C4, part 2

 

In this blog post, I discussed the background of C4 (Contraguitar number 4).  This blog post discusses some of the conversion work from a 17-string Hybrid Extended Classical guitar into an 18-string all steel-string Contraguitar.

The Contraguitar string sets have one sub-bass course and two added treble courses when compared to the concert 6-string configuration.  I consulted the D'Addario string tension reference, and configured a  new Contra set for this scale length.  Fortunately, in an all-nickel-wound set, the overall tension was only about 12% higher than the hybrid nylon/steel set, and actually 20 lbs. lower than the all-bronze set that Alistair approved.  I went much lighter than the 36-string Contraguitar gauges; for example, the sub B courses on the 36 are .135; I'm using .100 on C4. 

The tuning on C4 is (bass to treble):

B/b (sub-bass)

E/e (same as the low E on a bass)

A/a

D/d

G/g

B/b

E/e

a/a (unisons)

d/d (unisons)

I had to move a couple of tuners around to accommodate the .100 gauge bass string on the low sub B course.  I'd previously drilled out three of the tuner posts for the heavy lute strings that were part of the hybrid string set, so I didn't have to re-drill any tuners; just relocate a couple.  I didn't have to modify any nut slots, which was really surprising.  As an aside: the nut width on C4 is just under four inches (101mm).  C4 has two truss rods due to the extremely wide neck.  I didn't have to adjust the treble truss rod at all, which surprised me.  Action on the treble side is about 1.5/32", which is perfect for me.  I turned the bass truss rod maybe less than 1/8 of a turn.  With this adjustment, the neck has almost no relief, which is usually just about ideal for me.  However, these new gauges made the bass side action way too high at 4/32".  I like it around 2.5 /32" on the bass side, and on some instruments, 2/32".  C4 has a split saddle, with six courses on one saddle, and the three bass courses an another.  I'd carved a new bone saddle for the bass courses a couple of years ago.  I removed the bass saddle and shaved the saddle's base by about .025".  That brought the action down nicely, but I may pull it and remove another .005" or so.  

I had to drill out two of the string holes in the bridge.  I had a 12" aircraft 3/32" bit I'd used when I added the 18th string, so I tried using that.  However, it proved to be too small to accommodate the .100 gauge bass string.  I tracked down a 12" 1/8" aircraft bit, and opened up those two string holes.  

After getting the new string set on and tuned to pitch, I practiced with it for a couple of hours.  The voice on this instrument is super unique.  It always was, but I credited that to the nylon/steel combination.  Not so.  That voice is still there with an all-steel set.  It's very bassy, resonant, and rich, but not unbalanced.  It still has a sparkling and balanced treble response.   It's a really unique voice; nothing like the 36, 30, 28, or 24.  I had not considered the voice when I was thinking about turning it into a Contra, though I knew the voice would be well-balanced, and it is.  It works really well as a Contra as I suspected it would due to the multi-scale (fan fret) configuration.  This one has a more severe fan than the 15-string; I think this one is 4" and the 15's is maybe 2.5 or 3".  The voice is really beautiful; more so than I would have imagined.  It also has a different body depth than the other Contraguitars.  Its back is arched which also brings a tonal impact.  

The sub B and the low E are both nickel (bass strings), and they sound like a piano.  The low A and low D are both phosphor bronze, but don't have the articulation and clarity in the overtones as do the nickel strings, so after hearing it for a few days, I replaced the phosphor bronze diapason G, B, and high E strings with nickel-wound strings.   Additionally, this instrument has amazing sustain.  It's fascinating to me how well the carbon fiber instruments respond to and display the tonal differences in winding compounds.  It's like having an extra paint box of colors at your disposal.  At present, most of the string gauges are right.  After playing it for a few days, I may change a couple, but everything is really close.  I didn't have a string set in the archives like this; I had to look at the 36 octave sets as a starting point and alter those to be lighter overall gauges.  It's not really guesswork as I've been doing this long enough I can usually tell and know which gauges will work for which pitches/tunings and in which register.  However, drawing up a tuning and actually putting it on the instrument and hearing and playing it are two different things.  There are always adjustments to be made to the sets.  But I'm guessing that if I change any gauges, it will only be two or three strings; it's really close to being exactly right.

My early impressions are that I'll need to carve a new saddle for the other six courses.  The high A and D are both great, but the high E, B, G, and D are a bit higher than I'd like.  Just a tiny bit, but I can feel it.  I can't shave the base of that saddle section, as it will drop the high A and D, and then those would be too low.  When I made the other part of the saddle, I had to glue up two saddle blanks because it's so wide.  I was planning on carving a new saddle for it anyway, so no surprise here.  I am surprised that the bass section of the saddle is working so well, even though I had to shave it.

After practicing with it for a while, I took it back to the lab and added a few tactical string slots on the saddle to perfect the course spacing.  

In conclusion: the initiative to convert the hybrid 18 into a steel-string Contraguitar was less work than I'd imagined.  And a very different result in regards to the voice.  It's certainly a success and I'm already really happy with it.  It will be pressed into service on some upcoming album recording dates this month and beyond.

-kk