Mandolin Blueprinting4.b.i MANDOLIN BLUEPRINTING IN DEPTH
The basic concept is to get the individual pieces of wood making up the instrument
individually and collectively 'happy' and to adjust the bass/treble/brilliance. A few more
details play into the work. The pieces of wood possible to easily work in a mandolin are
the ribs, linings, bars, top, back, and bridge components. Also the F holes and F hole
edges. Keep in mind that each little step only makes a quite small difference. A possible
exception is the top plate which can suddenly hit a sweet spot that's quite pronounced.
We keep adding little touches here and there and may vary this schedule, but the steps below essentially outline what we do. Stephen Perry compiled the original process, blending and modifying steps from various workers, then extending those basic principles. Rebecca Rosenthal is learning this technique. Workshops and individual instruction are available. [LINK]
A.1. Ensure that the setup is excellent, including frets, bridge fit, and the tailpiece. Everything needs to be ship shape. Check all the screws, make sure nothing is amiss. Check/adjust truss rod to the right tension for very little relief. The bridge is kept off too allow an easier first pass on the body.
A.2 Clean up the inside edges of the F holes (or other ports), primarily to get the inside
edges smooth, without finish ridges and other junk hanging down. Irregularities degrade sound. It's not that a lot of air moves by the edge, but that pulsing around
the edge can move "noise" into the boundary layer around the instrument's top.
B. Bridge preliminaries – a crucial step. Even if you don't do anything else, the bridge is
worth working on. If the bridge isn't very good to begin with this step isn't going to make it suddenly become a good bridge. We eliminate this problem by replacing the stock bridge with a Cumberland Acoustics bridge when the stock bridge’s quality falls a bit short
B.1 Base. Past basic chalk fit, the wings outboard of the posts are pretty important. Many of these have a big lump towards the end. We take a compass, running the point under the bottom end and the lead along the side to mark a line indicating uniform thickness, then remove irregularities, making the wings pretty close to uniform thickness. Tap along the
wings with a pick, listening for a uniform pitch. Dull sounding spots are reduced a little
more, usually resulting in a gentle rollover at the end. Keep the tapped response even
along and across the base as much as feasible. Once done, the whole base is lighter and resonant.
B.2 Saddle. This piece of wood really influences the clarity of the instrument
substantially. We use the tap pitch to contour the piece, primarily along the top surface. Then later work the four edges of the ends, by the posts, like a marimba bar. We have made and adjusted some Red Henry style and other non-adjustable bridges, but generally find the adjustable action a great benefit.
B.2.a Several areas of transition all the top surface generally prove a bit dead. These spots
are where the thick ends go thin, and then the jogs in the top edge. We use a half-round fine
Grobet file to relieve, primarily working by sound.
B.2.b The bottom of the saddle is often a bit dead in the middle part. Just scraping this
down a tiny bit helps. The sides can be worked as well, but looks funny so we avoid doing that.
B.2.c The edges fore & aft of the post holes are very important, I think that's because
they're close to the posts, which transmit sound to and from the base and the rest of the
instrument. We get these to all tap about the same. Doesn't take much. This is a key
adjustment we return to several times.
C. Pre-setup body work
C.1 Ribs & kerfing/linings. We borrowed this technique from reading Deena Spears book. http://www.singingwoods.org/books.html I work on each segment of the ribs. This can't be done completely perfectly, but does make a difference in conjunction with everything else, especially in cleaning up the sound, reducing noise. Spears has a system linking each rib to a block and getting that balanced out. Works on mandolins, too.
On an A model, we tap at the end block to one side of the button and then at the widest part
of the instrument, about the middle of the rib. Normally the block will tap higher. If the
block taps lower, then we make a light scrape along that side of the end block. Use a
scraper on the end of a bent rod. Several in different lengths are required to go through an instrument. Usually a small amount (very very little) scraping will drop the tapped pitch at the block. Tapping along the ribs finds dull, lower pitched spots. We adjust these out with very light scraping. We also check the kerfing, usually finding several blocks that are interfering with sound. Usually they represent minor dull spots offset from the main one on the rib. This process of working over a rib can be done extensively, but the first few spots make the main difference. On an F model, there are 3 ribs to work, and I'll also test along the complex block at the neck. Eventually all this will work out to have no big dead spots around the ribs, just light variations. The tapped sound of the unstrung body becomes more focused and clear.
This process of finding the dull spot in a piece of wood that's in the instrument already is
behind most of the specific technique we use.
C.2 Tone bars or X bracing.
