuts up! Could be a whole new style of playing - just think you could arpeggio a chord and have it sit there. I looked at the website - they have a 'liquidmetal knife', it's hard to see what it does but it does boast A barrel hinge implemented utilizing Python programming.
Transients
I'm surprised that no one has mentioned the importance of transients at the beginning of the note. That is an important part of a distinctive sound. Maybe they did, it's such a long thread. The discussion so far seems to be a about the steady state.
Do the customisers make adjustments for the start-up sound?
Sorry to quote from wiki again, but it is a fine definition. My impression is that, particular in the blues-harp style, transients make up a lot of the characteristic sound. Percussive noises (slaps and pulls etc.) being an extreme example.
"In acoustics and audio, a transient is a high amplitude, short-duration sound at the beginning of a waveform that occurs in phenomena such as musical sounds, noises or speech. It can sometimes contain a high degree of non-periodic components and a higher magnitude of high frequencies than the harmonic content of that sound. Transients do not necessarily directly depend on the frequency of the tone they initiate"
"You don't have to explain or model the complexities to understand that this mechanism can create the timbre."
I think the fact that timbre (or any sound) can be measured as a pressure waveform is more of a "WHAT?" rather than a "WHY?" (or "How?") In creating a theoretical model, aren't all of those Ws important?
Yes, but what I'm saying is that what STME58 has proposed is a simple model that makes sense physically and can be tested. Ok it may not be the full explanation - when do we ever get that - but might prove useful.
Some of the other propositions e.g. the reed has natural modes that are non-harmonic, but somehow give rise to harmonics when you play it, or that it's somehow related to where or whether flow is laminar or turbulent, can't really be tested or involve some leaps of imagination, or invoking some not-understood processes. Doesn't mean they are wrong of course.
In science, it's a good principle to look at simple explanations first. That's Occam's Razor. Quite often things do turn out to be the more complex though. That's life. But the principle is to knock out the simple explanations first, specifically because they are more testable.
So if, for instance, you find you can change the timbre by changing the thickness of the reed plate, or how the reed 'shuts the door' by changing the arc, or building up the walls of the slot - then I'd suggest that adds weight to the 'air chopping' theory. Instead if you can do the slo-mo-strobe filming of a reed showing it vibrating with harmonic modes, that would add weight the other idea. Or do some smoke-wind-tunnel-esque film showing the flow turning from linear to turbulent and correlate that with changes in reed arc and timbre, that would suggest that one is important.
Quite a lot of science is about observing, classifying and cataloguing. I think that's the bit that's missing here, in the understandable desire to rush to an explanation.
Last Edited by MindTheGap on Jan 27, 2016 7:24 AM
Folks, unless you have a reason for using your user name as your “handle,” I'd really appreciate being able to call y'all by your first names. So if you haven't already and don't mind please let us know what your first name or preferred nickname is.
Doug, I understand partial differential equations but I too was educated in the last millenium and Chaos Theory wasn't in the curriculum back then. Fluid dynamics is some heavy stuff, bringing those PDEs to bear on a difficult physical problem is a tour de force in Applied Mathematics. People devote their lives to this stuff and still don't have all the answers. I most certainly don't. I'll have to dive into that paper when I have a couple quiet days to myself. Thanks for citing it.
MindTheGap -
I do appreciate your tenacity. You are a little honey badger on your quest for knowledge. Kudos!
I get overwhelmed thinking about all the physics of the entire system including non-compliant reed, reed chamber, cover plates, and compliant and time-variable oral and air cavities, the list is seemingly endless and hopelessly complex. Lots of interacting resonant chambers. I'm going to leave it to someone smarter than me. It's all tantalizing to think about but I'm unsure what bearing it has on this discussion.
I also admit I'm not quite understanding your valve-driven air chopping machine or your purpose in proposing it. It seems too complicated to be practical to prototype let alone manufacture. We already have sirens and our little harmonicas so...
Its very difficult to find a description of what happens in an overblow spelled out in plain English all in one place. I'm happy to go through the exercise of trying to do that because it really forces me to organize my thinking That Bahnson article is a treasure trove of information. Each time I re-read it I find new ways to look at it. Pulling different quotes together,
“Overblows and overdraws have been shown to be effected primarily by only one reed which functions as an opening reed—the normal function is closing—at a pitch outside the interval of the two notes in the hole... The overblow tone actually comes from the draw reed of the hole which abruptly begins to vibrate as an opening reed, with a pitch that is only a semitone higher than the draw reed’s natural frequency. Conversely, an overdraw tone was observed to come from the blow reed of the hole. In addition, stroboscopic analysis of the reeds during overblows showed that the blow reed becomes almost still, in spite of intensified vibration of the draw reed.”
