Acoustic Jumbos - Some Thoughts

The Gibson 2019 SJ 200 Deluxe Spruce over Rosewood

Hello friends. This time I want to share some recent thinking on jumbo bodied acoustics following some studio work.

Electric guitars come in all kinds of shapes and for the most part, the shape has nothing to do with the tone of the instrument. Acoustics are different because you may have an acoustic with a pickup, the design is to be heard without a pickup. Thus different shapes have different tonal responses, a very nice thing indeed.

When we look at acoustics, for the most part we see two body shapes, although a third is experiencing growth recently. The most common is the shape and size called a dreadnought, built by many but exemplified most widely by the Martin D-28 and its variants. Second most common is the Orchestra model, often delineated by 000 or OM. This is a slightly smaller body in dimension and in depth. Even smaller are the parlour sized guitars 0 and 00 identified that are increasingly popular, or more correctly becoming popular again. You will find lots of options of these types in most guitar stores.

The Wonderful Jumbo

Harder to find will be the Jumbo. The Jumbo is the biggest bodied acoustic guitar. It has the widest and deepest body. In addition to being physically large, a Jumbo sounds different and records differently. They are less popular, because they are so large that some people find them uncomfortable to play, particularly if the player is a small person in torso and arm length. This is a massive generalization because there are exceptions to this perspective. For example, the wonderful Emmylou Harris is not a big person, but is known best for playing a Jumbo sized guitar most often.

Taylor 615ce

Over the years I have acquired a number of acoustics and today have two jumbos in my selection. One is from Taylor. It’s about 14 years old and is labelled the 615ce. It has a spruce top and big leaf maple sides and back. It also has a cutaway and Taylor’s Expression system pickups. The other is a Gibson SJ-200 Deluxe from 2019. This was a limited run with a spruce top and rosewood sides and back, no cutaway and an LR Baggs pickup system.

As expected, they sound different. The Taylor sounds a bit brighter and hits faster and with fewer harmonic overtones. The Gibson is a bit warmer, with a slightly slower attack and a slight drop in the mids where the human voice might fit in the mix. We can attribute the difference in tone to the body woods.

With the advent of pickups, and increasingly better quality pickups for acoustics, players are more inclined to go for a smaller body as the volume advantage of the jumbo is somewhat negated by the presence of a pickup. I believe that those folks are missing something because even the good pickup systems that are not based on the (my opinion) nasally and icepicky piezo design, don’t capture the tone created by the air inside the body. The system that Maton uses which includes an in body condenser microphone would be an exception, but I have not tested that in the real world.

Acoustic bodies are designed to create sound by the movement of air inside the body that is then projected out the port that we call the soundhole. A jumbo body has a much larger airbox and thus is better suited to accurate low frequency projection without cancelling higher frequencies. Some players believe that jumbos do kill higher frequencies, but good ones don’t because they are delivering a wider frequency range and the human ear responds more quickly to low frequencies. Bass and drums drive rhythm sections for this very reason. The more air the body can move, the louder the instrument is going to be as well.

The top of an acoustic guitar is typically two pieces of solid wood edge glued to make a thin, flexible top. In my two examples, the wood is Sitka Spruce, a very popular guitar top wood. We like solid wood tops because this makes the top more able to move and thus to move air. While I and many players prefer solid sides and backs, that these are solid is less important. In fact, many independent custom luthiers advocate laminated sides to make the sides more rigid to provide a more stable frame for the top. Higher end guitars have solid wood sides and backs, mostly of a hardwood species and cut thicker so as to provide a solid reflection point. A flexible back is not acoustically desirable.

Why then this quest for solid sides and backs? It’s mostly about the vibration that we feel through the back. A single piece of wood, or two or three pieces edge glued together (such as a Martin D-35) can still vibrate in concert with the top and we feel that against our bodies. It is comfortable and feels alive. While the backs are braced, similar to the tops, they are thicker and need less bracing than a top so while they may not flex like a top, they can still resonate.

