Sub harmonics - what's driving them?

[Al Krow]

Fundamental plus harmonics = overtones. The musical notes we hear. Simples

If a low E fundamental is 41 Hz, how are the sub harmonics being generated and where are they primarily appearing in the signal chain?

Apologies if this is a noddy / well understood point, but I'm struggling to get my head around the string vibrations necessary to produce a wave at < 41 Hz on an E string, so I'm guessing it's a feature of the interaction of that 41 Hz (or any other plucked note) with the body of the bass and woods which are then picked up by the pups? 

[Bolo]

The pups do not pick up vibrations through the body.  They only register disturbances in their electro-magnetic field. Such as the strings vibrating or the phone in your pocket connecting to a network.

 

Other than that, good question, fun to read up on!

Let's get started with a bit from Wikipedia:

" In music, the undertone series or subharmonic series is a sequence of notes that results from inverting the intervals of the overtone series. While overtones naturally occur with the physical production of music on instruments, undertones must be produced in unusual ways. While the overtone series is based upon arithmetic multiplication of frequencies, resulting in a harmonic series, the undertone series is based on arithmetic division."

Edited April 23, 2019 by Bolo

[ikay]

Yes a bit of googling provides an interesting read! It would appear that a single string can't produce anything lower than the fundamental, but a combination of two notes can produce a tone lower than the fundamental of either. This is called a 'difference tone'. A good example is the power chord on guitar (root + fifth). Because these frequencies have a ratio of 2:3, they generate a difference tone with half the frequency of the fundamental (ie. an octave lower). Apparently this is why power chords sound so fat.

Edited April 23, 2019 by ikay

[Al Krow]

34 minutes ago, Bolo said:

The pups do not pick up vibrations through the body.  They only register disturbances in their electro-magnetic field. Such as the strings vibrating or the phone in your pocket connecting to a network.

Is that correct?

If so, then the whole debate around tone woods seems a bit otiose (sorry one of my fav words and totally appreciate the opp to sneak it in when I can 😀)

[BigRedX]

Just now, Al Krow said:

Is that correct?

If so, then the whole debate around tone woods seems a bit otiose (sorry one of my fav words and totally appreciate the opp to sneak it in when I can 😀)

The material(s) a solid stringed instrument is made out of will have some effect on the vibration characteristics of the string, but in the overall scheme of things this is fairly trivial compared with the other factors that have a more significant effect on tone.

[Al Krow]

1 minute ago, BigRedX said:

The material(s) a solid stringed instrument is made out of will have some effect on the vibration characteristics of the string, but in the overall scheme of things this is fairly trivial compared with the other factors that have a more significant effect on tone.

Well that's certainly been my view, but there's clearly another school of thought which says pretty much the opposite. Are they essentially pushing a gospel of snake oil which is not based on science? Are we saying that the wood of a bass is mostly about:

- look, feel, finish, durability and weight and sustain (all important factors, for sure)

- but has little impact on tone?

Oh dear, I seem to have side tracked my own thread within 5 posts...😂😂😂

[Thunderpaws]

21 minutes ago, Al Krow said:

Is that correct?

If so, then the whole debate around tone woods seems a bit otiose (sorry one of my fav words and totally appreciate the opp to sneak it in when I can 😀)

This is my non educated view...though i do have a materials engineering related background so it makes sense to me...

Strings vibrate when you pick, strum, etc...

They vibrate at a frequency and are held between the nut/fret and bridge. 

Everything else in the instrument acts as a mass damper absorbing some of the frequencies produced by the vibrating string. This in turn affects the vibrating frequency of the string to affect the tone of the instrument.

Simply put, the materials that make up the instrument take away from what’s  Beijing produced and remaining vibrations is what’s heard through the pickups. 

[dannybuoy]

A lot of these sub sonics come from the percussive element of hitting the strings. When you pluck, before the string is released, it moves over the pickup at a slower speed than a freely vibrating string would, as it's attached to your fingers. If there was no filtering whatsoever in the entire signal chain, you would be able to see the cone move just by wiggling the string slowly over the pickup.

Edited April 23, 2019 by dannybuoy

[Al Krow]

1 minute ago, dannybuoy said:

A lot of these sub sonics come from the percussive element of hitting the strings. When you pluck, before the string is released, it moves over the pickup at a slower speed than a freely vibrating string would. If there was no filtering whatsoever in the entire signal chain, you would be able to see the cone move just by wiggling the string slowly over the pickup.

That is a very interesting insight indeed, thanks dB.

(And completely not wood related either).

[BigRedX]

2 hours ago, Al Krow said:

Well that's certainly been my view, but there's clearly another school of thought which says pretty much the opposite. Are they essentially pushing a gospel of snake oil which is not based on science? Are we saying that the wood of a bass is mostly about:

- look, feel, finish, durability and weight and sustain (all important factors, for sure)

- but has little impact on tone?

