Shim under bone saddle: defeats the purpose?

[NAFIGATOR]

Originally Posted by ljguitar

...Unless a player is a machine, different takes more often than not end up sounding discernibly ''different''...not necessarily better or worse, just different.

Larry, I agree 100%. I've done a lot of recordings, albeit not nearly as many as you had and saw it myself: two recordings are never the same.

When I was "defending myself" on this topic it was merely trying to provide as much information as possible on the subject of shims. The reason I even did these recordings is because when I install a new saddle I thought I've heard the difference in tone, even though very-very subtle. Then I decided to record, so I could hear the sound from a side and back to back. This is how these recordings appeared.

While we are on the subject of the recording. There are so many more variables, other than one mentioned... For example I did make sure measurement of both saddles are identical, but I can not make sure the bone was from the same part of the same animal. Also, since it's hand made I can not completely control an angle of the saddle top. perhaps one was a few degrees different from another. And more...

The bottom line is that (IMHO) if shim can be avoided it should. Shim is not the end of the world, perhaps in some (most?) cases you can't even hear a difference at all. In some other cases the difference is so subtle it does not matter. But here is a big question: unless we are talking about very rare and expensive fossilized material, why even bother with a shim as a permanent solution?! Cutting a new saddle is 15-20 minutes job and cost of the bone blank is $1 to $5...

[Alan Carruth]

Steve S wrote:
"I think what is important to remember is how strings transmit energy to the guitar. Many think it is through the bottom of the saddle to the top through vertical movement of the strings as they vibrate. This may be true, but it is a very small part.

Most of the energy from the strings is due to strings changing length while vibrating. The energy is along the axis of the string as it applies torque on the bridge and vibrates the top by changing tension longitudinally. The bridge is rocked back and forth, not up and down. "

I have to disagree with that. I spent 'way to much time a few years ago measuring the forces that a string puts on the top of the saddle after it's plucked. It gets pretty complicated, and if you want all the gory details you can look up the paper at my web site, on the 'Acoustics' page; it's entitled 'String Theory'. Simplifying desperately:

1) The 'transverse' force signal averaged about seven times the amplitude of the 'tension change' signal.

2) You only get that much difference giong into the gutiar if the string is vibrating 'vertically' with respect to the plane of the top. However, it doesn't take much of a vertcial vector in the string's vibration plane to get at least as much signal out of the transverse force as the tension change.

3) In one experiment, I use a magnetic drive to push a string in both 'horizontal' and 'vertical' directions relative to the plane of a guitar top. In both cases the tension change signal would be the same, but in the 'vertical' motion the transverse signal would be driving the bridge, whereas in the 'horizontal' one it would not. The 'vertical' motion produced almost 20 dB more sound (100 times the power).

4) The big diference there has to do with the way the guitar top is built, and the way it produces sound. The most effective sound producing mechanism on the guitar has the top moving like a loudspeaker cone, pumping air in and out of the hole, and also making sound off the top. This is very effectively driven by the transverse force signal.

The tension change signal most effectively drives a bridge rocking movement, pulling the top up behind the bridge while pushing it down in front. The motion of the two areas of the top tends to cancel out, making this a much less effective sound producer for a given amplitude of vibration.

Guitar tops, of course, are built to resist bridge torque, since its the static force of the strings pulling the bridge forward that ruins guitars. It's very difficult to move the bridge in a 'rocking' sort of motion below the pitch of the top 'long dipole' resonant mode; usualy at about 350 Hz (F on the high E string). Since the tension change signal actually happens at twice the string fundamental, you'd expect any boost in output from it you start kicking in around F on the D string, 3d fret.

The bottom line is that, on every guitar I've measured, the transverse string signal is the one that matters most. The tension change signal does have an impact on timbre, and may well cause a change in the sound of the guitar when the string height off the top is changed. Any experiment looking at the effect of a shim needs to take that one into account (and total saddle/shim mass as well!).

I know there are experiments out there that seem to show the opposite of what I'm saying here. One problem I have with them is that I've never seen enough information about how they are conducted to be able to account for the differences. It makes a big difference, for example, just how you pluck the string, and aside from 'carefully' I've never seen much of a description of that. In my own experiments I did everything I could to control the variables, and I've looked at these things in several different ways. I always get the same results, and the guys who can do the math back me up. I'd be happy to discuss data, and data acquisition methods, with anybody, but based on what I've seen, "that's my story and I'm sticking with it".