For normal bends, “In order to cause self-sustaining oscillations, air must flow past the reed in a manner which reinforces this vibration... such pressure instabilities could result when air flow is sufficient to cause boundary layer separation at the edge of the reed surface [edit: translated this means turbulent flow]. When this occurs, the aerodynamic drag force on the reed increases as the gap decreases, and the reed moves against the air flow. Conversely, the drag force decreases when the gap increases, and the reed moves with the flow [edit: translated this means laminar flow]. This will thus inject energy into the reed motion, giving it a ‘‘kick.’’ [edit: the reed closes in the direction of the air flow, transferring its energy to the spring; the “kick” is what starts the reed back into the slot, releasing the energy stored in the spring and the cycle repeats.] This phenomenon can also be described in terms of acoustical impedance, as outlined by Johnston. The resulting frequency of oscillation will differ from the plucked frequency because of the coupling with the acoustical inertance and compliance of the air flow and airway of the player [edit: translated this means the player's internal impedance or effective resistance].
And finally, “Stringent control of breath and positioning of the player's vocal tract are required in order to play overblow and overdraw tones.”
[N.B., As I read this I'm recalling the Antaki slides showing air flowing backwards across the reed once it gets inside and the videos showing what is apparently laminar flow outside the chamber and visibly turbulent flow once it gets past the reed to the chamber interior.]
So here's my attempt to put it all together. Lets start with some definitions.
With natural blow and draw tones the “speaking”reeds are the blow and draw reeds, respectively. The other reed of the hole contributes little. With overblows the reverse is true.
When the player blows through a hole, the blow reed is a closing reed, and the draw reed is an opening reed. When the player draws on the hole, these actions are reversed and the draw reed becomes the closing reed.
So for, say, a hole 6 overblow, the blow reed becomes the closing reed and the draw reed the opening reed.
The player adjusts his/her oral cavity similarly to that of a high blow bend and alters his/her breath force (Stringent control of breath...) causing the blow reed's gap to decrease (choke) and air going through it to transition from laminar to turbulent flow (i.e., the Reynolds Number increases as the effective aperture of the reed/reed slot decreases and air velocity increases). As the blow reed closes, the aerodynamic drag over it decreases, the flow through it transitions from laminar to turbulent and the reed moves ~against~ the direction of air flow. At the same time as turbulent flow across the blow reed increases the acoustic impedance to the air flowing across the draw reed decreases abruptly (it “pops”) and it begins to speak. By maintaining turbulent flow the blow reed doesn't want to vibrate (it remains choked) and the draw reed speaks louder and louder, vibrating at a semitone above the pitch of the draw reed.
Whew!
Grey Owl, Isaac Newton is one of biggest heroes! Thanks for that quote. I'll have to remember that one.
Andrew -
First off, after reading the Bahnson article a dozen times, I finally ferreted out the kernel of information that describes how a sustained vibration undergoes alternating periods of both laminar AND turbulent flow: “In order to cause self-sustaining oscillations, air must flow past the reed in a manner which reinforces this vibration... such pressure instabilities could result when air flow is sufficient to cause boundary layer separation at the edge of the reed surface [edit: translated this means turbulent flow]. When this occurs, the aerodynamic drag force on the reed increases as the gap decreases, and the reed moves against the air flow.” So, congratulations! You were somehow able to intuit an esoteric and little known fact about the fluid dynamics of air flowing over a harmonica reed. Amazing. Is there a lottery in Canada? 8^)
I wrote: "Now, these different vibration modes give rise to harmonic overtones in the resulting chopped air stream. Even though the reed wants to vibrate at its natural frequencies, it's still vibrating at non-eigen frequencies. It's those non-eigen frequencies that give rise to the sound signature, if you will, of that reed. As to an experiment, you do it all the time when you plink reeds. No need to excite the reed at its natural frequency. A good plink is the physical equivalent of a mathematical impulse or Dirac delta function which excites all frequencies. You plink a reed an it will vibrate at its natural frequency."
And you asked, Does that explain the following: - “As you emboss the slot, the sound becomes brighter, there is more emphasis on the higher overtones.” ~ I think so. The closer reed/reed slot tolerance and sharper edges along embossed reed slots give rise to those higher frequencies. Increasing the tolerance via a stainless steel strip or an embossing tool, those sharp edges are dulled and the (annoying to my ears) higher overtones back off, right? - “As you improve the reed shape, there is more sustain as you plink.” Yes! However you manage to “improve” reed shape, I posit that you're re-distributing the center of mass in a way that makes for a cleaner, more symmetric vibration, resulting in greater sustain. - “As you change the reed shape, the timbre changes. I
Last Edited by mlefree on Jan 27, 2016 11:18 AM
Out of characters to edit this in my previous post, so...
If anyone spots an error in my thinking with respect to my above statement of the physics of an overblow, I'd appreciate you pointing out so we can change what I said to make a more accurate assessment for the record.
Thanks,
Michelle
---------- SilverWing Leather - Custom leather creations for musicians and other eccentrics.
In the interest of explaining things in plain English- I think I've heard people describing bends as the interaction between the two reeds in the hole, but I think maybe this confuses things. Both reeds have to bend or overblow, but the reed that isn't sounding needs to choke. It's not really interacting harmonically with the other reed, and you can demonstrate that by simply blocking the reed slot/reed altogether, right? In fact, Winslow's discreet chamber relies on that- one reed in a hole can do all sorts of things, it doesn't need the other reed. The trick is that in a hole with two reeds you have to get two reeds to do two separate things at the same time applying the same force.
