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Secrets of the Harp

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Viewing 13 posts - 16 through 28 (of 28 total)
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  • #195216
    wil-weten
    Participant

    Great secrets! I would love to hear more of them.

    #195217
    Biagio
    Participant

    Gold is one of the few metals that does not tarnish and yet is easy to elector-plate.  That is why for example, Truitt levers are gold plated – very effective if one has metal contacts.  I am interested to know what Saul has available in the way of quantifiable analysis wrt to the crown (and it’s carvings); I’ve never given much consideration to the acoustic qualities +/- other than the knowledge that the heavier the neck and pillar the better, acoustically.  So his comment is a revelation, if he would share his sources.

    Here’s another weight related “secret”: there is a trade off to be considered when designing a lever harp.  In an ideal world strings will double in length as the frequencies are halved i.e. if the A 440 string is  a fairly typical 36 cm in vibrating length and 0.80mm the next A down (220 Hz) would be ideally 72 cm and so on; some of the highest treble will be too short to play.  This obviously gets ridiculous if the harp is to be of any size and still manageable; so harp makers will use heavier strings lower down than they will in the treble and upper mid. But that sets up another “issue”:  if the neck and pillar are too light they will absorb some of the string vibrations rather than releasing those as sound.  Pedal harps are already quite heavy so the point for them is somewhat moot.  Next problem – how about that sound board?  It will have to be tapered top to bottom and side to side – but how much?

    For a seemingly simple instrument it can get pretty interesting!

    Biagio

    #195218
    Tacye
    Participant

    Several of them are not what I would expect from my understanding of physics – has anyone done a controlled trial or blind testing?

    When I visited the L&H factory and asked if they expected the gilt ones to sound any better I was told no, which is a surprising answer from the people selling the things if they do sound different.

    #195219
    Biagio
    Participant

    Tacye I was also surprised by some of them. I had always assumed that the gilt and carvings were solely decorative. Certainly, it is difficult for me to get my head around the idea that a metallic paint would have any acoustic value – and you cannot electro-plate wood so I assumed the crown carvings and pillar were painted.  Indeed, I would have thought that if carving had any value it would be negative compared to a smooth surface.

    Live and learn though…..

    Biagio

    #195220
    wil-weten
    Participant

    I love this thread! Biagio, I just read your: ‘<span style=”font-family: ‘Open Sans’, Arial, sans-serif; font-size: 14px; line-height: 25.998px;”> </span><span style=”font-family: ‘Open Sans’, Arial, sans-serif; font-size: 14px; line-height: 25.998px;”>if the neck and pillar are too light they will absorb some of the string vibrations rather than releasing those as sound.'</span>

    Now, I wonder, can the neck and pillar be too heavy (and how could one know, acoustically?). And would there perhaps be an ideal weight for the neck and pillar. And if so, would this be in relationship to the length and/or tension of the strings or…?  (Yes, indeed, I know little or nothing of harp building, but I am very curious in what things I may want to consider when dreaming of/ considering buying a new harp).

    #195221
    Biagio
    Participant

    Wil, some things in luthery are science and others more trial and error or if you like “art”. I’d have to say that one can apply engineering load bearing principles to how strong the neck and pillar must be but given the variability of wood even for one and the same tree that remains something of a guess.  I suppose one could also experiment by subjectively comparing the tone with and without a heavy weight clamped to a deliberately light neck – indeed a friend in Italy is dong this at the moment.  If the harp is any size at all the neck and pillar will be strengthened: hidden splines, a strip of metal underneath the neck, and a fore pillar, thicker or heavier wood and etc. Dusty Strings for example will not use walnut on their double 26 because they believe it is not strong enough.

    I think the most useful thing that makers could do would be to fully disclose the string design and relevant parameters: tension, percent of tensile strength, tension-to-length ratio for the entire band.  But they don’t so one must guess or just try one out.

    One may assume that the established professionals have done all of this experimenting on prototypes before releasing the design. Recognize that if you want a light weight the tension will also be light, longer strings will provide more sustain and resonance all else being equal, a wider board more volume than a narrower one, and so on.

    Someone really should write a book on this stuff but I don’t know of any written for the player!  Since I don’t know of any comprehensive one the next best thing to suggest is to study what successful harp makers have done – why a Dusty FH36 in bubinga will sound different from one in walnut (heavier wood in that case) and how both will sound different from a Troubadour or Salvi Egan  (maple pin block for the neck, longer higher tension gut strings).

    Or read the Harpmaker group archives….another readily available source would be The Science of Harp Making, a CD of relevant extracts from the early Folk Harp Journal issues (available from Music Makers). You would need to wade through a lot of esoteria however.  More readable but less comprehensive would be to read Rick Kemper’s discussion (Sligo harps).

    Biagio

     

    #195225
    Tacye
    Participant

    Some harps are painted, sometimes ‘bronzed’ rather than gold, but the gold standard (sorry) is water gilding, or a mixture of water and oil gilding.  I estimate around 3g of gold in total, though it will have gesso etc underneath. Picture frame technology.

    The usual rule of thumb is that sound waves are reflected by things which are the same size as the wavelength of the sound, or larger.  So I wouldn’t expect soundwaves below about 2000 hz (17cm wavelength) to be affected much by passing the column, carved or uncarved.

