Double Bass EUB design and build and some lessons learned

[Jaygetsreal]

A couple of years ago I was starting to lean towards jazz and wondered if my ear was good enough to play a fretless instrument. I reasoned that because I can hear when any instrument is slightly out of tune - much to the annoyance sometimes of my bandmates - it was worth a try.

I love the DB and wanted one but I'm a tight b@stard and wasn't in a position to buy a decent one.

OK I confess. I'm one of those guys with a home workshop ('shed' here in Australia) who likes to build amps, speakers, pedals etc which cost me less but the finished items have almost no resale value. But the creative pleasure I get is priceless.

So with time on my hands (I am 65) I decided to design and build an EUB. Many months of internet research later I had the basic dimensions and the build took just over a year in all.

I would not call myself a luthier. DB purists will think I'm just another nutter in a shed somewhere. But for what it's worth I'll share the story and some lessons I learned along the way:

Post 1 Key dimensions
Post 2 Work in materials you like working with
Post 3 The diabolical compound curvature fingerboard
Post 4 Don't skimp on the tuners
Post 5 Electronics
Post 6 Strings
Post 7 Strength where it's needed - carbon fibre
Post 8 Strength where it's needed - steel
Post 9 The elusive woody timbre

Stick with me. To my ears the end product sounds amazing!

It is my hope that this thread, including any suggestions you make, might help someone who's tackling a similar project. Happy to try and answer any questions if you're interested.

 

[Jaygetsreal]

Post 1 : Key Dimensions

I decided to design the instrument in 3/4 scale. Please reassure me that 3/4 is the de facto normal for DBs in jazz so one day I can easily migrate to a real one!

The finished instrument without its removable endpin ended up 1.55m (5 foot 1 inch) long. Nope, I won't be flying with it.

At the very beginning I put together the string geometry for 3/4 a bass from collected internet wisdom. Then I tested it out using weedwhacker line.


This allowed me to emipirically fill in the gaps in the measurements. Pretty soon I had all the string heights, string spacings, curvature radii etc I needed. This step also taught me just how much combined tension the bass has along its length, which helped me to design a strong enough skeleton (See Post 8 coming soon)

A note on weedwhacker line. I used 1.6 2.0 2.8 and 3.5 mm gauges. The sound was...well...thin. And frequent retuning was required. I subsequently upgraded to Helicore Hybrid Mediums which give me good all-round performance - and incredible sustain (which can be a bad thing I suppose). I tame the sustain with a couple of pipe cleaners woven between the strings at the bridge (Pipe cleaners? Gen Y and Z just ask your dad)

Anyway, back to the build. Here's a sketch of the key dimensions.


Post 2 is about choosing construction materials.

 

[PauFerro]

Interested in learning more about this. I had some luthier training and play a fretless I built 20 years ago. You probably learned a lot about tone, and what's really important in overall construction.

In terms of tone, it does sound like a very warm fretless bass. But I also think it's a good transition instrument to a 3/4 acoustic upright.

Looking forward to your other posts on the subject. I admire people who take risks and try something new to them like this. Even if it defies convention.

 

[Jaygetsreal]

Post 2 : Work in materials you like working with

With rudimentary tools I had to work with easy materials. I have always liked working with aluminium. For the structure I wanted something light and strong. Here in 'Stralya most people have surfboard racks - and hey I had a spare Rhino Rack bar in the shed! The design centred around this roof bar, which is 41X41mm in section and needed to be 1.37m (4ft 6in) long.


Another new material I'd been working with was acrylic, after our kitchen fitout people left me offcuts from our new benchtops. It works really easily and polishes well too. I made enquiries and they gave me some even bigger offcuts. The acrylic material is only 1/2" thick so to construct a headstock I built up a sandwich to the right dimensions, bonding the layers using acrylic cement.

Similarly the fingerboard had to be a sandwich. Was very pleased with the bond, which after machining (See next post)is completely invisible from the front of the instrument.

The carbon fibre in this picture will feature in Post 7

The holes drilled along the edge were for the fret markers, filled with black PC.7 epoxy and polished.

The next post is about actually making the diabolical compound curvature fingerboard

 

[Jaygetsreal]

Post 3 : The diabolical compound curvature fingerboard

A problem I had was power tools. I have a drill press but apart from that only portable hand tools. Clearly I had to get inventive to do any complicated machining - like the compound radius fingerboard.

To those not familiar with DB geometry, the fingerboard is not flat like a BG but curved, and the radius varies along its length from about 250mm at the nut to about 110mm at the end of the fingerboard. I needed to machine this using basic hand tools!

