The goals

• To allow assemblance time to become easier

• To allow better mantainance

• To allow a better position for the electronics

• To avoid completely the existence of noise in the pickup

Solved

• String angle

• General design

• Pickup position

• Visual orientation

• Speaker design

• Sound quality

• Easier inner mantainance

• Prevetions of electronic problems and better mantainance

What will be the Failure modes of this object? (new)

• String spacing

• Tuners position

• feedback

New Issues

• Soon, on the testing time!

The goals

• To allow assemblance time to become easier

• To allow better mantainance

• To allow a better position for the electronics

• To avoid completely the existence of noise in the pickup

Solved

• String angle

• General design

• Pickup position

• Visual orientation

• Speaker design

• Sound quality

• Easier inner mantainance

• Prevetions of electronic problems and better mantainance

What will be the Failure modes of this object? (new)

• String spacing

• Tuners position

• feedback

New Issues

• Soon, on the testing time!

The goals

• To allow assemblance time to become easier

• To allow better mantainance

• To allow a better position for the electronics

• To avoid completely the existence of noise in the pickup

Solved

• String angle

• General design

• Pickup position

• Visual orientation

• Speaker design

• Sound quality

• Easier inner mantainance

• Prevetions of electronic problems and better mantainance

What will be the Failure modes of this object? (new)

• String spacing

• Tuners position

• feedback

New Issues

• Soon, on the testing time!

The goals

• To allow assemblance time to become easier

• To allow better mantainance

• To allow a better position for the electronics

• To avoid completely the existence of noise in the pickup

Solved

• String angle

• General design

• Pickup position

• Visual orientation

• Speaker design

• Sound quality

• Easier inner mantainance

• Prevetions of electronic problems and better mantainance

What will be the Failure modes of this object? (new)

• String spacing

• Tuners position

• feedback

New Issues

• Soon, on the testing time!

The goals

• To allow assemblance time to become easier

• To allow better mantainance

• To allow a better position for the electronics

• To avoid completely the existence of noise in the pickup

Solved

• String angle

• General design

• Pickup position

• Visual orientation

• Speaker design

• Sound quality

• Easier inner mantainance

• Prevetions of electronic problems and better mantainance

What will be the Failure modes of this object? (new)

• String spacing

• Tuners position

• feedback

New Issues

• Soon, on the testing time!

For 2 years I followed an advice from a friend at the Revspace, hackerspace: 'Aesthetics comes in the end'.

Since then I have been testing all the possible tools, mechanisms, tecnologies, features, playing techniques that I could tried. I have the feeling its time to think about it, to share one single message on this design. This initiative is completely against my project planing, but I rather do it right instead of keeping dealing until next year with it.

The goals

• In my own belief, what Knurl wants to share to the world is that music can be designed and understand in multiple ways, multiple perceptions, you just have to turn your mindset. Therefore, Knurl is an instrument that should be designed to turn any single time. That should always represented on the fly. I simplified the geometry as a single circle and loft faces turning to different small angles.

• For the past month, I have been testing a future bela product that made me do a tone of sound tests with Knurl. I discover that the wifi dongle is being tracked by the pickups due its close placement to it. The board has to be placed far from the pick ups.

• The exteme strings of each set doesn't have enough space for the fingers and a proper string angle. The fingerboard has to become larger and more circular.

• The speaker have to be place outside the bottom with a rubber ring around it to avoid excessive vibration and feedback.

• The instrument needs to be made of a light color for performances played in the dark, which has been quite common and it was required in the coming concerts

• The soundpost can be combined with the suggestion of nicolo about applying veins on the instrument, so that the resonation force goesdirectly to the resonance chamber (the fingerboard). I have been using in this design a reciprocal frame structure.

• The visual orientation is pretty difficult on the previous design: I do often forget which button is what, or which potmeter produces volume of frequency. I have to place them all together in one single face cavity of the 'circular' shape

• The pickups aren't working in the place, they are quite far from the string making me add to much boost.

Solved

• String angle

• General design

• Pickup position

• Visual orientation

• Speaker design

• Sound quality

• Easier inner mantainance

New Issues

• The assemblance can be improved.

• The tuners can be place in the innerside

• The strings on the edge needs more space.

Nicolo has designed an

Solved

• Expression

• easy and mobile set up

New Issues

• The part has to be printed in one unity

• It works but it is super instable

Future improvements:

• I would problably make the tube connector a bit longer (In this version was 3cm , mabe I should do 6cm)

• I would also consider to add some sort of belt on the floor that hold the feats in a stable place

• Maybe To add some chamfers

Nicolo has designed an

Solved

• Expression

• easy and mobile set up

New Issues

• The part has to be printed in one unity

• It works but it is super instable

Future improvements:

• I would problably make the tube connector a bit longer (In this version was 3cm , mabe I should do 6cm)

• I would also consider to add some sort of belt on the floor that hold the feats in a stable place

• Maybe To add some chamfers

Nicolo has designed an

Solved

• Expression

• easy and mobile set up

New Issues

• The part has to be printed in one unity

• It works but it is super instable

Future improvements:

• I would problably make the tube connector a bit longer (In this version was 3cm , mabe I should do 6cm)

• I would also consider to add some sort of belt on the floor that hold the feats in a stable place

• Maybe To add some chamfers

Nicolo has designed a leg support for Knurl to play it standing

Solved

• The legs hold the weight of the instrument!

• The supports are super easy to remove

New Issues

• The wood legs are 1.5 mm bigger than its hole

• There are still a rebounce of the plastic part

Future improvements:

• The holes of the nut is wider than the actual nut, I would also put them down so that I can use the drill to scroll it

• It would be nice to use the same diameter of scroll for all the parts because if I need to transport, I don't need to bring a lot of tools with me (For example, if I go to Siena again or whatever, I dont need to bring a emmergency wardrobe :) ) .

• I would also consider to add some sort of belt on the floor that hold the feats in a stable place, but I will design myselft that when we are done with this part.

Nicolo has designed an

Solved

• