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How to interpret resonance freq.

5/27/2006 6:27 PM
How to interpret resonance freq.
Just curious. Suppose I have two pickups with the same DCR and same magnets. One has a resonant freq. of 5khz and the other is 6.5khz. What possible observations can I make about the pups construction? As in, wire gauge, tightness of winds, etc.?  
5/30/2006 4:00 PM
There's alot of discussion as to HOW you get that number, but disregarding that you can say the higher is going to be "brighter" and have it's "volume" focused at that frequency. Now, if you use a "standardized" testing procedure and you have a good idea of what a pickup of that type with a peak at 5khz is, then you can deduce what a variance from that will sound like...more experience more accurate deductions... Also important is the taper of the peak. Does it have a narrow frequency response with a strong peak, or a flatter frequency response with the peak just being somewhat higher...
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5/30/2006 7:54 PM

Thanks for the info SK. I hadn't even considered the resonance "curve". Part of what I'm trying to speculate on, in a very roundabout way, is whether or not two pickups, from the same manufacturer, with equal DCR but different magnets, might in fact be the same pup. But, I realize, there may be many other factors involved.
6/1/2006 6:30 PM

* One possibility is the wire gauge is thinner for the higher res pickup.  
* Another is that the coil of the lower res pickup might have a bit of a bulge in the coil rather than a straight up and down wall, or that for some other reason the lower res pickup just has a wider coil.  
* Still another possibility is that the lower res pickup might also have double-build wire instead of single (thicker insulation).  
* The higher res pickup might be wound tighter which would result in a more narrow coil.  
* The wind pattern of the higher res might have a very shallow pitch (angle of wire to bobbin) which would make the turns much closer together and increase coil capacitance. (This might also result in a more narrow coil)...  
*...while the lower res might have a very scattered wind.  
* The lower res pickup (in the case of Strats and Teles) might have a steel baseplate, which is pretty easy to tell, but I thought I'd throw this one in there anyway.  
* In the case of humbuckers, the lower res pickup might have shorter polepieces, thus concentrating the magnetic field more on the strings rather than drawing some of it below the baseplate and diluting it.  
* In the case of a particularly dark-sounding pickup, if it is potted, it may have been left in the wax pot a little too long.  
And those are just a few of the possibilities...
6/2/2006 5:34 PM

Thanks Zhangliqun. Great info. I was hoping you'ld see this.
6/2/2006 6:28 PM

Is this Artie from the Duncan Forum?  
Thought of a few more:  
* Bobbin size/height. Humbucker bobbins aren't always the same height, even from the same manufacturer. Guitar Jones sells 49.2mm spaced bobbins that are about the thickness of a bobbin flange taller than their 50mm space bobbins. I can get 5.3k of #42 wire on those easily whereas I'm pushing it at 4.7k no the 50mm's. Point being that an 8k humbucker made on the 49.2 bobbins will probably sound thinner than 8k on the 50mm bobbins because the coil will be more narrow.  
* Bobbin size/height, part 2: Strat and Tele bobbins are made by gluing the rod magnets to two separate pieces of flatwork. This allows you to play with the height of the bobbin, something I do a lot with my Strat and Tele models when I want to get a little more wire on the bobbin than I could normally. You can also get longer rod magnets to expand those possibilities.  
* Pole piece thickness: I've found that the larger heads on the Gibson pole pieces give a beefier tone than the poles with the smaller Duncan-size heads. This also applies to rod magnets, up to a point -- if they're a little thicker, the magnetic field is wider and you'll get a little more beef. But I theorize that if they're too thick (like 0.25" rod mags on the Quarter Pounder) the coil becomes more narrow on each side and starts to cancel out some of that beef. Not 100% sure about that though. I've ordered up some 0.205" A2, A3, and A5 rod mags for further R&D on this. (Typical for Strats and Teles is 0.187" to 0.195".)  
* Pole piece spacing: This one should be pretty obvious. It will sound a little thinner if the poles aren't lining up well with the strings.  
* F-space bobbins: This is purely theoretical at this point because I haven't wound identical pickups on normal spaced and F-spaced bobbins, but I would think the F-space version might sound a little thinner because F-space bobbins are slightly longer, which would make for a slightly narrower coil at the same DCR -- although if you use the same turn count (as I assume most winders do), it might be the same or even slightly beefier.  
IN OTHER WORDS, there's a lot about coil geometry that can give a pickup a different res peak even with the same DCR or same number of turns.
6/2/2006 8:49 PM

>>Is this Artie from the Duncan Forum?  
Yup. ;-)  
If Ampage had a "vault", this would belong there. More good info. Thanks again.
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