The tool alone took about six weeks to design and build. It is basically a router on rails, with the fingerboard blank attached to a hinged triangular panel below. I did all the calculations and experimented with pieces of plywood until I got exactly the variation in radius along its length I needed.

Once exact I spent a very happy couple of hours making snow cutting the acrylic blank, repeatedly adjusting and running the router back and forward along the rails.

There were a couple more challenges. For correct string height fingerboards have to have a slight dip along their length. Instead of machining this (which would have meant a triple compound curve) I simply arranged for the wooden wedge that attaches the fingerboard to the bar to be 3mm thinner in the middle. Like a long thin triangle with one side gently concaved.

This wedge - the only piece of wood I used in the whole design - gave me a headache for the first few months. Because it is so rigidly attached to the aluminium bar by four 1/4 inch bolts, changes in humidity were causing the timber to expand, bending the whole frame and upsetting the string height. I solved this by cutting it into two separate lengths so the wood had space to expand.

The next post is about the tuning machines. Stay...tuned.

 

[reverendrally]

That jig is FANTASTIC! Great Aussie injunuity (however you spell it). Very impressed. I might build one I reckon.

P.s. I own that very router. 1100watts. Scares the heck out of me, so it lives under my router table now.

 

[delta7fred]

Subbed!

Love the neck machining jig!

 

[Jaygetsreal]

Post 4 : Don't skimp on tuners

Made the mistake of ordering cheap tuning machines on eBay. The looked great but in a very short space of time, despite PTFE spray, the metal gears stripped under the load. Don't do it

I couldn't afford to replace them with Schallers so I got a set of middle-of-the-range tuners from Realparts.com.au: Australia's Premier Guitar Parts Resource which had similar screw positions and have been great.

Next post is about the piezo pickup and preamp

 

[Jaygetsreal]

Curious... you've done a ton a work over several years... are you looking just to share what you've learned and what you've done or are you looking for suggestions, ad hoc, about what you could have done?
Sharing vs planning?

Thanks Tom. Of course you're welcome to make suggestions! Perhaps I didn't make that clear at the beginning but I thought that was implicit in forums such as this (BTW it's my first EVER post on a forum!) My hope is that the thread might benefit anyone tackling a similar project, and the more combined knowledge in the thread the better I reckon.
I have edited the first post to make that clear.
Thanks

 

[Jaygetsreal]

Post 5 : Electronics

There are so many choices available for pickups and preamps. I kinda stumbled on the Fishman and am so glad I did.

The Sonicore piezo sensor is designed for a 5 string acoustic and is about 80mm long - almost exactly the right length to go under the saddle of a 4 string EUB. Also it is only 3mm diameter so it can be pushed through a very inconspicuous hole on the underside of the bridge.

Everything has to be 110% rattle-proof. This applies to all joins, screws, bolts, but also to the saddle which gave me some problems. It seems a LOT of energy is transferred from a heavy bass string to the saddle. The saddle sits snugly in a slot and it has to be free enough to transfer the energy down to the sensor but not be free enough to buzz. It's a fine line and I had to experiment a lot with thin strips of PTFE to get this result. Once fixed it hasn't buzzed at all.

The saddle is 8mm thick acrylic so I drilled lots of holes in an arty pattern to make it lighter. This certainly made an audible difference, helping the mid and upper harmonics to reach the electronics.

The Presys+ preamp came hardwired to the piezo. I mounted it in a folded aluminium housing on the back of the bass. No problems here. It's a fine little amp designed for the high impedance source and it has plenty of sound flexibility.

Next post I say goodbye to the weedwhacker test strings

 

[Jaygetsreal]

Post 6 : Strings

I am no expert on this and haven't anything to add to the many TB threads on the subject. However I am very happy with the Helicore Hybrid Mediums I have on the bass now.

 

[Jaygetsreal]

Post 7 : Strength where it's needed - carbon fibre

Having made the headstock using bonded acrylic I got nervous about its strength. As a precaution, before putting any strings on, I decided to put carbon fibre along the back to compensate for the string tension. Just two 3mmX1mm strips you get from the model aircraft store. Even carbon fibre is slightly elastic so I prestressed them while they were being epoxied in place.

Will never know if this was necessary but it's comforting, especially on days when the temperature here in Adelaide climbs over 40C (104F)

In the next post I discover the worst design fault of all which required major surgery.

