Sound of P/P - Vibrating thru body

David Doggett · Post by **David Doggett** » 15 Aug 2003 10:13 am

Okay, Bobbe is describing the "resonant body" theory. He thinks body resonance in a solid body magnetic pickup instrument can somehow feed back to the strings and add overtones and sustain that was not already there. Outside of this thread this seems to be the majority view. I don't completely disbelieve it, but I am skeptical.

The opposing view (the "subtraction only" theory) is that nothing can be added (where would the additional energy come from?). Instead, the timbre is affected by having the shrill or harsh overtones drained off and de-emphasized, thereby creating a more mellow and pleasing timbre (depending on body materials and changer designs), with possibly some loss of sustain. It doesn't matter whether we talk about timbre or sustain, because what we perceive as timbre is merely the mix of overtones that are sustained or not (according to the subtraction only theory), or whose sustain is reinforced or not (according to the resonant body theory).

I don't at all doubt that experimenting with different body materials, changer designs, and construction details as Bobbe and others have done will show that all of these things affect timbre. I am only questioning the common explanation of why and how that happens. Let's do some more thought experiments.

Okay, first for a real experiment. As Jeff suggested, I went home and tapped on my pedal steel with the strings damped and heard the tap through my amp. Well, that perplexed me for a moment, until I realized that to hear the tap through the amp, I had to have my volume pedal all the way on. My NV400 200 watt amp was about half-way up. If I had hit a string with my normal picking strength it would have blown out every window in the house. If I backed up to my playing volume on the pedal, I didn't hear diddly through the amp no matter how hard I tapped, even directly on the pickup. So maybe if you play at stadium volume body vibrations can be heard through the magnetic pickup, but I couldn't see how any body vibrations could be amplified at my playing level - yet I can clearly hear timbre differences between instruments at that level. Someone knowledgeable in electronics may be able to explain how a magnetic pickup amplifies non-magnetic vibrations, but regardless of that explanation, it doesn't seem relevant to what we are talking about, unless, as Bobbe says, the body imparts additional vibrations back to the metal strings.

Now for some thought experiments - well these aren't really thought experiments, because they are things any guitarist knows from experience. If body resonance improves timbre and sustain, why do they even bother to make solid body guitars? We all know that thin, strong-but-flexible, guitar tops are what make the timbre and volume of an acoustic guitar. But when you put a magnetic pickup on an acoustic guitar, all that resonance and acoustic volume is of no use. The Magnetic pickup will give a poor tone from the strings, with little sustain. That's why they invented acoustic pickups, which actually amplify the vibrations of the guitar top, not the strings. And as Bobbe says, if you put an acoustic pickup on a solid body instrument to really get all the body vibrations, it doesn't work well.

So after the invention of the magnetic pickup, there gradually came to be a whole assortment of electric guitar bodies for different kinds of tone. You've got the big box hollow-bodies, the thin box hollow-bodies, the semi-hollow-bodies, the hollow-solid bodies, and the solid bodies. With magnetic pickups, the more resonant the body is, the punchier and more mellow the tone is, with less sustain. The Jazz guys love that. They are also good for banging out punchy clean chords on rhythm guitar. The more solid the body is, the brassier the tone is, with more sustain. Thus, you have the twang of a tele for country, and the searing sustain of a strat for rock lead guitar.

Naturally, before the volume pedal started being used for sustain, electric lap steels were all made with solid bodies, for the maximum sustain. Pedal steels grew out of that. Great lenghts have been taken to get all the sustain-robbing and tone-dulling resonance out of these guitars, and to leave only that great solid-body sustain and timbre. So now you want me to believe that building in just the right amount of resonance will improve sustain and timbre?

I guess the true test of all this would be to build several lap steels (take the changer and roller nut problems out of the equation) exactly the same, with the same magnetic pickups, but with bodies of different thicknesses. According to the body resonance theory, the thicker bodies should sound duller and have less sustain. We already know that the ones with really thin bodies (approaching the thickness of hollow-body tops) would also sound duller with less sustain. But according to this theory, there will be some intermediate thickness body that will have just the right resonance to maximize both timbre and sustain.

I would have to hear this to believe it. It's not that strange an experiment, and it seems likely someone has already done it - maybe even Bobbe.

