Bass ring and sustain vs dull thump

[NeilG495]

Not sure if this is the correct section to post this question but here goes. Having owned and played a few high end guitars, I’ve invariably been disappointed with the sustain or ring of the bass E string, particularly when fretted on the 5th fret and above. When building a guitar, what would you do, during construction ( top, braces etc.) to maximise the bass ring and sustain and avoid the dreaded dull thump? All opinions very welcome.

[Kevin in California]

I don't know.
I built an OM last year walnut and spruce, and I can't believe how lively, loud and how much sustain I'm getting on the low E. Almost too much.
I built it the same as all my OMs.
You might just try different strings
I'm using Earthwoods

[NeilG495]

Thanks Kevin, I have experimented with strings with some success, I just wondered if there was anything firming the build process that could help with bass response.

[John Parchem]

First general comments for context: There are a few elements involved in sustain. stiffness, mass and "Q" dampening effect. Often there are tradeoffs. For example a Les Paul Almost has infinite sustain, because it is so heavy and stiff that nothing is moving except the string. No external factor is taking energy from the string. But acoustically it is very quiet. An opposite example would be a very lightly built guitar. When the string is vibrating the neck is moving, the sides are vibrating the back is vibrating and of course the top; all that movement is using energy from the pluck of the string. A good acoustic guitar is tight, minimal extraneous vibration, with the box tuned where there is a good balance across the range of the guitar. So minimal extraneous vibrations and a balance across the strings and a tradeoff between loudness and sustain. (A guitar can also have wolf notes where the guitar has a strong resonance to a frequency. In that case the energy is quickly eaten up and there could be dud notes. Maybe loud but short.)

For your example I suspect sustain might be the ability to hear the bass notes; how long they are loud vs how long the string actually vibrates. For a steel string I like the top resonance to be 170 or 180 Hz. Too stiff of a top can sound great in the trebles (easy on a steel string) but makes it hard to move the the top at bass frequencies. In that case there is actually good sustain on the string but the bass is not loud enough. If the guitar is very lightly built, the bass may be loud but the string is quickly drained of energy. Also at some point the trebles suffer, especially on a classical guitar. Thus the balance.

For a build, make sure the top is at a good thickness for the wood being used in the guitar. To thick of a top (even at a good box resonance) has more mass thus takes more mass to move. For steel strings Robbie and Kent Everett's sheet metal shaking test for thickness is really good. The sheet metal sound assure a balance of mass and stiffness. With the top thicknessed set then one can play with the brace stiffness to balance response between the strings. and also between loudness and sustain.

[NeilG495]

Thank you for the reply John, very informative. One of my biggest guitar owning disappointments was a new Martin D28 I bought back in the 80’s, a loud guitar but the bass E string was a total dud. I believe they were just over built at that time, non scalloped braces and probably thicker tops, so yes they would last a life time, with no warranty returns, but the sustain suffered for it. It does seem to be a very fine balance between top and brace thickness, too thick and kills sustain, too thin and it sounds amazing, for while, but structural stability could be an issue later down the line. Personally, I’ve gone down to 1/4” scalloped braces on my guitars now but I’m also experimenting with the amount that the top is thinned around the outer edge of the lower bout and it’s effect on sustain. I don’t suppose I’ll ever build one I’m completely happy with but it’s good fun trying