Curious about bridge height, break angle and string gauge

[HoGo]

A ' composite bow ' is is a laminated type of archery weapon.

Dave H

The graph of energy stored is completely wrong. Even if the limbs are pre-tensioned (actually they are pre-tensioned on standard self bow as well, just a bit smaller amount) the bowyer always starts the pull at zero and from there the force curve rises to full draw. The tension in the limbs and also the rigid ends that act as levers cause the curve be more steep at the beginning of pull and increase the surface which represents energy stored even with similar final draw weight. But in the end efficiency of the bow is what matters and bows with similar or same "curve" can in the end shoot the same arrow at lower speed. Efficiency of shooting s also dependent on arrow and string weight...
Modern compound bows are engineered for specific shape of this curve that lifts up in the middle to top draw weight and sinks down at the end so you don't have to hold full draw weight while taking aim.

[peter.coombe]

From my understanding and experience is that you cannot gain "energy" or tone, without sacrificing something else. So you get more volume, then something else is less. So you get more tone, then something else is sacrificed.

So even if you do achieve more volume by some means, you may find the resultant tone is less preferable to your ears.

Partially true. True you cannot gain energy, but you can gain efficiency, and that does not necessarily come at the expense of tone. It is certainly easy to make a mandolin or guitar sound louder by reducing the mass of the top and the result is louder but poor or terrible tone. It is also possible to reduce the mass of the top and maintain the tone or even improve tone, but that is much harder to do. The hypothesis that louder = worse tone has been thoroughly debunked by Australian luthiers Greg Smallman with classical guitars and Trevor Gore with steel string guitars. Greg Smallman is famous for lattice bracing and his guitars are much louder and sound just as good or better than any traditional braced guitar. Other Australian luthiers have followed his lead and lattice bracing is popular amongst Australian classical guitar builders. It has not caught on much in the USA. The thing is, if you reduce the mass of the top, but stiffness remains the same (it has to or the instrument will implode), it changes a lot of things. All the modes of vibration go up in frequency. If you don't bear that in mind and fundamentally change the way the instrument is built it will probably sound awful. A Smallman guitar is built fundamentally differently from a traditional classical guitar, a radically different way of building a classical guitar. The top is very thin, but the back and sides are laminated, heavy, and the back is arched. The guitar has a heavy stiff plywood frame that the top is glued to and there is a lot of carbon fiber used in the construction. They are heavy instruments, but because the top is so light, about 50% lighter than a traditional fan braced guitar, they are much more efficient in producing sound and all the sound comes from the lower bout of the top. This development was not easy, it took Smallman years to perfect it, but he now has around 30 years of experience working with this system. The classical guitar world has a lot of tradition associated with it (not as much as the violin world), and there is a lot of rubbish said about lattice bracing such as the more carbon fiber in a guitar the worse it sounds. Garbage if you properly compensate for the changes a lighter top makes to the way it vibrates.

In the steel string world, Trevor Gore has developed a bracing pattern he calls falcate bracing. It is a more efficient than an X brace and, like Smallmann, uses carbon fiber tow on the top and bottom of the braces so the braces become an I beam. That allows the top to be about 30% lighter and the falcate braced guitars are noticably louder, but if you follow Trevor's methods they do sound very good. I have played some falcate braced guitars and the most obvious thing is the huge dynamic range they have, even with tops made from Cedar which is not known for dynamic range. One in particular was one of the best sounding steel string guitars I have ever come across. Lattice bracing and falcate bracing is nicely described in the Gore and Gilet books if you want to follow it up.

