7

I've heard of the "Jazz Bass Mid Scoop", what exactly is this? Some people say that the "Scoop is generally 500-600 Hz", others say "The frequencies that cancel are different for each string and each fret position", and still other say "There is no 'mid scoop' in Jazzes". What's the deal?

("Jazz Bass" refers to the 2-pickup electric bass guitar models sold by Fender with the name "Jazz Bass", or more loosely, electric basses made in the same style by various instrument makers.)

4
  • 1
    Much appreciated if, for the uninitiated (i.e., me), you'd include a definition of what "mid scoop" is/sounds like. – Aaron Jan 24 at 22:23
  • So it's softer frequencies within a particular pitch, as opposed to individual pitches that are softer? – Aaron Jan 24 at 23:09
  • 1
    Right. The first spectra animation in my answer shows one note at a time, and a scoop can be seen within each note. – Edward Jan 24 at 23:23
  • Does this refer to the Fender Bass? Or is it about playing jazz in general? – chasly - supports Monica Jan 25 at 22:31
16

The "Jazz Bass Mid Scoop" is absolutely real!

When the Jazz bass is played with both pickups at the same volume, the sound will be mid-scooped. The term "mid-scooped" means that the mid frequencies, somewhere between bass and treble, will be reduced in volume.

When the pickups are set to different volumes, the scoop goes away and the mids return. Look at these spectra of notes played on my own 70's Jazz Bass, with both pickups on full volume:

Animated Spectra

You may notice that the exact location of the mid scoop changes. For this reason, simply boosting the mids on your amp to compensate for the scoop might not work well.

The location of the scoop depends on the pickup placement, string length, and string open pitch, but not on the fret. The Low B string's scoop appears at the same location for every note on the B string, but when you step up to the E string, the scoop's location moves. Look at these spectra of chromatic scales played on one string at a time:

Animated spectra - chromatic scales

You will notice that the scoop still appears. There are no notes where the scoop doesn't appear that could fill the gap.


What causes this scoop?

This "Jazz bass mid scoop" is a caused by having two pickups at different positions on the string. When a string is plucked, it vibrates at several frequencies, each with different wavelengths. The image below represents the first 7 harmonics of a plucked string.

first 7 harmonics of a plucked string

Image Source

If one of the harmonics oscillates such that the motion over one pickup is opposite the motion over the other pickup, then the two signals will cancel, and that frequency gets silenced- or "scooped". If you lower the volume on either of your two pickups, then the frequencies will not cancel fully, and you get your mids back.


Math nonsense

We can actually calculate the frequency of maximal cancellation. My Jazz bass's open E string is 86.4cm long, so the low E has a wavelength of 172.8cm (twice the string's length). The pickups are placed 10.45cm apart, so the scoop is centered where the wavelength is twice this, or 20.9cm†. This is 20.9/172.8 times the open string's wavelength, so the scoop from cancellation effects occurs where the frequency is 172.8/20.9 times the low E's frequency, or 41.20*(172.8/20.9) ≈ 341 Hz. That matches our image pretty closely! Using this method, we get:

B string scoop - 255 Hz

E string scoop - 341 Hz

A string scoop - 455 Hz

D string scoop - 607 Hz

G string scoop - 810 Hz

You may also notice there are many smaller scoops present too, in the higher frequencies. We expect cancellation at every frequency which has opposite motion over the two pickups, which accounts for these smaller scoops. These smaller scoops are less significant than the first one, but they all contribute to the sound of the Jazz Bass.

You could run these calculations for fretted notes by considering the length and pitch of the fretted string. For example, fret 5 shortens the string to about 64.7cm, and raises the low E's frequency to 55.00Hz (A). Doing the same calculation with these numbers, we get a scoop at 341Hz, which is the same as the open E.

†This uses a hidden assumption that the distance from the bridge to the bridge pickup is half the distance from the bridge pickup to the neck pickup. This is a good assumption for the 70s Jazz Bass, but may not hold for other models, such as the 60s Jazz Bass. For those cases, you can find the scoop qualitatively with a spectrum analyzer, like I did in the images above. The scoop will have similar properties, but it will be located at different frequencies.

9
  • You don't have a Rikki 4001 you could test too, do you? Mine's packed away right now, but I've always thought they did something similar. For the past 40 years I've also EQ'd mine differently on each pickup to accentuate it, front pu bass-heavy, back pu treble-heavy, leaving a hole in the middle. – Tetsujin Jan 25 at 7:12
  • Interesting that the open A’s scoop is ballpark 440, 3 octaves higher than the fundamental. Are they all about that? – John Belzaguy Jan 25 at 7:26
  • Nice detailed explanation. What si specific about the Jazz Bass, here? – Jérôme Jan 25 at 8:25
  • An interesting answer! You say that the scoop depends on the string length, open pitch, and pup placement. The 1st and 3rd of these remains constant, ony the pitch is a variable. The placement of pups is important - I guess, like a lot of guitars, the neck pup is actually on an open string harmonic node (I have many basses, but no Jazz, sadly!), and that node will change when different notes are fretted. That's what I don't understand - why it's only the open string that's important. – Tim Jan 25 at 9:10
  • @Tim A physical explanation for this is that the cancellation of a frequency depends on the distance between the pickups and the wavelength of the harmonic. Wavelength depends on frequency and the speed that waves propagate across the strings. This propagation speed does not change when you fret notes, because it depends on the weight and tension of the string, and not its length. And of course the distance between pickups is constant. – Edward Jan 25 at 13:37

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.