"However you manage to improve reed shape, I posit that you're re-distributing the center of mass in a way that makes for a cleaner, more symmetric vibration, resulting in greater sustain."
Could you explain a bit more about how that works?
"I have wondered if the goal of the reed all entering the gap at the same time is really what is desired."
Well, personally, I don't think so. I was doing some reed work this morning and noticed the seven draw seemed out of place; just by looking at it's gap, height, etc.- compared to the rest of the reeds, yet it performed just as well as the other reeds. Soooooo, I really doubt the 'gap theory'.
I don't and never ever even bothered to check this 'gap theory' as I see no sane reason to do so. :-) I just sorta lower them and adjust according to how the reed responds rather than measure the shit out of it. That is a going garden path w/ problems you'll have to remedy later, in my opinion.
Reeds of different sizes in different keys, makes, and models perform differently. Even if the same make, model, and key, all harp reeds perform just slightly differently. Sometimes really differently. I remember a batch of MBDs that sounded like party favors on the two draw. :-)
I treat reeds fairly the same but there are always certain reeds that defy technique.
I think on Spiers site he says that he only chooses the best of the best harps to build. Makes sense to me. Especially if you want consistency. You will not find consistency in mass produced products. Okay.. I'm off the soapbox now. Have a good day you intelligent person. :-) ----------
What I actually was saying is I fix the foundational problems first before doing the rest of my thing. If I only worked on harps that came perfect out of the box I'd never get anything done:) ---------- www.spiersharmonicas.com
Last Edited by harpwrench on Jan 27, 2016 5:53 PM
Nate, to answer your question, this figure from the Bahnson article shows the relative interaction between reeds for blow, draw, draw bend, double and triple draw bends and overblow notes.
As the legend says, +++ indicates vigorous action; ++ is moderate action, and + is minimal action. As you can see, in most situations, both reeds are interacting.
MP -
You and I are perfectly in sync. The bottom line is how a reed responds. And, there's no practical reason to go all analytic when setting up any given harp for play in a band or open mic. Set 'em up, test 'em and put 'em in the gig bag.
But there's more to extracting maximum performance from a harmonica than gapping the reeds. This thread concerns everyman. We all can't afford to buy a harp customized by a top-line pro like Joe. And even though he now offers affordable repairs and has kindly offered to tweak a harp for us to let us see his end result, there are those of us who have other reasons for exploring optimum reed shape. I'm an inveterate tinkerer. I've always liked taking things apart to see what makes them tick. So much so that I became an engineer to satisfy this craving and the desire to create new stuff.
Not only do I love to play 'em, unlike my truck or refrigerator, there's comparatively little downside to tinkering with them. Moreover, studying the technology embedded in this little instrument fascinates me. It amazes me how little real scientific research has been published about them. We clearly have, on Dirty South, some pretty schmardt cookies who are likewise passionate about the instrument. When I see original research being conducted with some pretty high-falutin' computing power and imaging technology right here on DS, it makes me wonder if we don't have the capacity to advance our collective understanding and make a lasting contribution to other's understanding as well. That's very appealing to me.
So that's why those of us on the lunatic fringe love to dive as deeply as we can into what we can learn together and teach each other about this amazing little tin sandwich.
Michelle
---------- SilverWing Leather - Custom leather creations for musicians and other eccentrics.
Last Edited by mlefree on Jan 27, 2016 8:24 PM
@ Michelle I read your first post and I'm not going to rifle through all the other in puts on the subject. First No that is not correct the reed does not go through the slot all at once. If you set it up so that it does you won't be able to hit it hard. Kills dynamics. You would have to play with a very light attack. Anyway The best way to approach this is by throwing everything you've learned right out the window and just remember the can't be bend the wrong of course! Then just play one of your harps. Right down what rees play well and which ones don't. Crack it open and look at it with a magnifing glass. Look down the side, look at the end to see if the reed is parallel to the plate. Then hold it up to a light sorce and check to see if it is centered. Do this for reeds that don't play well and reeds that do. It is just important to know why reeds play well as it is why they don't. Teach yourself! If it plays well it's right! If it doesn't it's wrong! Look closely at the reeds that play well and see what is different? Comparative analysis!
One more weird thought- I've seen pictures of some distant relatives on the free reed family tree, and the rectangle reed we all know and love isn't universal. I've seen reeds that are triangular, pointing towards the tip, and reeds that are triangular with the fat end at the tip. Fanning out, I'd think, would give you more air on the movable tip part of the reed, but the tapering triangle might give your reed more stability against squeal, since the base would be wider and less prone to flapping side to side. Maybe. And of course, they'd be a nightmare to manufacture, and there might be much simpler to address with mensur, but I thought I'd throw it out there as a variable that might work on other free reeds.
