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Post by cynical1 on Aug 8, 2016 3:27:34 GMT -5
So, I'm working on the details for the rehab of the old Peavey Foundation and discovered a little gotcha. Because the p-bass pickup is being mounted significantly closer to the neck, the footprint of the template is too wide to allow the pickup poles to naturally line up with the four strings. No big deal, just block half the template and route it in two setups. Now, since I've got to do two setups anyway...I started thinking that as I'm already using the reversed location on the E-A side to tighten up the extreme low end a bit...what would happen if I mounted the E-A side further from the neck than typical. Here's a picture to make is easier to follow my line of thought:  NOT TO SCALE, but you get the ideaAs you can see, the existing Middle pickup, (used to be the neck, but that's another post) bisects the 30th fret node almost dead center. The GREEN pickups are what would be a typical reverse p-bass install with the pair split at the 25th fret. The D-G side hits the 24th node almost dead center, but the E-A side just misses the 26th fret due to the narrowing distance between the fret\node positions. What I'm curious about is what would happen if I moved the E-A side further from the neck. The PINK pickup is the E-A moved to the 27th node and the YELLOW is the E-A moved to the 28th node. I used to have a link to an interactive applet that would let you position pickups and see a graph of what you hit and what you missed in different locations. If anyone remembers that site, or still has the link, please feel free to post it in here. My Google-Fu appears to be weak on this one... This post is really for general discussion, opinions or input on what you think...or preferably know...about screwing with a p-bass pickup like this. No pickups or bass bodies have been harmed in this scenario...yet... Happy Trails Cynical One |
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Post by newey on Aug 8, 2016 5:50:11 GMT -5
Well, for starters, I assume the cable between the two halves is long enough to allow this to happen? It can of course be dismembered and lengthened, but better if you don't have to do so.
Given your stated goal of "tightening" the low end, it would make sense to move it closer to the bridge. But of course once you rout it out, you're stuck with the positioning. And, an app isn't going to tell you much, even if we knew where to find it. The nuances of this are something you have to hear, I'm thinking.
So, given that when you rout it, it has to be right, I'm thinking test mule. Buy the cheapest P-bass clone (say, $50) you can find online or at a pawnshop, do a bathtub rout at the neck big enough to cover all those fret positions, and then move the E-A side around to suit your ears. If the mule is halfway playable, it's a bonus and you can dress it up with a piece of pickguard and keep it for a spare.
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Post by sumgai on Aug 8, 2016 11:10:50 GMT -5
Here's the link to the aforementioned site, wherein one can enter all kinds of info, and watch the graph to see the results. And it is indeed interactive:
www.till.com/articles/PickupResponseDemo/index.html
My thoughts are, if one were to play open-string harmonics on a bass (or a guitar, for that matter), then anything placed under the 24th fret will not sound out. IOW, another pickup will have to be in play in order to hear those harmonics. Placing the pickup anywhere else within the picking zone will work (unless one gets rowdy and tries to put a pup under the 36th fret location). Hence, it may make sense to move both pup halves forward a bit, depending on one's playing style, current or anticipated.
As to the "once done, permanent is" sentiment, why not indeed just do a bathtub route and be done with it. Plastic pickguards can be hammered out as needed, both during and after the "go crazy" portion of this experiment. Beats the cost of yet another body, amiright.
Spare axe, indeed. newey, c1 has a whole man-cave full of these things... see gumbo's signature!
HTH
sumgai
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Post by JohnH on Aug 8, 2016 16:20:36 GMT -5
I dont reckon these node locations are really all that significant. They only apply to open strings, and once you fret a string, all those node points are off.
Also, on an open string, the 24th node does have some significance as a pickup position (it negates the 4th harmonic) since its 1/4 the string length from the bridge. But 25th upwards have no significance, they are not muliples of string harmonics. Instead, the corresponding interesting points would be 1/5, 1/6, 1/7 etc of string length, measured from tbe bridge. But again, only for open strings.
In splitting the P Bass PU, the low side is moving closer to the middle PU. Will this cause concern with it starting to sound dissapointingly similar to it? Also, will there be a significant tonal change between the upper and lower string pairs using the seperated pickup, and is that good or bad?
