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  #1  
Old 04-12-2016, 03:43 AM
matt301273 matt301273 is offline
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Default Get More Sustain Out of An Acoustic?

Hello All,

My name is Matt and I am an amateur builder. I have made a few acoustic guitars which you can check out at my site:

www.customguitarbuilding.com

The latest guitar I made has plenty of warm bass resonance and volume due to forward shifted, scalloped bracing, and is very light overall because I used Spanish Cedar for the neck. However, it lacks the sustain of my cheapy smaller bodied Vintage V300. That guitar is much heavier and smaller though. You can see and hear the guitar here:

https://www.youtube.com/watch?v=KCcO...&nohtml5=False

I wonder if there is a trade off between having an extremely responsive top where the energy quickly dissipates and the sustain.

Just want those plucked notes to last longer on the next build without losing volume and warmth.

Any thoughts appreciated

Matt
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Old 04-12-2016, 06:20 AM
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fazool fazool is offline
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Matt,

I cannot comment from a builder's perspective, but I've worked in vibration analysis/measurement/damping engineering on and off for several decades so I can inject some foundational thoughts on sustain.

Your amount of sustain is the product of only two things:

The first is simply how much energy is put into the vibrating member in the first place. This will simply create more amplitude (volume) at the beginning. Another way to think of it is to think of it as volume - if you start louder, it will take longer for the volume to quiet down.

So, you want to get as much energy INPUT to the top first. The best way to do this is with higher string tension from longer strings and heavier gauges. This will require/translate stronger picking/strumming into more amplitude.


The second item is damping. This is where energy is actually lost. In a perfect world, 100% of the input energy would create output-ed sound waves. If that was the case, the sound would be tremendous and go on ridiculously long. In reality a majority of the energy is lost very quickly due to damping.

Damping comes from the energy being absorbed in a way that the vibration waves interfere, cancelling each other, and by the materials absorbing the energy and converting it to motion or heat.

Basically, the wrong stuff vibrates and the right stuff doesn't.

So, like above, where you wanted to maximize input energy from the strings, you want to minimize damping losses after the strings.

This comes from the structure's shape itself (which is where the vibrational analysis gets so complex as to need a supercomputer to model it. Fortunately skilled artisinal luthiers have done this over centuries with talent/skill and trial-and-error methods until we know the basic best ways.

For example, if you over-brace a top, the vibration energy from the string is the same, but now it moves that energy from the oversized brace into the entire body. The string energy now spreads around the whole guitar and dissipates - lost as imperceptible vibrations of the back, sides, and all the attached wood. The opposite of that would be a lightly braced top where the structure isn't TOO rigid and the vibration energy sets the top in motion, instead of just sending the energy somewhere else.

OK, so the big (huge/gigantic) part of this is entirely in the design and build of the structure but it's so complex that describing the math would take a volume the size of an encyclopedia set (and not that I could ever do that).

But there are other areas where damping will occur and usually its from material choices themselves. If you make a guitar out of cork - its a soft spongy material and will absorb the vibration. What happens is microscopically the energy is distorting and moving the wood structure. Because the wood is so randomly shaped the is no cohesive vibrations it just jiggles all over and the internal friction of the wood micro-microscopically heats up consuming the energy as well as initiating random movements.

But, if you use a nice resonant wood, you won't have that effect - it will "ring".

So, top of your list is structure, next on your list is material choices, then finally (?) comes connections/joints. This is where poor connections like glue joints etcetera will absorb some of the energy causing damping effects.

Again, its so very complex because, for example, the glue material itself has some inherent damping (think of it like a rubbery layer), and if the joint is not tight you don't get good transmission - this goes back to miniscule variations in build quality.

This is one of the reasons very good guitars are 1) so expensive and 2) really so much better. This is part of the reason why an artisinal luthier is so very much worth their costs.
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  #3  
Old 04-12-2016, 07:03 AM
redir redir is offline
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Flemenco guitars are made very light and with the intent on having much less sustain and more punch. The choice of Spanish Cedar on a flamenco guitar neck is traditional for that reason.
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Old 04-12-2016, 11:49 AM
Pat Foster Pat Foster is offline
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Speaking in gross generalizations, heavy guitars often have more sustain, lighter ones less. Just as it takes more energy to get a larger mass (bridge, top, and sometimes the back) moving, that mass tends to stay in motion longer. They tend to have less "punch." In lighter guitars, getting their mass moving takes less energy, but that movement dissipates more quickly. Thus, the light construction and punchy delivery in flamencos. Again, a gross generalization.

Some people like the effect of brass bridge pins, adding mass that way, possibly giving up some volume and brightness. MIght be worth investigating, if just for the sake of experimentation, though I personally wouldn't use them in my builds. Also for experimentation, try clamping a C clamp to your headstock and see what happens. I wouldn't use a C-clamp in my builds either! In building, bridge weight can be a factor, as can the neck. A stiff neck can be helpful here. Lots to experiment with.