Chromaticblues, I do appreciate you chiming in to share your considered, experience-based approach. I agree that close observation and comparative analysis are key to improving one's technical harmonica customization skills. It's a good recipe for improving one's self in most any area in life. It's also at the core of the Scientific Method.
But we've covered a lot of territory in this amazing thread in the hopes of using science to shorten the learning curve and to potentially plow new ground in the process. One must admit, whether this way of thinking ever bears fruit or not, it is a tantalizing concept. Exploring it with other like-thinkers as well as nay sayers has taught me a lot and helped me to understand how the little 10-hole diatonic harmonica works. I hope a few others have learned a few things as well.
Nate, your ideas about non-rectangular reeds are exactly the kind of thing Finite Element Analysis is so useful to explore.
But it wouldn't be too difficult to make an experimental apparatus to try them out if you are handy with a needle file. You already have reed plates that you could create such reed slots and brass feeler gauge from which to make reeds. Heck, Smokey Joe has made reeds out of spent pistol shell casings. Also, if you don't already know, you might check out how accordions are put together. Individual reeds reside in interchangeable single-reed chambers that are ganged together and fixed in place in "reed banks" with bee's wax. You could make or procure an individual reed chamber/reed setup as a starting point.
Give 'er a try. 8^)
Michelle
---------- SilverWing Leather - Custom leather creations for musicians and other eccentrics.
Last Edited by mlefree on Jan 29, 2016 3:51 AM
I've enjoyed this thread, thank you for starting it. There are umpteen threads dedicated to the art of the harmonica, and very few dedicated to the science of it.
If anything thinks this is OTT, have a look at the level of study that's gone into other instruments e.g. the violin. You'll find plenty of eigenvalue talk too! :)
It looks to me there's very little investigation been done - a few papers without much follow-up or corroboration.
Good scientific discussion involves a degree of challenge that can get heated - that's how it goes. If everyone cosily agrees with each other just coz they say something, it doesn't mean much. Newton was pretty argumentative I understand (massive understatement).
I don't understand much of what's in the papers I've seen - I'm not up on boundary layer separation. Well, I know what it is roughly, but I couldn't possibly state that it's definitely the mechanism to make a reed vibrate. Seems like a good enough candidate - vortex shedding can cause vibrations: "I hear you singing in the wire, I can hear you through the whine...". But if I saw a series of papers, peered reviewed and referring to each other, all saying the same thing, that'd be different.
Last Edited by MindTheGap on Jan 29, 2016 4:15 AM
MindTheGap, you've been a key participant. Your lust for learning and probing mind have made me better explore and articulate the esoterica of the physics of harmonica reed performance and interaction. I genuinely appreciate all of it.
It's been a captivating and fun ride for me and my interest and curiosity have only increased. I'm saving up for a Spiers harp. 8^)
Many Thanks,
Michelle
---------- SilverWing Leather - Custom leather creations for musicians and other eccentrics.
Last Edited by mlefree on Jan 29, 2016 4:30 AM
I agree with chromaticblues that "the proof of the pudding is in the tasting", but disagree about the reed having a state where it enters the slot all at once. I bet that's a good attitude for the reed to have--granted that is not its resting state. Again I think of Joe (the Jesus of harmonica setup, as in WWJSD?), I will have to take a look at my one Stage One . . .
My thinking and techniques have both evolved a lot, especially over the past few months. So when checking things out keep in mind you're only looking at what I was doing at the time a harp was done. Anything from prior to this year wasn't (intentionally) done exactly to recent specs. Anything done during 2015 will reflect a long process of mastering my current thinking and techniques, and the last couple weeks have pretty much put the finishing touches on that. The only reason I'm confident enough to say that is because it's becoming more common that there'll be very little to no "tweaking from there" required after I do my thing. ---------- www.spiersharmonicas.com Harp repair and upgrade menu
@Gnarly No I either miss-typed or was thinking one thing and typed another? I'll check my post after this. I was disagreeing with Michelle's original post that she said she learned that the reed has to enter the slot all at once. To my knowledge that is not the case at all! The very tip of the reed has to be the last part going through. Michelle didn't seem to care for my idea of teaching herself, but because we all play differently how much slope is needed in the reed will different from one person to the next. Now everyone has to realize the amount of slope in a reed can't be very much. So actually make them almost straight with the slightest curve. Then I play it! When it plays real well I take one last look and make a mental note of the end product. Edit after reading my earlier post Gary I'm not sure what you don't agree with? I guess we agree to disagree?
Last Edited by chromaticblues on Jan 29, 2016 9:34 AM
I don't think I made my point very well. Our thinking isn't as far apart as you believe.
Interestingly, this thread that could be called, "To arc or not to arc," has itself undergone an arc. I started with the idea that "flat is where it's at" is/was the condition for optimum harmonica performance. I didn't invent the concept, it was put forth by two of the top customizers in existence: Richard Sleigh's "Hotrod Your Harmonica, The Movie" videos and Joe Spiers' communication in a thread, probably on this forum. So you would have an uphill battle with me arguing against the effectiveness of setting reed curvature as they have suggested. But as I have discovered, flat is an "initial condition" and that further refinement from there that creates an upwards arc in the reed improves performance even more. This is what the 170-some posts since my initial one have been about.
And just to clarify, it was in my own feedback process of observing and applying changes that appear to work that I tried something new using Richard's methods. I put a slight dogleg at the root -- a negative "zero point" -- and made the reed as straight from there as possible. Then, per Richard's instructions, I set a relatively narrow gap to accommodate my soft playing style. Bingo! Grosse différence.
This is a point where I too disagree with your assertion that "If you set it up so that it does you won't be able to hit it hard. Kills dynamics. You would have to play with a very light attack." I believe that it's a low gap that would cause the conditions you describe. As far as I know, it's generally accepted wisdom that the gap is what determines determines how hard an attack can be applied before choking a reed. Since that doesn't match your experience I'd like to know more of the details.
Anyway, back to my quest for shaping reeds. Where you and I diverge is that I feel most comfortable with an orderly, directed approach that applies what science we know about this deceptively simply little instrument. Shortens the learning curve. For example, I've seen apparently differently shaped reeds that differ little in their performance. What to do then?
This where computer technology has the capacity to help us create mathematical models of harmonica reeds and allow us to experiment with ideas or hypotheses about different shapes without actually touching any brass. Once "virtual" testing seems to point at a particular reed design, actual physical testing with real reeds can proceed.
We can use the the "scientific method" to direct our quest for the perfect reed shape.
To paraphrase Wikipedia:
"The scientific method is an ongoing process which begins with hypotheses developed from observations about the natural world. The SM tests these hypotheses via carefully controlled and replicated experiments that gather empirical data. Depending on how well the tests match the predictions, the original hypothesis may require refinement, alteration, expansion or even rejection. If a particular hypothesis becomes very well supported a general theory may be developed."
That sounds like another way of describing what you do when you "teach yourself" does it not?
It seems to me to be difficult to argue against applying some science to our quest if it can be brought to bear on the difficult question of the optimal reed shape. It's just possible that we may not need to accumulate the real-world experience of Joe Spiers, who's tweaked 150,000 reeds. Few, if any of us will ever achieve that level of real-word experience. I can't speak for Joe but I presume that he used a process not unlike the one you outline to refine his ideas of reed shape over time. And as he has stated he has continued to change right up to recent time. I wager that his process of continual improvement (see W. Edwards Deming) will not end any time soon, either.
The beauty of computer modeling is that you don't end up with a pile of failed brass reeds, a sore neck and calluses on your fingers. Once you've created a mathematical model you can just sit back and let the computer do the work.
That's the way I see it. But, as you say, we may just have to agree to disagree.
In any case, your insights are very much appreciated!
Thanks,
Michelle
---------- SilverWing Leather - Custom leather creations for musicians and other eccentrics.
Last Edited by mlefree on Jan 31, 2016 9:58 AM
@Michelle I'm not saying the most scientific way of doing something isn't best. I absolutely agree whole heartedly! OK lets get back to messing with harps. To do what you are talking about you would need to have a wind tunnel. Then you have to run it at a similar velocity as a person playing the harp. I'm sure this possible, but I think it cost so much to do something like this it is reasonable. This is my reason for saying it more "practical" trying to teach yourself. You can't completely rely on what you rad online! I agree all your research is right direction. I've been through this also. That is the only reason why I'm going back and forth with you! Yes of course the amount of gap affects the attack. That should be not in the conversation! There is more to it than gap! The shape of the reed, The way you emboss! Not all harps need to be embossed, but when you do. How do you do it? People emboss different ways and I think that would affect how the reed is set up. Michelle I'm not arguing with you! I'm trying to give you food for thought! I try to teach people how to think for themselves and when I can give them the information to do so successfully! If you have a specific question Email me. I would be glad to help if I can! If I have posted anything that made you think that wasn't trying to help or that I can't! Please Email me.
@ S-Harp: Thanks for the link to Dick Sjoeberg's detailed description of how he uses forceful breath control to arc the reeds. Here it is again for anyone who missed it, well worth a look:
Joel Andersson, a very talented young Swedish customiser and player, uses the Sjoeberg method of reed arcing, and his harps are fantastic. (Incidentally Joel will be offering his customising services once he has his new workshop set up later this year).
Speaking of fantastic harps: Joe, you said your 'thinking and techniques have evolved a lot, especially over the past few months.' That sounds interesting, and surprising, because you have been known for many years as already making fabulous harmonicas. How can you evolve from perfection?
Last Edited by Brendan Power on Feb 02, 2016 12:42 AM
Brendan (and S-Harp), I read that Sjoeberg thread but quite honestly found it fascination but difficult to imagine how it could work. Intrigued, I tried it on a few reeds of different lengths, using several long hard breaths on each to give it a good shot. I blew until I was literally blue in the face but I could not detect any visible change in the shape of the reeds or their performance on regular draw breaths (non-overblow). I'm not an overblower so I've no opinion on how the long, forceful breaths might affect those when the harp is assembled. I don't know what I may have done wrong but in the end, I didn't know then and I still don't know what to make of this.