My prediction, according to the "subtraction only" theory, would be that as the body gets thicker and more rigid, the sustain will improve and the timbre will get brighter (not necessarily more pleasant), up to some point where additional thickness has no further effect. I bet that point will be about the thickness of present bodies, which builders have arrived at through trial and error.

As for the affect of different neck materials, Bobbe said in a post not long ago that experiments in the building of the Sho-Bud SuperPro III showed that the neck material had no effect on tone. If the nut, changer and pickup are attached directly to the body (as in most pedal steels) rather than the neck, why should the neck have any effect on tone? It just sits passively on top of the body.

What do you think, Bobbe, good buddy?

David Mason · Post by **David Mason** » 15 Aug 2003 10:49 am

I have to agree with Mr. Doggett's "subtraction only" theory, here. The resonance of the body is something that happens in response to the vibration of a string, not something that can be magically added to it. As he points out, where would the additional energy be coming from?

Bobbe Seymour · Post by **Bobbe Seymour** » 15 Aug 2003 10:51 am

What do I think? I think you are thinking real hard, using good thought and intelligence, as is Jeff Smith. Only when people ask these questions , will guitars start sounding better than they do now, and Lord knows, there sure is a lot of room for improvment.

David, there is no "additional energy", it's a "reflective,sympathetic energy that is put into the guitar body by the string itself. Key word here is reflective,re- shaking the string with reflective energy from the original energized motion of the string, feeding it back into the string via the changer end, and very little from the keyhead end. However, vibrating strings in the keyhead do add a quality to the timbre, ever notice that the Emmons keyhead stringlength is exactly 1/4th the stringlegnth of the guitar, just so it will vibrate sympatheticaly?????? Strike strings 5 and 6 in a Emmons keyhead, then pick 5 & 6 open on the neck, The same Notes!!! Why? now you can tell me. Backfeeding the strings sympatheticaly is why. There is a great tone message from the master himself here, Ron Lashley, did he know or was he lucky? I'm not sure, but he taught several of us well.

Ever notice what happens when you hold the bar in the center (12th fret) of the stringlegnth? Pick the strings on one side of the bar and the strings on the back side of the bar ring sympathetically? Yes, this is the same thing the body itself is doing to a much lessor extent, but VERY importantly, it is doing it. This is your good or bad timbre, depending on the quality of sonic design in your steel guitar from the factory. What determines good or bad sonic design? Expermenting with all the factors I have mentioned and having someone that knows what he's listening to make intelligent choices. No manufacturer that I personally know of is doing this today, and hasen't during the design of what they are building today. If they had, we'd be hearing better sounding guitars in this day and time.
I recently offered to help one company that needs help very badly, the response I recieved was: "There's nothing wrong with our tone! Ours sounds as good as anybodys!" . This particular guitar is horrifying too. Unfortunatly, it seems that just machine shops are building steel guitars now, not musicians and sonic engineers.

Not to put ALL companies down,some guitars sound fine, luckily, AND as I have said before, "If a player can't hear the difference,it makes no difference anyway".

You guys are doing some good thinking. This post seems to have the most informitive, intelligent thoughts I've ever seen on a forum. [This message was edited by BobbeSeymour on 15 August 2003 at 12:37 PM.]

Terry Edwards · Post by **Terry Edwards** » 15 Aug 2003 11:30 am

Periodically the Discovery channel will show "Galloping Gerty", the Tacoma Narrows bridge that undulated and shook itself apart because of resonant frequencies multiplying to the point of distruction! Where did that extra energy come from?

Maybe it is not "extra energy" that "backfeeds" the strings. Maybe it is just string energy that resonates thru the body and then comes back to effect the strings by slightly altering the resonance of string (timbre change).

This is starting to hurt my brain!

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Terry Edwards
Fessy D-10; Nash 1000
Martin D-21; Flatiron F-5

Bobbe Seymour · Post by **Bobbe Seymour** » 15 Aug 2003 11:40 am

Terry! Brilliant similarity. Good anology.

David Doggett · Post by **David Doggett** » 15 Aug 2003 2:21 pm

Well, there may be something to this body resonance idea, and that's why I can't completely discount it. You can't get more energy from nowhere, but you can redistribute it. That's what happened with the Tacoma Narrows suspension bridge.

The bridge was designed to take the force of its own weight or the wind distributed evenly over the whole bridge. The waves in the bridge set in motion (by a strong wind?) redistributed the forces to come to bear unevenly, with unanticipated force at the wave maximums. Snap!

When you push on a spring, you transfer energy into it. When you let go, that energy pushes the spring back out. If the spring is attached to something else it can transfer that kinetic energy into whatever that is.

Now, suppose the guitar body acts like such a spring. Some of the string vibration is transferred through the changer into the body. If the body is soft and mushy, it dies there (you used the wrong kind of wood). But if the body is springy, it can return a portion of the energy back through the changer to the strings. That could be good or bad. It could cancel out the string vibrations and deaden the sustain of the overtones, or even the fundamentals. Or it could be good and reinforce the desired overtones and/or the fundamentals.

That's how a bass reflex speaker works. The natural resonance frequency of the cabinet is designed to be just below the frequencies where the speaker response begins to drop off at the low end. So the sympathetic resonance boosts the sound vibrations around that point and pushes the drop off frequency down a little lower. It works really good on bass because a small change in frequency means a big change in perceived pitch. Whereas, up at the treble end, each perceived change in pitch requires a big change in frequency.

Now here's where things get subtle. On a pedal steel you've got 10 or 12 strings of different guages, whose effective lengths are constantly changed by the bar. How likely is it that the body resonance will be precisely right to have a good effect on even one string at one frequency, much less all strings at all frequencies? And how likely is it that the effect will be good for both the fundamentals and overtones? Isn't there a Murphy's law that unintended bad consequences greatly outnumber unintended (or intended) good consequencies?

In the bass reflex speaker cabinet analogy, apart from that magic bass region where the reflex idea works, any resonances in a speaker cabinet will selectively enhance one or a few frequencies and will cause the speaker to depart from flat response and have a boxy sound. Consequently, the more rigid and thick the the body walls, the less resonance, and the flatter the response.

On the other hand, if (according to the subtraction theory) the only thing the body resonance does is drain away the low energy highest overtones in general, over a fairly broad high frequency range, this could mellow or darken the tone and cut sustain. Conversely, less of this very general dampening of high frequencies would brighten (and possibly harshen) the timbre, and add a little sustain.

Being a firm believer in Murphy's laws (from many hard experiences), it just seems more likely to me that any body absorption of vibrational energy would have this very imprecise and general subtraction effect, rather than that it would be reflected back at precisely the right multiple frequencies to reinforce all fundamentals and overtones in a good way.

Call me a cynic. But this is actually an application of Occam's razor. This is a very useful informal strategy in science that says that, given two possible explanations, one simple and direct that requires few fortunate coincidences, and the other contrived and complicated and requiring amazing coincidences, the simpler explanation is the one to place your money on.

Of course in reality, things are rarely simple. The subtraction theory and the body resonance theory are not mutually exclusive. They could both be going on at once, and what we hear is some kind of combination.

Maybe we could write up some kind of gu'mint grant and get funded for me to go down and do some experiments in Bobbe's back shop to sort all this out. The gu'mint has soitonly funded plenty of stranger and less important stuff. All we need is some Southern congressman who likes steel guitar to tack this onto his usual pork barrel funding requests.

Well, this has been loads of fun, but it's not making my pitiful steel guitar playing any better. And I've got two steels sittin' at home in my basement that need complete setup conversions. And I never got around to spring cleaning this year. Ain't life a bitch?

Jeff A. Smith · Post by **Jeff A. Smith** » 15 Aug 2003 5:33 pm

David, I don't read Bobbe's replies as contradicting your basic idea of no new overall energy. For example, he says:

David, there is no "additional energy", it's a "reflective,sympathetic energy that is put into the guitar body by the string itself. Key word here is reflective,re- shaking the string with reflective energy from the original energized motion of the string,

It seems to me that he isn't suggesting anywhere that more energy is created after the string is picked; he's just describing things that happen within the range allowed by the original amount of energy. All the backfeeding can exist without necessarily adding anything to the original level of energy.

It seems to me that when some energy is allowed to leave the string, it's perfectly reasonable to assume that it can re-enter it, while not increasing the original amount.