BTW I built the Tillman theory as in his app into GuitarFreak, so if there are particular plots that would help to explore this Id be happy to make them. Can overlay several on one chart, and can show a single string or an envelope of several. Scale length, plucking, fretting and PU positions can all be entered numerically.
The Tillman app, with its comb filters, is an envelope of all the frequencies that a particular string and PU position can provide. But at a given moment, you only get the particular discreet frequencies that are the harmonics of the string based on fretting position. Also, upper harmonics have a smaller amplitude than lower ones.
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Post by cynical1 on Aug 8, 2016 17:31:10 GMT -5
Well, for starters, I assume the cable between the two halves is long enough to allow this to happen? These pickups are NOS and were never installed. I have more wire then sense. Which is what lead me to this momentary over-complication in the project. That, and the "what if" factor. Therein lies the rub. I toyed with the idea of making the E-A side moveable, but there isn't a lot of room to play with to make the differences worthy of the effort involved in making it fit between the D-G half and the existing middle pickup route. Agreed, to an extent. Remember, I live in EmpiricalLand as I lack any formal education on most of this stuff. Gerald Ford was in office when I took my last Physics class. For me, the charts and apps are really there to tell me where the bear traps are. I have a theory that most of our cell phone issues on this this hill are related, in some measure, to the quantity of wound coils existing in close proximity to each other... As sumgai pointed out, about the last thing I need around here is another bass\guitar laying around. My new bride is exceptionally agreeable to my dirty little habit. I'm sure one day I'll push the envelope too far. I'm just leery of doing it today or tomorrow... As I said, I started this post out of curiosity hoping to learn something along the way. There is no real information out there on putting a p-bass pickup this close to the neck. Aside from Gibson and Rickenbacker, no one else really made a habit of locating bass pickups this close to the neck on a solid body bass. I did find a few images that make it easier for me to narrow down how stupid I want to get with this.  Two things struck me with this one. First, it actually was for a bass, and secondly, it points to exactly what sumgai said in his post. The 24th fret\node is a dead zone for harmonics. This does seem to dictate a change in the location of the D-G side up to the 25th fret\node. Originally I was looking for the "magic node". Now it seems that avoiding the harmonic dead zone is more to the point. I'm going to have to take a closer look at how much real estate I have to work with in moving everything South.  This one I found interesting because it give you some comparison between where existing "standard" pickup positions live in relation to what's going on with the string on a bass. Thanks. I was all over that site and couldn't find it. Great little tool...and it doesn't require you to do the heavy lifting math, either...
After reading on this more I agree. As I said, I need to get the metal rules out and see just how much space I have to work with. It certainly looks like the D-G side has to move South. I have to double check on how much room I have left to fit the E-A side and how much extra real estate I have to consider moving it even further South than normal.
I do have one question. Since the Peavey pickups are single coil blades with a big ceramic magnet, am I going to reach a point of diminishing returns if I put the p-bass E-A half too close to it? Does the placement of the Schaller p-bass N or S coil (They are literally two different pickups with two wires coming out of each one) make a difference going neck to the Peavey pickup?
I thought about working out a permanent slide for the E-A side pickup, but for the little bit of room you could move it there didn't seem to be much return on that investment.
And she has no idea about the two bodies and three necks in a box in the garage... Happy Trails Cynical One |
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Post by b4nj0 on Aug 8, 2016 17:59:57 GMT -5
"And she has no idea about the two bodies and three necks in a box in the garage..."
Mine has evolved sufficiently to identify certain obvious types and thus any new (or different) guitars.
But she does not (yet) recognise one black case from any other... She hasn't tumbled the Tacoma built Guild 512 12 string yet for that reason! (She doesn't read this forum either!)
Regarding the node position and lack of output; I seem to recall a thread (on here was it?) where someone placed a treble pick up right next to the bridge saddles (was it even behind the bridge?- CRS!) and I convinced myself that the string vibration would be so tiny that it would not cross the magnetic field sufficiently (or at all) to produce any appreciable output- especially given that we adjust pick up heights depending on the distance from the bridge saddles to maintain an even output, but it turned out that I was completelywrong. I would have put money on it too. That's the trouble with theory. The beater with a bath tub rout is the way I'd go too C1.