There is a trend to refer to either solid wood sides and back to <species> sides and back. When you see the latter, it means that sides and back are laminated sheets of the same species. This is, respectfully, plywood and is a vibration killer. It gets worse when you get a documented laminate sides and back even if it uses weasel words such as HPL, which stands for high pressure laminate. Worse from a resonance and natural vibration perspective. However laminates whether all the same species or mixes of different woods with a thin veneer on the top and bottom, are much more dimensionally stable. They handle temperature and humidity changes much better than solid wood backs and sides.

In the case of the jumbo, we want that air to move and we want to gather all the tonality produced by that big air box. Some offerings exist that use digital signal processing to try to make an input signal sound like a particular body size and wood species. The Fishman Aura box that was introduced a long time ago and is still sold is one such offering. Trust me when I tell you that it does not deliver accuracy and save your money. Similarly, even having a really good pickup in a small body acoustic guitar will not make it sound like a jumbo. Only a real jumbo sounds like a jumbo. If you are a singer songwriter who plays gigs and would prefer to get the tone from the guitar, you owe it to yourself to try out a jumbo. Gibson still makes the SJ-200 as well as the SJ-150 and SJ-100. Taylor still does 18 series bodies which are their jumbos. It’s easier to find a jumbo with maple sides and back, because those guitars are often played live and are somewhat less prone to feedback than rosewood and as noted have a slighter faster attack. Having both build types, I can confirm that they are different, but I will not say that one is better than another.

Audio Samples

I’m adding a screen shot of the Blue Cat frequency analyzer for the Taylor 615ce. The frequency response for the Gibson was nearly identical, and I would need more skill with the tool to be able to show the different attack times. In the cast of the maple bodied Taylor it’s a pretty smooth line with a clear notch at about 1KHz. This trace is right out of guitar with no processing applied and the tone controls on the Expression System at noon.

I’ve attached a couple of short recordings for your interest. Be advised that while I went direct from the guitar’s pickup to the interface and into Logic Pro, that these recordings have been edited and mixed. Partly because I did not find that the pickup reproduction sounded like the guitars did acoustically and I wanted to get closer to what I heard acoustically and partly because these recordings were made following a different recording project where I had already gone to the process of creating an acoustic mix that I liked.

For those curious, I went straight from the guitar to the Apollo’s Hi-Z input. I did not use any Apollo preamp, so this is right out of the guitar pickup output. The Gibson has an LR Baggs pickup and I don’t really care for it as I find it cuts high end. The final Taylor recording needed less work in mixing, so I would say that the Expression System does a better job at this level.

Each signal was then put through Izotope Neutron 4. I made some minor tweaks to the suggestions provided by their AI tool in both cases, minor because what was done by the tool was pretty bang on. The next plugin was Izotope Ozone Pro which is their production tool. I started with their Acoustic guitar preset, then did a run with their AI tool and compared the two. I made some minor changes in both guitar cases and was quite happy.

In Neutron Pro 4 I used the mono-stereo function, so everything afterwards was working on a stereo signal. While I liked what I was getting, I felt that both tracks needed a bit more space, so my final plugin before final mixdown was a Lexicon MPXiReverb using the Small Plate with the mix around 9 o’clock. I like the sound of plate reverbs and the Lexicon plugin gives very fine control over your dry/wet mix so things don’t get swampy.

Summary

Acoustic guitars coming in different shapes and sizes is a boon to all of us. However if you’ve only played one or two body styles and a jumbo is not one of them, you owe it to yourself to give a jumbo a try. From a pickup perspective, the Taylor Expression System 2 is a decent offering, although I would personally choose to install a K&K Trinity System which comprises their Pure Mini transducers with a Trinity in body microphone and external preamp. K&K Trinity System I use Pure Minis in my acoustics that did not come with factory pickups and some that used to have other pickups before. The Trinity System takes things to the next level if amplifying your acoustic is where you need to be. If you don’t have or want an in body pickup and want to use a microphone instead, it’s more work but I recommend the Aston Origin or RODE NT-5 as excellent options. The Neumann KM-184 is a superb choice but is to my mind, too expensive for casual users.

Thanks for reading and until next time, peace.