It doesn't matter whether we talk about timbre or sustain, because what we perceive as timbre is merely the mix of overtones that are sustained or not (according to the subtraction only theory), or whose sustain is reinforced or not (according to the resonant body theory).

I agree with that, if you view both terms as having only a quantitative significance. To my way of thinking, "adding sustain" after the original impact on the string means that new energy would be added that was not originally present. On the other hand, "adding tone" or "adding timbre" strikes me as having an additional qualitative significance. Changes in timbre could be "added" after the initial impact without increasing the overall level
of energy.

But then, maybe I'm missing part of your idea. Are you saying that no backfeeding happens, and that all alterations on timbre are already present, as the string initially vibrates against the fingers and nut?

Another way of approaching this is to simply ask if you think that when energy leaves the string, it in no way re-enters it.

If the nut, changer and pickup are attached directly to the body (as in most pedal steels) rather than the neck, why should the neck have any effect on tone?

I'm not personally advocating or not advocating this idea, but I may have encountered the idea that it is through the way the neck is attached, and how it affects the vibrating body.

I've tried to read the latest posts in a detailed way, but forgive me if I've overlooked something. [This message was edited by Jeff A. Smith on 15 August 2003 at 08:18 PM.]

Jeff A. Smith · Post by **Jeff A. Smith** » 15 Aug 2003 6:22 pm

Something else that just occurred to me:

In this proposed backfeeding to the string, it would be interesting to distinguish between energy that actually reenters the string, and that which merely exerts an influence by encountering the vibrations which are newly created by the string. The second type of influence, which is of an inhibitive nature, might be considerable; the fingers and nut are caused reflexively to vibrate, thus cancelling out or influencing new vibrations from the string. [This message was edited by Jeff A. Smith on 15 August 2003 at 08:22 PM.]

Bobby Lee · Post by **Bobby Lee** » 15 Aug 2003 7:23 pm

Wouldn't it be better to keep the vibration energy in the string, rather than relying on this feedback mechanism to re-excite the string?

What if the reason that string-through-the-body guitars (like Strats or bakelite Ricks) sound better is the lack of resonance of the body, compared to the vibration-sucking resonant charactistics of bridges and tailpieces? If that is true, what would be the best way to terminate a string on a pedal steel?

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<img align=right src="http://b0b.com/Hotb0b.gif" width="96 height="96">Bobby Lee - email: quasar@b0b.com - gigs - CDs, Open Hearts
Sierra Session 12 (E9), Williams 400X (Emaj9, D6), Sierra Olympic 12 (C6add9),
Sierra Laptop 8 (D13), Fender Stringmaster (E13, A6),
Roland Handsonic, Line 6 Variax

Bobby Lee · Post by **Bobby Lee** » 15 Aug 2003 7:38 pm

I guess the true test of all this would be to build several lap steels (take the changer and roller nut problems out of the equation) exactly the same, with the same magnetic pickups, but with bodies of different thicknesses. According to the body resonance theory, the thicker bodies should sound duller and have less sustain. We already know that the ones with really thin bodies (approaching the thickness of hollow-body tops) would also sound duller with less sustain.

I can hear that effect on my Fender Stringmaster D-8. It has identical electronic components on both necks, and each is a separate piece of wood. The thicker front neck sounds brighter and sustains better.

Also, I once had the S-8 version (I think it's called a Champ). Very similar, if not identical, electronics, but made of thinner, less dense wood. It had very poor sustain, especially at the upper frets, and not much bite. It didn't sound at all like the Stringmaster, despite the electronic similarities.

Jeff A. Smith · Post by **Jeff A. Smith** » 15 Aug 2003 8:03 pm

<BLOCKQUOTE>quote:<HR>Wouldn't it be better to keep the vibration energy in the string, rather than relying on this feedback mechanism to re-excite the string?
<HR></BLOCKQUOTE>To what extent? If the goal is pure length of sustain, or having all of the original overtone signature present, I don't see that anyone is really contradicting that. But can't there also be something said for how a particular material reflexively (or subtractively) influences tone in such a way that you can actually guess what the guitar is made out of? Is what we want really the pure sound of a vibrating string? With any material this side of perfectly non-resonant, I think there could still be an identifiable character to the timbre.