Pat
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Old 04-12-2016, 12:29 PM
Alan Carruth Alan Carruth is offline
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Sustain is the length of time the tone remains audible; that is, above a certain threshold of hearing acuity. There are two ways to do this. One is to use a light structure that extracts energy from the string quickly, and can maintain a high output with minimal input. This is 'banjo' sustain. It builds fast, and dies out relatively quickly, but you can hear it for a reasonably long time. It also tends to 'cut' well; an advantage for the sorts of loud parties where the banjo and Flamenco guitar originated.

The other sort of sustain is what I think of as 'Les Paul' sustain. A heavy, rigid top keeps most of the energy in the string, which has (relatively) low damping, and it 'leaks' into the guitar slowly. The sound level is low, and dies out very slowly.

Both of these have been covered, of course, but the posts may have seemed contradictory as each mentions only one sort of sustain.
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Old 04-12-2016, 12:48 PM
charles Tauber charles Tauber is offline
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From the video page on your website:

Quote:
You do not have to have any experience of woodwork to make a really high-end acoustic guitar on your kitchen table on a shoestring budget. This highly-detailed 3 hour video guide will guide you through every little detail of every little step of making an acoustic guitar at home. It's way better than any book because you can see it all being done rather than just reading about and looking at pictures of the process. You can watch the first hour free here and then click the button below to instantly download the full 3 hour film.
http://customguitarbuilding.com/buil...%20course.html

I watched part of your video. My observation is that your top is likely too thick and the braces too tall and wide. (In addition, many makers thin the edges of the top more than the middle to decrease stiffness near the edges.) Depending upon what other things you have going on, these might improve sound quality/sustain.

As you are, perhaps, discovering, making "a really high-end acoustic guitar" involves more than basic woodworking skills and following a purchased pattern. I don't mean to sound harsh, but it just isn't as easy as that.
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Old 04-12-2016, 01:06 PM
LouieAtienza LouieAtienza is offline
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My belief is for a certain guitar - it's tonewoods, hardware, bone, nut, fret wire, truss rod, etc. - and a certain player, playing in a certain style, there is a maximum total output he/she can get for the input put into the guitar. The obvious output is the volume, and as discussed here how long can that certain volume swell, sustain, and decay. Some output maybe not readily sensed may be how the strings themselves interact with the air surrounding it, or maybe the friction of the strings through the air (and where there's friction there will be heat, however imperceptible); other parts of the guitar which either absorb or reflect sound; even "feedback" from vibrations driving the strings further...

So I believe this total "output" is similar to a pie chart. Each "slice" of the pie would be a different output. So as one slice gets bigger, one or more of the other slices get smaller. Probably the biggest slice would be losses due to damping, whether we do it when we play (how we hold the guitar or rest our picking hand for example) or whether there's something in the construction of the guitar that dampens vibrations, such as certain woods, saddle material...

We could take just one component of the guitar, the bridge, for an example. In one extreme, I could make the bridge out of stainless steel. It would be relatively heavy, and thus the strings could experience longer sustain than whatever wood. But I would hazard that it would act as a vibration "sink" of sorts, preventing the strings' vibrations from transferring to the soundboard. And the weight would potentially make the top harder to drive, reducing volume further. On an electric guitar this is usually not a problem because we can make the pickups as hot as necessary and turn the volume up on the amp as much as possible... the acoustic guitar is the amp as well.

On the other hand, we could make a bridge of structural foam. Very light, but I would guess the strings' vibrations may be dampened significantly by it. And whatever vibrations reach the soundboard may not be the most pleasant to the ear.

I feel a fretboard can have an effect on perceived sustain. I prefer ebony fretboards on acoustic and maple on electric. I find the notes seem to jump out faster, then taper and decay. I find on a rosewood fretboard the notes seem to swell to full volume, then decay slowly, like "frown" on a graph.

As far as back and side woods, I feel that the denser hardwoods like rosewoods tend to "resonate" more than say maple or walnut or cherry... Maybe something the audience can't perceive, but they're not the ones playing the instrument. I feel if an instrument inspires you and your performance, then that is what is conveyed to the audience. But of course sustain may not be of importance to you if you're a flamenco player, or chickin' picker, or even jazz player. But maybe so if your repertoire includes some classical, or Celtic tunes popular right now, other modern fingerstyle playing. Meaning, the sustain should not be the end-all be-all goal, if you are happy with the bass and treble response and overall tone of the instrument.

