As every now and then, I tend to spend some time online on a certain well-known webpage that's famous for their wast amount of different videos. The websites main purpose is to let any registered user upload various videos to share with the rest of the people on the internet. Of course this brings a splendid opportunity for any manufacturers and marketing oriented users to post their videos of their products for online viewing. I am of course talking about the fenomenon almost everyone has heard of, the Youtube. Anyway, I once stumbled upon a video show-casing the Kala U-Bass. Kala is a company mostly known for their ukuleles (a.k.a. ukes), and now Kala had developed and started producing both hollow and solid body basses using polyurethane strings. Thanks to these polyurethane strings it's possible to get a very good bass sound on a very short scale length (also sometimes refered to as the mensure).
A full sized double bass has a scale length of about 43", the standard and most common for electric basses is 34", but this little monster had only a scale length of 21" (half of the double bass). It was small, light in weight, easy to play, great sound and small for transport.

A few weeks earlier my godfather had given me some blocks of tropical wood that he had laying around in his basement. One of those blocks was a fairly nice piece of a chocolate brown wood, not wide enough to get a standard sized 2-piece bass body, so that piece was a obvious choise for the body wings. I'm not shure what species it is, but one possible candidate is Malabayabas (Tristania decorticata), but there are way too many species with the same color, grain pattern etc. to be 100% shure.
Earlier I had glued together a neck block for future use, with birch, merbau and some beech, which just happened to be long enough for a neck-through construction and a fairly nice fingerboard piece of Brush Box (Tristania sp.) that was too short to be used for a standard bass fingerboard.

Time to lay down some specs;

Time to start working on the fretboard, marking and sawing the fretslots, shaping the sides and ends, and finally install the frets and filing and dress them nice and round. Naturally I had to make a new template for the body shape for this build, all I basically did was taking the same body template used on the "Black Pearl" and "Willow" and just reduced the size of it to about 3/4 of the original, and printed it out.

Once that was done it was easy to lay out the body wings by the neck block and just pencil out the shape on the body wings.
The body wings was cut to shape and the edges rounded at this point, because once they would be glued to the neckblock it would have been impossible to round the edges with the table-router. The neckblock was pre-shaped, marked and glued together with the body wings, after the headstocks scarf joint was glued and the head pre-shaped too.
The head was shaped using the bandsaw and a electric file (a very useful tool for shaping wood etc.), holes drilled for the tuners, then the body wings glued to the neckblock. A new router template for routing out the smaller-than-usual control cavity had to be made, but once the template is done the actual routing is a breeze.
Fingerboard was glued in place, no need for some sort of truss rod on a small tension/small scale instrument like this one, and the exact placement of the bridge marked. The bridge is my own design, a simple oval(y) thingy that holds the Shadow piezo pickup in place in a slot and supports the strings just below/behind the pickup.

The bridge is held in place by two screws and the strings are anchored to the body in individual recessed holes, basically a strings-through-body concept going on there. The ebony nut was cut, shaped, glued in place and slotted along with the bridge pickups slots. I had to dig up some larger-than-usual roundfiles for this, the diameter on the E-string is an awesome 5mm (that's 0.197").
The placement and drilling of the pots holes was done along with some other small stuff drilling etc. and of course the final shaping and sanding of the hole thing. Just as on "Jessica" I applied three coats of Danish Oil on it, letting each coat dry for about a week.
Time to put some copper tape inside the control cavity to isolate it, along with all the hardware that had to be installed.

Installed the bridge pickup and electronics, but once I got as far as putting on the strings I ran into a serious problem.
The strings themselves are so slippery that it's redicoulusly difficult to wind them up around the tuner post. As soon as there is some tension building up they start to slowly slip out of the slot and eventually snap off the post.

The simple solution for this was to drill slightly bigger holes than the diameter of the strings through the posts, slip the string through the hole and then start winding up some tension. That way the more tension you wind up on the posts/strings, the more the string itself grabs the edges of the holes.

