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harpo

optimizing after length sympathetic string harmonics.

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I wish to have conversation to learn of sympathetic string harmonics properties. To apply to instrument project.. I wish to build Sitar type instrument. I am curious if possible to utilize, optimize  the string length from main bridge to tailpiece as sympathetic tonal enhancements. I realize this forum perhaps inappropriate for such topic. Thank you.

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You'd have to make the afterlengths really quite long and almost any resonance you get out of that will be undesirable.

The stiffness of the afterlength has a much greater effect on sound (longer afterlength gives less resistance to the bridge and thus a more punchy sound—shorter ones the opposite).

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1 hour ago, Deo Lawson said:

You'd have to make the afterlengths really quite long and almost any resonance you get out of that will be undesirable.

The stiffness of the afterlength has a much greater effect on sound (longer afterlength gives less resistance to the bridge and thus a more punchy sound—shorter ones the opposite).

Very interesting point. Shorter means stiffer and stiffer means more “punchy?”

I’m not sure what you mean by “punchy” it’s very hard to describe sound. Can you be a bit more specific?

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Thank you! Since I have garnered an audience with my query I shall add a bit of insight to help. As I mentioned the instrument in mind will be of a Sitar fashioned design. An unconventional acoustic guitar shape melding in the attributes of Sitar characteristics. A six string, 25.5" scale length, utilizing a bridge of design to acquire the Sitar sound. A traditional Sitar has an array of separate sympathetic strings. I wish not have the separate strings. So I was exploring if the after length of the six strings could be a possibility. A Sitar is supposed to sound unusual anyway, so perhaps some harmonics from the after length would be interesting. My goal of asking for knowledge on the topic is to determine if an length could be acertained as a favorable starting point. 

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Afterlengths are usually made to be in a simple numerical relationship to the stringlength, such as 1/2, 1/3 ect.

so that the fundamental frequency or some harmonics of the afterlength will correspond to some harmonics of the open strings

not being fingered. Your maximum possible afterlength will probably be determined by other physical exigencies of your body

design. Other variables you could experiment with include 1. attaching small weights at selected points on the afterlength strings

to lower their frequencies and 2. keeping the afterlength strings parallel to each other to loosen things up for the bridge

rather than having them converge at the saddle as is conventional.

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14 hours ago, PhilipKT said:

Very interesting point. Shorter means stiffer and stiffer means more “punchy?”

I’m not sure what you mean by “punchy” it’s very hard to describe sound. Can you be a bit more specific?

I read it the opposite, long after leanth , results in a more flexible system, allowing the bridge to rock to a greater degree, generating more amplitude, producing more sound. Now if that is true or not in practice...I have no idea, but it seems like it could be true. Within reason. Loud is not necessarily good if overtones are wrong. 

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2 hours ago, James M. Jones said:

I read it the opposite, long after leanth , results in a more flexible system, allowing the bridge to rock to a greater degree, generating more amplitude, producing more sound. Now if that is true or not in practice...I have no idea, but it seems like it could be true. Within reason. Loud is not necessarily good if overtones are wrong. 

Exactly my thought. Longer means more flexible and more free. “Punchy” implies, to me anyway, a negative sound quality.

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To make the after length vibrate at a harmonic of the OPEN string, make it the length of the string from nut to bridge divided by an integer.

So if the string length is 20cm, then an after length of 10cm (20/2) will make the after length at the frequency of the second harmonic.

An after length of 5cm (20/4) will make the after length vibrate at the frequency of the 4th harmonic.

However, once you finger the string, the after length will no longer be at a harmonic of the note you are playing except for  octaves of the open string.

So basically, your carefully chosen after lengths will not be vibrating vigorously for most of the notes you play.

After lengths let you adjust the resistance of the bridge to vibration. Tuning for specific sympathetic vibrations is only useful for playing very specific notes.

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7 hours ago, ctanzio said:

To make the after length vibrate at a harmonic of the OPEN string, make it the length of the string from nut to bridge divided by an integer.

So if the string length is 20cm, then an after length of 10cm (20/2) will make the after length at the frequency of the second harmonic.

An after length of 5cm (20/4) will make the after length vibrate at the frequency of the 4th harmonic.

However, once you finger the string, the after length will no longer be at a harmonic of the note you are playing except for  octaves of the open string.

So basically, your carefully chosen after lengths will not be vibrating vigorously for most of the notes you play.

After lengths let you adjust the resistance of the bridge to vibration. Tuning for specific sympathetic vibrations is only useful for playing very specific notes.

I agree however the after length includes the thread overwrap and a doubling up of the core (and winding?) so the after length doesn't have the same mass per unit length that the bowed portion has.

So the ratios might not be exactly 1/6, 1/5 etc. to hit a harmonic of the open string.  I suggest the after length should be adjusted to achieve the correct pitch rather than a certain length ratio.

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If you want to tune the afterlengths to exact pitches (which is completely pointless, but whatever), you should also consider the dead region on either end of the string that doesn't vibrate. The strings are too stiff to vibrate freely at such a short length.

You'd also have to strip the silk winding, or everything will be moot.

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This has been an interesting discussion for me as well, for stringing my cornerless Chanot. The after length is 13cm -  longer than typical, and definitely not an integer multiple. I've pondered switching to a conventional tailpiece or creating some kind of experimental string harness, so it could use standard strings, but I like the idea of preserving its historical purity.

 

PB170896.jpg

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6 hours ago, Tom Fid said:

 longer than typical, and definitely not an integer multiple.

Integer multiple (adjusting for end wraps as Marty pointed out) would get the strongest sympathetic vibration, but any after length that is an integer RATIO of lengths will also do nicely. For example, divide the string length by 3, then multiply by 2 to get an after length frequency that is a perfect fifth.

Are you sure the maker used extra long after lengths as some sort of sympathetic vibration strategy?

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12 minutes ago, ctanzio said:

Are you sure the maker used extra long after lengths as some sort of sympathetic vibration strategy?

I'm not sure at all. Upon reflection, the ratio actually is pretty close to 5:2. It's a little ambiguous where the bridge belongs though. I'll have to go back and reread the accounts of Chanot's patent and Academy trials. That should keep me busy for a while - French scientific and musical legalese is not my strong suit.

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A sitar is a very ringy instrument. Sympathetic strings will give slightly weaker loudness àt its notes, but may give a an extra kind of ring in a bowed instrument like the Kleven Hardanger fiddle Salve show pictures of here. For a bowed instrument the s strings might improve the playability. That is the resonances will reduce the mobility of the bridge a little and thus reduce the minimum bow force a little.

For a plucked instrument like the sitar, I would believe you will have a hard time noticing a difference, as the instrument is so ringy by nature. The best way to figure out is to try it. If you plan to use electronic pickup the story might change. Then you can decide how well the s strings should be heard. A project Id like to work on for the HF.

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Thank you all for the insight. I will study the interger/ratio subject. (for a 25.5" scale length), The next area of study will be how best to capture the after length tones for amplification. Magnetic or piezo.? For your amusement I include an early rough sketch and link to my craft works so far. ( A fiddle is in there somewhere, lol. ) Again, thank you all for contributing. I have learned from you. Thank you Anders Buen for accepting my invitation. 

https://mtouch.facebook.com/CatFish-Guitars-185651282048875/?ref=bookmarks

IMG_20181120_150031.jpg

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