It's really the law of the conservation of energy... It is neither created nor lost. Our goal as builders is to minimize the "losses" and adjust the slices to give us the best balance of volume, tone, and sustain, for the music being played.
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Old 04-13-2016, 11:18 AM
matt301273 matt301273 is offline
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Hi,

That's a different guitar in the video. The first one I made. And yes, I did go to heavy on the bracing. I'm trying to sell the film to first timers as a kind of 'If I can do it, so can you'

But thanks very much for the input
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Old 04-13-2016, 12:42 PM
matt301273 matt301273 is offline
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Wow...Thanks everyone for your kind input...Certainly is food for thought...
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Old 04-13-2016, 10:40 PM
tadol tadol is offline
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Try a denser neck and larger headstock - you could also try a small c-clamp on the headstock and see if that helps -
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Old 04-14-2016, 08:20 AM
Truckjohn Truckjohn is offline
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I built a parlor guitar out of red oak... Including an oak neck, head block, and tail block.

It's a great guitar and all - but carving that neck was a royal pain.... And all that oak is kinda heavy compared to making all those parts out of "normal" stuff. The neck also requires more force on the trussrod because the oak is just so stiff...

One caution about C-clamps on the headstock....
Adding weight tends to mirror the sort of results you experience by making things far more flexible.

Guitars behave differently with a clamp clamped to the end of a conventional neck than they do with a heavy, stiff neck like the oak neck. C-clamps produce a very audible change in sound that I don't really like. This is because they accentuate the "marimba bar" moment on the guitar where the whole thing flexes end to end and reduce its frequency considerably. It makes the guitar sound "woofy" in a bad way.

Normally constructed necks made with heavier woods tend to be WAY stiffer - and the weight is spread out across the entire neck... As such, it has a completely different effect than just adding some clamps.

Thanks
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Old 04-14-2016, 08:30 AM
6L6 6L6 is offline
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I would recommend taking a tour of Bill Collings factory and pay very close attention.
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Old 04-14-2016, 08:38 AM
tadol tadol is offline
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Quote:
Originally Posted by Truckjohn View Post
I built a parlor guitar out of red oak... Including an oak neck, head block, and tail block.

It's a great guitar and all - but carving that neck was a royal pain.... And all that oak is kinda heavy compared to making all those parts out of "normal" stuff. The neck also requires more force on the trussrod because the oak is just so stiff...

One caution about C-clamps on the headstock....
Adding weight tends to mirror the sort of results you experience by making things far more flexible.

Guitars behave differently with a clamp clamped to the end of a conventional neck than they do with a heavy, stiff neck like the oak neck. C-clamps produce a very audible change in sound that I don't really like. This is because they accentuate the "marimba bar" moment on the guitar where the whole thing flexes end to end and reduce its frequency considerably. It makes the guitar sound "woofy" in a bad way.

Normally constructed necks made with heavier woods tend to be WAY stiffer - and the weight is spread out across the entire neck... As such, it has a completely different effect than just adding some clamps.

Thanks
Was only pointing to other ways that I hadn't seen mentioned to help with sustain - a small clamp is a quick way to see what effect a larger/heavier headstock could make - can't imagine anyone would think to keep one clamped on - the density of neck stock and finished dimension does affect weight, flexibility, tone, and playability - solid single species v laminated will as well - truss rod and reinforcements will too - lots and lots of variables that will affect tone and sustain, and none of them have anything to do with the body of the guitar even though thats all many focus on or pay attention to -
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Old 04-14-2016, 06:18 PM
Truckjohn Truckjohn is offline
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I mention the clamp on the headstock because I have heard similar and tried it out.

I think you can mirror the effects of the weight more closely by clamping a soft face clamp to the neck heel.

Anyway - I think it would be worthwhile to make sure you are talking about sustain and not overtones. Guitars like Collings tend to have more overtones but the sustain may the same as a straight braced Martin. The classic J45 "thump" is what very little sustain sounds like in a steel string acoustic.

Thanks
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Old 04-14-2016, 08:23 PM
LouieAtienza LouieAtienza is offline
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They make a weight that "clamps" onto the headstock called a "Fat Finger".

Of course there's always trade-offs. If you make the neck heavier, it can make playing uncomfortable for certain styles, as the tendency is for the guitar to "tip" in that direction, causing the fretting hand to "hold" the neck up as well.

In Somogyi's epic books, he describes the process of inlaying a counterweight in the headstock, before applying its faceplate. If I remember, he does not say implicitly that he actually does this himself, but does say that it potentially helps.

If you look at McPherson, or PRS, necks (check YouTube), they both have ginormous carbon fiber rods in them. McPherson has a huge CF rod, that's anchored to a large brass plug going down the heel, and all that is triangulated with a stainless steel screw. The neck bolts are attached from inside the guitar to that large brass block. PRS uses Peruvian walnut (Nogal) for their necks, and is probably a bit denser than Claro walnut.

To amplify truckkjohn's post, yes I believe there is a difference, or should I say distinction, between the sustain of the string and the "resonance" of the guitar body. And I believe that is due partly to construction, and partly to material.
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