Do Different Pole Piece Shapes and Sizes Impact Tone?

[two fingers]

like the SUHR designed Jazz Bass pickups during his time at Fender.....did anyone ever compare the sound of his pickup designed (single pole per string) with the more traditional Fender dual pole per string?

I have owned a Suhr era Jazz Deluxe 5 and several other version of the J. The Suhr pickups (and preamp) were WAY too scooped for me. (Just personal preference) But surely (pun intended) his design had an affect on the tone of that era of J basses.

 

[Sean Sweeney]

Thanks for clearing so much of that up! I was thinking that actives were what you described, just some of them have such a unique sound. As I mentioned, the Jazz bass pickup gave me the idea originally... as I watched the guy charge the magnets... and basically my initial idea was to use this 7 pole vintage alnico single pickup for a 6 string strat... but alternating the poles and installing the pickup at a sharp angle, to defeat any dead spots. I found one cheap, so tried to do it, but the pickup had a short and no bass to it. It had SOME output, though and seemed to work as I thought. And I don't think the whole concept of push pull is that irrelevant, since if you have two pickups straddling a string on either side, the frequencies they have in common would be out of phase, at least the movement horizontally, and primarily bass frequencies... the same reason a push pull amp splits and inverts the phase. Considering rewinding that pickup I have just to see. Lol. Thanks for the info. I pictured it making a neck pickup better. Hopefully with a little more "quack", but if it's to work, it will need a pretty extreme angle and precise positioning... and solos on the neck pickup suffer slightly from some issues like bending notes away from the hot spots over the pole piece. Also I installed some "mu metal" sheets in my strat, under the pickups, with standard grounded foil shielding on the guard. Anyone ever experiment with singles such as early P-bsss pickups and mu- metal? I've never had issues with RF in clubs that were always problematic before. (Though I originally got it to eliminate RF on a turntable with a big motor).

 

[BlueTalon]

I was under the impression that the double pole jazz bass pickups have alternating north/south magnets

Another common design that uses both polarities in a single pickup is a split-coil Jazz pickup. These feature two smaller coils in line with each other stuffed into a normal jazz shell. Each coil senses two strings. The two coils typically have opposite magnetic polarities so they they are hum cancelling (when wired together with reversed wind directions as well). Split coil jazz pickups often have a dead zone right in the middle. If you put the design in a magnetic field simulator, you can see why - in that area between the two coils, the field lines are really strong down inside the pickup, but weak in that narrow swath up where the strings are. If you built a pickup with two poles per string and had the polarities of the two poles alternating, you'd basically be building a mini version of that dead zone directly in line with each string.

I love split-coil jazz pickups. I have three of them on my main bass (the one in my avatar). Perhaps it's because the Fender Super 55 pickup is an excellent design, or perhaps it's because it's impossible to bend a string into more than one dead zone at a time (unless they are very wide dead zones), but I personally have never had a problem with a dead zone with a split-coil jazz pickup.

That said, I think alternating polarity of the two string sensing magnets put the dead spot directly under the string, and that's probably just begging for problems. Which is not to say I wouldn't be interested in the results of someone wanted to try it.

 

[Sean Sweeney]

I see what you're saying and I've understood that the split pickup is better suited for bass. But maybe that's just a matter of scale? And, my answer to the dead spots is to angle the pickup, because the dead spot shrinks away to NIL as you angle it... and likely this was thoughtful of before my inspiration... but likely was tried as a prototype, and failed to yield a successful pickup... but maybe scale is the real issue... and how many prototypes do you try before you give up! Maybe two small 6 pole singles at symmetrical angles... all together making the same mass as one single PU.

I love split-coil jazz pickups. I have three of them on my main bass (the one in my avatar). Perhaps it's because the Fender Super 55 pickup is an excellent design, or perhaps it's because it's impossible to bend a string into more than one dead zone at a time (unless they are very wide dead zones), but I personally have never had a problem with a dead zone with a split-coil jazz pickup.

That said, I think alternating polarity of the two string sensing magnets put the dead spot directly under the string, and that's probably just begging for problems. Which is not to say I wouldn't be interested in the results of someone wanted to try it.

 

[Sean Sweeney]

I wonder how hard it would be to create a computer program that simulates all of these factors... if there already is one... and if not, it shouldn't be impossible to create specialized pickups for many things that were considered impractical.

 

[Sean Sweeney]

These guys!! Holy crap! It's like we're driving around in Model T"s with the keys to a spaceship... maybe... or maybe we spend tons of money and years... and come up with a pickup that has little fins on it. Essentially the same as all the others... but with FINS. lol
Magnets | INTEGRATED Engineering Software

 

[Passinwind]

I wonder if there is anything besides a magnetic pickup that could sense the movement of ferrous strings?

Are you familiar with the Lightwave technology, which has been around in one form or another since at least the mid-70s?

 

[A9X]

I was thinking that actives were what you described, just some of them have such a unique sound.