I'm not saying that it is nonsense, just that I wasn't able to make it work nor do I understand the physics of the mechanism that makes if happen. Dick talks about the moment of a reed being greater with longer reeds. That is true enough but by itself doesn't say anything about the dynamics of the physical forces that would make the reed bend itself.
In addition many of those longer reeds are double-thickness at their tips and therefore of variable stiffness along their length. They are so stiff in that doubled-over section that when I find a reed with convex curvature underneath I have to literally hammer on it with an anvil under it to change its arc. I just wonder how blowing hard works on a practical basis. Maybe you have insights that might shed more light on how this works?
I don't recall having seen you advocate or mention self-shaping of reeds to achieve optimal arc in the past. Since you call our attention to it now, may we assume that you are able to make it work and possibly even advocate the method? If so can you tell us more about it since Dick Sjoeberg isn't here himself?
Thanks,
Michelle
---------- SilverWing Leather - Custom leather creations for musicians and other eccentrics.
Last Edited by mlefree on Feb 02, 2016 1:50 AM
When I read the idea of forming the read with breath pressure I was skeptical. I reviewed some work I had done using the beam equations and measurements of a reed and saw that yield will occur somewhere around 1 psi (51mm hg) on the reed. Trumpet players can get over 150mm hg so bending a reed with breath force is definitely feasible from a beam theory point of view. The pressure will drop off as the reed opens so I don't know at what point the pressure will be too low to yield the material in the reed. This does seem to be feedback in the correct direction, a closely gapped reed will be bent but the bending forces drop off as the reed opens.
Last Edited by STME58 on Feb 02, 2016 8:10 AM
Interesting, Steve. I'm trying to understand the mechanics of what's happening here.
You seem to be saying that:
- At 51mm hg of breath pressure, a brass beam the dimensions of a reed reaches the yield (bending) point. - Further, the forces impacting the beam are in the correct direction to be bent upwards. - This is because the force is coming from underneath the reed because it is being overblown. - That even though the forces are maximum at the time the reed is closing the slot (when it is presumably straightest), there forces when the reed is at its widest swing (and at its maximum curvature) are sufficient to bend the metal. - The beam equations indicate that the point of maximum permanent bend is toward the tip in the location it should be.
I assume your model considers the opposing forces when the reed swings back through the slot. I imagine that the swing in the opposite direction of breath isn't as wide as that with the breath force. That would account for the closing reed's forces exceeding those of the opening reed in the aggregate and the final arc being on the correct side.
Whether I understand the mechanics or not, why not use your FEA software to model this? If you can reverse the direction and magnitude of air force and let the software calculate the resting shape after applying that 150mm hg for the duration of a deep breath or two, we'll be done here.
Thanks,
Michelle
PS: Can you model low-toned reeds with a double thickness at their ends?
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Last Edited by mlefree on Feb 02, 2016 10:58 AM
It is hard to accept that like anything else, tweaking a harp is not an exact science and there is not point of perfection and nirvana.
You can strive for consistency, but there is always something that could be improved...and just when you think you've got it, the design of the harp or alloy is changed, ha!
At some point, you can reach diminishing returns, and IMHO, the best thing to do is practice, practice, practice. There is no substitute for experience and all the proprietary knowledge is for not if you can't apply it.
I've had sticking points where I felt I could improve and struggle with outside of the box thinking...for example, for years I tried to find an efficient way to flatten blow plates without removing all the reeds first.
Another area was centering reeds without removing them...then there was the merits of embossing vs reshaping the slot and whether the reed fillet or tip should be the focus, etc....
I am always fishing for information and ask more questions than I give answers, I guess.
IMHO, he more you can examine and repeat the characteristics of a harp that plays great, the better. You have to have benchmarks to measure against.
Finally, unless you are building for others, there comes a point where you stop giving a shit. As technique, voice, and confidence increase, you find you can do more with less. I've gotten so bad, that I've been buying Session Steels and doing next to no work on them. I play really fast with a lot of bends, and would rather spend time practicing than building. ---------- Mike My Website My Harmonica Effects Blog
I read the thread and he says it's correct because the breath force acts equally along the reed length, and of course the moment = force x distance. So there you are. And somehow that makes the reed arc in the way that is 'normal' for the metal and results in minimum stress. Eh?
Ok fine, in that case all you have to do to get the perfect arc is press the reed with the same force all along it's length, say bit by bit with a toothpick, each time making sure it's past it's elastic limit so it takes a set.
Are there really no other physicists on this site? Most music sites are crawling with them, going on about fipples and turbulence :)
Last Edited by MindTheGap on Feb 02, 2016 11:35 AM
Michelle, you give the beam equations too much credit. They are powerful and accurate but they only consider static loads. What I have analyzed it the shape the beam (reed) would take under a constant and evenly distributed load and what the max stress would be. The max stress occurs at the root of the cantilever beam and this is where the beam will bend if the pressure is high enough to cause the stress to exceed yield. AN FEA analysis of static load would give the same result as the beam equations.