Work done on the unstrung instrument will get refined, once there's pressure on the top. Work on the bracing proceeds in the same manner as on the ribs. Tap along the path of the bar to find high pitch and dull flat pitch. Scrape the bar at the dull flat spot lightly - can tap around with the tool to find the most dull spot. Very little material is involved, especially if the spot is located precisely by tapping with the tool. Then tap again, find where the dull spot is and scrape. Pretty soon the bar rings and the overall tapped sound of the instrument clears up more.
C.3 First tone adjustments.
C.3.a Tone - The area between the treble foot of the bridge towards the fingerboard is
important. Tap around that area of the top, listening for dull spots. Very lightly scrape (or
sand) the inside of the top at that spot. A few passes and that area will be more even.
Tone will end up more open and "ah" in character. This can be extended to the entire top, but the area by that treble foot is most important
C.3.b Balance - Tap the region between the upper eye of the treble F hole and the rim
along the grain mostly. There's often a dull spot. Scrape lightly - we mean lightly,
this isn't really about removing any mass to speak of - to get rid of that dull spot mostly.
A little bit is OK for this part. Just don't want a big dead zone.
C.3.c Brilliance. Wing of the treble F hole - if there's a small dead or dull spot on this
wing or back along the edge to the notch, then gently scrape under that dull spot. A
substantial dull spot indicates a lifeless top end is likely.
C.3.d Sequencing top and back. This is a bit more difficult. Tap all around the whole top,
listening for the brighest, highest pitch spot. Lightly scrape under that spot. Repeat until
the top is pretty even. The character of the response should change a lot, often rather
suddenly sounding more open. Do the same for the back. A good example of this was a
Weber Yellowstone we went through. The top and back were so close to being dead on -
very impressive work. And with the most tiny adjustment the instrument just lit up! Weber does nice work.
Note that we require scraping access to the entire interior. We have a wide range of
scrapers on rods bent to do various things. We also have a bent wire scraper that
incorporates a guide to show exactly where we are scraping. Once the instrument has been gone through completely, we run the sequence again, remedying any changes that have occurred.
D. Refining the adjustments. String up the instrument, making sure the intonation is set and the bridge is well seated. Let it rest under tension for a few hours to settle in.
D.1 Ribs - Check the ribs as described above. Usually they'll be a few changes.
D.2 Check the bars as described above
D.3 Tap around the area between treble foot of bridge up to along side fingerboard. Listen
for any dull spots. These are usually more stable now, and can be gradually reduced with
very light scraping. Can clean up the tone quite a bit. If the tone seems as if it could be or
should be a little more bell-like, check from treble side of bridge towards tailpiece. If time allows, check the entire top and back.
D.4 Listen to bass/treble balance. There is often still too much treble emphasis. Find a dull spot up from the treble F hole. Almost always if the instrument is too trebly that spot is present. This may take a bit more vigorous scraping. Still not much at all. Just dust. Try until the balance sets right. Usually this is a fairly sudden transition. The bass F hole also benefits from this work.
D.5 Listen for clarity of upper harmonics. Usually just a little lacking. Find dull spots
outboard of the F holes onto the wings and lightly (lightly!) scrape under these! Doesn't take much. Usually there’s an important dead spot about 1" from the wingtip. This makes a tremendous difference in perception of lively response, projection, excitement.
D.6 go through the top and back as described above. This regularly gives a big boost in
response and apparent volume.
D.7 Check ribs and bars, repeat above as required for stability of adjustments.
D.8 Final work on bridge
D.8.a The wings out from the bridge - tap along them listening for a dull spot. Lightly
scrape until no dull spot. Buff.
D.8.b Tap each of the four junctions of top and side of the wings. One will be higher
pitch. Lightly scrape that corner/edge. Repeat until they are all about the same in pitch.
D.8.c Tap along top of saddle, checking for dull spots. Scrape dull spots.
D.8.d Tap the four edge/corners by the post holes and adjust as is D.8.b.
D.8.e Go back and check the bridge base wings again. This may take a few go arounds.
D.9 Tap around edges of F holes for dull spots. Light pass (very very light) with a file
will remove dull spots. Once these all balance out, polish inner edge with fine abrasive
paper and recheck.
D.10 Ears of the Angels step. This one is a bit odd. Tap the back along the path of the
bars. Often they'll be a dull spot. Find the spot on the bar opposite that dull spot and give
it a light scrape. Usually a small dead spot can be found on the bar there. Makes a subtle
but surprisingly difference.
E. Repeat all of the above from the beginning until the instrument is stable and sounds
good. Stain the inside edge of the F holes if you like.