Electromagnetic Pickups and Solidbody Guitars

[Stratman76]

Once again, I'm seeking the truth and there is some converse information being projected out there in net land.

Electromagnetic pickups are receiving string vibration information within their magnetic field. How is wood resonance part of the equation? I read a purely physics-based answer to this that stated wood on a solidbody had the effect of simply dampening string vibration and that different woods simply have different dampening (vibration reduction) characteristics. The "science" here stated wood resonance was not part of what electromagetic pickups actually "pickup" in a solidbody guitar. Is this true?

Are there any trusted information sources out there to refer to on this subject?

[David Collins]

The material the pickup is anchored to certainly effects the tone directly, as since the wood is vibrating and the pickup is screwed to it, it will be vibrating as well. While it may seem at first glance that there would not be enough vibration in the body to make a difference, it really doesn't take much movement at all to create or influence a signal.

Two examples in acoustic guitars. One is Taylor's Expression system, which uses two coils with suspended magnets, where there is little doubt the coils vibrate enough to generate a signal. The other is the Baggs M1, where the fact that the secondary coil is cushion mounted, or somewhat "floating" creates a very notable difference in tone compared to if it were mounted solid to the housing.

On solidbody guitars the wood movement is certainly less than an acoustic or hollow body, but it's still there and certainly does move. The motion of the strings of course generates the signal, but the key point is that it is motion relative to the pickups. It may seem the difference between something like a body mount and a pickguard mount may be so slight as to be trivial, but certainly can make a difference in the timbre.

The most drastic example I've ever seen was in an aluminum neck through guitar (Travis Bean / Veleno style) I had in a year or so ago. From the headstock to the bridge was machined of solid aluminum, with a wood body screwed on around it. The two humbuckers were screwed hard down to the aluminum frame - no springs, foam, or anything. The customer was unhappy with how bright it was, and that it would squeal like a loose coil too easily at high volumes, but any swell or warm kind of feedback was impossible. I machined clearance for the pickups to mount them floating on tubing, foam, I tried all kinds of variations, each making a distinct difference. I finally ended up making brass brackets screwed to the wood body, and bent over to mount the pickups to.

Going from hard mount to cushioned mount on the aluminum made a noticeable difference in tone, and eliminated almost all of the squeal. With the change to brackets mounted to the wood though, it became a totally different instrument. No more squeal, much warmer tone, wonderful mid range feedback swells. I have to admit that I never expected to find difference to the extent that I heard, but it was inarguable night and day.

Now that is an extreme example, but the same mechanics follow through to a lesser degree with more subtle changes. Springs vs. tubing, pickguard (that big diaphragm on the face of your guitar) resting on a traditional Strat route vs. a swimming pool route, Tele neck pickup screwed to the body vs. a pickguard mount. Some differences may be so small as to make little to no difference, but others can certainly play a noticeable role in shaping the tone.

[Stratman76]

Thanks for the post, David. As always, you provide some great information and I appreciate it! What I understand you saying is that pickups will react to ("pick up") any vibration and certainly wood is part of that. Would this be a vibration that essentially "shakes/vibrates" the pickup as opposed to being part what the pickup is receiving through it's magnetic (string-reading) field? If so, could this extraneous vibration be affecting the properties of the pickups' magnetic field?

Your experience with the aluminum/wood flanked guitar sounds like it could have been a microphonic condition created by the direct metal contact with the aluminum? Even the mount to metal squealing effect you still experienced makes me wonder about typical Strat pup mounts. Do you find a big difference in using springs vs. tubing in mounting Strat singles? Have you tried a wood pickguard vs. conventional plastic?

[Dana Olsen]

Originally Posted by David Collins

Now that is an extreme example, but the same mechanics follow through to a lesser degree with more subtle changes. Springs vs. tubing, pickguard (that big diaphragm on the face of your guitar) resting on a traditional Strat route vs. a swimming pool route, Tele neck pickup screwed to the body vs. a pickguard mount. Some differences may be so small as to make little to no difference, but others can certainly play a noticeable role in shaping the tone.

Hi David -

Your post and story were so interesting, that's a great one. Not a lot of guys get to "experiment" with a Valeno, hell, not a lot of guys get to even SEE a Valeno, much less work on one.

David, do you have any comments about tone and Tele/ Strat/ Les Paul pickup mounting systems - you know, springs, tubes (I guess here I'm thinking of Strats and Teles in particular). I've shied away from tubing, but I don't have a good reason, or actually ANY reason, for doing so.

I won't hold you to any theories, but I'd sure be interested in your thoughts. Do you prefer tubing or springs in Strat and Tele pickups, and why (is I thiink the question I'm asking). What differences have you noticed in tone between springs and tubing, if any?

Maybe I should start a new thread .... (GRIN)

Thanks in advance David, Dana Olsen

[Stratman76]

I'm going to post some of the definitions I've found regarding how electromagnetic pickups work. This may help in determining what these pups can do with wood vibrations.

How Electromagnetic Pickups Work - Definition 1
"I'm still pondering the "exactly how does a pickup work" question. My best explanation right now has to do with the fact that a voltage is induced in a coil of wire when it is subjected to a changing magnetic field. As the string vibrates, it makes the amount of magnetic flux increase and decrease, which produces a voltage in the coil proportional to, and with the same frequencies as, the vibrating string.

Also, that the electrical signal for strings wavering horizontally over the pickup cause an electrical signal that is twice the frequency of the motion (as the string moves from extreme left to extreme right, the signal goes from min to max to min, and the string has only gone from min to max). Strings moving vertically (moving away from the pole piece and then towards the pole piece) create a signal that is the same frequency."
(End Defintion 1)

Upon reading this and assuming the information is "sound," I wonder if solidbody guitar wood imparts a variation of the frequency of the vibrating string.

Another idea is that microphonic electromagnetic pickups would receive and pass wood resonance (along with everything else they pick up!)

How Electromagnetic Pickups Work - Definition 2
a pickup, in it's simplest form, is a magnet wrapped with wire. when a magnetic metal (like a string) passes through the pickup magnet's magnetic field, an electrical current is induced in the wires that are wrapped around the magnet. the frequency of this current corresponds with the frequency (back-and-forth speed) that the string was passing through the magnetic field.
(End definition 2)

The simpler approach... I don't believe the dampening effect of wood in relationship to string vibration duration has really been disputed here. I'm still wondering if some shred of the strings' tonal signature is affected by body and neck wood.

[kimock]

Originally Posted by Stratman76

I'm still wondering if some shred of the strings' frequency is affected by body and neck wood.

Say that again?

[David Collins]

Dana, I've worked on one Valeno, and seen one or two others, but this wasn't one. It was made by "Electrical Guitar Company" out of Florida. Kind of in the style of a Travis Bean or Valeno, but a modern version.

As to how what type of and much an effect mounting has in other guitars, I can't say for sure as I've not experimented with it enough. This was a singular case I had experience with, but it was quite an eye opener because it was such a dramatic difference. I'm sure the differences still exist in simpler changes, but how much of an effect changes may cause I can't say. I'm sure the difference can be caused between things like springs vs tubing on a Strat pickup, but how notable a difference that single change can cause in that setting, I really can't say.

I'm sure there are differences between body mount and pickguard mount, but again I can't say how much from any controlled experiences. Probably differences between 3-ply and single-ply pickguards, wood ones, etc. As with most subtle changes I'm sure there's more a big gray area rather than a clearly defined threshold. What kind of change is enough to cause a real difference I'm sure varies between even similar pickups and guitars. Beyond that though, I really can't say.

Stratman, I think the definitions you found reveal a few minor misunderstandings of the author on how pickups work. For example, pickups work the same way as a generator - whenever a coil moves through a magnetic field perpendicular to the lines of flux a signal is generated. Movement parallel with the lines of flux will produce no current at all. It's all relative of course, so whether the field is moving (cause by the change in position of a string resulting in a change in shape of the field) or the coil/wires were to move, they are still moving relative to each other just the same. I won't try to get in to all the details, but in a real world scenario you won't find vibrations parallel to the coil generating much in the way of 2x frequency signals.

