Is there a difference in sound between stack coils for a strat and those rectangular humbuckers a la Gibson.
Since they are both humbuckers. what makes them different/
I am just trying to learn these things.
Ronald

Because a stack coil has one coil on top of the other, they both sense the exact same portion of the strings. A regular humbucker has the coils side by side (one a little closer to the bridge, the other a little closer to the neck), so they sense different portions of the strings. The harmonics/overtones vary along the length of the strings so side by side coils emphasize some harmonics while partially cancelling others. That gives a "fatter" "thicker" tone than sensing just a single narrow portion of the strings which gives a "clearer" "crisper" tone.

There's a large variety of side by side humbuckers. There are full size ones, mini ones (Firebird, LP Deluxe, Rickenbackers), and single-coil sized ones (Duncan Little'59, JB Jr, DiMarzio Fast Track, Bardens). The full size ones tend to be the darkest, fattest sounding, the single-coil sized ones tend to be the brightest, most "focused" sounding, with the mini's somewhere in between. (Fenderphiles often call Strat/Tele single-coil sized ones "minis" but that's sloppy terminology.)

There are also a variety of stacked coils. Besides Strat & Tele sized stacks, there are P90 sized stacks, and again the P90 ones sound a bit darker and "bigger" because they're physically broader and sense a larger portion of the strings.

Same with true single-coils. Jazzmasters and P90s have a bigger fatter sound than Tele & Strat single-coils.

There are other factors at play too -- output, inductance, the shape of the magnetic fields. Duncan's site has literally hundreds of pages explaining the subleties and nuances of pickups. Bill Lawrence's and Kinman's sites also have lots of info.

Excellent dissertation, SS.

I'd add only that many of the stacked-style humbuckers are intended to mimic a true single-coil pickup in tone and timbre while simultaneously eliminating the spurious noise typical of the single-coil design. Some examples of these are Fender's Vintage Noiseless, Lace Sensors, and the SCN's, plus Dimarzio's "Virtual Vintage" and "Area" series, and the Kinman's. The stacked-coil humbuckers require only a single-coil body rout, which spares one the aggravation of irreversibly altering a guitar and, in the case of a Strat or Tele, preserves the instrument's visual vibe.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY