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Double Bass Bridge Design Issues with EUB Project - Need Help!

Nate74

Nate74

Mar 3, 2007
789
78
DFW
#1
About two years ago I built an EUB. I thought I'd come up with a pretty sound design and one I really like the look and playability of. I went with a K&K big twin for the pickups and first tried them on the side of my homemade bridge. The output was incredibly low even with the K&K Pure XLR preamp I eventually purchased. Then somebody here suggested putting the piezos between the body and the bridge. I did it and did get quite a bit more gain but eventually that configuration crushed one of the piezos.

I used it for quiet practicing for the past few years but recently decided I'd like to use it live so I've returned to trying to figure out what's going on.

I purchased another Big Twin and now have three piezos mounted to the bridge. Even with the gain all the way up on the K&K, I'm getting very low, tinny sounding output. I'm wondering if the bridge design is just wrong. A lot of the other designs I'm seeing for EUB bridges are taller and slimmer with the various cut outs I'm used to seeing on DBs.

I can't make the bridge taller because of the pitch between the neck and body so I'm wondering if anybody here has any ideas on ways to get some frikin' output out of this thing... I'm open to any and all thoughts. Thanks in advance.

secondbridge-1.gif
 
#2
I was worried that short distance between the string anchor and the bridge might have been an issue but I see on the Fichter design something similar.

I guess I'll try taking a bunch of mass out of it and see if I can increase the vibration???

fichterbasses12.jpg
 
#3
I also used that PU w/my EUB and it took a lot of experimentation to come up w/a good placement. I also found that placing the pads close to the strings did not result in the best volume/tone. I finally placed two of them under the bridge feet with cork shims placed between the bass body and the PU - i put the other two pads inside the body of the instrument. Check out Bob's EUB page Building an Electric Upright Bass
 
#4
Thanks powerbass. What are the approx. dimensions of your bridge? I can't help but think I'd be better off with something thinner and taller.

Also, I managed to damage one of the piezo pads by placing it under the bridge. Does the cork keep this from happening?

Thanks again!
 
#5
yes the cork does help protect the PU but you need to look at the shape of the PU pad. it is flat on one side, the side that contacts the surface and the other side has a ridge where the wire comes into the element. you need to accommodate this ridge if you place it under the bridge otherwise you will compress and damage it. I used gasket material from an auto parts store. before you alter the bridge I would try placing the PU under the bridge with cork, this may help.
 
#6
If you checked out my project you'll see I did the Double Big Twin piezos under the bridge with the cork for buffering. If I were you I would consider slimming the bridge down whether you stay with the contact piezo position or the under the bridge configuration.

When you get right down to it, when we're talking solid body EUBs, the bridge IS the bass when vibration sensing pickups are on or in it (IMHO). Surface mounted piezos don't produce a lot of signal; they produce more juice when they are under pressure. If you've experimented you probably also noted that, the further they are from the string contact point, the more diffused and less direct the notes become.

You can certainly experiment with a thinner bridge and different bridge positions for the surface mounted piezos. Another concept (no reality, merely theory based on experiences) I'll introduce would be to cut the bridge, say, 2/3rds of the way down, then drill two matching vertical holes at the cut, so you can stick a dowel or metal rod that is not tight, so the bridge parts are kept in place but can freely slide up and down... and insert the three piezos between the strings. I'd try varying thicknesses of wine cork (perfect size, be careful slicing!) on the bottom or both sides to arrive at the best result.

Good luck with your project! It looks great.
 
#8
That's a good point. The Fishman BP-100 uses those clips to press the piezos against the face of the bridge. Maybe a whole new EUB bridge design could evolve, using flexible slots/spaces on the face of the bridge to press these piezos into action. OTH, just one KK Bass Max (or your lone surviving Big Twin) in a slot on the bass side of your existing bridge could work.
 
#9
MR PC said:
That's a good point. The Fishman BP-100 uses those clips to press the piezos against the face of the bridge. Maybe a whole new EUB bridge design could evolve, using flexible slots/spaces on the face of the bridge to press these piezos into action. OTH, just one KK Bass Max (or your lone surviving Big Twin) in a slot on the bass side of your existing bridge could work.
Click to expand...

Rick Turner made the UB-1 pickup, it was four transducers placed under pressure in a slot adjacent to each string.
 
#11
If putting the piezos underneath the bridge damages them, that means you're subjecting them to too much pressure, measured in psi, pounds per square inch. The pounds part of that is determined by the way the strings are set up: the square inch part is a design element in the bridge.
 
#13
If you elect to use a Full Circle or similar pickup with a transducer only on one side, I'd recommend engineering it so it would be in the center. To my eyes there isn't sufficient wood for all four strings to diffuse equally by the time it got to one side, so that side strings would be louder than the others.
 
#14
i tried that with one Bass Max on my Azola. the results were less than spectacular. one Bass Max on the bass side is very good, but true, with that placement the d and g strings are more diffused than the E and A. on my bass, it's quite usable that way. the arco sound is way more usable, due to the phase problems that **sometimes** occur when using two transducers.
 
#15
MR PC said:
i tried that with one Bass Max on my Azola. the results were less than spectacular. one Bass Max on the bass side is very good, but true, with that placement the d and g strings are more diffused than the E and A. on my bass, it's quite usable that way. the arco sound is way more usable, due to the phase problems that **sometimes** occur when using two transducers.
Click to expand...

The result will almost always depend upon the height of the bridge. If you check later Azolas Steve often used two Bass Max pickups, or two of those he made himself, in a tombstone style bridge with a notch at one side and another, higher, at an angle, on the G and D side, and had separate passive volume controls for each. I believe that one was wired out of phase with the other.
 
#16
that's right, on the bridge height. only way to know if that placement works on your bass is to try it.:)

my Azola came with 2 Bass Max pu's wired to a passive balance pot and a master volume. first of all, passive pots degrade the sound quality of these pu's, ime/imo. second, in the 50/50 mix, you only get 50% output of each pu, the result is muddy tone. i hate to say it, though it was a great idea, it was a poor design in use. if there is a potentiometer out there that doesn't color/degrade the tone of these transducers, please let us know what the value/brand and source is. if Azola had used individual preamps for the pickups, it might have worked. overall, i think his best sounding basses use one transducer with a preamp.

the Azola angled slot design was a great idea, it works sometimes, but sometimes isn't consistent enough, imo. the nature of the wood is to shrink, expand, dry, ect. those actions change the way the pickups sound in terms of phase relationship to each other. at least on my bass it does...... maybe a different material like graphite or aluminum would be more consistent with that design.

for the record, i think Azola started with a one pickup system, went two pickups for a period, and then back to one pickup with a preamp. a great company, i wish they had been able to keep it going.:bawl:

but Nate74 has 3 pu's over there........what to do?:D
 
#17
Some outstanding input here guys. Thanks to all of you. I've done some experimenting with some cork and with some rubber. Currently, I have a thin (maybe 1/32") layer of rubber under the bridge base then two of the piezos between the rubber bottom of the bridge base and the body. The flat (gold) part of the piezos is up agains the body and the little "bump" where the wires are isn't under the bridge, just the flat part where the K&K logo is. The sound is as good as I've gotten out of this instrument so far. I tried the some configuration (Bridge/Cork/Piezo/body) but with the cork isolating the bridge from the piezos, the sound was weakend and the clarity was lacking.

I have some time later in the week and I'm going to try some other bridge designs and slim them way way down. Maybe some scroll saw patterns to further decrease the mass.

Thanks again to everybody who's chimed in here. I'll report back with updates and results.
 
#18
great news, please do let us know what kind of bridge design you cook up.:)

with that third transducer, you might think about experimenting with placing it under the fingerboard or, in the neck joint if possible. the old Clevenger Bennett Bass had that arrangement with a separate preamps for the bridge and neck pu. some rockabilly players stick a transducer under the fingerboard in an effort to get more "click" for slapping, but on the EUB it's a way to a get little more wood into the electric tone
 

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