Julien's second build: an accoustic bass?

[julien]

ok,ok, I know I am not done yet with my current project, but I can't wait...

here are some ideas, facts, points about my new build, just ideas out of the brain, nothing really decided yet.

4 or 5 srtinged bass 34 inches scale, fretted

very probably a hollow body too:
Well, the first project was more inspired from the 2 by 4: "take a big board and take away the wood you don't need", the next project will be more like "glue on the things you need to add". I dream about a neck through design with a resonance box, a bit like a good old flamenco guitar (I know these are not neckthrough but…).
I might want to bend the top and back of the “box” to a slightly cylindrical shape.

Will I use it for tapping? well probably not, since I already own a tapper ( almost) and because of the piezo I'd like to use (on a tapper you just hear the impact)

I’d like to have a neck with several woods, a laminate like this one for instance:
Maple
Browner exotic wood (rosewood or mahogany or else - i'l kie to focus on structure strenght and have a color contrast)
Maple
Browner exotic wood
maple

very probably with piezo pickups, but I don't have any experience in there, so any hint is welcome. The goal is mostly to hear the wood instead of the 50Hz Hum. I’d like to keep the electronics to the basic. I have a “no knob” goal.

I like ABM saddles, so I might use them. But I don't know if it's a good combination with piezo.I think those that similar on Ibanez Basses look really cool.

woods... well. the biggest problem right now is to find a place where to buy it... there nust be a place here in Sweden. Any help is welcome from the one building in the north. I got today the number of a guy who built several electric guitars is the area, I'll give him a call.

the peghead will be tilted, as I found the one I made on my first tapper pretty ugly and too beefy around the nut.

I like to see the wood grain so I might go again for a clear coat. But I would like to have it very very glossy, so I don't really know what to choose yet. maybe shellac?

I would like woods with nice patterns: birds eye, leopard, something like this.

This will be a very long project, way longer than the build off. Mostly since it’s a lot woodworking.

I'll later post pictures of existing instruments I find inspiring.

Please leave your comments !

Julien

[lactose]

I will be interested to see what you do. Is this your first acoustic instrument ? Lately I have been trying to build a couple of acoustic things. One is a cigar box guitar here (http://www.youtube.com/watch?v=A10PMoIJIvs).

Another is a hollow body (but not arched top) jazz guitar. I am finding buiilding an acoustic instrument more challenging. I am getting better at wood bending.

I see people putting piezos on their tappers, so I figure the body noise must not be too bad. I would like to hear some clips of just the piezo pickups on a tapper. The body noise on my bass with piezos is not too bad.

As far as finishes, my understanding is that polyurethane is quick and easy but does not let the wood breathe as much. Nitro cellulose is slower and more hazardous, but lets the wood breathe and age better. I only use poly, and I have only done satin, not gloss finishes. I am getting ready to do my first painted body, a 30" fretless headless 5 string bass, using an Uncle Bob type headless tuner bridge. I seem to make more basses as that is what I play in a little band, but I am mostly a guitarists.

I am still following your other project. Keep up posted.

[HylerTouchstyle]

We've gotten a lot of experience with piezo pickups since starting our upright bass line. After a lot of trial and error with "expensive" piezo elements vs. the standard rounds you can get at any electronics store, we discovered that the main element in getting that dark and 'woody' sound from piezo pickups are to make sure the imapact which creates the sound is not too intense. Basically, I've never gotten a great sound from piezos when they were floating or sandwhiched between wood and/or metal. In our comparison, placing our piezo within a solid oak upright bass and lining the top and bottom with a small layer of foam and rubber to dampen it, we removed that harsh impact that is usually associated with piezos and got a better sound than we did with the more expensive stick and cable piezos. The part that amazed us is we did not lose any noticeable output in doing so. Just a little food for thought, they're also much less cost than magnetics so experiment with lots of arrangements. Since you're building a hollowbody, I'd say more sound will come from the preamp you use than the piezo element itself.

[julien]

So you basically mean that I can buy a cheap piezo from stewmac, glue it onto a "bike tube piece of rubber glued to the wood", and I'll get a decent sound for tapping? (less impact sound)

You say you didn't notice a big level loss doing so, was it in the low, mids or high frequencies?

Another question: What's the point in expensive piezo cells, since it doesn't seem to work better?

/ Julien

[HylerTouchstyle]

Well take everything I say with a grain of salt. There are some cases where simply ordering a circular piezo from Stewart Mac, or whatever types they sell, will not be as ideal as one specifically made for a certain guitar.

In my case, for our Upright Bass, the round cheap-Os probably responded better due to the higher radius on our instrument, our piezo is installed right below the cocobolo bridge which is cut to have all it's tension from the strings being brought down on the center point above that piezo. So in this case, the expensive flat acoustic piezo or piezo cable, did not work as well in this application. The expensive piezo cells are more than likely expensive for their application, for example it costs a lot more to make a piezo cable than it does two pieces of round metal that are joined together.

As far as dampening it with "bike rubber", not exactly sure what that is, but the best result we've found is removing it from the wood/metal so the entire surface of the piezo is making contact with something. This is usually impossible with woods and metals as they are rigid, so any gaps under the piezo will not be filled, however if there is a thin enough flexible surface, it can compress in some areas where the instrument material meets the piezo and expand in those where it does not when it is held up against it.

While we didn't have a spectrum analyzer going while we were testing this, it was very audible that a lot of the high end "bite" and metallic sounds were removed when dampening was added. The overall levels stayed the same throughout the range of the instrument, it almost sounds as if the dampener acts as some sort of crude passive compressor, attenuating the spikes in the sound to level it out.

Again, I haven't seen too many standards or articles on piezo dampening, so take everything I say with a grain of salt and just experiment til you have a combination that sounds well enough.

[lactose]

I am building a weird bass guitar at the moment and have been thinking a lot about piezos. On my last bass I bought the piezo bridge then built a little preamp. I did an experiment on my Squire Jazz Bass putting a piezo under the bridge plate and found that there was a huge volume difference between the strings close to the pickup, and farther from the pickup. So I guess I would need a piezo element under each string.

So I keep trying to come up with some design, where, I presume I would have some tapped piece of aluminum with a set screw (for height adjustment) that would sit on the piezo element, which would sit on the body or plate.

Hyler: Do you use just one piezo element ?

The foam might take away some treble but that would not be bad since the instrument I am building is fretless.

[julien]

well well welll...

I know that wood bending will be a part of the deal. I didn't really know how to handle that but I have an idea now. I found a "local" wood shop, and they have a lot of veneer. I was thinking buying maple or oak 1millimeter veneer without nice patterns (just for the structure) as it can be way easier to bend. gluing several veneers on top of each other could let me easily reach the shape I need. But it might be very expensive. Any tip linked to wood bending is welcome.

As I wrote, I have found a wood store that has a lot to sell, maybe not the sizes I need, but I'll go there and check. so I am happy about that, It was my biggest problem.

Polyurethane finish is pretty easy, yes, and quick. But I did not reach the very high gloss finish I am hoping for for my next instrument, this is why I am asking. I heard about shellac polish as something that was a long ancient method, but also quite rewarding and easy to repair. Also, it does not cost too much if I remember well. I never heard about nitro cellulose, but I might give it a try if it seems promising.

Piezos...
Well I was thinking about it to avoid complicated electronics that might result into a hum anyway... but I wasn't really into buying a preamp and such. I might consider it now.
It is normal to loose sound on the high end, it is called a low pass filter (it works also with mechanics - not only electronics).
What I call bike tube is the tube you put inside the tire, to inflate it. you can cut it to do whatever you want, from rubber bands to small rubber sheets. I was thinking about gluing a piezo on it to dampen the first impact. I think I understood what hyler means with piezos. I will continue thinking about it.

Julien

[julien]

Here are some picture of instruments that I find inspiring :

the five string bass from madmannmatt:
(seen here on the forum)
I like the body shape, the pattern of the body wood, the laminated necktrough, the saddles... I find it very appealing.
http://tappistry.org/forum/showpost.php?p=12916&postcount=5

this one has really interesting bodywood patterns:
(or should I say these ones?)
http://www.noguera-basses.com/basses_serie.php?serie_b=Harmonie

Ibanez single string bridges and ABM bridges (I have never seen these for real). Here for instance:
http://ibanez.com/BassGuitars/model-BTB570MFM

Brenda used ABM on her project. Any feedback?