The FEA results I presented were a modal analysis, not a load analysis. They show they shapes and frequencies the beam will ring at if excited. No loads are modeled in a modal analysis.
All I have really shown with the beam equations and the research into breath pressure is that bending a beam the size of a harmonica reed with breath force is quite feasible.
FEA typically works in the linear area of the stress strain relationship of materials. Once you yield a material this relationship is no longer linear. Predicting the shape an object will yield to is much harder than predicting that it will yield. It can be done with FEA. I don't know if the package I use can do this or not.
Adding a thick area on the end of the reed I have modeled and seeing what the new mode shapes and frequencies are would not take much time. I will try that and report the results.
In a perfect world, I wonder if the mensur would be zero?. The whole reed pad to the fillet would be level with the reed pad and not on top of it. You could do this now in a variety of ways, but it is impractical.
There are some ways of compensating this that are really neat, but again, time consuming unless you are riveting reeds on your own.
I have always wanted my own blank reed plates with the ability to rivet my own reeds.
The Mensur if very important to the playability of the harp, and in my not-so-expert opinion a big reason why many Seydels squeal on overbends and Manjis seem stiff and breathy. ---------- Mike My Website My Harmonica Effects Blog
Last Edited by HarpNinja on Feb 02, 2016 1:04 PM
@harpwrench- sorry to mis- paraphrase you. Maybe I was reading another customizers web site.
Anyway.....it is physically impossible for a reed to be shaped so that it sits completly flat in it's slot yet still perform w/out choking intermittently and playing very softly. It'll overblow just fine if it's the blow reed and the draw is pretty tight too. ...:-) At worst it won't play at all. A well set up reed needs to be lowered at the rear by the seated pad and then the reed makes a very gentle incline that graduates almost imperceptibly till the tip end where there needs to be a slight gap. My reeds tend to ride a bit higher than other folks but sound and perform in a similar manner. The closest I've seen to reeds sitting amost completely flat and very low in the slots are Filisko's, Sleighs, Spiers, and a Michaleck where the harps actually sound and play great.
On my harps the shorter higher pitched reeds; 4 through ten have almost zero gap. Depending on key, the #4 may or may not have much of a gap.
I have to use very sharp edged plinking tools to plink them. Forget using most tools. I've even sharped a brass Sleigh, a Lee Oskar, and a Hetrick tool just so I could plink the damn reeds w/out having to lift them. I've found the Seydel tool no fun to use. Too many design flaws...well, maybe not flaws but I don't like the tool or even like to size slots w/ it. For sizing I swing my reeds to a very radical angle and use a socket and a small gas station slotted screwdriver for the tip end. I smooth the end w/ an exacto knife then further smoothing w/ the screwdriver again. People who say this makes the rivet loose are just heavy handed. You swing it out once, and swing it back once. You can use a tool to size the rivet end but my method eliminates this step. Besides; if you're scared of loose rivets you just get a nail set and a 2oz hammer w/ a mini anvil to set your mind at rest. You can use clear nail polish as LockTight too. I use it on screw posts as insurance so the nut does't get loose. ----------
PS harpwrench. All that was wrong w. your harp was lint seizing the reed. I have no idea why your work wound up w/ me. You may have been too busy at the time and told your customer it would be a while.....or not. :-)
Have good day. M.A.P. .
Last Edited by MP on Feb 02, 2016 3:58 PM
Michelle, I don't use the breath method myself but Joel demonstrated it for me. It's not hard breath per se, but forcing them to overblow on their own on the bare plate without an opposing reed, as normally.
I'll ask Joel if he could explain it more; not sure if he's on MBH.
My approach is to eschew arcing altogether, instead bringing Mohammed to the Mountain by building up the reedplate on either side of the reed to close the gap - either by micro-chiselling or adding material. It achieves the 'uniform reed closing' objective in a different way and works for me (though how it would be for overblows I have no idea, as I eschew them as well).
But if I were an arcist the elegance, speed and low-impact quality of Dick Sjoeberg's organic approach appeals. Having seen/heard Joel do it and tried his excellent harps, I can attest it works in practice too.
Last Edited by Brendan Power on Feb 02, 2016 5:51 PM
On a theoretical level, there isn't a one-size-fits-all arc as far as I approach things. For example, one shape can suit a certain breath force level but the arc would need to be adjusted if you change the gap and want to keep the same qualities for which you have adjusted the arc (but at a higher breath force). I'm not certain how a self-shaping reed would adjust itself automagically to hit every criteria required every single time.
On a practical level, I blow and overblow each and every single reed I adjust as I work on them as a way to get sensory feedback and fine-tune the reed shape. I've worked on thousands of reeds this way. Playing the reed off the comb in either direction doesn't change the shape of the reed in any significant way. In fact, plinking can cause a bigger change in shape if you do it hard enough.
Perhaps there is more to it than what has been described?