Why assume the electronics inside the pickup shell are flat? The designer may have added frequency response shaping on board for all any of us know.

 

[Bruce Johnson]

I see what you're saying and I've understood that the split pickup is better suited for bass. But maybe that's just a matter of scale? And, my answer to the dead spots is to angle the pickup, because the dead spot shrinks away to NIL as you angle it... and likely this was thoughtful of before my inspiration... but likely was tried as a prototype, and failed to yield a successful pickup... but maybe scale is the real issue... and how many prototypes do you try before you give up! Maybe two small 6 pole singles at symmetrical angles... all together making the same mass as one single PU.

If you are really interested in pickup design theory, we have a special thread tucked away over in Luthier's Corner. It's where us folks who design and build crazy custom pickups hang out and show off our wild ideas. Lots of detail discussions about shaping magnetic fields, building weird magnetic structures, etc. Come on over and join the discussions.

Magnets & Copper Wire: A Pickup Building Thread

 

[dwizum]

since if you have two pickups straddling a string on either side, the frequencies they have in common would be out of phase, at least the movement horizontally,

That's not true though. The two coils in a humbucker are opposite magnetic polarity but are also wired oppositely - the two opposites cancel each other and the signals are 100% in phase. I know the analogy seems attractive to you but it's not meaningful. (Sorry!)

solos on the neck pickup suffer slightly from some issues like bending notes away from the hot spots over the pole piece.

The easiest way to solve for that is to use a blade pickup. You can make it as wide as you want. Common pickup shapes allow for plenty more width than you'd ever actually need. The field is uniform, no hot spots or alignments to worry about. You can bend any string as far as you want in any direction. You can use any number of strings with any spacing, as long as the total string spread is narrower than the sensing range. It's easy to build a blade pickup and they can drop into standard routes, no special positioning, size, shape, or angle required. Problem solved, case closed.

my answer to the dead spots is to angle the pickup, because the dead spot shrinks away to NIL as you angle it...

See above. Also - it's worth pointing out that the dead spots in your alternating polarity design don't come at no cost - the field will be weaker everywhere in your design. You're "spending" a lot of the field's strength in the region directly between the poles, which is nowhere near the strings.

I don't want to come off as totally negative here - you should try your idea and let us know how it works. The way we learn new things is by trying them out, and sometimes an idea will work well despite the theory. Or you end up with a surprise benefit you weren't expecting. Or you can overcome the weaknesses in the design by compensating elsewhere (using much stronger magnets or something like that). And at worst, you learn something (which is a pretty good outcome). But ultimately, I do not think the solution you're proposing is the most direct way to solve the problem of dead spots when bending strings, if that's what you're after.

Also, come visit the thread Bruce linked!

 

[Sean Sweeney]

Why assume the electronics inside the pickup shell are flat? The designer may have added frequency response shaping on board for all any of us know.

 

[Sean Sweeney]

I wasn't assuming they were flat at all, I just thought that maybe they used a method apart from the normal magnets and wire, since none of the literature I've seen on them mention that. My strat has small preamps in the guitar that are in close proximity to the pickups they control, that have specific eq curves already in them. But I never considered my vintage singles "active" and every active single I've used was some one piece design with no pole pieces or anything you would see in a standard pickup, do it's not like they haven't tried to foster that belief, it would seem, IMO.

 

[A9X]

I just thought that maybe they used a method apart from the normal magnets and wire,

The Fishman Fluence are the only ones that I know of that don't use a variation of the traditional build techniques. They use stacked PCBs with copper traces on them in instead of normal windings. There are still magnets of course, and I gather from the mode switch there is tone shaping inherent in the internal electronics.

 

[BlueTalon]

The Fishman Fluence are the only ones that I know of that don't use a variation of the traditional build techniques. They use stacked PCBs with copper traces on them in instead of normal windings. There are still magnets of course, and I gather from the mode switch there is tone shaping inherent in the internal electronics.

There was a effort to produce pickups using liquid magnetic fluid, but apparently that project is either on the back burner or has been abandoned.

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ferrokings | Creators of the World's First "Liquid Pickups™" (wordpress.com)

 

[dwizum]

And let's not forget Lace Alumintones if we're doing a roundup of weird pickups that don't have traditional coils!

every active single I've used was some one piece design with no pole pieces or anything you would see in a standard pickup, do it's not like they haven't tried to foster that belief, it would seem, IMO

I think this is more about taking a modern approach to pickup making than it is about trying to obscure the details. Look at a PAF style humbucker - there are a bunch of pieces that are really only there to hold the thing together or space parts correctly, etc. It looks and feels like exactly what it is - a fairly crude "prototype" from 70 years ago. Pickup makers have had a lot of time since then to focus on efficiency and streamlining. No need to do any of that special hardware or assembly if you're just casting the thing solid. You can wind the coil (on a blade in most cases - another streamlining/efficiency step), solder up the preamp, connect it to the coil and and wiring terminals, and then just drop it in a mold.