Strings - a (mostly) physics question

[GAD]

I've been doing some recording for an upcoming article and we were comparing different archtops through my AxeFX III using a Roland JC120 model.

The comparisons were going great until we got to one guitar which sounded awful, mostly because it was overdriving the amp in an absolutely unpleasant way. We quickly realized that the offending guitar had round-wound strings on it and when I restrung it with flat-wounds the problem completely went away. The guitar in question was a Guild Benedetto X700 Stuart, so not a junker.

This got me wondering... why? I know round-wounds are brighter and higher frequencies drive an amp harder, but this was worse than I expected. It sounded a bit like when the pickup is too close to the strings - just harsh and nasty. My main question:

• Is it possible that composition of the strings was so different that the round-wounds were causing more magnetic flux and thus a stronger signal? Or am I missing something else?

The strings in question were Thomastik Jazz Swing 12s (flat) and Thomastik-Infeld Jazz BeBop 11s (round). Neither of these are cheap strings so there has to be something fundamental to the strings that caused the difference.

Thomastik-Infeld describes the Jazz Swings as glassy smooth polished nickel winding on a round core. [Source]

Thomastik-Infeld describes the Jazz Bebops as A similarity to the JAZZ SWING in materials and string architecture, but with a small gauge round wound nickel winding, produces a strong, fundamental rich jazzy tone that is somewhat bigger than a flat-wound. [Source]

Any (helpful) thoughts are appreciated! Sadly, I did not save the round-wound recording.

 

[walrus]

Simple questions first - were the strings in question old? Is it possibly a case of the wrong string on the that particular guitar?

But my big question is did it sound good unplugged? If so, that would make your questions more difficult (and interesting!).

walrus

 

[chazmo]

GAD, I just looked up the Jazz Swing strings and there's a pretty complicated array of different materials in use for these strings. I'm not sure that price is a good guide for suitability, especially with Thomastik strings, on a given instrument. Apparently, there's a choice of whether tin or brass is being used to plate the unwound strings, depending on the set you buy. The wound strings are all flat, nickel wire wrapping round steel core, as you said. Was it the wound strings that you were talking about?

Just wondering if you're comparing apples to apples here. If it was the wound strings, then I agree that you are.

 

[Walter Broes]

That's odd indeed. Different core sizes between flat and round is about the only thing I can think of?

 

[GAD]

Simple questions first - were the strings in question old? Is it possibly a case of the wrong string on the that particular guitar?

But my big question is did it sound good unplugged? If so, that would make your questions more difficult (and interesting!).

walrus

This wasn’t an “old strings” sound.

Guitar sounded fine unplugged as I recall. This was strictly an amplified problem.

 

[GAD]

GAD, I just looked up the Jazz Swing strings and there's a pretty complicated array of different materials in use for these strings. I'm not sure that price is a good guide for suitability, especially with Thomastik strings, on a given instrument. Apparently, there's a choice of whether tin or brass is being used to plate the unwound strings, depending on the set you buy. The wound strings are all flat, nickel wire wrapping round steel core, as you said. Was it the wound strings that you were talking about?

Just wondering if you're comparing apples to apples here. If it was the wound strings, then I agree that you are.

While I get where you’re coming from, I don’t think it would have made the difference we were hearing.

The flatwound plain strings are different, though because they’re goldish in color.

 

[GAD]

That's odd indeed. Different core sizes between flat and round is about the only thing I can think of?

Now that’s a theory I could get behind. Now I want to get a set of each and weigh them to see if the round-wounds have more mass. I’ll dig in my drawer and see if I have any more.

At one point I thought I’d like round-wounds on an X700 because that’s what I’ve used on everything forever, but the more I dig into the jazz guitar world the more I get the love of flat-wounds for a nice hand-carved archtop.

 

[Walter Broes]

I don't know if more or less mass would be a factor - I'd think more or less magnetic material would be...?

 

[fronobulax]

There are several opinions about how a guitar pickup works. Many people focus on a magnetic field generated by a pole piece and look at the string interacting with that. But you can also analyze the magnetic field created by the string. If that is the case then a difference in materials that generate the field could account for the difference.

How Does a Pickup Really Work? — Lawing Musical Products

In the first couple of installments, I outlined my early efforts at pickup development, up to the point at which the Zexcoil® platform as it currently exists was more or less solidified. Before we continue with the Zexcoil story, let’s set the stage. We’ll back up a bit and re-consider for a second

lawingmusicalproducts.com

 

[GAD]

I don't know if more or less mass would be a factor - I'd think more or less magnetic material would be...?

Mass was too generic a word for me to use.

 

[jp]

I have a feeling it's related to the range at which the strings vibrate--the vibrational wavelength. Because flatwounds are more tightly wound and compact and have a higher tension when tuned, they tend to have a lower vibrational wavelength. Roundwounds vibrating at a higher wavelength will be moving in closer proximity to the pickups, which I think is what you're hearing. Just a theory.

Maybe you can try lowering the pickups slightly when you have the roundwounds on to see if the nastiness subsides?

 

[GAD]

I have a feeling it's related to the range at which the strings vibrate--the vibrational wavelength. Because flatwounds are more tightly wound and compact and have a higher tension when tuned, they tend to have a lower vibrational wavelength. Roundwounds vibrating at a higher wavelength will be moving in closer proximity to the pickups, which I think is what you're hearing. Just a theory.