I've tried it a couple three times over the years since it was presented. I have seen it set a correct shape a couple times on thinner shorter reeds but haven't had success on longer reeds. Doing it hurts my ears anyway:) ---------- www.spiersharmonicas.com Harp repair and upgrade menu
MP wrote: A well set up reed needs to be lowered at the rear by the seated pad and then the reed makes a very gentle incline that graduates almost imperceptibly till the tip end where there needs to be a slight gap.
That sounds exactly right to me.
Ooops, edit: The Suzuki reeds need less lowering at the pad, IMHO.
Last Edited by Gnarly on Feb 03, 2016 8:30 AM
Two reed setting strategies I know of for shaping reeds without direct pressure are smacking the plates and overblowing all the reeds off the comb.
While I didn't have a lot of issues with it, I stopped smacking later in the process for fear of warping the reed plate.
The overblowing I still do, but mostly as a check. The amount of pressure needed for the return maybe makes it not worth it. You really have to hit the reed hard with a long breath.
IMO, they work best for settling reeds that have been adjusted - similar to plinking.
Both, at some level are intended to release tension in the metal. There are other mods that do this too. While some of it can be tested and replicated, I'll be the first to admit I don't know the science behind it. ---------- Mike My Website My Harmonica Effects Blog
I kinda wanted to see where these last ideas about the Sjoeberg overblow method of reshaping reeds would go before I laid this great thread to rest.
Mike, I fully agree that we are now in territory governed by the harmonica tweaker's equivalent of the software developer's “ninety-nine” rule:
“The first 90 percent of the code accounts for the first 90 percent of the development time. The remaining 10 percent of the code accounts for the other 90 percent of the development time.” — Tom Cargill, Bell Labs
I have but an infinitesimal amount of experience at modifying harmonicas for better performance that you, Brendan, Joe and other acknowledged experts who've contributed to this thread have. But when I first embarked on my own reed-tweaking journey almost a decade and a half ago I quickly found out what simple things like gapping can do to help remove my instruments as obstacles to my learning to play. Since then it's been a hare and hound chase for me to find out how far I can personally go to extract the most performance out of a harmonica that I can. My learning has been one of drudgery, mostly trial and error punctuated by an occasional spurt of discovery, new information or a new resource added to my library.
So the question is where does one stop on such a Quixotic search? That's a question that has highly personalized answers. Honestly, it's a bit puzzling and sometimes troubling to me that I seem to have gotten to the point where I enjoy studying and working on harmonicas almost as much as I enjoy playing them. And as an engineer and scientist I am always attracted to the hunt as much as the quarry. 8^)
In terms of zero mensur, I think that's what Brendan is shooting for with his idea of building up the reed plate. Brendan?
Steve, I am not hip to current FEA technology or the capabilities of your software package. And, I'll defer to your expertise. But I am pretty sure that I've seen FEA has the capacity to model structural stress and strain forces even to the point of finding potential overload regions that might result in yield. I might easily be mistaken, though.
MP, wouldn't you have to swing the reed back to the other side to get at the root end of the slot on the opposite side? I personally take care to minimize the occasions when I have to take hammer to a reed plate. I guess I am not so fearless as you.
Brendan, thanks for getting back. I'm sure that we'd all like very much to hear what Joel could add. I wonder if your or Mike could entice Dick to joining MBH if only to help us understand his method?
Gents, this has been one of the best threads I have ever had the pleasure to participate in. And it was all y'all's participation that made it so vibrant and captivating.
Heartfelt thanks to all!
Michelle
---------- SilverWing Leather - Custom leather creations for musicians and other eccentrics.
Last Edited by mlefree on Feb 06, 2016 1:25 PM
Michelle, You are correct that FEA is commonly used to predict the high stress areas of a part under load. I use it for this all the time to determine where to put stiffening ribs on a molded part (or in some cases where to make the part thinner so it flexes rather than breaks). When only static loads are considered this works quite well. Finding how far a diving board will deflect with a 100 pound load on the tip or finding out the max load the board can take without breaking and where it will break when overloaded are all quite straightforward. Predicting the modal frequencies and mode shapes is also pretty easy to do. If you look at the colors in the reed mode shapes I posted, the red represents the highest stress. The red area in the first vibration mode is where reeds tend to break. Here is a photo of the broken reed I measured to make the CAD model along with the first mode analysis. There is very good correlation. The frequency predicted was also withing about 5% of the reed's frequency. Where things get complex and go beyond my current level of expertise is considering dynamic loads along with the modal frequencies. For example, if you drop that load on the end of the diving board from some height rather than just setting it there. I am sure this can be done, but it is not something I have experience with.
Last Edited by STME58 on Feb 07, 2016 3:30 PM
Here is a photo of the broken reed I measured to make the CAD model along with the first mode analysis. There is very good correlation. The frequency predicted was also withing about 5% of the reed's frequency. Where things get complex and go beyond my current level of expertise is considering dynamic loads along with the modal frequencies. For example, if you drop that load on the end of the diving board from some height rather than just setting it there. I am sure this can be done, but it is not something I have experience with.
Last Edited by 