Dreadnoughts and jumbos — a visual comparison and a few rambling thoughts

[ataylor]

Disclaimer: potentially divisive subject matter! If this is a something that interests you and you're open to some healthy conversation, keep reading! If you've already seen one too many slope-shoulder dreadnought vs jumbo threads, get out while you can! If you're undecided, enter at your own risk!


Dreadnoughts and jumbos: some brief historical context

In 1934, Martin introduced the modern "dreadnought" with their 14-fret D-18 and D-28 designs. The same year, Gibson introduced their 14-fret "jumbo" model, which would eventually evolve into the J-45 and a handful of other guitars.

Aside from a detour Gibson took with the J-45 (and other models that shared the design) in the 60s/70s/80s, the Martin and Gibson shapes remain relatively the same today, with some very slight variation over the years due to manufacturing changes and such.

Here's the confusing part: decades later, many now refer to the J-45 and similarly-shaped guitars as a variation of "dreadnought" style guitar. Others insist on the original "jumbo" name. Who's wrong? Who's right? And why?

I thought it might be helpful to compare the two silhouettes, as well as some others for context.


Dreadnoughts and jumbos: a visual comparison

Another disclaimer: these shapes aren't exact facsimiles, but are tracings I've done to scale that should be close enough for our purposes. Apologies that the text and lines are a little grainy — it appears the images got overly compressed at some point.

Let's look at the D-28 and J-45 shapes.



There are subtle differences to be sure — the shoulders being the primary deviation — but overall, the visual footprint of these shapes is very similar! It's not difficult to see why the guitars eventually have come to be categorized together.

Now, let's look at these two silhouettes with the context of a couple other shapes from the same brands. Several years after introducing the "Jumbo" model, Gibson launched an even larger guitar with their "Super Jumbo" style, included here. Also included is the Martin 14-fret OM/000 shape, which was introduced four or five years prior to the 14-fret dreadnought shape.



The similarities between the D-28 and the J-45 become even more apparent when looking at these other two shapes from Gibson and Martin. The wide waist and the pear-shaped silhouette look nearly identical when compared to the narrower waists and different sizes of both the SJ-200 and the OM-28.

Now let's look at the D-28 and J-45 along with a few other similarly-sized guitars.



Like the first image, there is some slight deviation between the silhouettes, with the primary differences being at the shoulders — the Hummingbird being slightly more squared off, and the J-45 and 717 models a bit more rounded. Overall, however, they're all a lot more similar than they are different.

Finally, let's bring the SJ-200 and OM-28 back into the mix, along with another familiar "jumbo" shape from Guild and an "auditorium" shape from Taylor.



It's clear where the deviations are — the tighter waists of the auditorium sizes and the wider, more rounded lower bouts of the jumbo sizes are obvious outliers here, while the dreadnought sizes look even more consistent with the contrast of the other styles.


Dreadnoughts and jumbos — some final thoughts

So... are the J-45s and similar guitars dreadnoughts or jumbos? I believe the answer is a resounding... yes. Historically, there's no denying the Gibson style was called a jumbo. But it's also very clear that the style's silhouette shares more than a little in common with the Martin equivalent, and that most players, brands, and builders choose to categorize them together with the now-ubiquitous Martin term.

How did this happen? While these terms were initially more closely associated with specific brands and models, they have since become industry-wide sizing classifications, elevating them above use exclusive to a particular brand or model.

Part of the reason this happened was that the Martin and Gibson brands continued to make more guitar styles, and weren't always consistent in how they classified their guitars outside the model name.

For instance, the D-18 and D-18 were initially called orchestra models along with the other models with 14-frets clear of the body. The 14-fret dreadnought was even referred to as a bass guitar early on. Gibson introduced larger guitars after their original "jumbo" guitars with the larger SJ shape, and later the square-shouldered Hummingbird shape. By 1960 they were classifying all of these guitars as jumbos.

