BJH Archtop Jazz Guitars: Their Design and Evolution
The design of the BJH jazz guitar is based on the classic archtop shape, the hand carved body measuring 17 inches wide and 3 inches deep at the edges, with a spruce top plate and maple sides and back plate. The underside of the top plate is normally fitted with “cross” bracing, but “parallel” bracing has been used on some seven string guitars. Kerfed linings support the joints inside the body between the sides and the top and back plates. There is traditional black and white binding on all of the body edges, including the f-holes.
The Back Plate
In line with best practice for hand made archtop guitars great care is taken when tuning the back plate of the completed body. This is achieved by checking the vibration of all areas of the back plate repeatedly whilst the re-curve is shaped. The shaping of the re-curve is not complete until the back plate vibrates evenly across its whole width. Then, and only then, it will operate as an evenly balanced flexible membrane to produce the full rich sound of these instruments.
The maple headstock, which is a continuation of the neck, is ebony veneered, inlaid with mother of pearl and has black and white binding. Its shape was determined by meeting the following two criteria. The strings from the nut to the respective tuning machines are parallel with one another for optimum movement through the bone nut slots when tuning. The weight of the headstock is kept to a minimum, consistent with having adequate strength, to provide a good balance to the instrument. The resultant shape is easily adapted for six or seven string guitars. Grover black chrome tuning machines are fitted unless an alternative is desired.
The neck is carved from maple with a 21-fret ebony fingerboard and a single truss rod with adjustment in the headstock. The fingerboard has a 12inch radius with black and white bound edges. The width, depth and shape of the neck are made to the customer’s requirements. One particular seven string instrument was required to have a very thin neck which raised concerns about its stability, particularly with the extra tension of seven strings. Carbon fibre reinforcement rods were therefore fitted either side of the truss rod within the neck to provide torsional support. That neck has retained its true shape very well, so these carbon fibre rods are now fitted as standard in all BJH guitar necks.
Original BJH instruments followed tradition by making the section of the neck to be situated over the body as a separate extension piece, which was fitted to the neck’s main section after forming the neck’s tenon (to mate with the body mortise). Whilst this joint was made very carefully, and the grains at the neck sides were matched as far as possible, the joint was still visible. The design was modified to eliminate this joint. The resultant continuous neck without this joint is thought to be stronger as well as being more pleasing to the eye.
A floating or fixed pickup with either a bright or mellow tone is fitted, as required. Each pickup is custom made by Kent Armstrong from an appropriate pattern supplied by BJH to ensure that the pole pieces align with the strings for optimum performance.
The bridge is carved from ebony and is fitted with two conventional knurled height adjustment wheels. It is positioned for a 25 inch scale length and is calibrated for accurate intonation. Its underside is shaped for an exact fit to the body’s top plate. On the latest model its underside is arched so it has two points of contact with the top plate directly over the inside cross braces, with a gap at its centre. This arrangement is intended to improve the transmission of the strings’ vibrations to the top plate. The results are pleasing. Further development will be carried out on the design of the bridges for BJH guitars.
A carved ebony tailpiece with slotted string holes to facilitate rapid string changing is fitted as standard. It is held in position by a conventional nylon coated stranded steel wire fastener looped around the endpin jack socket connector. An additional collet is added to the endpin to cater for this wire fastener, enabling the collet supplied with the endpin to be used for attachment of the guitar strap as intended. The original BJH seven string model had an endpin jack socket fitted into a hole drilled in the end of the guitar in line with normal practice. It was found that the alignment of the endpin changed slightly over a long period as its threaded section was gradually forced into the wooden tail block within the body by the pressure applied by the strings. Whilst this had no detrimental effect on the instrument’s performance, it spoilt its appearance. To overcome this problem a brass tube with a wall thickness of 0.5mm was positioned over the threaded section of the jackpin within the hole in the body. Since this modification was carried out the jackpin has retained its correct alignment. All subsequent BJH guitars include this feature.
The ebony finger-rest is black and white bound and is fitted with a volume control. A tone control can also be fitted if required. If a floating pickup is utilised, this is mounted on the underside of the finger-rest. Traditionally floating pickups are glued to the finger-rest, but for security the BJH pickups are glued and screwed in position, the design being such that the screw heads are hidden from view. Initially, these finger-rests were flat-topped. It was found from experience that occasionally there was accidental contact with the finger-rest because of its close proximity to the high E string. To overcome this problem various curved finger-rests were developed, each shaped to provide a substantial vertical distance between the strings and the inner edge of the finger-rest. These shapes are now used as standard.
Charles Alexander’s BJH Guitar
The latest BJH guitar, built for Charles Alexander, includes all the above features and developments. Charles requested a modified volume control system. He asked for a duel set of volume controls with a selector to enable him to switch instantly from one volume setting to the other whilst playing, both volume levels being adjustable at all times when selected. This arrangement is built into his new guitar. He also requested a lockable strap button to be fitted at the neck end of the body. This was supplied. It is not necessary, nor possible, to fit one of these at the tail end because the strap is held in position by the amplifier lead, and can only be removed once the lead is unplugged. The arrangement supplied therefore prevents the strap becoming unfastened at either end whilst the instrument is in use. Charles took delivery of his guitar in February, 2007.
About BJH Guitars
Bryan Hill accepts commissions for seven string and six string archtop jazz guitars with a delivery period of around eight months.
Bryan James Hill