What controls/influences deep bass on dreadnought

[6ixxer]

I had posted a question on the general part of the forum trying to get an understanding of what exactly in a guitar influences the bass on a dreadnought and hoping some knowledgeable builders could chime in here. I have played several different mid to higher end dreads and noticed how some have a really nice deep full bass on the low E (almost like a chug bass response) while others have a less full and more thin bass sound. I don't know how to describe it any better but here is a list of some guitars that do/don't have the bass feel/sound I prefer.

Nice deep/full(chuggy) bass

-Martin HD-28V
-Larrivee D-40R (my current guitar)
-Taylor 410eR (current model The older 410r doesn't have it)
-Martin D-15 Custom
-Taylor 918 (Jumbo not dreadnought)


Thinner/kind of tinny bass

-Martin D-28
-Taylor 810
-All Collings dreads I have played
-Mcpherson 4.5xp (Indian Rosewood/Adirondack Spruce)
-Santa Cruz Tony Rice
-Huss and Dalton Dreadnought (can't remember model)
-Wilborn Dreadnought (Brazilian/Ceder)

There may be more but these are the ones that come to mind right now. Funny but the Mcpherson I owned had really nice bass response on the A string but lacked it on the low E. You could actually feel the bass through the bak of the guitar on your body on the open A string and it was a pretty neat and rare feeling that I have never experienced on any other guitar.

Thanks for any ideas or help you can provide!!

Btw I am beginning a build of my own and looking to get as much info on manipulating the sound I want out of the guitar as possible.

[John Arnold]

Top braces, primarily. The lower the brace, the less stiffness, which accentuates bass. And to a lesser degree, top thickness affects bass response. The thinner the top, the more bass.

Funny but the Mcpherson I owned had really nice bass response on the A string but lacked it on the low E. You could actually feel the bass through the bak of the guitar on your body on the open A string and it was a pretty neat and rare feeling that I have never experienced on any other guitar.

Feeling bass in the back of the guitar is primarily a function of the back braces. Again, lower braces make a 'looser' back that is more active. Also, ladder braces make a top or back stiffer than X or fan braces.
A guitar like the McPherson that is responsive on the low A but not the low E probably has an air resonance that is close to A.
A Martin HD-28 (scalloped braces) tends to have an air resonance around an E or F. So they tend to respond well on the low E. In general, a dreadnought that has an air resonance as low as the low E tends to sound 'tubby', which means lacking in treble.

[6ixxer]

Originally Posted by John Arnold

Top braces, primarily. The lower the brace, the less stiffness, which accentuates bass. And to a lesser degree, top thickness affects bass response. The thinner the top, the more bass.

Feeling bass in the back of the guitar is primarily a function of the back braces. Again, lower braces make a 'looser' back that is more active. Also, ladder braces make a top or back stiffer than X or fan braces.
A guitar like the McPherson that is responsive on the low A but not the low E probably has an air resonance that is close to A.
A Martin HD-28 (scalloped braces) tends to have an air resonance around an E or F. So they tend to respond well on the low E. In general, a dreadnought that has an air resonance as low as the low E tends to sound 'tubby', which means lacking in treble.

By lower, do you mean the overall height of the brace or being scalloped more deeply so there is less material in the brace? Also, is there a way to tell what end of the spectrum the guitar is "tuned" or leaning towards?

[John Arnold]

Yes, I am referring to the brace height. There are instruments that measure air resonance and top resonance, but I just hum over the soundhole or tap on the bridge to determine them. The air resonance (AKA Helmholz resonance) is the lowest (usually between the low E and G on a dread), and the top resonance is roughly an octave above the air resonance.
Air resonance is a function of the air volume and the size and shape of the aperture. Guitars are not rigid, so the air resonance is lower than that predicted by Helmholz formulas. As the top and back get looser (lower frequency), the air resonance also gets lower, which tends to produce more bass.

[redir]

Originally Posted by John Arnold

A Martin HD-28 (scalloped braces) tends to have an air resonance around an E or F. So they tend to respond well on the low E. In general, a dreadnought that has an air resonance as low as the low E tends to sound 'tubby', which means lacking in treble.