[fishstick_kitty]

Originally Posted by Dogberry415

Hmm. I'm familiar with Colosi's products, and his opinion does carry a lot of weight around here. And yeah, in my case, both the shim and the bridge are ebony, as he describes. Guess it's good to know that, shim or no shim, the difference is nil.

I had a Webber Roundbody w/ a UST in it. I wanted to get rid of the UST, so I shimmed it using one of Jims kits. The shim was perfect, guitar sounded great, but it still bugged me. So I bought a new saddle (from Webber) made out of bone. And guess what, it sounded different. Better or worse? Dunno, that's subjective, but different definitely.

[rick-slo]

Very interesting Alan. Thanks for sharing that.

[ljguitar]

Originally Posted by Alan Carruth

...I spent 'way to much time a few years ago measuring the forces that a string puts on the top of the saddle after it's plucked. It gets pretty complicated...
...I always get the same results, and the guys who can do the math back me up. I'd be happy to discuss data, and data acquisition methods, with anybody, but based on what I've seen, "that's my story and I'm sticking with it".

Hi Alan…
It's your contributions which always make me keep checking back on these threads which are seemingly going nowhere. At least this one is going that direction with style.

Aside:
By nowhere I mean just banter being tossed back-n-forth with only here-say evidence. At least Alan you have legitimate math and thought-out procedures (like moving the string magnetically).

[steveyam]

Alan, so what happens when a bridge doctor is fitted, which to some degree 'stops' back and forth rocking/vibrating of the bridge due to tension changes? Anecdotally, I have found that with a BD fitted - just like the guy says - volume goes up and so does bass response. I'm sure it's complex, but have you anything to say? I'm thinking, if the termination point of the string is more 'solid' - as it must be with a BD, then would that cause more transverse vibration to happen to replace the tension vibration on the basis that the plucked energy input must go somewhere?

[Taildragger]

Originally Posted by kec

Well, I think Frank said it best...

Quote:

Originally Posted by Frank Ford

If I go too far in lowering my saddle, I can shim it back up with little slips of wood veneer. But, I'd much rather make a new saddle rather than shim the old one both for tonal and structural reasons.

Source: http://www.frets.com/fretspages/Musi...raction02.html

Frank Ford also said this on the same website:

"Even though a shim is not integral with the saddle or even made of the same material, it is unlikely to have an adverse effect on tone."

So???

-mike

[murrmac123]

Originally Posted by Taildragger

Frank Ford also said this on the same website:

"Even though a shim is not integral with the saddle or even made of the same material, it is unlikely to have an adverse effect on tone."

So???

-mike

I know this will come as a shock to many, but .....Frank Ford is actually... human

And we all know what being human means ...

[mr. beaumont]

Originally Posted by walternewton

If the shim is done correctly, I doubt there's much, if any, discernable difference - but I'd hope that anyone passing themself off as a pro would have enough pride in their work to start over and get the job done right (saddle blanks are cheap).

This, exactly.

[SteveS]

Originally Posted by Alan Carruth

.....The bottom line is that, on every guitar I've measured, the transverse string signal is the one that matters most. .........

Alan,
I always appreciate your thoughtful replies. I have a lot of respect for you and your work. Thank you for being so willing to share!

I understand what you are saying about your testing and the transverse string signal being the strongest. What I don't understand is how this necessitates that this motion translates into a vertical movement of the bridge. If the vertical movement of the bridge was the essential factor, then the height of the bridge would have little impact on the output of the guitar. If a rocking of the bridge was the major contributor to volume, then the bridge height would play a major roll in volume. The fit of the bridge would also be important because a lose bridge would not transmit rocking motion. Because these two cases are true, it seems evident that the motion on the bridge is primarily rocking, not up and down.
It seems to me that the best explanation is that strings vibrate in all planes and the vertical vibration is the most important contributor of bridge motion. This bridge motion is apparently a rocking motion.

I freely admit that I could be wrong. Please help me understand the breakdown in my thinking.
Thanks!