What is the relevance to mandolins? Mandolins vibrate like guitars so the same principles apply. There is no reason why a much louder mandolin with good tone cannot be built, but it is likely to be built fundamentally differently around a very light top and an efficient bracing pattern that contains carbon fiber. There are some important differences between a guitar and a mandolin so it won't be easy, you can't just adapt a guitar brace to a mandolin. The size difference is relatively easy, but the forces are different, a guitar bridge rotates, a mandolin bridge does not rotate, it sinks, but the tailpiece does rotate. There is also more tension on the strings. So there are lots of unknowns that need to be worked out and solved. Some have tried and failed. I played a mandolin made by Australian luthier Doug Eaton that was lattice braced that was the loudest mandolin I have ever played by a huge margin, but it sounded obnoxious. So, volume is impressive, tone needs a bit of work. There is work to be done and I intend to give it a go. I enjoy difficult challenges and can't resist this one.

[Tavy]

+1 on what Peter says, but to add to that there are a lot of things in a stringed instrument that basically just waste energy and convert it to heat. In fact anything that's not a mode of vibration which is directly generating sound *could* be argued to be just lost/wasted energy. I say *could* because some vibrational modes will give energy back to the top over time and this will effect the tone: the prime and most extreme example is the much discussed Virzi sitting inside vibrating and doing nothing that will generate sound directly, but none the less modifying the tone somewhat. Less extreme but rather common examples include neck and truss rod vibration, ribs moving, top uselessly flapping about around the weaker (oval) sound hole area, and of course poor bridge material, all resulting in vibrational losses and effectively working as filters to reduce specific frequencies. Other than the bridge these are all rather hard to address on an existing instrument, but there are building tricks that will address all of these to some degree, and all can produce very marked increases in volume even before you look at changing the top/back.

Of course because "vibrational loss reduction" necessarily tends to effect some frequencies more than others, there is a change in tone, but I would argue that we're really just getting the instrument into optimal shape. One extreme example was a very dark but rather quiet sounding mandolin which had a fractured bridge that was just filtering out all the trebles. Fitting a new high quality bridge produced a loud, but slightly over-bright mandolin, one could argue this wasn't much an improvement, but I would argue the "fix" just unleashed what was waiting there, and certainly I wouldn't recommend a broken bridge as a fix for a bright mandolin!

[Richard500]

“ top uselessly flapping about around the weaker (oval) sound hole area”
Frequently also observed in politicians.

[Tavy]

“ top uselessly flapping about around the weaker (oval) sound hole area”
Frequently also observed in politicians.

Hmmm, I could suggest some structural support...

[s11141827]

A Higher break angle does allow for lighter strings for ease of playability.

[HoGo]

A Higher break angle does allow for lighter strings for ease of playability.

That is not correct. Break angle over bridge has nothing to do with playability.
Break angle may cause higher pre-load on the structure of the instrument (AKA "bridge pressure") but the string tension and neck/ string geometry noticeable to player is still the same. Some may argue that mandolins with higher break angle are easier to play or something like that but unless you reset neck to a different angle on the same instrument you cannot generalize.

[peter.coombe]

Following on from my Jan post, the first prototype is almost finished, made from Engelmann Spruce and Australian Blackwood. It is completed except for the bridge. I ran out of Brekke flat top bridges and didn't realize, so has been frustrating having it ready but not able to put the strings on. The bridge is somewhere between the USA and Australia at the moment. It is fan braced with the fan braces made from Balsa wood topped with carbon fiber tow. I left the main structural cross braces as red spruce to reduce at least one unknown and to retain structural integrity. Once the carbon fiber is installed you can't adjust the braces so I thinned the top, it was obviously too stiff. The top ended up 2.5mm thick in the center and 2mm thick on the edges which is significantly thinner than around 3mm which is what I would normally use for Engelmann. The savings on mass of the top is about 30%, and that can probably be improved on as I tweek the design. Everything measures ok, all within what I would expect to sound good so can hardly wait for the bridge to arrive. I did make another prototype top with lattice bracing, but it measured pretty much the same as the fan brace, but lattice bracing is more difficult and time consuming to implement so I decided to stick with the fan braces. Watch this space.

