P and j bass mid frequency focus point

[thebassbuilder]

Does anyone know what the mid frequency focus point is for a p bass and a j bass? For the j I am meaning when both pickups are on evenly. I am wanting to know the mid frequency for these as this is what sets them apart I feel like. This way if I want to add an active pre amp, I will know what mid frequency to select for each bass type so it keeps its original character. I hope this makes sense.

 

[sikamikanico]

You mean resonant peak frequency? It really will vary by pickup, cable capacitance, etc… but according to this data sheet, it’s about 2.5kHz for P bass. For J, they only list it for each pickup separately, at around 3.5kHz for neck and slightly lower for bridge, maybe 3.2 kHz (I’m on my phone, so eyeballing). You could probably estimate the combined peak by plugging inductance and capacitance data into the resonant frequency formula. Remember J’s are wired in parallel, so make sure you add up your L and C using the correct formula. Also, the J’s in parallel will have some mids scooped due to phase cancellation that the formula won’t take into account, but in my estimate/experience the mid scoop is 600-1000 Hz area if I remember correctly.

@micguy might have some good insights into these things.

 

[micguy]

You mean resonant peak frequency? It really will vary by pickup, cable capacitance, etc… but according to this data sheet, it’s about 2.5kHz for P bass.

The resonant peak is formed by the inductance of the pickup(s) and the loading capacitance - which is partly in the pickups themselves (different winding techniques will give different interwinding capacitance), and the rest (usually most of it) in the cable.

Some manufacturers will quote a resonant frequency of the pickup itself (without the cable) - this is interesting information, but incomplete - the reality is that the peak will be lower in frequency when in use.

If we start with a relatively low capacitance cable - say 600 pF for a 15 footer, Most traditional P pickups will give you a resonance around 2 to 2.2 kHz. A soloed J pickup will land you a bit North of that - 2.2 to 2.4 kHz. Both pickups on with a Jazz bass, and you're at 2.8 to 3 kHz.

When you turn down the volume control(s) (especially on a J), the resonant peak is damped - it doesn't really resonate.

The J scoop has nothing to do with pickups loading each other electrically - it's in the positions of the pickups entirely. It doesn't happen at one frequency - it happens at 4 (or 5, or 6, or) - the scoop is a wavelength phenomenon, and as each string has a different propagation velocity, the frequency at which a give wavelength occurs is different on every string. So if you try to eq out the scoop, you can fix one string, but the other 3 will be even more messed up - it is literally unfixable with one signal path.

A lot of folks talk about pickups sounding "scooped" - practically speaking, they don't - the "scoop" you hear from different pickups is that the upper mid peak is distracting you, so you hear that rather than the lower mids.

 

[pbass2]

I just did a little very unscientific experiment - I recorded a Pbass and a single coil Jazz both with the same flatwound strings, DI. Played the exact same thing on both, plucking over the PU on the P and the neck PU on the J. Everything on both basses dimed (so the J in its presumably "scooped" mode). Well, if you look at an EQ analyzer of them both playing back, they are nearly identical (except there's a little more information in the highs with the Jazz). The mids/low mids look the same. Naturally, they both sound quite different. Lotsa other variables of course, and maybe using the same strings closes the gap a bit between these two particular axes, but I thought it was kind of interesting (I thought to do it because I usually play P's live but have been using this Jazz of late and consistently find that the tightest, most focused sound - you know, the "sit in the mix" factor - is with both pickups dimed).