[charles Tauber]

"Simple harmonic motion":

[drive-south]

A few years back I bought a Tacoma Papoose. It had 2 shims under the saddle when I received it. I asked a guitar tech at a local music store to replace the saddle and eliminate the shims as I wanted a direct coupling between the saddle and the bridge. He was busy and I had to wait a few weeks for an appointment. I asked him to make sure he had the right size saddles in stock so he could complete the job when the time came.

When my appointment arrived, I left the guitar with the store for a day. When I picked it up, the tech explained that he didn't have a saddle blank in stock that was high enough, so he ended up using a single layer of shim material under the new saddle. I ended up paying $60 to have a new saddle made and still had a shim under it so needless to say I wasn't too happy with the work that was performed. Apparently he didn't bother checking his saddle stock and just left it to chance that he would have what he needed. I've made a promise to myself not to use this tech again.

Perhaps there is little or no differance between having a shim/not having one but I believe the tech was unprofessional and dropped the ball by not checking his stock. He should have called and communicated with me before proceeding with the work knowing it would not accomplish what I requested.

So if having a single shim doesn't affect tone, would 2 shims affect tone? How about 3 layers of shim? Would that affect tone? At some point, there has to be a loss of coupling and transmission from having multiple layers of material between the saddle and bridge. We get worked up comparing bone, tusq, FWI, or other materials as they vary in density. Why would we go to great lengths to get the material of our choosing, then spoil the equation with a shim?

Just my opinion.

[steveyam]

Originally Posted by drive-south

A few years back I bought a Tacoma Papoose. It had 2 shims under the saddle when I received it. I asked a guitar tech at a local music store to replace the saddle and eliminate the shims as I wanted a direct coupling between the saddle and the bridge. He was busy and I had to wait a few weeks for an appointment. I asked him to make sure he had the right size saddles in stock so he could complete the job when the time came.

When my appointment arrived, I left the guitar with the store for a day. When I picked it up, the tech explained that he didn't have a saddle blank in stock that was high enough, so he ended up using a single layer of shim material under the new saddle. I ended up paying $60 to have a new saddle made and still had a shim under it so needless to say I wasn't too happy with the work that was performed. Apparently he didn't bother checking his saddle stock and just left it to chance that he would have what he needed. I've made a promise to myself not to use this tech again.

Perhaps there is little or no differance between having a shim/not having one but I believe the tech was unprofessional and dropped the ball by not checking his stock. He should have called and communicated with me before proceeding with the work knowing it would not accomplish what I requested.

So if having a single shim doesn't affect tone, would 2 shims affect tone? How about 3 layers of shim? Would that affect tone? At some point, there has to be a loss of coupling and transmission from having multiple layers of material between the saddle and bridge. We get worked up comparing bone, tusq, FWI, or other materials as they vary in density. Why would we go to great lengths to get the material of our choosing, then spoil the equation with a shim?

Just my opinion.

It's all down to the shim material. If the shim has tonal sapping qualities eg a piece of soft wood, then yes it will degrade the sound. Using a tonewood shim such as ebony or maple will be fine because it won't compress any more than the parent bridge material; vibrations will be transmitted just fine. In some of my guitars I have two shims and I don't believe it is affecting my tone one tenth as much as the lack of practise that I put in. And I don't practise..

[rockinrebel]

That's why I buy bone saddles from Bob Colosi and SLOWLY sand them down myself.

[fishstick_kitty]

Originally Posted by steveyam

It's all down to the shim material. If the shim has tonal sapping qualities eg a piece of soft wood, then yes it will degrade the sound. Using a tonewood shim such as ebony or maple will be fine because it won't compress any more than the parent bridge material; vibrations will be transmitted just fine. In some of my guitars I have two shims and I don't believe it is affecting my tone one tenth as much as the lack of practise that I put in. And I don't practise..

It just seems weird to me that everybody can notice a difference between tusq and bone and ivory, etc...then in the same breath, how can we sit here and claim that a shim won't degrade the saddles "tonal" qualities?

Also, if (according to Alan...who gave a detailed and excellent explanation) most of the energy is being "transversally" transmitted, then would it not be better for a saddle to fit tight in the slot so it is able to transmit energy better to the bridge? I have seen many saddles that kind of just sit fairly loosely (e.g. I can easily pull it out w/ my thumb and fore-finger).

Color me curious