Michael F. Lazar
Luthier
Hand crafted classic concert guitars since 1980
St. Albert, Alberta Canada

Design and Construction

Here is a picture of the prototype that I now base my guitars upon. The top design  was developed by Greg Byers and I chose to use it in order to apply the learning he provided during my studies with him. The asymmetric fan bracing with the treble bar angled out from the transverse bar below the sound hole is not unlike the design found in many guitars. 

The sides are joined to the neck using a modified approach to the  traditional Spanish way. Both of the upper transverse bars are taken into the linings and a reinforcing pad strengthens the sound hole perimeter.

Two more cross grain pads above the soundhole protect the top from cracking along the edges of the fingerboard. 

The linings are from ash and are laminated, 3 ply for the top and 2 for the back. The transverse bar below the sound hole is quite massive and is made from maple. All of this combines to form a very rigid foundation for the active area of the top. The mass imparted by  the high density ash &  maple coupled with the rigidity of body perimeter  contribute to a desirable level of sustain throughout the full range of bass and treble tones.  


In 2003 I modified my design to so as to incorporate an elevated fret board. 

The benefits I was looking for from the elevated fret board  included improved quality in the treble notes above the 12th fret to the extent that they would be more consistent with the notes below the 12th fret. I expected this to result from the continuance of neck wood supporting the fret board all the way to the sound hole. 

I also anticipated having more control over the fret board action again due to consistent fret board support.

Lastly, I anticipated improved playability above the 12th fret based upon the observations made by most players when they experience a raised fingerboard. 

The two most significant examples of a raised fret board design that I know of are the guitars made by Greg Byers and Thomas Humphrey. However, these guitars do not employ the Spanish heel construction architecture and I believe that the Spanish heel architecture produces a number of benefits that I'm not prepared to relinquish. So, in order to achieve my objectives I developed a design 

that incorporates both a raised fret board  and a Spanish heel type architecture. 

 

My expectations were met by the new design, however, two additional benefits became apparent when the instruments were completed and tested. The new guitars were even louder than the previous design. This may have resulted from the downward slope to the top which results in the strings pulling from a slightly different angle. Another possibility is the top doming wherein the whole top is domed with the apex of the dome located at the mid point of the top. Previously only the lower bouts were domed with the apex of the dome located at the mid point of the saddle. It may also be that both of these factors contributed to increased volume. 

 

As is common with high quality guitars, I experienced a certain amount of fan brace "imprinting" wherein the location of the fan braces was visible on the face of the tops when they were polished. This imprinting has reduced considerably  and I am quite certain that this is a result of the change in the doming.

 

The elevated fret board design has proved to be so successful that I now use it almost exclusively. 


This view shows how my tail block is integrated with the linings using an approach I ran into some years ago. The traditional tail block often creates unsightly depressions in the top and back with changes in humidity. Here the top and back attach to uninterrupted  linings around the perimeter of the lower bout. A larger benefit arises out of an expansion of the active top area as the tail block no longer intrudes into the top.   Note that the strut design can now be expanded out to the linings.   Construction  begins with the neck which is carbon fiber reinforced. The neck is completed in its entirety including fret board, frets and shaping to its final dimensions.  Next, the sides are bent, profiled, joined using a tail block and lined. The top begins with  joining of the two halves, planting the rosette & rough thinning to about 2.4 mm. Density & stiffness of the wood are measured & the top is thinned further until it resonates at a desired frequency. Thickness might then be from 1.9 mm to as little as 1.4 mm.  

One of Greg Byers' very interesting innovations is the device shown here. Called a "corbel", it is made from mahogany and it connects the maple transverse bar to the linings. The gluing surfaces are ingenious and the result is amazing solidarity and rigidity in this important area.  

Going back to the construction process, the final top stiffness is measured again and the fan braces are glued in. Fan strut heights are adjusted while again checking for a desired resonance. 

 When complete the top is attached to the neck and then the sides are affixed to both the top and the neck at the same time. The top resonance will change as a result and it is again measured. The top may then be thinned further around the edges to reduce the resonant frequency if necessary.

The guitar is now ready to receive the back.  The back braces are a little heavier than usual for additional mass.  


When the back is on, the box is now closed and a cavity resonance can be determined. If adjustments are needed, the back perimeter can be thinned as well as the perimeter of the top if not already done.  If all has gone well, both the top and cavity resonance will be where I want them to be.

Finally I decide upon the weight of the bridge. If the resonance is on the high side of my targets, the bridge may be made a little heavier if lower, it may be lighter. 

Before gluing on the bridge, the bindings and purflings are put in. When the bridge is glued on,  the resonance of both the top and cavity are checked one last time. If, at this point the perimeter of the top still has not been thinned in order to achieve a desired response, there is one last opportunity to do so.

I then fashion the compensated nut and saddle, install the tuners,  string the guitar, adjust the action and play it for a few days until it fully "wakes up". If deemed desirable I may make further adjustments by thinning the top closer to the center, removing wood from the bridge to lighten it etc. When I'm satisfied that the guitar is the best that it can be, I then remove the strings and tuners and  weigh the completed guitar. Finally, I french polish the instrument and the work is done.  

So, to summarize the decision making or "voicing" part of construction process, tapping and feeling are replaced by measuring resonance and stiffness with specific instruments. A laboratory scale is used to calculate density and measure the weights of the braced top and back to ensure that they fall within predetermined parameters. Stiffness and elasticity are measured by placing the top in a special frame and measuring the amount of deflection and return when a specific amount of weight (force) is applied to the top and removed. Resonance is measured by applying variant frequencies to the top with a tone generator until it reaches its maximum vibration amplitude. The top is thinned until the target resonance is achieved.  In order to work this way, one must know what the density, stiffness and resonance targets should be and this is part of what Greg Byers teaches. 

At the completion of each stage of the voicing process using measuring instruments (most of which were not in existence during the time when Torres built guitars) I then "tap and feel" so that my hands begin to get an education. This is important to me as I believe that the hands can be incredibly sensitive measuring devices and I am hoping that mine will eventually become calibrated in this way. 

Greg also teaches that records should be kept regarding the final measurements for each guitar made along with comments covering a subjective assessment of the guitars characteristics when it has been completed. These records begin to form a collection of empirical data upon which to base further evolution. 

While my guitars will differ somewhat in character as a result of unique qualities in the materials making up each instrument,  the overall quality has been very consistent from one to the next. 

Back to home page