Maybe you can try lowering the pickups slightly when you have the roundwounds on to see if the nastiness subsides?

I think you're on to something but I'd like to clarify some terms. In electronics (physics) wavelength = frequency = the notes we hear. I think what you mean is amplitude meaning that the height of the wave is higher with round-wounds though the frequency is the same. In essence the stings moving more with round-wounds than with flat-wounds. Is that a correct assumption?

Helpful pic:

If that's what you mean, then that would absolutely cause what I heard because increased amplitude = more energy = more signal and more signal would overdrive an amp if the "regular" signal was just at the edge.

 

[fronobulax]

Going back to the kind of simplistic analysis which is sometimes Good Science but sometimes Bad Science...

The "only" thing that changes between the two cases is the strings.

One setup sounds fine. One setup does not. The "unfine sound" is due to overdriving the amplifier.

Moving on to areas of less certainty - the amplifier is overdriven because there are one or more frequencies present in the input each at an amplitude greater than what the amplifier is expecting/designed for and thus "clipping".

So a worthwhile veer might be to look at the output of the pickup with an oscilloscope or a spectrum analyzer since doing so might verify clipping or identify the frequencies one string favors over the other.

If the string is acting as a magnet a second avenue might be to measure the magnetic fields generated by each string. Presumable the unfine string would have the more powerful field and this produce greater amplitudes at the amplifier.

In either case you have a measurable characteristic that can probably be traced to the material composition or construction of the string.

If I had to place a bet I would say the difference is due to the materials used. That said I worked with a team that traced the variations in the radar cross section of a helicopter to waves that bounced around between the body and rotor(s) before returning to the radar so if someone claimed that the geometry of the windings effected the magnetic field I wouldn't argue about the possibility.

I'm thinking you already have what you need to take measurements if you are motivated enough

 

[GGJaguar]

I'm thinking you already have what you need to take measurements if you are motivated enough

That could mean more graphs and charts! Hurray for science!

 

[GAD]

Frono that is very much my kind of project but I don’t know if it’s the right time (selling a house right now).

“Materials used” might be partially true but I have a feeling that, to jp’s point, construction is the root cause. Of course in the real world it’s likely a combination of both

What I need is a way to measure the physical movement of the strings and I’m not sure I have that unless…

I could rig up a high-contrast lighting rig where I could take high-speed video of a plucked string from the side with a visual scale behind. The challenge there would be ensuring the same plucking force/angle for each test. Hmm…

 

[jp]

I think you're on to something but I'd like to clarify some terms. In electronics (physics) wavelength = frequency = the notes we hear. I think what you mean is amplitude meaning that the height of the wave is higher with round-wounds though the frequency is the same. In essence the stings moving more with round-wounds than with flat-wounds. Is that a correct assumption?

Helpful pic:

If that's what you mean, then that would absolutely cause what I heard because increased amplitude = more energy = more signal and more signal would overdrive an amp if the "regular" signal was just at the edge.

Ah, yes. Forgive my late night terminology flubbery. Amplitude was what I meant.

Regardless, it might be a simple test to just lower the pickup slightly with the roundwounds to see if that takes away the harshness. It definitely won't nail down the exact cause, but it might help you get your recordings done. :C)

 

[GAD]

Ah, yes. Forgive my late night terminology flubbery. Amplitude was what I meant.

Regardless, it might be a simple test to just lower the pickup slightly with the roundwounds to see if that takes away the harshness. It definitely won't nail down the exact cause, but it might help you get your recordings done. :C)

Awesome!

The recordings are long done, but thanks! I was really more interested in the "why" than a way to fix it (though it was "fixed" with flat-wounds. )

 

[teleharmonium]

I think you're on to something but I'd like to clarify some terms. In electronics (physics) wavelength = frequency = the notes we hear.

True of a sine wave, and of the fundamental tone, but with real world sound sources much of what we hear is overtones. This matters in this scenario because the AxeFX is to a great extent tasked with modeling overtones, since other than wave shape they are what makes one sound (at the same fundamental pitch) different than another.

It could be finessing the spot where distortion occurs and how it onsets, and giving some more control over that via settings than a real amp could, although you wouldn't expect much in a JC120 model.

As far as the basic question, rounds tend to have a stronger attack and more harmonic content than flats. Comparing amplitude of complex sounds is tricky and can be subjective, but if an amplifier (or one part of an amp) is on the verge of distortion, it's certainly possible that relatively more harmonics could be enough to push it over the edge. After all, we're talking about adding harmonics to something that already has a lot of harmonics, which means some of those pitches are getting further away from what the string sounds like acoustically, and some pitches are piling up in the same areas of bandwidth, especially where the amp and/or speaker (or model) has a frequency spike, or is in the midrange where our hearing is the most sensitive.

 

[lungimsam]

Looks like I got here just in time.
Guys, it’s so obvious what the problem is:
Thomastik mis-packaged a set of their prototype HardBop strings into your BeBop string package.

But seriously:
Can’t comment on their guitar strings but their flatwound bass JF324 stringset is much louder than all flats sets I have tried. Don’t know why. And in the set I have, the d and g are louder than the a and e strings. To the point I’ve had to lower the Bisonic pup and adjust the pole pieces downward on the d and g strings and upward on the a and e strings.