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Al,

Thanks - fascinating stuff as usual. What sort of scale length harps does the T/L rule of thumb come from? If its Concert harps, those beauties are nearly six feet high and have nylon, gut and copper/steel wound nylon big to small. Given David's point about string arc ( and perhaps feel/energy?) being logarithmic with scale then I can see why you would be in 1.5 territory here with 3-4 feet scale lengths. But a guitar at 29"? A standard tuned 25.5" guitar in EADGBE tuning has an average T/L of 1.07 and the first two strings are both 0.9.

What range of string tension does Ken's guitar sit in mostly?

David,

The two strings with T/L below 1 are the first two - not really the baritone territory where I am struggling to get volume and feel of the string. But I could replace them with an 18 and 22w which wouild push them over unity with a total string tension of 181lb. I've even used a set of EJ16's, throwing away the first and using a 70 on the bottom : 16, 24, 32, 42, 52, 70 and this gives a total of 207lb. This is certainly louder but not necessarily better tone but I would be prepared to live in this territory. It's 220-260lb that I have issue with.

J,

I'm sure your guitar sounds fabulous - as I say I'm not trying to convert anyone here. I think my guitars sound fabulous too. The development of the D'Addrio EXP23 set is interesting. Their website shows it in B-B tuning on a 29" scale guitar but was it "specifically developed" for this or are they making a set for a growing market in consultation with or observing the strings used by the major builders of baritone guitars - David, Linda, Lance etc? The development of this gauge set looks very close to the ones David B and JIm Rickard developed for A-A tuning on a 29" scale guitar. This gives 211lb string tension.

_________________
Dave White
De Faoite Stringed Instruments
". . . the one thing a machine just can't do is give you character and personalities and sometimes that comes with flaws, but it always comes with humanity" Monty Don talking about hand weaving, "Mastercrafts", Weaving, BBC March 2010

Dave White asked:
"What range of string tension does Ken's guitar sit in mostly?"

Offhand I couldn't say: I don't know exactly what strings he has on it at the moment.

The T/L rules apply to all sizes of harps, from the little 22 string lap harps up to the monsters they play in orchestras. The top strings on most harps will be about 4" long, and even at 6-8# of tension can feel pretty tight. When you start adding in those longer strings the total tension rises fast: even a common 3-1/2 octave lap harp can be pulling well over a thousand pounds. Good joinery is critical!

In fact, most harp makers these days use some variant of the sort of computer program first devised, so far as I know, by Mark Bolles, back in the day. He wrote it in GWBasic, to run on a TRS-80, and it starts out by figuring the T/L ratios of all the strings, given the tuning range and length contraints. It's axiomatic that if you can come up with a good set of strings it's pretty easy to make a good sounding harp. Making a good sounding harp that will hold together, now that's another thing.....

At any rate, there's a lot more to getting guitar strings 'right' than just the T/L ratio, although that's not a negligable consideration. I mostly brought it up because it's a different, and useful, perspective on things.

Another thing to think about is impedance. It has been said, ever since Leopold Mozart, that on something like a violin or guitar, you want all of the strings to have the same tension. This should give them all the same 'feel'. However, if you look at the tensions that most people use in a set, you'll find that they are not normally equal. The reason for that is that if you did use equal tension, the 'characteristic impedance' of the strings would vary a fair amount across the fretboard. This is, in a sense, a measure of how hard the string can push on the bridge for a given amplitude. If the impedance varies too much the volume of the different strings will also vary, and it wil be difficult to play evenly. In practice it seems as though a compromise is reached between equal tension and equal impedance in setting up string sets, and it's entirely likely that this is arrived at pretty much empirically.

As with most things related to the guitar, the more you get into this, the more complicated it gets.

Al,

Thanks again. The impedance idea is interesting as is the string tension "balance" across the guitar strings. I've always been puzzled as to why the string tensions are so much higher on the 3rd 4th and to some extent 5th strings. One explanation that I have heard - and it could be just another urban folklore myth - was that they evolved to give the mids more balance on guitars that were braced to deliver a bass heavy sound eg Dreads. There is a limit to how much time string manufacturers can devote to "evolutionary" research as opposed to running a profitable business and sometimes "Tradition" takes a deep and lasting hold - "I didn't get where I was today by being different".

The EXP23 string tension profile shift (B-B on a 29" scale guitar) compared with 12-53 on a 25.5" scale length guitar is very interesting too. The figures below show the ratio of each individual strings tension to the average (first figure is EXP23 B-B 29" scale and the second EJ16 E-E 25.5" scale) :

1st 0.86 0.86
2nd 1.00 0.86
3rd 1.32 1.11
4th 1.17 1.12
5th 0.94 1.10
6th 0.71 0.96

The baritone one is putting much more impedence on strings 4 to 2 in the A-F# range. Is this mid range "roar" helping the listeners ears to hide the problems of sustaining the very low register? I wouldn't have thoght that it was these particular strings that needed the impedance boost to make them feel the same, more the bottom three or four strings - but I could well be wrong. Interesting stuff.

_________________
Dave White
De Faoite Stringed Instruments
". . . the one thing a machine just can't do is give you character and personalities and sometimes that comes with flaws, but it always comes with humanity" Monty Don talking about hand weaving, "Mastercrafts", Weaving, BBC March 2010

Where are you guys getting the info that the EXP23s are for a 29 inch scale, at those tensions ?? The back of the packs I have show the tensions for a 29.75 (756mm) inch scale ???

_________________
Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

Tony,

Apologies - I was quoting the 29" scale from J's post and looking again at the D'Addario website it doesn't quote a scale length for the B-B tensions. B-B on a 29" scale length they would give 214lb total string tension.

For the string tension profile in my recent post I was using the string gauges David Berkowitz used in his post - which I see now aren't the D'Addario EXP23 set - blame it on my senile dementia Re-calculating the profile gives the following figures for the ratio of each individual strings tension to the average (first figure is EXP23 B-B 29" scale and the second EJ16 E-E 25.5" scale) :

1st 0.82 0.86
2nd 0.87 0.86
3rd 0.89 1.11
4th 1.36 1.12
5th 1.18 1.10
6th 0.71 0.96

This looks to be more in line but I still think that the 4th and 5th strings are too much necessary tension to generate tone and feel. Low 200lb's is the top of the range I would contemplate - I still think that 220-260lb range is too high for me.

_________________
Dave White
De Faoite Stringed Instruments
". . . the one thing a machine just can't do is give you character and personalities and sometimes that comes with flaws, but it always comes with humanity" Monty Don talking about hand weaving, "Mastercrafts", Weaving, BBC March 2010