Acoustic Bass build completed

[IanC Hemphill]

I’ve just finished my first acoustic bass guitar and I’m very happy with the results.  It’s a Gore/Gilet based OM-size body with falcate bracing and a live back. Walnut back, sides, fingerboard and headstock veneers.  Maple neck and bridge.  Copper dots for fret markers and side markers. The rosette is walnut with ebony inlays. French polished (thanks for the course, Robbie!  It’s the only finish I use these days, love it).  I use Ratio tuners for my guitars, so I thought I’d give the bass ones a try, and they are great. I really like them.

Small acoustic basses are notoriously quiet in the bottom end (double basses are really big for a good reason).  So I thought that the falcate bracings would help out, and it worked out really well.  The guitar has a lovely voice and is loud enough to comfortably hold its own in an acoustic living room jam, which is what the customer wants it for. The scale is 724mm (~28.5”) which is shorter than the ‘normal’ electric’s 34” scale, which the customer really loves, the larger scale instruments give her wrist problems.  I did include an LR Baggs “Element Active” pickup for those sessions where she’s playing in a more demanding space, and it seems a pretty good match to the instrument.

[JohnParchem]

Nice!  Did you have a measurement for the top resonant frequency?

[IanC Hemphill]

thanks, John.  Yes I do:  my initial design targets for T(1,1)1, 2 and 3 were 95/180/226.  Initially the completed build came very nicely onto those, with the 3 being a bit high but in a pretty good location.  Then I unfortunately subjected my little darling to an unplanned, unscheduled, you-clumsy-idiot "drop test".  

After recovering from the initial heart attack, I luckily found no damage except for some dings and scratches on the soundboard. After I cleaned off the shellac, I was able to steam the dings out, but some of the scratches had to be sanded out, which thinned my top quite a bit from its design target. After refinishing and retesting, the final frequencies were 89 (F2+35c)/172 (F3-35c)/250 (B3+28c).  I was happy with the distance from scale tones and the separation of the 2 and 3, so I left things alone at that point.

I wanted good volume with lot's of top activity, so during the design I tweaked the falcate heights down at their peak from Gore/Gilet's 7mm to 5mm.  Still lots of meat since the static load from the strings is so much lower than for a 6-string.  It's turned out a lively guitar with good volume, which is reflected the Monopole mobility, which came out at a pretty respectable 21.  

I thought that the lighter braces might result in more bridge rotation, but that didn't happen, I ended up with 1 degree rotation, which seems pretty typical for all my builds, x-brace or falcate.  I guess that means I could still back off a tad on the bracing in each type, but I haven't tried that yet.

I was a bit surprised at how high I had to set up the strings though - I haven't done a bass before, so I wasn't sure what the set up height should be for a 'normal' setup.  The web wasn't much help, the most common comment I found was "set it so that it feels right".  very helpful.   So I just started really high and brought it down very slowly. The size of the strings and the size of the vibrating displacement was a bit surprising to me - I ended up stopping with the height at the 12th fret at 4.0mm!  Quite a difference from my six strings!  doesn't seem to affect the playability though, it's an easily fretable and smooth player.  The client was delighted, which of course is the final test of all.

[Michael Hudkins]

Beautiful.  I have built two acoustic basses (one lefty, and it is interesting that it feels clumsy during setup).  I used a J45 body a little deeper, and originally used 32" scale.  Both customers have given very high marks, but finding cases can be difficult.  I am in process of designing an acoustic bass for myself, but I think I am going to use the 30" (Hofner-esque) scale.  I use an adapted version of the Gen One plans for bracing.  

[JohnParchem]

Actually I think I would have voiced the top around 160-170 Hz, So I think it came out well after the drop test. When I was with Trevor he said the 2 mm bridge rotation was not magic. He basically wanted some (otherwise it can be very stiff) but not too much. One mm of rotation checks that box. 

[Rick Molloy]

What strings did you end up using? I find that if I'm doing atypical tunings or different scale lengths that picking strings and tunings whose tension matches appropriate counterparts can (help) bring things back in line... 

because strings can get quite floppy sometimes - especially on 5 strings that are drop tuned or short scale basses... and 4mm seems high for the twelfth fret

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[IanC Hemphill]

John: I agree -  recall Trevor's comment on rotation from the course also, and I'm satisfied with 1degree. My comment was more "have some room to play with this if I think it's worth tweaking", but I've never felt the need yet :-).

Rick: I used D'Addario XT phosphor bronze short scale strings.  They are wound on a fibre core and quite low tension.  Lovely strings really.  I agree that 4mm seems high, but there is no issue with fretting notes easily (the strings are very pliable), and the intonation is very much on the money all over the fretboard, so I didn't feel like I needed less than that.  Just went with the flow :-)