Oh dear, I seem to have side tracked my own thread within 5 posts...😂😂😂

I outlined what I consider is wrong with assumptions about "tone woods" for solid instruments  in this post.

[Frank Blank]

2 hours ago, Al Krow said:

seems a bit otiose (sorry one of my fav words and totally appreciate the opp to sneak it in when I can 😀)

*applause* a beautiful word (otiose, not applause).

[fleabag]

I'm anaspeptic, phrasmotic, even compunctuous to have caused you such pericombobulation.

[Bolo]

37 minutes ago, fleabag said:

I'm anaspeptic, phrasmotic, even compunctuous to have caused you such pericombobulation.

Well done Bladder!

[Dan Dare]

5 hours ago, Bolo said:

The pups do not pick up vibrations through the body.  They only register disturbances in their electro-magnetic field. Such as the strings vibrating or the phone in your pocket connecting to a network.

Agreed. The best answer I've heard to the tone wood debate is "pickups aren't microphones". Seems to sum it up pretty succinctly. 

[dannybuoy]

The materials and construction will affect the acoustic tone, but the pickups don't hear those vibrations emanating from the wood itself, as you say they are not microphones.

But the vibration of the string is affected by the system it is connected to or coupled with, as said by fellow engineer @Thunderpaws up above.

For instance, certain wider grained softer woods can result in a dulled high end, as the intermingling wooden fibres with microscopic gaps inbetween can dampen higher frequencies, just as when you add a foam mute to your bridge. Hence the differences often heard between rosewood and maple boards.

Edited April 24, 2019 by dannybuoy

[drTStingray]

Strangely, I had thought they were something produced when I pressed the button and turned the knob on my Ashdown amplifier stating sub harmonic generator. I subsequently found this is effectively similar to an octaver producing one octave below the plucked note........ I think - as well as the plucked one - or is it an additional low harmonic? Doesn't sound like it to me. 

As for wood resonance, if the materials had no impact at all on the string resonance (and thus the vibrations which the pick up takes) then all Bass guitars would generally be literally planks with pick ups attached (or made of hardboard like Danelectros). 

I have similar makes and designs of bass, some with differing body woods, or neck woods and there is quite an effect between say poplar and ash, alder and mahogany. It possibly doesn't make that much difference if you're looking for thump rather than more defined notes - the different body wood tends to accentuate, for instance, highs, low mids or bass. The effect is probably more subtle to the casual observer - to the player it can be quite significant, for instance in impeding or assisting playing certain phrases and nuances of style. The ability to accomplish those or not would be audible to someone listening. 

Edited April 23, 2019 by drTStingray

[Davo-London]

Actually, it's a really good question and when you play an open string say an E through a 12" speaker it sounds good but not necessarily face melting.  Play the same E through a 15" or an 18" speaker (remember them) and it does sound different (more rounded, heavier, richer?) but it's the same note.  When I play alone through my church sub-woofer my face does indeed begin to melt. 

Not sure any of the explanations so far cover my facial deformations.

Davo

[Davo-London]

Then if I play reggae style with my thumb and palm muting - well frankly folk start to run for the hills.

Davo

[Woodinblack]

14 hours ago, Bolo said:

The pups do not pick up vibrations through the body.  They only register disturbances in their electro-magnetic field. Such as the strings vibrating or the phone in your pocket connecting to a network.

They of course pick up vibrations in the body as they are attached to the body, and as the strings move relative to the body, it follows that the body moves relative to the strings - the combined relative movement between the strings and the body. It is a far smaller amount but it is there.

Personally I believe the bigger effect is the effect of the body on the string vibration but you can't rule out anything

 

[songofthewind]

Stewart Ward, of Session amps fame, recounts how changing necks on a Telecaster (sorry guys) changed its tone significantly. 

The stiffness of the necks, due to differing thicknesses, seemed to be the deciding factor, not body material.

[steve-bbb]

10 minutes ago, songofthewind said:

Stewart Ward, of Session amps fame, recounts how changing necks on a Telecaster (sorry guys) changed its tone significantly. 

The stiffness of the necks, due to differing thicknesses, seemed to be the deciding factor, not body material.

 the fundamental difference between P tone and J tone (notwithstanding the pickup difference of course)

Edited April 24, 2019 by steve-bbb

[songofthewind]

Yep, I reckon so too. 

[BassTractor]

As any professional archer can tell you, only the arrow matters. The bow doesn't come into it at all.
😐

[Davo-London]

Wiki states that string players can get sub-harmonics (undertones) by applying a lot of pressure from the bow onto the string.  How do we do that with our hands?

Davo

[Woodinblack]

Wiggle the string side to side!