Another huge factor has been the ever-expanding number of guitar brands and builders over the years since Martin and Gibson introduced these shapes. Many of these newer guitars have been inspired by and patterned after these two classic and successful Martin and Gibson shapes. As such, there was a need for an industry-wide term for guitars that shared the same overall silhouette.

Because Martin had been more consistent with their classification and had arguably been more successful and well-known, and because the jumbo term had come to be more closely associated with larger guitars, the dreadnought term was categorically used for guitars with the same overall silhouette as the Martin and Gibson shapes, with the latter shape often subcategorized as a slope-shoulder or round-shoulder dreadnought.

So in summary, someone who calls the J-45 a jumbo is right — it is, after all, what the 'J' stands for and was the original name for that Gibson body style. And someone who calls it a slope-shoulder dreadnought is equally right — today the guitar typically falls into an industry-wide, "dreadnought" classification, as supported by the visuals above.

Hopefully this helps clear up any confusion some might have about the these terms — apologies in advance for any errors. Thanks for humoring me and high five for reading to the end.

[Rosewood99]

Maybe the J45 is Drumbo.

Very informative. Thanks for providing the illustrations. Great stuff.

[HodgdonExtreme]

I think it's rather incredible how such (seemingly) minor variations in shape can have such dramatic effects on tone.

[LeftyKev]

I'm not sure what you're trying to do, re-invent history or something. The J-45 is obviously a dreadnought.

[ataylor]

Originally Posted by paulzoom

Maybe the J45 is Drumbo.

Very informative. Thanks for providing the illustrations. Great stuff.

Thanks and you're welcome!

What about Jumbnought? I like yours better.

Originally Posted by HodgdonExtreme

I think it's rather incredible how such (seemingly) minor variations in shape can have such dramatic effects on tone.

Agreed. Bracing, bridge placement, and other construction details would bring additional variables, all resulting in the tonal signature of the various brands and models.

Originally Posted by LeftyKev

I'm not sure what you're trying to do, re-invent history or something. The J-45 is obviously a dreadnought.

Not reinventing anything — just providing context and some visual examples.

[gfirob]

Well, you would need a whole new set of comparative drawings with bracing patterns and profiles, and the number of different options boggles the mind. I am boggled...

[Shadowfox]

I'd love to see a side profile to see how much depth of the body plays into the tone!

[KalamazooGuy]

Well done.

[Brucebubs]

Nicely done. It's interesting to see a SJ-200 super jumbo has the same size waist as a Martin OM and just how much narrower they both are compared with a Martin D and Gibson J.

[ataylor]

Originally Posted by gfirob

Well, you would need a whole new set of comparative drawings with bracing patterns and profiles, and the number of different options boggles the mind. I am boggled...

Yeah, that would definitely make for a lot more work! The number of different Martin bracing variants alone is daunting enough.

Originally Posted by Shadowfox

I'd love to see a side profile to see how much depth of the body plays into the tone!

Yep, good call — the body depth would absolutely be a factor as well. For instance, I have several dreadnought-shape guitars and the clear outlier is my Taylor 210, which has a noticeably shallower body. As such, the tone is a bit more balanced, more akin to an auditorium-shaped guitar like a Martin OM or a Taylor x14 shape, but with just a little more bass and overall volume.

Originally Posted by KalamazooGuy

Well done.

Originally Posted by Brucebubs

Nicely done. It's interesting to see a SJ-200 super jumbo has the same size waist as a Martin OM and just how much narrower they both are compared with a Martin D and Gibson J.

Thanks folks!

Yes, I was surprised to see that as well. I think the overall shape of those big jumbo guitars is so impactful and overwhelming when you see them in isolation that you wouldn’t expect any part of the silhouette to be that close to a Martin OM.

[FLRon]

I appreciate the work that went into this informative post. Thanks for doing this.

