D Holes are Warmer: Myth or Reality?

MichaelHorowitz

Probably the #1 guitar related question I get asked is: what is the sonic difference between an oval hole and a D hole guitar?

The most commonly heard analysis is that D holes are warmer, have more bass, and are better for rhythm. And that oval holes are louder, have more treble, and cut better for leads.

However, I haven't really found this to be the case. We often have two Dell Arte Hommages models in the stock, one a D hole and one an oval. The exact same guitar, same woods, same builder, etc. When compared, the results were inconclusive. More often then not, it was the D hole that was louder, brighter, and had more treble. Sometimes not, but there definitely wasn't any sort of generalization I could make between the two. Other factors, such as the woods and other construction details seem far more important in the overall sound then the sound hole.

Much of this myth seems to stem from the fact that the original D holes were always 12 fret guitars. And the oval holes, except for a few transitional models, were always 14 fret guitars. Totally different designs, hence the obvious sonic differences. For some reason people attributed these differences to the sound holes. However, the short scale length of the originals D holes was the most important factor in giving the guitar a "warmer" sound with more bass.

In recent years it has become very trendy to make 14 fret D holes. So now there seems to be a lot of confusion, with people attributing the sonic characteristics of a 12 fret sort scale to D hole to a 14 fret D hole. As mentioned earlier, I haven't found that the sound hole itself makes that much of a difference.

Interestingly, Michael Simmons, the editor of The Fretboard Journal, just sent me the recent issue. The cover story is about Tony Rice's famous pre-war D-28, which at some point had it's soundhole greatly enlarged:



This guitar has been copied and mass produced by the Santa Cruz guitar Company, Collings, and Martin. Just like with Selmer's, there seems to be a lot of conjecture about what sort of difference the larger sound hole makes. Richard Hoover, the founder of SCGC, remarks that:

We can put the whole subject on sound scientific footing - and put all the myths to rest - by invoking the acoustics physics principal called the Helmholtz effect: "The larger the aperture of a resonating chamber, the higher the fundamental pitch of the chamber." So, in guitar terms, this means that the bigger the soundhole, the more midrange and treble are accentuated.

This would suggest that 14 fret D holes should have a more pronounced high end then their oval hole counterparts.

I'd like to know other people's observations and opinions.

-Michael

Stackabones

Fascinating thread. I don't have much to offer--I've only recently acquired a 12-fret D-hole. It sure seems louder than my flat top (a Tak), but I don't know how it would compare with an oval hole. Tonally, it seems more balanced compared to the boominess of my flat top.

The neck's scale and width feel similar to a classical. Does the zero fret contribute to tone--I've heard it minimizes the effect of the nut.

I like the look of the D-hole more than the oval.

a

i think that scale length has the most effect on feel and tone. maybe django tuned his oval hole down a couple of steps to get back more of the bounce that the 12 frets had.

manoucheguitars

Great topic Michael! I get asked that question at least once a week. I have had a guitarist who took both models, played and recorded with them and told me from across the room you could scarcely tell the difference... both projecting nicely with great tone. He also said (in his opinion) that the difference was more evident to the player who could more easily hear the low and mid range of the 12 fret D when playing... rather than listening from 12 feet away. I think that's probably my experience too. I do agree with your conclusions. Thanks for addressing this question!

Robert

Stringswinger

I have played very bright short scale D holes and very warm long scale oval holes. Every acoustic guitar is as different as the trees that their primary materials came from.

Buying an acoustic guitar sight unseen is a bit like betting on the horses.

Cheers,

Marc

www.hotclubpacific.com

Ken Bloom

That guitar of Tony Rice's is Clarence White's old D-28.The soundhole is elnlarged because Clarence wore out the wood around the hole.I saw him play many times with the Kentucky Colonels and there wasn't a lot of wood left around that hole from the way he played it. Others then took this anomolly and copied it, attributing magic things to this.
D holes usually only have four braces as opposed to the five in most oval holes. More bracing accompanied by a longer string length,thus higher tension, gives more treble and punch. Fewer braces, a looser vibrating plate and thus more bass. Problem is the whole is the SUM of the parts. The design of the bridge, height of the action, technique of the player etc., etc. all play a part. The D hole does give more ventage. When I built my guitar I used a simple round hole but a bit oversized. I'll do a D hole next time. My own feeling is that I get a fuller tone with alarger soundhole. I think Selmer went to the oval hole just so they could avoid Maccaferri's patents but I'm sure more knowlegable folks than I can contribute to this. Just my 2p.

djadam

I think I remember Tony saying that Clarence White cut the hole bigger with a pen knife!

It's a funny topic when it comes to Selmacs because these things really sound different to the guy sitting in front of you that to you while you play it. My theory was always that the sound of a D-hole simply diffuses more widely and thus the player gets a little more direct reference from the instrument than with an oval hole. But if that's the case, I can imagine that the oval hole will sound a little more mellow to the player, since the player is getting less sound directly and more sound "through the wood".

When I got my custom park, I was tempted to ask for a dreadnaught-style soundhole, just becuase it sort of splits the difference. I ended up going with the oval though and I couldn't be happier. Still, maybe I'll try that someday.

Bob Holo

Is there a doctor in the house? No? How about an acoustical engineer? ...

Well, here's the truth of it: In general - all else held equal - enlarging the cross sectional area of a port without increasing the depth of that port will indeed raise the fundamental resonance frequency of the port. He's right about that. But - how that raised resonance frequency affects the guitar's tone is a function of the system with which the port is interacting and the frequency of the port before and after enlargement. A guitar is a transducer which is to say that it converts energy into sound... it would produce sound in response to stimuli if you covered the port. Adding a port is essentially adding "another voice" to the guitar - a voice that is generally narrower than the system's response - and that generally rolls off twice as steep (24db/oct on both sides) as the lower rolloff of the non ported system. Think of blowing across the opening of a coke bottle... that sort of pipe resonance is what you add to the guitar's response by adding a port. The size and depth of the port relative to the chamber control several things - but for purposes of this conversation - the most important is the center frequency of that added response. If you want to know what your guitar's port tuning is... hold your guitar by the strings/back/soundboard (so nothing can resonate) and hum in front of the port. When you find the frequency that hums back at you... you've found your port tuning. The port is making that chamber more efficient at that frequency. Where that frequency is in relation to the overall frequency range of the guitar and what the non-ported SPL curve was prior to the port... add all that together and you'll know how the port contributes to the sound. Guitar ports are a little weird because they're so shallow and so big that there are some odd harmonic things going on that affect the system performance - but in general - that's the story on ports.

The really big thing that affects the efficiency and tonal qualities of a guitar is its design as a transducer and its stimuli. There is a complex interaction between the system represented by the transducer which in the case of a guitar is constituted by the: (area & mass & damping & stiffness & compliance of the soundboard and all its constituent structural components relative to the load, the mass & damping of the bridge, the mass & tension & compliance & length of the strings, the size & shape of the interior chamber and any elements that may make it not function like a true HH resonator (like Macaferri secondary resonators), the size and placement of the port(s) and any sources of port or response nonlinearity or harmonics etc... the rigidity and/or damping of any large structural devices such as the neck... and most important - the power level and characteristic of the stimulus... (the player / pick / power / where on the strings the power is applied relative to harmonic & null spaces on the strings...) The motor structure (player) is really important. Did you ever hear anyone say: "Yeah, but Tchavolo makes all guitars sound like that." well... there is some hard scientific truth to support that Tchavolo is a very unique "motor structure" and in general his style swamps a lot of the subtler design differences between guitars.

MichaelHorowitz

djadam wrote:

I think I remember Tony saying that Clarence White cut the hole bigger with a pen knife!

The article in the Fretboard Journal says it already had the larger hole when he bought it. But who knows!

Charlie Ayers

My impression, tonally, has been that D holes have more midgrange prominence, and not really any particular characteristics in regard to treble or bass response (the prominent midrange is what makes them desirable for rhythm playing, in my mind). I agree that the 14 fret D hole is a different animal than the original 12 fret, short scale design.

Charlie

Josh Hegg

It depends on the builder.


Cheers,
Josh