Interesting. I have only ever built one Dred, a mahogany body with a red wood top, and the main air came right out on E. It sounds amazing when playing blues in E but "tubby" in anything else. Of the 65+ guitars I have built none of them have ever been that low, usually they are around G.

[hat]

Originally Posted by John Arnold

Yes, I am referring to the brace height. There are instruments that measure air resonance and top resonance, but I just hum over the soundhole or tap on the bridge to determine them. The air resonance (AKA Helmholz resonance) is the lowest (usually between the low E and G on a dread), and the top resonance is roughly an octave above the air resonance.
Air resonance is a function of the air volume and the size and shape of the aperture. Guitars are not rigid, so the air resonance is lower than that predicted by Helmholz formulas. As the top and back get looser (lower frequency), the air resonance also gets lower, which tends to produce more bass.

So, John - can one make the assumption that the more forward shifted the braces are, then the lower the freq also?

[fazool]

Originally Posted by 6ixxer

...what exactly in a guitar influences the bass on a dreadnought ...

It's very simple. It is the interaction of:

• The body shape
• the body size
• the wood selection
• the bracing wood
• the bracing pattern
• the joining methods
• the builders technique
• the bridge placement
• the features like cutaway/sound port bevel etc.
• the string selection
• pickguard thickness
• playing technique
• barometric pressure and relative humidity
• and a couple dozen others I failed to list

[12barBill]

What causes a guitar to have a deeper (lower frequency?) bass but its tubby, floppy, not focused, not tight and another guitar to have that deep bass but it is tight, not tubby, more focused? If you know what I mean. I realize those descriptive terms are not precise.

[Alan Carruth]

As John says, the low 'main air' resonance pitch has a lot to do with how 'bassy' a guitar sounds. And, of course, there's a lot of things that go into determining how low pitched that resonance is. I've found, for example, that shaving back braces can often be the best and most effective way to enhance the bass response of a guitar. Getting the 'main back'tap tone (resonance) close in pitch to the 'main top' resonance strengthens their interaction and drops the 'air' pitch, sometimes by as much as a couple of semitones.

When I took voice lessons my teacher said that:"The way to make your low notes sound better is to work on the high notes". 'Tubby' basses are often as much a function of the clarity of the tone as shear power. 'Clear' tone seems (to me) to come from getting the top and it's bracing working well together. I've seen guitars with 'marshmallow' tops that still had nice clarity, and clean bass tone that was not at all 'tubby'.

[tadol]

Scalloped vs tapered braces. The stiffness of the top vs the thickness. The bracing material. The size and weight of the bridge. The size of the soundhole. There are a few of the things to consider. If it were just a matter of adjusting one, or maybe two variables, then you (and everyone else) would have no problem making great sounding guitars with full, thick bass that was also very crisp and articulate, while still being in balance with the mids and highs. But its pretty tricky - far more art than science for most builders. Your choices of guitars with good vs poor bass are interesting - but while a few of them make sense (as they are probably not built to meet your criteria of “good” bass) a number of them strike me as possibly being the particular guitar you played.

I wish I could offer more, but it seems like you are getting alot of good info - the only problem is, it probably leaves you with even more questions -

[phavriluk]

I think OP's cart is way in front of his horse. OP's going to be plenty busy building neatly and precisely to have much time to speculate about indistinct acoustic subtleties. I suggest OP follow the plans and do his best to copy the design on the plans. I found Stew-Mac's Herringbone dread plan a good one to copy first time out. Unless OP's building under skilled and experienced instruction, in which case do what the teacher says.

[6ixxer]

I'm asking for different reasons than for my first build. It's a question that I have been wondering about for a few years and if I can learn now what I want to know, it will help me down the road when I am building guitars more frequently. At the same time I am going to consider what I have learned so far and incorporate that knowledge into my first build.

Originally Posted by phavriluk

I think OP's cart is way in front of his horse. OP's going to be plenty busy building neatly and precisely to have much time to speculate about indistinct acoustic subtleties. I suggest OP follow the plans and do his best to copy the design on the plans. I found Stew-Mac's Herringbone dread plan a good one to copy first time out. Unless OP's building under skilled and experienced instruction, in which case do what the teacher says.

[Silly Moustache]

But :