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Post by sumgai on Aug 8, 2016 19:10:48 GMT -5
And she has no idea about the two bodies and three necks in a box in the garage...
So that's why you made sure I didn't go too near that wall, and kept distracting me by pointing out various bits of old wood around other parts of the carriage house. I get it now! 
All I know is, some players like to strike open-string harmonics, often in strength, for effect. Fretting a guitar string and executing a so-called pinch harmonic is not real difficult for those who practice it, but it is easier on the smaller-diameter strings. I can imagine that doing such on a bass (particularly without a pick!) would be difficult, probably more so than herding cats. 
A new thread aboonds......
sumgai
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Post by cynical1 on Aug 8, 2016 20:17:10 GMT -5
You can do pinch harmonics on a bass...I've done it unintentionally a few times... It's more like harmonics when you're tuning. I pulled out the metal rule, grabbed some blue masking tape and laid out where the nodes are between the end of the neck and the pickup ring on the middle pickup. As John points out, moving the E-A side of the p-bass pickup closer to the bridge puts it so close to the existing middle pickup as to ask "why bother?"... Using this chart as guide... ...and assuming I want to avoid the 24th fret\node completely...after physically moving the pickups within the 23rd and 27th fret\node...it seems that the best place for them is with the D-G side at the 23rd fret\node and the E-A side at the 25th fret\node. This seems to split everything nicely off the 24th fret convergence and they line up as you'd expect a p-bass pickup to line up. So, John, if you're still offering, would you be kind enough to chart this out, just for reference? I'd be curious to hear what the GuitarFreak Oracle has to say. DETAILS: SCALE: 34" TUNING: EADG - .105 - .045 flatwound strings D-G String Centerline: @23rd fret\node - 24.995"\63.487cm from nut - 7.995"\20.307cm from 12th fret\node E-A String Centerline: @25th fret\node - 25.977"\66.032cm from nut - 8.977"\22.801cm from 12th fret\node Let me know if you need anything else, John. As an aside, all the electronics are here. After the wood butchery has completed it shouldn't be long to get it all wired up and find out just what kind of creature crawls from the swamp... Happy Trails - Cynical One |
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Post by JohnH on Aug 10, 2016 8:08:18 GMT -5
Here is something: This plot is an envelope of the tones available from each separate string, as modulated by the pickup halves being at those two fret positions, 23rd and 25th, for the relevant string pairs. Overall, it looks quite balanced to me.  You don't get all those frequencies at once, but rather, each string will produce a series of discreet frequencies under its own line. Here is just the E string, with the envelope, and also the harmonics generated by plucking, in this case, fretted at the first fret:  I showed that, because it demonstrates that with certain frets, certain harmonics disappear into the notches in the response. In this case, the 4th harmonic as gone, because the EA pickup is at 25th fret, being 24 frets = 2 octaves above where the string is fretted at 1. If you fretted at the 13th the 2nd harmonic would go. Also if at the 6th fret, the 3rd harmonic is taken out. This may not be a problem at all, but it is a consequence of picking whole fret numbers on which to place pickups. |
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Post by cynical1 on Aug 10, 2016 13:15:14 GMT -5
John -
First off, I want to thank you for running these graphs for me. I've been playing with GuitarFreak working to get my head wrapped around what it can do. It's a lot like learning Chinese by standing in the middle of a Beijing intersection at rush hour. Plenty of input thrown your way, minimal understanding to process it intelligibly...
I've been reversing Leo's position of the E-A & D-G side of a P-Bass pickup for years. It always sounded more even to me. This graph seems to detail what my ears seem to have heard. Granted, they're not in their typical "cast in stone" position, but I'd be curious what the chart would read if the positions were in their expected "Leo" orientation?
I appreciate certain harmonics and fundamentals will vary based on fretted position. Most every instrument has dead spots, or areas that just sound sweeter somewhere on the neck. The bass has these now.
Ask most bass players how they vary the tone on their bass and you'll find they use the individual volume controls to shape the sound heavy or light...and all points in between. Look at most basses and you'll find a conspicuous absence of pickup switches versus guitars. That said, in all likelihood, all three pickups will be engaged to some degree when playing this bass. Some just enough to fluff up the low end or help refine the high end, but I'm relatively confident that anything I may miss with all three engaged will be minimal.