These strings "give"/stretch a lot. 5 minutes after you have tuned it properly with new strings, the tuning will be way too low, especially on the thinner strings (G and D). But eventually they will stop stretching and stay in tune (I hope).

The feel/touch of the polyurethane strings under your fingers is quite special. If you press the strings down with the tip of your fingers the strings tend to slip away or roll off from under your fingertip, due to the low tension and large diameter of the strings. But by using more of your fingerpads instead of your fingertips it works just fine, at least for me. That way the sound get even more upright-like too. Next time you see someone playing on a upright bass notice the way he/she presses down the strings with his/hers left hand. Does he/she use the fingertips or the fingerpads?
Another thing that gets some getting-used-to is the very short scale, the frets are so close together that at first it's a bit difficult to hit the right spot with the ring- and littlefinger. It almost seems like you would have to keep the fingers on your left hand right next to each other, not streching them apart from each other at all. Not that easy to do after all these years of playing on 34" scale basses. Also the thick strings makes it difficult to feel the exact position of the frets under the strings, something that we don't always notice or even think about when we're playing.

So what about the sound then?

This is how it sounds using only the Shadow SH064 bridge pickup. All tone controls set to neutral, recorded thru my Zoom B9.1ut multieffect pedal.



A very upright bassy sound, although it does sound kind of "rubbery". However a very useful sound.

I suddenly remembered that I once heard a standard Jazz bass sized fretless on the web somewhere. The company that made these basses had developed a partially hollow body with some sort of piezo pickup mounted on a piece of spruce inside the body. This construction made it possible to get some very authentic sounding upright bass sound out of this electric fretless bass.
So I started pondering how to apply something similar to this bass, and I did a simple test by attaching a thin piece of pine firmly to the bridge and placed a small piezo pickup between the body and the piece of pine. And it worked! A very warm and "woody" sound was pickup by the piezo although the placement and amount of pressure applied on the piezo affected the sound a great deal. So I had to figure out how to construct this type of system into the body. Back to the drawingboard.
I desided to drill and route out a fairly big cavity on the backside of the body and the bridge design had to be done way different than the standard Kala U-bass solid body version. I drilled three holes from the the backside of the body exactly below the slot for the bridge pickup and then inserted three plugs that moves freely in the holes and are in contact with the bridge piezo. Then a thin, long stick (sort of like a over-sized icecream wooden stick) was attached to these three plugs inside the cavity. A small amount of pressure had to be applied to the plugs so they would be in contact with the piezo bridge, thus vibrating along with the bridge pickup and thus making the thin stick vibrate.
Now came the tricky part, since piezo pickups needs a certain amount of pressure on them to sound properly. This lead to a problem, since applying pressure on the piezo which is in contact with the stick that vibrates, the more pressure is applied onto the piezo the less the stick is able to vibrate.
After hours of testing different placement of the piezo and different amounts of pressure I finally got it to work somewhat properly, although there is infinite possibilities. Different placement of the piezo, multiple piezos, thickness width and length of the stick, type of wood of the stick, etc. etc.



A very warm and "woody" sound. Quite low in level, but a sound that you wouldn't think comes from a small sized instrument like this one, (and I don't know where those annoying interferences come from).

Time to try some blending (50/50) with the bridge and stick pickups.



Compared to the stick pickup there's way more tone and definition in the sound, yet a deep, warm and fairly "woody" thing going on there.
However, just as I stated earlier, there's tons of possibilities to get an as authentic upright bass sound out of this kind of system...

UPDATE! (November 2014)

I found this manufacturer of pickups for acoustic instruments called B-Band.
B-Band is a manufacturer of high quality pickup systems for acoustic guitars, double basses and drums. All B-Band pickups use our proprietary patented electret film technology, instead of common piezo materials.

I ordered the AST 1470 pickup along with the necessary preamp A1.2. Mounted the pickup directly onto the "stick" with its adhesive, ditched the volume control and connected the pickup straight to the preamp. From there the signal goes to the blend pot.

And this is the B-Band AST 1470 mounted on the stick with the A1.2.

This is both bridge piezo pickup and the B-Band together, blended 50/50.