 

[PauFerro]

Post 3 : The diabolical compound curvature fingerboard

A problem I had was power tools. I have a drill press but apart from that only portable hand tools. Clearly I had to get inventive to do any complicated machining - like the compound radius fingerboard.

To those not familiar with DB geometry, the fingerboard is not flat like a BG but curved, and the radius varies along its length from about 250mm at the nut to about 110mm at the end of the fingerboard. I needed to machine this using basic hand tools!

View attachment 2825299
The tool alone took about six weeks to design and build. It is basically a router on rails, with the fingerboard blank attached to a hinged triangular panel below. I did all the calculations and experimented with pieces of plywood until I got exactly the variation in radius along its length I needed.
View attachment 2825301

Once exact I spent a very happy couple of hours making snow cutting the acrylic blank, repeatedly adjusting and running the router back and forward along the rails.View attachment 2825302
There were a couple more challenges. For correct string height fingerboards have to have a slight dip along their length. Instead of machining this (which would have meant a triple compound curve) I simply arranged for the wooden wedge that attaches the fingerboard to the bar to be 3mm thinner in the middle. Like a long thin triangle with one side gently concaved.

This wedge - the only piece of wood I used in the whole design - gave me a headache for the first few months. Because it is so rigidly attached to the aluminium bar by four 1/4 inch bolts, changes in humidity were causing the timber to expand, bending the whole frame and upsetting the string height. I solved this by cutting it into two separate lengths so the wood had space to expand.

The next post is about the tuning machines. Stay...tuned.

I guess I don't understand how the fingerboard moves so the router can create the radius. Is the triangular carriage for the fingerboard constructed so it moves from sided to side? can you post a picture of the hinges?

 

[Jaygetsreal]

No worries Paul.
In the sketch below the shaded parts are rigid and bolted to the bench.
The triangular panel and hinges are placed so as to make the required radii from one end of the fingerboard to the other.
The fingerboard blank (firmly screwed to the triangular panel which can swing side to side) and the router are the only two moving parts.
The triangular panel had to be clamped firmly for each pass of the router overhead.

I wish I had done a bit of video when it was all set up and working.

Hope this makes sense.

 

[PauFerro]

That is what I thought -- is there any reason you made it a triangular carriage for the fingerboard? Is this to create different radiuses (radii??) for the compound radius fingerboard?

You said you clamped the triangle firmly to the bench -- I assume you tilted the triangle partway through its radius, clamped it in place, ran the router lengthwise over it, and then tilted the triangle a bit more, clamped it in place, and then ran the router over it again. Do I have that right?

If so, my question is how you clamped the triangle in place when it was tilting in different positions and didn't have anything to really clamp it to in each position?

 

[Jaygetsreal]

That is what I thought -- is there any reason you made it a triangular carriage for the fingerboard? Is this to create different radiuses (radii??) for the compound radius fingerboard?

You said you clamped the triangle firmly to the bench -- I assume you tilted the triangle partway through its radius, clamped it in place, ran the router lengthwise over it, and then tilted the triangle a bit more, clamped it in place, and then ran the router over it again. Do I have that right?

If so, my question is how you clamped the triangle in place when it was tilting in different positions and didn't have anything to really clamp it to in each position?

Exactly right. Because the hinge is further away from the nut-end it arcs a bigger radius.

And exactly right on the sequence too.

There are probably lots of ways you could clamp the triangular panel. The most elegant would be to have a semicircular disk on the right-hand end and a caliper - like a disk brake. I had a very inelegant system of a wooden handle attached to it (coming towards you from the diagram) that could be clamped down on various numbers of wooden blocks!! #shame

I still have the rig and could cut a fingerboard in any non-metal material. Ebony?? Mammoth tusk?

 

[Jaygetsreal]

Could you tell us a bit more about your goals? Have you played a DB before you started your project? Do you own one now? Was your goal to create a DB-like instrument? Is the tone of the DB important for your project? What do you hope to do with this instrument going forward?

Ha, very simple answer. I am currently in the 'valley of death' - too old to be employed but not old enough to draw a pension. Have been cashless for 5 years. But wanted a DB because I really wanted to learn to play straight jazz. Managed to build this crazy thing for almost nothing. Now working hard to learn scales and technique. Hence my loitering on TB. Perhaps soon I'll find some guys crazy enough to let me join their band. I might die before reaching my goal but I'm loving the journey.

You?

 

[Jaygetsreal]

Could you tell us a bit more about your goals? Have you played a DB before you started your project? Do you own one now? Was your goal to create a DB-like instrument? Is the tone of the DB important for your project? What do you hope to do with this instrument going forward?