As to the influence of materials on tone, there are a lot of ways it happens. Basic basic guitar physics 101. Three things can happen with the energy of a wave in a string as it hits a boundary (like the bridge or a fret). Energy can be reflected back in to the string, transfered in to the bridge, or pass over it to continue along the string toward the tailpiece or tuners (this is where breakover angle can make a big difference). Of the energy transfered to the bridge, that can then be transfered to the body or reflected back in to the bridge (though most gets transfered to the wood. The body, neck, everything on the guitar is set in to motion, and all these transfers work in reverse as well, sending energy back in to the string. All this stuff adds up, certain vibrations are absorbed more than others and eventually turned to heat, and all this shapes the tone of an instrument. Every part of the guitar matters to some point, though some too small to really notice individually.

For those who doubt the influence of things like body material on tone, it helps to imagine the extremes. Picture playing a guitar with a solid granite body, and one made out of luffa sponge. It's pretty easy and reasonable to expect a notable difference. The differences exist just the same with typical body woods, though to a smaller degree.

These vibrations make their way to the pickups as well, and how they are anchored is going to effect how the vibrations are absorbed or transferred to the pickup. However the pickup ends up vibrating, those vibrations are no different than if the pickup were perfectly static and those vibrations were in the string - it's all relative.

Another important thing happens as well. Coils are rarely solid, and even potted coils can vibrate. Now we have the coils actually vibrating around the magnets, which can have a huge influence on tone. With a really microphonic coil for example, you could screw it to the guitar body well away from any strings and still pick up a generous signal.

So I think it's safe to say that the looser the coils, the more the pickup mounting style will play a role in shaping the tone. Even in a vacuum or epoxy potted coil though (as the were in the case of the aluminum guitar), mounting style will certainly play at least some role.

[Boris Bubbanov]

Very helpful explanation.

Much obliged.

[Stratman76]

Originally Posted by kimock

Say that again?

Thanks. Corrected.

[Dana Olsen]

Originally Posted by Boris Bubbanov

Very helpful explanation.

Much obliged.

Me too - Thanks David, Dana O.

[Structo]

I always wondered about the tone wood theories especially in regards with the Fender Strat or other guitars that have their pickups mounted on a pickguard.
You don't get that coupling effect from the wood to the pickups as much as if they were mounted to the wood.

But I have witnessed first hand the difference a good neck can make which I feel is one of the most important part in the equation.

Some feel if the guitar does not sound good unplugged that it won't sound good plugged in to the amp.
I'm not sure I agree with that theory for several reasons but I do feel that a guitar is a sum of it's parts with some playing more important roles than others.

[RvChevron]

Originally Posted by Structo

I always wondered about the tone wood theories especially in regards with the Fender Strat or other guitars that have their pickups mounted on a pickguard.
You don't get that coupling effect from the wood to the pickups as much as if they were mounted to the wood.

But I have witnessed first hand the difference a good neck can make which I feel is one of the most important part in the equation.

Some feel if the guitar does not sound good unplugged that it won't sound good plugged in to the amp.
I'm not sure I agree with that theory for several reasons but I do feel that a guitar is a sum of it's parts with some playing more important roles than others.

The pickups sense/read the changes of the magnetic field.

The magnetic field movement is caused by how the strings vibrate or not vibrate.

The body and neck wood "dampen" the string movement. Different woods would dampen the string movement differently.

Anchor both ends of the string on two blocks of concrete would make the string vibrates very differently from two pieces of wood I think.

That's how I think and feel the body and neck wood affect tone.

Of course if the pickup winding is even just ever so slightly loose, the pickup will not only sense the magentic field movement but also the physical vibration of the body/neck/pickguard.....etc as it becomes microphonic.

Just imho, ymmv.