I would like to do some wood binding to hide the fret slots, like on this one for instance:
http://ibanez.com/ElectricGuitars/model-ARX500

I might go for side inlays just like I did on my tapper.

I was thinking about pretty standard string spacing, and 34 inches scale. I don't have special requirements on this.

Wood choice again...
Well I just took a look at Ibanez accoustic basses to see what they use. Seems like there is a bit aof everything and no "do and don't". I really have the feeling that the wood is one thing, but if you'll have some electronics in there, electronics will let you change the sound almost as much as you wish. So I might follow this rule:
The "structural parts" need to be done in strong and stable woods that can bear loads: neck and some parts of the body. The rest is just cosmetics and I will follow what I think looks good. Doesn't sound too bad, or do you have any idea?

anyway... I have to make some drawings before ;-)
Scale one, as usual

Have a nice week end,

Julien

[lactose]

Any tip linked to wood bending is welcome.
Here is what I have learned so far:

1 You want the wood to be around .1 inches (2.5mm) thick.
2 Soak the wood in water about 30 minutes before bending (and let the iron warm up). I bought the bending iron from StewMac.
3 Have a spray bottle of water handy, the can wood dry out in a few seconds when bending.
4 Keep the wood wet so it doesn't crack.
5 The metal strap behind the wood keeps it moist longer and helps prevent cracks.
6 Get some gloves for heat protection.
7 Rock the wood back and forth while applying bending pressure. Don't let the wood get crooked with respect to the iron.
8 Make a mold that has water sealer on it and have it ready to compare to as you are bending. This will hold the piece when you are done bending.
9 Plan on practicing with 4 or 5 scrap pieces before bending expensive wood.

Pic of my mold:
http://www.think600.com/mold.jpg

[julien]

I was thinking about the mold idea too.

But I it seems quite hard here to find wood that is around 0.1 thick
I found a company that sells veneer (about0.03 thick), so I was thinking about using it, and glue several thicknesses together to obtain the right thickness, stiffness and strenght.
As venner ir much thinner, it should be no problem to bend neither. What do you think?

(otherwise I will have to make the thin boards myself...)

[lactose]

You may be on to something with the veneer idea. The glued veneers probably wouldn't sound as good as read wood, but the sides probably don't contribute that much anyway. Especially then they are being muted by your leg and arm.

[julien]

smart thought!

because I was also planning to laminate the top and back...

there might be some design re-think...

[lactose]

I typically sit with my instruments. That means my right arm is muting the top side, my leg is muting the bottom side, and my stomach is muting the back. So I think the top wood is most important.

[baev_al]

Hi all!!!
Is there some more detail information about piezo and its installation? It would be great to see pictures too. Julien, good luck with your another project!

[HylerTouchstyle]

Hyler: Do you use just one piezo element ?

The foam might take away some treble but that would not be bad since the instrument I am building is fretless.

One is sufficient for our upright basses. The key is to focus all the pressure towards the center of the piezo element. IE, for our basses, our bridge bottoms are flat while the body is contoured, essentially making the only point of contact the center where the transducer is located.

When it comes to tapping instruments however, piezos are a completely different world. We use a minimum of 2 (regardless of stereo or mono) on our current instruments that have piezo bridges, direct contact with the metal bridge, rubber isolation underneath the piezo and between a stereo split bridge to keep sound bleeding to a minimum. We then have to make a decision about the resistance of the electronics. Running 250k is a nice way to imitate a magnetic pickup, but loses a lot of the range of the piezo, 500k is similar with a little more of the range, and 1m is usually preferred though usually not available stacked and the range is still not as large as hardwiring it directly to the jack. We have been toying with the idea of mounting active preamps directly into our Model II as we did earlier with a couple of our larger prototypes, still has a lot of logistics left to research however.