Think of the difference in character between a Sho-Bud and an instrument where you can't hear the distinctive sound of wood. Maybe someone prefers that, but others will not.

Or think of the difference between something like a Steinberger guitar and a Les Paul. Maybe one isn't better than the other, but they sure suggest diferent things. Wood imparts a very organic character to the tone, I think.

This may be heresy to say, but other than length of sustain and the full-bodied sound, I'm personally not all that crazy about how a Bakelite Rick sounds. I've only heard others play them. Maybe I'd feel differently if I experienced one in the first-person. [This message was edited by Jeff A. Smith on 15 August 2003 at 09:44 PM.]

Bobbe Seymour · Post by **Bobbe Seymour** » 15 Aug 2003 9:29 pm

Whats all this "energy" discussion? What needs to be focused on is Timbre. What makes it and what things make it good or bad. I've had great sounding guitars without much sustain also. And no, the body of a steel isn't "tuned" to one frequency, It should reflect/resonate a wide spectrum, and not just the body either. "Cross talk" between strings at the bridge and nut along with body resonance has a large effect on backfeeding the strings, as do several other structrual factors.
Now my question, which of you guys have conducted steel guitar experiments on this subject, and with what guitars? Tell us how you did any experiments and what your conclusions were. How many years have you gone into this subject and what do you know about what a nice sounding tone looks like on a voice print machine as opposed to a bad sounding noise type tone? What do I know ? Just some,a little, but I have seen some pretty interesting things in the last few years that opened up some new doors to seeing and hearing good and bad. (It's not all subjective either!) But everyone here seems to realize this , obviously.
Get down real close someday and watch, with your naked eyes how a string vibrates. Put a strobe light on it and you'll see that both ends aren't even vibrating together!
Anyway, this subject is starting to bore me again, come to one of my classes someday and I'll demonstrate this whole complete subject. No way I can do it at two in the morning on this forum, besides, I get paid the other way! (Ha! Ha!)
Good night. [This message was edited by BobbeSeymour on 15 August 2003 at 10:31 PM.]

Jeff A. Smith · Post by **Jeff A. Smith** » 15 Aug 2003 9:35 pm

Hey Bobbe, when you say:

Sympathic vibrations in the total body construction backfeed the strings causing secondary vibrations in the vibrating string, in other words, loops and lodes. These are what make warm pleasing tones/timbre.

Wouldn't it be correct to include David's subtractive theory, by saying that the string's initial vibration (and tone)is considerably affected by the lack of perfect rigidity in the fingers and nut?

In other words, isn't there some existent tonal character, created by the string's initial relationship with finger and nut of a certain type, which preceeds any backfeeding?

It seems we posted at the same time again, Bobbe. Nevermind. Go ahead and sleep.

[This message was edited by Jeff A. Smith on 15 August 2003 at 10:40 PM.]

Bobbe Seymour · Post by **Bobbe Seymour** » 15 Aug 2003 10:32 pm

Yes, possibly, but I think David (my good friend) is approaching the problem backwards, but we may be coming to a very similar conclusion. David is a very smart guy, I want to see what he comes up with in the next five years if he keeps working on this problem. He's an interesting thinker, as are you Jeff.

In this day and time, steel guitar needs more thought in this direction. This is a wonderful thread, not that I agree with everything, but it shows that somewhere folks are starting to think about the most important thing a steel is loved for, It's sound, tone, timbre, beauty.

Bobbe Seymour · Post by **Bobbe Seymour** » 16 Aug 2003 5:54 pm

Anyone noticed that this thread is ahead of the Bill Hanky thread? (For the moment anyway).

I sure wonder what he'd have to say on this subject, and how he'd say it! And what kind of words he'd say it with.

Come on in Bill!

Pete Burak · Post by **Pete Burak** » 16 Aug 2003 7:47 pm

Why is Blocking (pick, palm, etc) so important?... it kills the string vibration i.e. sustain, which are so important, no?

Damir Besic · Post by **Damir Besic** » 16 Aug 2003 7:53 pm

"he`ll be coming around the mountain when he comes"...pling pling plong (banjo solo in case you didn`t know)
dang,Pete ,you got in here second before me,this was supposed to be for Bill...pling pling...

