This Instructable will show how I converted a $20 thrift shop 6 string acoustic guitar into a 9 string acoustic. The D,G and B strings are doubled just like on a twelve string guitar while the high and low E string and the A string are left un-altered. The result is a rich and full sounding acoustic guitar. It sounds like a 12 string guitar but the neck isn't as wide so it's easier to hold and play. No special tools are required but you will need the usual woodworking types. Also needed will be at least 9 tuners. These are available on-line starting at $10 per 6pack or at a instrument supply store perhaps.
Step 1: Select a Guitar
Any full size guitar will do. Don't worry about body damage as you will probably want to repaint the guitar anyway. As long as there is no structural damage the guitar should hold up to the extra tension created by the extra 3 strings. Thrift shops sometimes have really cheap guitars that are missing tuners so people don't want them. These are perfect because your going to replace them all anyway.
Step 2: Remove Hardware
First you remove all the strings and then the tuners from the headstock. Usually two small screws will hold the tuner. Remove these screws and pull the tuners out of the headstock. Don't lose any parts as these can be reused on different projects or for quick repairs on other guitars. This guitar has only one screw holding the tuner.
Step 3: Altering the Bridge
The bridge on the guitar will have 6 holes drilled through it where the strings pass through. I drilled three more holes with the bridge still attached to the guitar. Just make sure the new holes are spaced evenly and be especially careful to drill them for the right strings. The D, G and B strings are the strings that will receive the extra high octave compliment string. In the photo the new holes are the ones above the original row of six. The strings will be very close together so be careful not to drill into the hole beside it!
Step 4: Altering the Headstock
This is the biggest change you will make to the guitar. An extra three tuner holes will have to be drilled to accommodate the extra strings. To make room on the headstock and to evenly space all the tuners, the old holes will have to be filled, sanded and the headstock repainted to have a blank slate to work with. In the photo the headstock is filled and painted black and ready for drilling the new holes.
Step 5: Drilling New Tuner Holes
Drill the new holes using a drill bit to correspond with the diameter of your tuner shaft. I put four tuners on the treble side of the headstock and five tuners on the bass side. Make sure you install the tuners in such a way that they all turn the same direction to tighten or loosen the string on each side of the headstock. Tuners are left and right designated.
Step 6: Tuner Installation
Here are more pictures of the finished headstock with the tuners installed.
Step 7: Altering the Nut
The nut will need to have 3 new slots filed into it to hold the new strings. I cut a new nut from a bone blank but the original nut can easily be filed instead. The space between the slots of the doubled strings should be about 1/8 inch. Too close and the strings will vibrate and hit each other. Too far and the strings will be hard to fret with one finger.
Step 8: Altering the Bridge Saddle
If there are slots in the original saddle use those as a guide to file shallow slots for your new strings. If there are no slots don't worry the new strings should rest on the saddle in the right position IF their new holes were drilled in the right spot. If the string is too far away or too close to the string it is doubling, then file a shallow slot in the saddle for it to rest in ensuring the slot is the right distance from the next string (1/8 inch or so).
Step 9: Restringing the Now 9 String Guitar
Time to string it up! I used a regular 12 gauge acoustic string set for the six original strings. They are installed and tuned totally the regular way. Low E,A,D,G,B and high E. The new strings will be strung along side the D,G and B strings. All three new strings can be .10 or .12 high E strings. These light strings will enable you to tune up to an octave above the original tone of the D,G and B strings. Once tuned you are ready to play and enjoy the new wider sound of your new guitar!
Step 10: Sample Video
Here is a short video of the finished guitar
Thanks for watching