Oh, forgot to mention I have played electric bass since school days but only in amateur rock bands.

 

[PauFerro]

Exactly right. Because the hinge is further away from the nut-end it arcs a bigger radius.

And exactly right on the sequence too.

There are probably lots of ways you could clamp the triangular panel. The most elegant would be to have a semicircular disk on the right-hand end and a caliper - like a disk brake. I had a very inelegant system of a wooden handle attached to it (coming towards you from the diagram) that could be clamped down on various numbers of wooden blocks!! #shame

I still have the rig and could cut a fingerboard in any non-metal material. Ebony?? Mammoth tusk?

Kudos on this -- I have to say that this is probably the most doable, functional fingerboard radiusing jig I have ever seen! I have been watching for something like this for about 15 years. This is because I find using a radius block a major hassle, time consuming, tedious, and laborious. I've considered a duplicator (the plans required building a wooden "machine" taking up half my basement at the time), an overhead swing to which you afix the fingerboard face down, traversing a a massive sander, a swing over a moving router, and then a router on rails mounted on a curved carriage that moved over top the fixed fingerboard. And none of them could do a compound radius.

But this one is far better. Keeping the router fixed probably minimizes any tear out or problems with the heavy router movement. The apparatus is relatively small compared to some of the other plans. And you can do a compound radius. Plus I could pretty much visualize how it works from your picture, although I did need you to fill in the blanks, which I had mostly right. So often you get a picture and you can't see enough detail to figure out how it works.

Brilliant! I will probably try building one of these myself as some point. I wish the idea could be expanded to also shape the back of the neck....I don't really enjoy carving the neck at all.

I had an idea a while ago about how to get an upright sound from ane EUB without the awkward body. And that was to run the signal from the EUB to a speaker that sits in a wooden box with f holes in the front. the box is made of the same thickness of plywood or solid wood that you find in upright/acoustic bass bodies. You send the signal from the upright pickup into the speaker that sits in this box, which then resonates like an upright bass to bring acoustic properties to the party. This means you are decoupling the neck, bridge and slab from the body, allowing for transportability. Put a Piezo on the sound box and then amplify that. Complicated but hey, ideas are my energy source. I might try it some day with a cardboard box as the sound box just to see if it has any legs at all.

 

[Jaygetsreal]

Kudos on this -- I have to say that this is probably the most doable, functional fingerboard radiusing jig I have ever seen! I have been watching for something like this for about 15 years. This is because I find using a radius block a major hassle, time consuming, tedious, and laborious. I've considered a duplicator (the plans required building a wooden "machine" taking up half my basement at the time), an overhead swing to which you afix the fingerboard face down, traversing a a massive sander, a swing over a moving router, and then a router on rails mounted on a curved carriage that moved over top the fixed fingerboard. And none of them could do a compound radius.

But this one is far better. Keeping the router fixed probably minimizes any tear out or problems with the heavy router movement. The apparatus is relatively small compared to some of the other plans. And you can do a compound radius. Plus I could pretty much visualize how it works from your picture, although I did need you to fill in the blanks, which I had mostly right. So often you get a picture and you can't see enough detail to figure out how it works.

Brilliant! I will probably try building one of these myself as some point. I wish the idea could be expanded to also shape the back of the neck....I don't really enjoy carving the neck at all.

I had an idea a while ago about how to get an upright sound from ane EUB without the awkward body. And that was to run the signal from the EUB to a speaker that sits in a wooden box with f holes in the front. the box is made of the same thickness of plywood or solid wood that you find in upright/acoustic bass bodies. You send the signal from the upright pickup into the speaker that sits in this box, which then resonates like an upright bass to bring acoustic properties to the party. This means you are decoupling the neck, bridge and slab from the body, allowing for transportability. Put a Piezo on the sound box and then amplify that. Complicated but hey, ideas are my energy source. I might try it some day with a cardboard box as the sound box just to see if it has any legs at all.

Thanks. I really like that idea too. Intriguing because it radically breaks all the rules of speaker construction, which are all about avoiding coloring sound. When you say put a piezo on the sound box do you mean a second pickup - so the string vibration goes through the first pickup, amplified, into the speaker box, picked up by a second pickup, and amplified again?

You'd have to choose the speaker carefully so it can replicate the dynamics of a vibrating acoustic bass bridge and sound post. Thanks for the idea, I might do some experimenting too. BTW I have some woody magic to share in Post 10.