[Skip Kelley]

I had a mandolin in the shop once for a set-up. The strings at the 15th fret were almost 1/4 off the fretboard. The owner said the higher action made it louder. I set it up like normal and lowered the action to something reasonable. It was low. The mandolin came alive. The owner couldn't believe it. I told him, I felt the higher bridge height was too much pressure for the top. It couldn't vibrate as intended.

[pops1]

My mandolin is quite loud, and has very low action. I don't believe that high action makes a mandolin louder.

[s11141827]

An Allen Tailpiece might allow you to have a sharper break angle w/o having too much tension which might cause the top to collapse, plus you can use Ball & Loop End Strings of every kind. My idea was exposed Core Mandolin strings so that you can lower the action further

I got that idea from Piano Strings plus they're compound wound to make them more flexible.

[s11141827]

For mine I had to crank down the angle of the tailpiece so I can switch to the lightest gauge of strings.

[DavidBlair]

Im curious if there are any opinions about the lemgth of wire between the saddle and tailpiece? Are there some sympathetic overtones? And some tailpieces are made to shorten the length on the bass strings side or the treble side...
And sometimes i see an instrument with a forward leaning bridge.

[j. condino]

Since I first started playing, I've always wondered why there is no commonly available mandolin tailpiece that can be adjusted in multiple directions to find the optimal angle, height, and afterlength for the desired tone and volume outcomes. Even a workshop model that I only used for problem solving would be very useful.

In the violin family and double bass world, I adjust all of these on a regular basis and they are universally agreed to have measurable effects on the instrument's voice. On the mandolin world it all just seems to be bolt it on and call it good, while anything else is, "...a whole lotta nuthin'." I never hear mandolin people talking about string afterlength behind the bridge.

Even though there are likely 100 people who would hear nothing, if it just worked for one person with exceptional hearing, it would be worth it. With a well made & high performing mandolin, I can detect tremendous differences in subtle changes to everything on the instrument. I also recognize that not everyone does, but it matters to me.

As always, 1000 points of laughter go out to all of the half deaf old geezers arguing about "tone"...

[Don Grieser]

Well, you should design a tailpiece and put it into production. I've always wondered about string length after the nut and before the bridge. Phoenix mandolins had long headstocks and string length after the nut and every one I had played like butter. String length behind the bridge seemed pretty standard on them.

Epiphone did frequesator tailpieces with longer spacing on the higher strings and shorter spacing on the lower strings on their archtop guitars. Randy Wood did a similar thing, but I don't think he sells or uses those any more.

Let's see what you come up with. I'm old and deaf, but I'm in on it.

[peter.coombe]

Im curious if there are any opinions about the lemgth of wire between the saddle and tailpiece? Are there some sympathetic overtones? And some tailpieces are made to shorten the length on the bass strings side or the treble side...
And sometimes i see an instrument with a forward leaning bridge.

You can get sympathetic overtones, and when it is close to a note on the scale it can make the mandolin sound out of tune on that note. Can get very frustrating because no amount of tuning will fix the problem, and if you don't know what is going on, is difficult to track down. This is why some tailpieces are designed to dampen the strings between the bridge and the tailpiece. As for length, it does matter because that will determine the frequency of the sympathetic vibration. Lyon and Healy patented their quite interesting tailpiece design. It is designed such that the sympathetic vibration is in tune with the string. It works reasonably well, but it is much easier to dampen it out completely.

[Dave Hanson]

' frequesator ' ?

what does that mean ?


Dave H

[Ray(T)]

It’s some sort of trade name for a trapeze style tailpiece used on Epiphone guitars (they may even have invented it?) - in a similar way as saying you’re “hoovering”, if you get my drift.

[pops1]

A longer string length from tuner to tailpiece would have more available string length to stretch than a shorter string and have minimally less tension. I believe that is the reason for tailpieces like the frequesator tailpiece that had longer treble strings.

[Dale Ludewig]

An Allen tailpiece, or any other kind of tailpiece, has nothing to do with how much tension the top can take due to break angle. Break angle is break angle. The same with downward pressure.