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[This message was edited by Damir Besic on 16 August 2003 at 08:55 PM.]

rhcarden · Post by **rhcarden** » 23 Aug 2003 9:05 am

One of you with an all pull guitar that has a tuneable split, do this test. Does your tone get better (or change) when the pull finger is in contact with the split tuning screw? My guess is, there is no difference! I do not let the pull fingers hit the body on the A and B pedals and I don't hear any change in tone from the ones that do.

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Bob Carden 66 Emmons P/P 8/9
BMI 13 string 7/7

Damir Besic · Post by **Damir Besic** » 23 Aug 2003 10:10 am

you can`t hear any change Bob my man,you have the King of Kings, `66 Emmons.You would hear a change if you would sit behind another steel,but don`t do that,its not worth it...

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ed packard · Post by **ed packard** » 23 Aug 2003 10:28 am

Lots of definitions needed for the verbage in this thread, and none if any to be found!

"Good Tone" is a matter of taste; But any tone can be defined in terms of its harmonic content at any given moment, and the change in its harmonic content with time. The piece of test equipment to do this is the Spectrum Analyzer. Do a search on a search engine and you can find a number of Spectrum Analyzer programs for free, and for pay. The one that I prefer is called "TRUE RTA". Now that we can measure and quantify what comes out of the pickup as a function of the other variables such as where you pick the string, the direction of picking motion, string material/tension/age, where the bar terminates the string (Hughey Land?)we can proceed to the mechanisms of changer, roller/nut, string length beyond the nut, fingers, axles, bridge material and radius, interstring coupling via the bridge/changer mechanism(s), the body (material/dimensions), coupling of the string Vibes to the body, vibration in the body and coupling back to the string, etc., etc..

There is no one controlling element re tone, ..each of the above mentioned, plus the pickup and its loading/position/field shape may/will have an effect upon the resulting sound. Different materials and configurations in any of the above will have different effects.

Exciting the strings will cause vibrations to travel back and forth along the excited string. These vibrations are also passed thru the roller/nut/bridge into the attached mechanisms, = axles, tuning structures, fingers, strings on the same axle, and finaly to the body and beyond. "Sympathetic vibrations" play a part. The "acoustic impedance" of the various parts determine how much of the vibrational excitement is passed from any string to the other strings, and to the rest of the mechanisms, ..loose/tight screws change the amount of coupling as do the various materials, materials, dimensions, and shapes.

Anything that vibrates in response to the string vibration may either add or subtract from the harmonic content of the vibrating string depending upon its "phase" relationship and "coefficient of coupling" to the other mechanisms involved. Addition is by "in phase" feedback, subtraction is by "out of phase feedback. The "feedback" here is "returned vibrations". Even vibrations in the air from the local speaker cabinet has a measureable effect.

Just to complicate matters, any given string vibrates at many frequencies at once; The result is that the resulting feedback (via the acoustic impedances, coefficients of coupling, etc.) of the connected mechanisms may be in phase for one or more of the source vibrations and out of phase for others in varying degrees.

Is it better or worse to confine the "string vibrations to the string"? Since this cannot be done except perhaps in a single stringed instrument, suffice to say that "energy" leaving the string, at any of the harmonic frequencies involved in the strings vibration will cause the harmonic content of the vibrating string to change with time. This will result in a change of tone and amplitude with time, hence less sustain. All of this is measureable and quantifieable these days; But then each picker will have to decide what is "best" from their perspective.

Pickup location, construction, magnet field (wide/narrow/strength)where it intercepts the vibrating string adds to the problem, as does the pickup's impedance/load etc..and the magnets damping effect upon the various harmonics in strings vibration.

The simpler the mechanisms involved the less the variables that can affect the resulting sound parameters.

And we all know that BLACK guitars sound better, so pay attention to the paint color as well as type!

Edp

Jerry Tillman · Post by **Jerry Tillman** » 23 Aug 2003 7:29 pm

I agree with Bobby Seymour about sympathetic vibrations coming from his steel,thats why I tie one of those springs that come off a screen door to the undercarrige and legs of my 66 white leather Emmons,it really seems to bring the sound around,specially when I,m drinkin.lakeshrk