[David Rance]

VERY interesting. Had thought the differences would be more. Fascinating that major differences are in lower bout perhaps in an attempt to make more 'boom'?? Get too big and the instrument becomes more difficult to hold I suppose. We are lucky that the design and especially the shape and size of the top, what classical luthiers call the plantilla which is sort of what you are describing, is still evolving and remains a subject for experimentation. Much of it remains empirical. Compare that with the violin which has evolved to the point where the design is much more fixed. Others have made the point that whatever you do to a guitar will alter the sound. Thank you so much for info and effort taken. Is there a 'most interesting thread of the month' prize?

[elmcmeen]

Fabulous job! Did you have time for anything else while doing this post, like eating or sleeping?

[ataylor]

Originally Posted by FLRon

I appreciate the work that went into this informative post. Thanks for doing this.

Originally Posted by elmcmeen

Fabulous job! Did you have time for anything else while doing this post, like eating or sleeping?

Thanks!

I had started on the tracings a week or so ago to contribute to another thread which the OP ended up asking to have closed. I ended up deciding it was worth finishing and posting after the fact as its own thread.

I'm a designer, so the graphics weren't too much of a hassle, and I've done enough research into these body styles for my own purposes in the past (I own both a Martin dreadnought and a Gibson-style jumbo/slope-shoulder dreadnought) that the writing was pretty straightforward.

Originally Posted by David Rance

VERY interesting. Had thought the differences would be more. Fascinating that major differences are in lower bout perhaps in an attempt to make more 'boom'?? Get too big and the instrument becomes more difficult to hold I suppose. We are lucky that the design and especially the shape and size of the top, what classical luthiers call the plantilla which is sort of what you are describing, is still evolving and remains a subject for experimentation. Much of it remains empirical. Compare that with the violin which has evolved to the point where the design is much more fixed. Others have made the point that whatever you do to a guitar will alter the sound. Thank you so much for info and effort taken. Is there a 'most interesting thread of the month' prize?

Thanks and you're welcome. In comparing the shapes of the dreadnought-sized guitars I own, I knew the differences were pretty subtle, but I too was surprised to see just how subtle they were. The difference between the current Martin dreadnought shoulder and the Gibson sloped shoulder isn't as drastic as it often appears.

Here's a theory for that: it may be partly to do with the fact that Gibson slope-shoulder guitars are typically finished in sunburst, with the top bout approaching a black or semi-opaque brown color, which has a "slimming effect" on the guitar, with contrasting cream binding that accentuates the radius of the curve. Meanwhile, Martins are typically natural tops with either white/cream binding that blends more with the natural top or dark/tortoise binding that blends more with the back/sides and makes the top and shoulders of the guitar appear larger and fuller compared to a similar guitar with a dark finish.

Just a theory!

As for the lower bout, everything I've read points to that being where most of the top's vibration comes from, which makes sense given that's where you see the most variation across different sizes/shapes and why it would seem bridge placement, bracing patterns and thicknesses, and wood types (both tonewood and bracing) are key in differentiating between various guitars that are the same or similar in size/shape — such as the D-28 vs HD-28 vs D-35, or a J-45 vs a Roy Smeck type guitar with the fretboard and bridge moved two frets down.

The violin comparison is an interesting one. I don't have much background in orchestral instruments, but I think you're right in that they seem to have reached a pretty uniform silhouette because the evolution took place at a different time and pace than the guitar has. I'm sure there are some alternate violin shapes and builds, but they would seem to be much less commonplace than the variations you see in guitars.

I wonder if another factor might be that music has seemingly become more common, accessible, and diverse over the last 200 years, particularly over the past 50–100 years, with the guitar playing a prominent role in much of that cultural evolution: from blues to jazz, rock, folk, country, bluegrass, punk, disco, metal, alternative, et cetera. The guitar's ability to take on different forms as well as sounds and styles has fueled a lot of that differentiation.

As music moves more and more to digital and AI-based creation, I suspect the differentiation will slow, and the instrument will eventually settle around a smaller number of standards — likely to be those we already see the most today, particularly those favored by genres of music most likely to favor analog guitar (whether acoustic or electric) over digital soundscapes.

[vintage40s]

Originally Posted by FLRon

I appreciate the work that went into this informative post. Thanks for doing this.

I second that!!