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Split J pickup anyone? Why not?

...frankly I don't know if my bridge Bartolini Jazz pickup is a multiple bobbins prototype or a strange single coil or a stacked... thus the curiosity. I only remember that when it arrived, looking at its bottom you could see the epoxy (epoxy, am I right?) and several wires sort of mixed with the epoxy. Only two wires came out and I used those to finish my bass. I should remove the strings and unmount it, to check it carefully. Never seen another pickup like that in my life. And I exclude that anybody made something strange to it: it seemed completely untouched, stock... any Bartolini expert?

For the curious ones, why did I buy a pickup like that, without much info, on impulse? Because I already had a proper Bartolini J neck pickup; on the local Mecatinomusicale I checked and there was this bridge Bartolini and for only a few euro, so I just bought it unseen.
 
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If I get your idea correctly, then I think my bud / builder friend just did this in one of his builds and I'm tempted to go the same way on my next one. This is two Avedission custom singles, wired together with a 3-way toggle.

305668009_497858895041542_5069625792668424631_n.jpg
 
26861335[/URL], member: 309154"]That’s all a little weirdly different from what I’ve heard about wiring things parallel and series, and what people say about split coils and the like. I haven’t experimented with different pickups and tried experimental rewiring things etc. to know for sure myself.

I studied Acoustical Physics - specifically the Physics of musical instruments. I have a degree in this stuff. There are a lot of things people pass around that have no basis in fact, or that make conclusions based on false premises.

For example, a humbucker in a guitar usually means it’s going to have less high frequencies. Why is that? Is it because it cancels hum? No. Is it because it has two coils? No. Then why?

It has less high frequencies for two reasons:

1) Guitar humbuckers have pole pieces at 2 locations on each string. Just like having two pickups on a jazz bass, that means it’s going to have a dip somewhere. Because the two locations are fairly close, that dip is in the high frequencies. By the way, the frequency of the dip (this also applies to the jazz bass) is different on every string - it’s a wavelength filter. So, a dip in the treble = less highs.

2) Most guitar humbuckers have more inductance than the typical single coil pickup. This changes the peak frequency (lowers it), and where the roll off begins. So, more inductance = less highs.

Now, we move to inline jazz hum cancelling pickups. There are a lot of die hard single coil folks that “know” they don’t sound like a single coil - they’re humbuckers, and we know that means less treble - right?

Here’s the thing - most in line hum cancelling jazz pickups don’t have more inductance than the single coils - they’re wound to the same inductance. Yes, there are 2 coils, but each coil has half the magnetic material - the net result is the same inductance. By changing the windings, you can make a hum canceller with less inductance ( a Dimarzio Area J fits this description) - it has MORE high frequencies than most single coils. If you did a good blind A/B test, and there was no hum in either bass, the bass with Area J’s would probably be mistaken for the single coil one. You can also achieve this by wiring the coils in a hum canceller in parallel - indeed, that usually gives you too much high end, but that can be tuned to whatever you want with a loading capacitor.

In line jazz hum cancellers also don’t listen to the string at 2 points - their magnetic circuit geometry is the same as a single coil, albeit with a magnet polarity flip for half the strings.

So, we have a lot of folks that “know” that they don’t sound like single coils, based on reasons that… don’t apply to the situation. Because there are so many people that think this, they keep repeating the same myth, and the myth lives on. When you look at the Physics of what’s going on, however, there is nothing to the myth - it’s not based on any relevant facts.
 
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1) Guitar humbuckers have pole pieces at 2 locations on each string. Just like having two pickups on a jazz bass, that means it’s going to have a dip somewhere. Because the two locations are fairly close, that dip is in the high frequencies. By the way, the frequency of the dip (this also applies to the jazz bass) is different on every string - it’s a wavelength filter. So, a dip in the treble = less highs.

Can you explain why having pole pieces at 2 locations means there will be a dip somewhere? Or any idea where I can read about this in depth? Not scared of math. Also not at all challenging you, just genuinely interested and totally new to the world of sound electronics.
 
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series vs parallel has nothing to do with the scoop - that is all due to combining two pickups at different places.
Sorry to bring the discussion back off topic from split J pickups. Does series wiring of the coils (in conventional humbuckers or between singlecoil pickups in a JJ configuration) change the position of the scoop, compared to parallel? or perchance its width/shape? I haven't found much about the topic (and I have zero theory to guide me to an answer). Thanks in advance.
 
When you say “honest question” it comes off as pissy and argumentative.
I actually made the point of saying it because I thought the question itself might have sounded argumentative without it. It apparently had the opposite effect of what was intended. Sorry about that.
 
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26861868[/URL], member: 392539"]Can you explain why having pole pieces at 2 locations means there will be a dip somewhere? Or any idea where I can read about this in depth? Not scared of math. Also not at all challenging you, just genuinely interested and totally new to the world of sound electronics.

The strings on on your bass (or guitar) vibrate at many frequencies - the fundamental and a bunch of overtones/harmonics. The fundamental's wavelength is twice the length of the string from the fret you're fretting (or the nut for an open string). The first harmonic (an octave up) has a wavelength equal to the vibrating string length - at any given time, half of the string is going one way, the other half is going the opposite direction.

