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Double Bass EUB prototype

radii

radii

Feb 16, 2007
111
1
#1
I usually "hang around" the Luthier's corner, but thought that I would post my DIY-EUB over here :)

Not everything came out the way wanted it to ( bridge for example ), but overall, it satisfies my upright needs.

The pickup is abunch of Piezo tabs pressed against the bridge. Far from elegant, but cheap (2$ a piece) and good sounding, even bowed. I'll work on a sound sample, if so desired ... ( I am NOT an upright bass player by trade :smug: )

more pics ...

and some more
 

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#6
bongomania said:
I really like the lines of the curves and their pointy intersections. Classy yet metal \m/. The rear view of the headstock is especially tight. I'm curious, what was it about the bridge that isn't quite right?
Click to expand...

I originally envisioned a bridge that was much more slender at the top, with piezo tabs under the bridge feet.
But due to the relatively sharp angle at which the strings break over the bridge and the resulting pull towards the fingerboard, a thin and slender bridge was just giving in and distorting under the string pull. It didn't seem to affect the sound acoustically that much, if anything, but just didn't feel kosher.
The piezo tabs under the bridge didn't work either, again because of the strong forward pressure toward the fingerboard. The bridge would actually slowly slide on the plastic tabs and tear them apart. Sandwiching them between thin veneers really dulled the sound.
Regardless of the mechanical problems, the pizz sound was ok, bowing just terrible. The lower strings sounded like a farting tuba :hmm:

Mounting four tabs on the bridge however, yields a far superior sound (to my ears at least), gives me much more options for adjusting string-to-string balance and bowing actually sounds good . It's just my intonation that needs years of work :)

If I can drum up the energy at some point, I'll try to make a more refined version of the bridge. I still have to deal with how to ground the strings :hmm: I never thought that that would actually be necessary, but like I said, it's a prototype ....
 
#12
Basshole said:
Beautiful instrument! Congratulations on some really fine work and elegant design.
Click to expand...

Thank you very much.
I've been building electric basses with pretty much the same design for a while now, and though I had to try something new.

I played it through my Walter Woods Amp today for the first time, and was not totally thrilled by the sound. Because of my kids sleeping, I had to always test-listen through headphones.
The midrange seems to be missing a bit :(

And the quest for tone continues ...
 
#14
The main reason why the bridge has become so thick, is that the thinner version i made previously would not withstand the strong pull of the strings toward the fingerboard. A greater neck angle would increase this problem, as the breaking angle of the strings at the bridge would be even smaller, hence putting even more pressure on the bridge.
I have however not considered that the thickness off the bridge would have an impact on the frequency content of the sound. Is this common knowledge in the upright bass world, that a thick bridge kills the mids ?
On second "listen" though, the frequencies seem fairly balanced, just as they are with piezo pickups, as opposed to magnetic pickups, that tend to have a definit mid-hump. Maybe that's what I'm just so used to and was somehow looking for in these piezos.
Right now, the pickups give me an adequate sound to play with. It's not 100% there yet, but pretty good.
I'm thinking about making a system that would allow each string to be volume-controled by it's own potentiometer. From what I understand, that would best be done after buffering the signal, which means 5 (!) seperate buffer/preamp :rollno:
If I could get away with one battery for all of them, I might give it a go ...
 
#17
It depends on several things, but it can be used that way.
I first tried them under the feet before putting them in the wings, à la Underwood.
But my home-made bridge is like a normal DB bridge, with cut legs.

The Kydd EUB uses a Fishman BP-100 under the feet.
Other people here are also using that concept.
 
#18
I am trying to do it the cheapest way possible for now, until it doesn't go any further. So, no, I have not bought a commercially made pickup system (not yet anyway ... )
The 2 $ piezo film tabs that I use, are conceptually the same material as any other 3rd party would use, except that they are not neatly packaged in a suitable housing. It's just the actual film with 2 solder tabs.

I have put them under the bridge, but not with great results (see my previous posts). My EUB's body is semi-hollow, but is not build in a way that the top would resonate freely. There might be more acoustic energy on the bridge, near the strings, then at the top of the body.

What I would really like, are ceramic, cylinder shaped piezo elements. Does anybody have a source for these AND knows how to wire them up :smug: ?
 
#19
radii said:
The main reason why the bridge has become so thick, is that the thinner version i made previously would not withstand the strong pull of the strings toward the fingerboard. A greater neck angle would increase this problem, as the breaking angle of the strings at the bridge would be even smaller, hence putting even more pressure on the bridge.
Click to expand...

I have this problem on an acoustic bass guitar I built. I intend moving the neck and bridge away from the end of the body to increase the length of the strings between the bridge and the feedthrough anchor points as much as possible. I am also considering putting something(?) like a pre-bridge close to the string feedthrough holes to raise the strings closer to bridge height before they turn the 90deg on their way to the bridge, if you get my drift. Rather like the so-called "tension lowering devices" for double bass which raise the height of the far end of the tailpiece away from the top in order to reduce the string bend angle at the bridge. This reduces the force exerted by the bridge on the top.
 
#20
radii said:
I still have to deal with how to ground the strings :hmm: I never thought that that would actually be necessary, but like I said, it's a prototype ....
Click to expand...

You don't have to ground the strings but you do need to shield piezo pickups using copper foil tape: see Link Removed. Grounding the strings is a bit of a bodge/kluge borrowed from the BG manufacturers :ninja:. It grounds your body to shield the back of the pickup (not very effectively) while you are touching the strings. Shielding the pickups directly is much more effective. Besides if you decide to use gut strings, what're you going to do then :smug:?
 

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