[Stratman76]

Originally Posted by RvChevron

Of course if the pickup winding is even just ever so slightly loose, the pickup will not only sense the magentic field movement but also the physical vibration of the body/neck/pickguard.....etc as it becomes microphonic.
Just imho, ymmv.

If I am to draw a conclusion from this thread it might be that loose pickup winds will make a pickup microphonic. Not only can the pole pieces get rattled by an solidbody's inherent vibration but wood resonance is more likely to be picked up. If this is also true, one might want a SLIGHTLY microphonic pickup.

BTW- This is great stuff thanks to all!

[fullerplast]

Originally Posted by RvChevron

The pickups sense/read the changes of the magnetic field.

The magnetic field movement is caused by how the strings vibrate or not vibrate.

The body and neck wood "dampen" the string movement. Different woods would dampen the string movement differently.

Anchor both ends of the string on two blocks of concrete would make the string vibrates very differently from two pieces of wood I think.

That's how I think and feel the body and neck wood affect tone.

Of course if the pickup winding is even just ever so slightly loose, the pickup will not only sense the magentic field movement but also the physical vibration of the body/neck/pickguard.....etc as it becomes microphonic.

Just imho, ymmv.

Yeah, that's how I think of it also. Every component of the guitar affects the resonance of the guitar in some way......think of it as layered "filters". The way the string vibrates is a function of the resonance of all these layered resonance filters and that is what is converted into an electrical signal by the pickups. That's the primary element.

Secondary elements include the vibrational coupling of the pickup itself to the body...essentially the "microphonic" component of the pickup. Whether the pickup is mounted to a pickguard, bridge plate (tele), or screwed into the wood, and then the type of spacer used; spring, rubber tubing, or solid tubing. Examples of direct wood mounting would be Anderson teles and the Fender GE Smith tele bridge pickups, and all vintage style tele neck pickups. The microphonic coupling component is additive to the magnetic field component and both affect the composite electrical signal.

Jay Monterose used to experiment with brass tubing cut to length for mounting some of Danny's pickups. That gives a real direct vibrational coupling to the body, well beyond what springs or rubber tubing would give. The downside of course is lack of adjustability, so you don't see this too often.

The microphonic component of the pickup is a balancing act....the best pickups seem to be microphonic but don't squeal; a difficult balance sometimes, and often a function of the resonance of the guitar and pickup mounting technique.

Yet another contributing factor to the string-pickup relationship is the affect of the pickup itself on string vibrations....the magnetic poles dampen vibrations. That's why we don't like them too close to the strings and it's why Esquires often will resonate differently than Teles. So in effect, the pickup itself is another layered resonance filter on top of everything else.

The entire system is an incredibly complex filter, and all the variables are why no two guitars ever sound quite the same.

[Stratman76]

Originally Posted by fullerplast

Yeah, that's how I think of it also. Every component of the guitar affects the resonance of the guitar in some way......think of it as layered "filters". The way the string vibrates is a function of the resonance of all these layered resonance filters and that is what is converted into an electrical signal by the pickups. That's the primary element.

This is an element I'm trying to pin down. And please correct me if I'm wrong.

The Basics
String Length, Thickness, Tension= frequency (what note)
String Struck = amplitude (how loud)

Considering the known dampening effect of wood and how a guitars neck is playing a large role in this effect simply because of it's proximity to the strings as well as coverage area beneath the strings. We know this dampening effect is the sum of a guitars' parts, but let me use the neck in this example as my take is string vibration/movement would be quite influenced by the neck.

Aluminum Neck = less dampening/greater reflection and more sustain
Maple Neck = more dampening/less reflection and less sustain

An aluminum neck would also be inherently brighter
A maple neck would be inherently darker than aluminum

Why?

I believe there is a slight neck vibration frequency imparted here that gets back to the strings. Or what gets sent and/or reflected back to the strings?

Neck Vibration/Radiation Frequency = tone imparted element (to strings...?)

This might be off, but it seems close. Please fire away.