As you go to higher harmonics, the wavelengths shorten. At a high enough frequency (this depends on the string’s tuning), the wavelength is twice the distance between the two points where your pickup (or pickups) are “ listening” to the string. At that frequency, one of those points is going one way, the other is moving the opposite direction. The sun in the output therefore goes to zero - it’s a dip.

All pickup locations have dips - even a single pickup ends up listening to the wave traveling towards the bridge AND the wave reflecting off of it. A P bass has a simple comb filter for each string - every few hundred Hertz, you have a dip. With multiple pickups, you get a different character to the dips - there are a few frequencies where multiple dips pile up, and the dip is more audible. This we call a “scoop”. See next post.
 
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Here are a couple of curves to see the effect of comb filtering - the green curve is the comb filter of a P pickup position (we're looking at an A string here (there is also electrical stuff going on, but I've left that out for clarity)), the other is for J position (2 pickups - 60's spacing in this case). Note that the Green curve (the P) always returns to 0 dB between dips, but the red curve does not, and there are "wide dips" (aka scoops - they're frequencies where the spacing between pickups and from the bridge result in multiple dips in the same frequency range) where there is less energy over a wider range than what you have in the P. The J also has less low end - the bridge pickup lacks low end (it's listening close to the bridge, where the string doesn't move much), and when you listen to both pickups, they load each other, and you get the average of the two responses, which...has less low end.

So, a P is more.....even. A J is more..."interesting" - acoustic instruments have complicated response curves, due to different kinds of modes adding in complicate ways. A J is one step towards that kind of response.

Comb filtering - P vs J.jpg
 
Hey, that's awesome. Helps contextualize a LOT of conversations on talkbass tbh. Thanks for taking the time and going the extra mile with the visual aid. Really appreciated.

You're welcome. The real time investment was in setting up the simulation - I did that to understand myself what was going on in detail. Luckily, a few decades doing development work on pro audio stuff means I have the understanding and the tools to do this stuff - otherwise, this would have been a much bigger endeavor.
 
26862288[/URL], member: 392539"]Not sure how accurate this simulation I found just googling is, but it seems to capture the gist of what you're saying and is fun to play around with in any case

That simulation looks right - for a humbucker with multiple pole piece locations on each string, those big wide dips in the treble show up.

I have simulations that include the electrical response as well, which that one ignores (as I did on what I posted previously).
 
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@micguy :
(only in case you missed my question in post #85 above, here below reproduced; in case you hadn't missed it, please by all means disregard)

Does series wiring of the coils (in conventional humbuckers or between singlecoil pickups in a JJ configuration) change the position of the scoop, compared to parallel? or perchance its width/shape? I haven't found much about the topic (and I have zero theory to guide me to an answer). Thanks in advance.
 
The DiMarzio Model J is one of the darker versions of a split coil J. It's not designed to try to sound like a normal J. It's middy and wooly. For a normal Jazz tone without noise you want the Ultra Jazz or the Area J, if you're shopping DiMarzio.
I bought a used set from Daddy's Junky Music back in the '90's. They were in a fretless for a while, but didn't deliver the desired tone. Haven't tried other models. Thanks for the info.
 
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26863051[/URL], member: 253901"]

Does series wiring of the coils (in conventional humbuckers or between singlecoil pickups in a JJ configuration) change the position of the scoop, compared to parallel? or perchance its width/shape? I haven't found much about the topic (and I have zero theory to guide me to an answer). Thanks in advance.

Not at all. It changes the electrical loading, but the scoop arises strictly from the pickup positions.

Changing the electrical loading ( what series vs parallel does) changes the upper mid peak, and the treble above that - that may distract your attention from the scoop, but the scoop doesn’t change one bit.
 
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I bought a used set from Daddy's Junky Music back in the '90's. They were in a fretless for a while, but didn't deliver the desired tone. Haven't tried other models. Thanks for the info.

If you wire them in parallel (each pickup), your opinion would likely change - they're very different wired that way. In series, they're "P-ish", and in parallel, they have much more of the J vibe - bright enough so that you may want to back them off a bit with a loading capacitor. The Area J's are a different animal altogether - those in series are "more J" than a single coil J.
 
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Not at all. It changes the electrical loading, but the scoop arises strictly from the pickup positions.

Changing the electrical loading ( what series vs parallel does) changes the upper mid peak, and the treble above that - that may distract your attention from the scoop, but the scoop doesn’t change one bit.
Oh that’s odd. I’d heard the parallel wiring creates the scoop somehow, phase cancellation, interference or something. It seems to make sense, especially given people report the scoop apparently going away with rewiring a Jazz to series. But it doesn’t explain why a Starfire 2 bass seems not to have the J scoop even though it has two single coils wired (probably) parallel. Starfire 2 with both pickups just sounds like a straight blend of the two but a bit “softer,” which I’ve wondered about.

Makes sense that wiring in series would “get rid of the scoop” not by restoring the mids but shaving off the high end and increasing volume.

Related, here is a Starfire 1, it has a split coils that seems can be switched parallel or series. He compares the parallel and series mode at about 6:20. Series is a bit darker, more mids, but maybe not louder; parallel is brighter.