Guitar construction over the past 150 years has tremendous variety and has expanded greatly in the modern world with new innovation. No construction techniques are overlooked by today's custom luthiers. Some of those techniques will be discussed here. Our choice for the methods we use are based on some of the earliest known techniques of violin and guitar makers and also from modern manufacturers and contemporary custom builders.
The two commonly used tuners for the harp guitar sub bass strings are standard geared right angle guitar tuners, and geared banjo tuners. The two main differences are where the tuner knob is accessed on the harp head and the gear ratio of each tuner.
The right angle sealed gear guitar tuners are accessed off the end of the peg head and have a higher gear ratio enabling more fine adjustment when tuning steel core subs. The design of the Tonedevil S-12 harp guitar accommodates right angle tuners using Gotoh 16:1 ratio sealed gear tuners, while the S-12N nylon string harp guitar uses the lower gear ratio banjo tuners for the more flexible nylon core subs.
In early 1900 Gibson, Chris Knutsen and the Larson Brothers were innovating the harp guitar. Prior to the invention of the truss rod, the guitar neck was connected to the harp head with a small bracket. This was advantageous because it kept the guitar neck straight over the years of the tension from the guitar strings, and the bracket they used could allow adjustment of the neck relief.
With the invention of the truss rod these issues were remedied, and its wide usage has become standard on most fretted instruments today. It also renders the connection bracket between the harp head and guitar head of the harp guitar obsolete and provides more contemporary adjustment to the guitar neck.
The neck joint is one of the main innovations differentiating modern guitar manufacturers. Some of them use a bolt on neck joint allowing the neck to be easily installed, removed and adjusted. Others use a dovetail joint where the neck is glued into the neck block.
Tonedevil Guitars has capitalized on the tonal advantages of a "neck through" construction design that is gained by using a traditional "Spanish Heel" neck joint where the neck and the neck block are not separate but are integrated into the rim prior to the top and back being attached. This technique extends from traditional violin making. It has always been used on nylon string classical and flamenco guitars and is widely being used today by contemporary custom builders especially in the development of harp guitar designs. Tonal advantages occur by having the neck not separated from the body of the instrument.
Having the Tonedevil facility located in north Idaho has gained easy access to superb tone woods. While still using standard guitar tone woods like African mahogany, rosewood, and Alaskan Sitka spruce the options have been widened to also include other domestic varieties including maple, black walnut, cherry, and redwood.
The lining is what is glued onto the side rim inside the guitar where the top and back sheets attach, so there is more gluing surface area. Many makers have chosen "kerfed" lining allowing them to bend the tight curves necessary. However solid pre-bent lining has been traditionally used in high end guitars and violin family instruments.
Purfling is the thin wood strip installed in the edge of the spruce top and maple back of a violin family instrument top preventing cracks from extending to the edge. Guitar makers developed binding that essentially adds trim to the edge accomplishing the same thing, seals the end grain and hides the top and back to side joint. Most manufacturers use some kind of plastic binding. Tonedevil instruments offer the option of wood purfling around the edge of the top as well as solid wood binding.
One of the most requested feature by players is a way to amplify their instrument. This opens up a new category in luthery that was once not ventured into very frequently. Today, one of the primary ways to perform on large venue stages is using pickups to amplify the soundboard. This information is covered in another article here on pickups and the different types available. A Tonedevil passive contact pickup is installed in every S-12 harp guitar, and when properly installed takes full advantage of the wider range of strings on a harp guitar.
Harp guitars from the early 1900's including Chris Knutsen's and the Dyer harp guitars by the Larson Brothers, have been copied by some of today's top luthiers. While this is a fantastic way to capture the essence of these early relics, there are some contemporary design modifications that can greatly benefit today's players like using truss rods and pickup systems as discussed earlier.
Also the Dyer harp guitar has its bridge very close to the outside edge thus diminishing the lower harp strings (which are already difficult to get enough volume from). The design of the S-12 is similar to the Dyer, but balances the energy to all the strings equally by shifting the bridge towards the center of the top slightly allowing for better overall movement of the top. This shift along with the compensated bracing design is what gives it a richer and louder response from all the strings.