    I am ready to revise my expectations to a nice controlled experiment, which would be simple enough to plan, but the logistics of carrying it out would require rather a lot of harps.

    #195266
    balfour-knight
    Participant

    Fascinating reading, friends!  Thanks for all these posts, and I have enjoyed catching up with this thread.  Of course, Biagio, you know my favorite wood for sound and appearance is cherry, no other is quite the same!  I have enjoyed working with this beautiful wood again, making a matching stool for my Dusty FH36S.  I am just waiting now for a good dry time to apply the satin lacquer finish to it, but I am already enjoying sitting on it to play this gorgeous harp.  And, “Cherie” seems to appreciate all the work I have done on the stool–she whispers that to me as I play–another “secret” of the harp, ha, ha!

    Have a great day folks,

    Balfour

    #195402

    I’m confused by your analysis, Tacye. Are you talking about soundwaves bouncing off of the gold or passing through it as they emerge from the column? But the soundwaves that vibrate in the column also return into the body and then emanate, so it is fairly complex, if you intend to somehow measure this. The ear is the best measure. But it would not surprise me if the gold is only affecting the higher frequencies, as it is the treble which noticably gains brilliance.

    I believe you have to pay a lot extra to get naturally aged wood in your harp, at least aged more than two years. Yet, while harps may be made with younger wood, and take longer to age to a mature sound, new harps also have a fuller sound to begin with, which compensates for the youngness of the wood or how it is dried.

    #195405
    Biagio
    Participant

    Saul brings up another interesting (and fairly important) “secret”: viz. how wood is aged and for how long.  The best harps are made from wood that has been air dried to about 12-15% moisture content and then very slowly kiln dried to 8%. Indeed, “kiln dried” in this case  is a misnomer as it is typically done in a box with a 200W light bulb!

    Wood that has been industrially kiln dried – which is what you will find in big box stores- is entirely unsuitable: the wood is stacked in a kiln at over 50 degrees C for only a week or so to reach 15% MC- there is little “life” left in it after that.

    Of course the long careful air drying takes much longer – a year or more per 2cm of thickness. Another reason why high quality harps cost what they do.

     

    Biagio

    #195541
    renaissancemanohio
    Participant

    This discussion is intriguing. I know there are acoustical analyses of various instruments in the literature. Can anyone recommend a good resource that describes the physics of the harp that is beyond the basics?

    #195545
    Biagio
    Participant

    John, there are a number of papers on this though I don’t know of any that are complete – in the sense that they cover everything.  That would be a life’s work and still not be entirely comprehensive (nor without controversy LOL).  So one must dig through various sources.

    Chris Waltham has submitted several papers to the ASA/CAA physics conference; only one of them is available online without a subscription and here it is:

    http://acoustics.org/pressroom/httpdocs/149th/waltham.html

    In another of his papers (which I seem to have lost) he discusses the string access holes and their effect on certain frequency ranges.  A little searching would no doubt turn it up and I’ll see if I can find it.

    Turning from the pedal to the “folk” instruments Rick Kemper (Sligo harps) has a detailed analysis of how he makes his harps and other data that are very useful:

    http://www.sligoharps.com

    Most of the available discussions focus on the strings since that is one of the two most critical elements to design (the other being the sound board).  An outstanding discussion by Michael Billinge appears on the wire strung harp website:

    http://www.wirestrungharp.com/materiality.html

    On the subject of the board, discussion (mostly polite) have raged for years over the best wood to use for folk harps with increasingly frequent heretics advocating for aircraft grade laminate over the traditional spruce, while others suggest composite boards: Dusty Strings for example uses spruce and mahogany, Rees poplar, Heartland Harps (before they went to carbon fiber) used basswood.

    It is perhaps interesting to note that at least one concert grade harp (the Oranmore by Phil Boulding) uses a/c laminate, and so do a few others.  I doubt that the discussion will ever be entirely settled. I will not delve further except to say that a harp maker first determines his or her string band and then selects the board to match the desired tone and other characteristics.  Side note: a/c laminate has the virtue of being less sensitive to temperature and humidity for instance, so that is a good choice for playing outdoors.  Sitka spruce is the generally preferred choice for a concert pedal harp.  And so it goes…..

    While Michael’s discussion deals (obviously) with metal strungs the principles are applicable to any instrument. If you really want to dig deeply you can order a CD from Music Makers – The Science of Harp Making – which consists of articles that have appeared in The Folk Harp Journal:

    https://www.harpkit.com/mm5/merchant.mvc?Session_ID=99d46ffbb8c6ffd97239bdf5ad8634a1&Screen=SRCH

    Again, many of the principles are applicable to all harps.

    Hope that helps,

    Biagio

     

    #195547
    Tacye
    Participant

    For science with equations try the chapter by Chris Waltham in Rossing’s Science of String Instruments.  There are some things I think are relevant which need to be pulled in from other instruments still.  I have been writing a version with more demonstrations to try out on harps but it is very far from finished.

    Sorry I was confusing, Saul – when I talked about reflection I was thinking of the sound distribution from a harp and whether it needs to face the audience.

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