John's stupid question No. 257.
Looking at photos of guitars with magnetic pickups, particularly those with multiple pickups, there is sometimes one pickup at an angle. Where it is angled it seems to be most often the one nearest the bridge and the pickup is further from the bridge beneath the bass strings. Does anyone have a good explanation for this that can be understood by someone like me (guitar muppet).
Thanks.
Replies
Hi Skeesix and Eric.
Lots of great information. The way I read this then is that it is a way of bringing out the brightness of the treble and the richness of the bass. Makes sense.
On the subject of tone of different instruments, I read years ago about a test where they recorded various instruments and then removed the very first part of the notes on each. People found it very difficult to identify which instrument it was being played. It shows how important the attack part of the note is in our awareness of tone.
P.S. I love the word treblier. I shall use it at any possible opportunity.
Simple question, sorry massive answer to follow!
When you play a note on an instrument which produces it's sounds mechanically ( reeds, strings, air column, vibrating diaphragm) the sound you hear is not just the fundamental frequency you fretted, fingered, blew etc. The Fundamental carries a great number of harmonics too. These harmonics are integer multiples of the fundamental. For A4(440Hz), the 1st harmonic is 2x = 880Hz(A5), one octave above A4.
The 2nd harmonic is 3x =1320Hz(near E6), an octave and a just 5th above A4.
The 3rd harmonic is 4x = 1760Hz(A6), 2 ocaves above A4.
These harmonics continue 5x, 6x, 7x, etc... getting closer together according to our 12 note octave, as they get higher in frequency, but becoming smaller in amplitude.
The diffent timbre produced by particular instruments, is due to the particular harmonics they emphasise and at what levels. This is why A440 played on a french horn doesn't sound the same as A440 played on a piano, or even a trumpet. Or why an open D played on a dreadnought doesn't sound the same as an open D played on a Dobro, or a National.
OK, so strings don't vibrate as a single section, but have many smaller vibrating sections within that big fundamental, and the makeup of the higher frequencies determines your tone.
Now magnetic pickups. All good sounding passive pickups have a resonant peak well above the highest note that can be fretted on the guitar (24th fret e string, E6(1318.51Hz)). This means that the pickups are able to amplify the harmonics which give your guitar it's tone and shimmer. Pickups that bring the resonant peak down too far (usually through extreme overwinding) sound very flat and lifeless. Paf style humbuckers usually have a resonant peak >6.5KHz, and Strat style single coils a resonant peak >8KHz - this is why humbuckers generally sound a bit warmer, and realy can't get that Strat quack.
So, strings have smaller vibrating sections within the fundamental one, and magnetic pickups can reproduce these frequencies.
If you were to place a pickup at the 12th fret position, and play an open string, the pickup would amplify a very clean fundamental. Other harmonics without a nodal point around to 24th fret would be picked up too, but the half way point on the string is where the fundamental has it's greatest amplitude, and it would drown out the harmonics convincingly.
If we move the pickup away from the middle of the string, towards the bridge, the amplitude of the fandamental is less, but the shorter wave harmonics (higher frequencies) are unaffected, so the ratio of fundamental to harmonics changes. The amplitude of the upper order harmonics doesn't increase, but they become a greater part of the generally lessening output. The closer the pickup is placed to the end of the string, the smaller the amplitude of the fundamental, and once it's really close, we also start to lose the lower order harmonics in the same way... Viola! brighter output.
It seems to defeat the purpose of having bass strings to only emphasise the upper harmonics, so best to keep these a little further away to pickup the fundamental more.
Leo was reportedly on a quest for brighter and brighter tone, and it's probably thanks to him we have this pickup layout.
Sorry about such a long answer - I'm sure there are those out there who could say explain this in a much more simple and sensible way, but they haven't, so here you are.
cheers
oh, this is "perfect world" correct, not allowing for how or where YOU pluck the string. The further you pluck the string away from the middle of it's vibrating length, the more you mess with the harmonics produced. Playing away from the middle will also set up standing waves travelling from one end of the string to the other which will emphasise certain frequencies too. massive topic.
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If you take a guitar without any pickup on it and pick near the bridge, it will sound treblier. If you pick closer to the neck it will sound bassier.
When you angle a pickup, it will simply amplify what happens naturally with the unamplified string.
"String vibrates at a higher frequency" - I think what they mean to say is the string has less amplitude near the bridge (less up and down motion) and therefore vibrates quicker - which emphasizes the higher frequencies of the string (but does not change it's pitch).
Hi David.
Thanks for the information. Sometimes an answer to one thing throws up a question to something else (so stupid question No. 258). If as was quoted, "strings vibrate at a higher frequency the closer they are to their point of contact (the bridge)" then the string would be sounding more than one pitch, as the pitch is determined by the frequency of the vibration - or am I wrong. Surely the whole string must vibrate at one frequency in order to sound one note (A bit like a skipping rope. It travels furthest in the middle but does the same number of rotations all along its length).
It may be that I am misunderstanding something rather badly, but since that bit makes no sense to me I don't quite follow the other bit. Sorry. It is probably me being rather thick.
Why do you get more bass by moving the pickup away from the bridge (more string movement further away from the bridge, so makes sense) and more treble by moving the pickup closer to the bridge (less string movement nearer to the bridge, and now I am confused).
Thanks anyway for trying to get this information through to someone with little grasp of the concept (I did say I am a guitar muppet).
David Lloyd said:
Taken from this site http://www.guitartricks.com/forum/archive/index.php/t-13131.html