The more I look at this bass rehab the more I like it. I'm already scouring eBay for an ABY switch and Craigslist for another 2 X 10 or 4 x 10 cabinet. Thinking about what I can do with two outputs on this bass makes me more anxious to get it done. I'm still working out how I'm going to sneak the extra cabinet in, though...
This set off the lightbulb the minute I read it...and begs the next question: How far off a node should a pickup be located to minimize these cancellations? By moving off of a specific node to center a pickup, will that introduce other variables less desirable that placing the pickup centerline directly on the node? OK, so that was two questions...
A part of me also wonders how these "precise" locations actually measure up when you consider the inherent nature of the inefficiencies and compromises incorporated into the thing we call a guitar or bass neck. I can still hear the laugh of the tech behind the counter after a 13 year old Cynical One explained how his guitar was broken because it wouldn't intonate cleanly all the way up the neck...
I hope you guys are having as much fun with this theoretical crap as I am...
Happy Trails
Cynical One
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Post by JohnH on Aug 10, 2016 15:28:58 GMT -5
Yes I also think this is interesting, and for me its helping me develop the ways my spreadsheet can work. So, this harmonic cancellation effect, which can occur anytime you pick a pickup centreline that is on a theoretical fret position. If you do that, there may be real frets that are x2, x3 or x4 further away from the bridge (ie 12, 19 or 24 frets lower in tone), at which time the 3nd, 3rd or 4th harmonic will cancel out. If this is actually significant and if it is really a problem, then the best that can be done to dodge it is if the pickup is centred halfway between fret positions, eg like fret 24.5 or 25.5 instead of 25. The most dramatic effect might be if it was the 2nd harmonic that was lost. Here is a plot, E string fretted at 13, an octave below the pickup at 25, so 2nd harmonic has been eaten by the black hole in the response:  See also that the 4th harmonic has also been sucked into the void. Here it is with the PU shifted to fret 24.5 (209.7mm from the bridge):  The 2nd harmonic is depleted, but still just about there to be heard. The 4th is also back into the mix. BTW The graph of the blue curve appears to not notch so deeply. That is just because the calcs in the spreadsheet only occur at chromatic intervals, where the main string frequencies exist. There is theoretically a deep notch, 1/2 semitone away from that 2nd harmonic. |
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Post by cynical1 on Aug 10, 2016 17:25:47 GMT -5
This is, indeed, very interesting. It makes you begin to ponder all sorts of questions. I really need to learn how to use your tool better. Just screwing around after reading your last post I started thinking about slanting the p-bass pickups. Keep in mind these are not precise measurements, as I just used a wooden ruler and a ball point pen to mark this out from the 12th fret, but:  Just placing the pickups under the strings and pushing the pair as far South as they'd go, in a very non-precise way, you can see where you still keep two pole on each string, mostly, and dodge an exact node on 6 of the 8 poles. With some more time and work, I'm guessing you could dodge a node on all 8. This does put the pickup much closer to the new middle pickup, thereby negating a portion of the primary design consideration. I do have to wonder how much of the thin low end on this bass was due to the OOP wiring on the Super Ferrite pickups to make them humbucking. I know this p-bass pickup will thunder pretty good, even with it being significantly closer to the bridge, as it's about 20% hotter than a traditional Fender p-bass pickup. Hmmm...weighing all the trade-offs... Happy Trails Cynical One |
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Post by newey on Aug 11, 2016 5:15:55 GMT -5
And, particularly on a bass neck, where even the existence of frets isn't necessarily a "given" . . .
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Post by sumgai on Aug 11, 2016 10:36:47 GMT -5
newey, are you intentionally trying to give gumbo a reason to throw water on this party?  |
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Post by cynical1 on Aug 13, 2016 16:27:45 GMT -5
newey, are you intentionally trying to give gumbo a reason to throw water on this party? Let me give the ol' gumbo a leg up on this. Tutorial On Slanting A Pickup:
 No harmonics were cancelled in the derailing of this thread... HTC1 |
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