Seymour Duncan Quarter Pound P Bass, Analysis and Review

[antigua]

www.seymourduncan.com/pickup/quarter-pound-p-bass


These are a little dark for my tastes. They do well for distorted bass, but if you're into slap bass, they don't snap like vintage output pickups. I think it makes more sense to go active than to go for QP's, but if you're not a demanding tone connoisseur and don't want to deal with dead batteries, it's a viable option.



Seymour Duncan Quarter Pound P Bass
- DC Resistance: 11.43K ohms
- Measured L: 7.043H
- Calculated C: 38pF (48 - 10)
- Gauss: 825G

unloaded: dV: 14.6dB f: 8.65kHz (black)
loaded (200k & 470pF): dV: 3.7dB f: 2.36kHz (red)





It appears that all split humbuckers of this variety have an impressively low capacitance, but they also have a high inductance when wire in series, meaning that a fairly small amount of added cable capacitance has a dramatic effect on the resonant peak.
Notice how closer the peak frequnecies are in the Jazz Bass Quarter Pound:


Seymour Duncan Quarter Pound Jazz Bass






This might mean you have to be more cable conscious when using P-Bass pickups, relative to Jazz Bass and other non split-style humbucker pickups.

Pickups that are wired in parallel have the opposite issue; the parallel capacitance is quite high and the inductance low, so they are a bit less impacted by added cable capacitance.

[wgen]

Thanks man also for these last analysis, the quarter pound for P bass for some reasons (mainly, lots of pro rock bassists who use this and even have "artist model" basses which come stock with this pickup) is quite a common choice among bassists.

Thanks to your work we can compare the tonal response of a pickup like this one with the more "vintage correct" examples, like the '58 P bass model.

Honestly I expected an even more "muddy" pickup from the response of this one, which is in the ballpark of some PAF humbuckers for guitars more or less, instead of those super dull high output ceramic humbuckers, which I thought it could have been compared to, before your test.

I wonder if the bigger pole pieces in the specific case of the quarter pound could represent a wider sampling area of the strings, when toying with the Tillman model, in respect to standard thinner pole pieces.

It's interesting how the lower capacitance of this humbucker Precision bass type has to do with its design...and I remember that Fender did import this design also to some models of guitar later on, when he worked for G&L guitars.

[antigua]

If you use Tillman's comb filtering calculator and change the width from 0.18 to 0.25, you only see a mild fall off above 10kHz. The rule of thumb is, thinner window = higher frequency response.  There comes a point where the width causes any filtering above 5kHz, at which point it's irrelevant, and it seems that nearly all single coil pickups are the market are sufficiently narrow to where the filtering is above 5kHz, include single coil sized humbuckers. 

I think we might have to embrace the possibility that the larger magnet is more of a marketing device than something of technical merits. I think what really sets this pickup apart from the Fenders is the very high inductance. 

[ms]

Mar 8, 2017 1:38:24 GMT -5 antigua said:

These are a little dark for my tastes. They do well for distorted bass, but if you're into slap bass, they don't snap like vintage output pickups. I think it makes more sense to go active than to go for QP's, but if you're not a demanding tone connoisseur and don't want to deal with dead batteries, it's a viable option.

In another discussion, we heard the desire to put things learned in these measurements and discussions to use to make better pickups.  In particular, there was the tradeoff in pole piece materials between Alnico (low loss, but also low inductance) and steel (high loss and high inductance).  Then there are ferrite rods (usually known as beads, www.amidoncorp.com/fb-73-1801 ***) which give high inductance and very low loss.  They can be used to make higher Q pickup coils, and, although this can be useful for certain tradeoffs in guitar pickups, the application to a bass pickup seems obvious.  With the right design, you should be able to get significantly more "snap" with a passive system.   Something I will try when I get some time.

***This link does not work when you click on  it.  But if you copy/paste it (I need to start outside the link to get it to copy and then delete the extra characters after pasting), it does.