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Thread: Single Most Important Factor For Volume/Projection?

  1. #11
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    Quote Originally Posted by Red Cliff View Post
    Others may know something I don't but I'm not sure the shape of the back (arched Vs flat) is actually as important as the rigidity. Arched backs tend to be heavier and stiffer and it is this the reflects the sound I believe rather than the profile. If you make a flat back equally rigid it will sound the same in my opinion. Certainly I have never seen any evidence to the contrary.
    If you look at other instruments such as guitars or mandolins it is noticeable that those with arched backs or even bowl shaped bodies have much higher volume and projection than their flat backed cousins. The size, shape, and position of soundhole(s) may also be related to that. There's is probably some scientific literature on this available.

  2. #12
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    I'd have a hard time believing that the level of radius typically put on a uke back has any impact on volume (assuming all else remained the same). For me, our slight radii on top and back plates is more about resilience than volume or tone. If a totally flat plate tries to expand/contract with humidity changes, it has nowhere to go and is likely to crack. A small radius gives a sort of spring factor - if the top needs to grow or shrink because of humidity changes, it can push/pull into a tighter or wider radius easily without cracking.

  3. #13
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    I taper my ukes (3/16th of an inch or 5 mm over 1 foot or 30 cm) and compound radius the back (14 foot - 4.2 meters at the lower bout). Frankly I have never really come across any data other than anecdotal that this increases volume or projection, but I do it anyway and my ukes sound good. I do it because other instrument makers do it and have for hundreds of years which is not really a good reason but there you have it. I figure they must be on to something so I do it. Hey it couldn't hurt. There are other things in building acoustic instruments that also might not bear up under scrutiny. Tradition plays a big role.

  4. #14
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    Quote Originally Posted by merlin666 View Post
    If you look at other instruments such as guitars or mandolins it is noticeable that those with arched backs or even bowl shaped bodies have much higher volume and projection than their flat backed cousins. The size, shape, and position of soundhole(s) may also be related to that. There's is probably some scientific literature on this available.
    I think that is the point I am making. All else being equal they don't, people think they do and as Sequoia says many of us (me included) build with an arched back because tradition says we should. But so far there is no evidence it does. People expect it to sound louder so that is what they hear. And there is a history that says cheaper instruments have flat tops and backs and expensive ones have arched. But that doesn't mean it is so.

    In the.end as others have said it can't hurt and has other benefits such as resistance to splitting in humidity fluctuations. But the volume thing appears to be so far unproven, in a scientific sense.

  5. #15
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    Quote Originally Posted by Michael N. View Post
    Thin soundboard, thick sides, very thick back. That should move things more towards the Smallman concept. Of course one could go all the way and build a stripped down lattice with carbon fibre. Then couple it with immovable sides and multi-laminated back. It would end up rather heavy (Smallman's are hugely heavy). You should gain volume. The whole idea of the construction is to keep the string energy in the top, maximium efficiency.
    Whether you like the resulting sound is another matter. Many think you gain volume but at the expense of a sound that they dislike. I have heard the odd Smallman that sounds very impressive but I've also heard some that I could barely listen to.
    I guess someone somewhere must be making a uke version?? Other than that, yes the banjo version.
    Yes indeed to all this.
    Stiff sides (with mass and proper density) are major contributors. A reflective back (ie a stiff back) is an easy and sure way to further promote it.

    A responsive top and good construction in general too but you should have that in any instrument.

    The the exact opposite to a flamenco guitar, which needs to be built wobbly to dissipate that top energy down the thin sides and into a thin back.

  6. #16
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    The arch of the back has one effect on the volume, it makes the back stiffer and less subject to vibrate. In the projection end you do not want to waste energy vibrating a back that is most likely up against the player. I hate the term, 'reflective back' as the wavelength of sound in the box is generally much larger than the distance between the top and back. There is no reflection, building stiff and heavy as with a speaker cabinet leaves the energy in the top and not wasted.

  7. #17
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    Quote Originally Posted by printer2 View Post
    The arch of the back has one effect on the volume, it makes the back stiffer and less subject to vibrate. In the projection end you do not want to waste energy vibrating a back that is most likely up against the player. I hate the term, 'reflective back' as the wavelength of sound in the box is generally much larger than the distance between the top and back. There is no reflection, building stiff and heavy as with a speaker cabinet leaves the energy in the top and not wasted.
    A flat or concave back fits nice and snug to the players tum, and deadens the volume...an arched back only makes contact to a small area in the centre to the players tum. So less deadening....just a thought
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  8. #18
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    Quote Originally Posted by Timbuck View Post
    A flat or concave back fits nice and snug to the players tum, and deadens the volume...an arched back only makes contact to a small area in the centre to the players tum. So less deadening....just a thought
    That is if the back is made flexible. The whole point is not to. It can be flat or concave (better for humidity changes) and made fairly ridged. I lust took a junk plywood guitar and shaved the lumber-like back braces down by at least a third and shaped them. It changed the back from a non-resonant back to one that is. It added some depth bass response and is now pleasing enough to listen to.

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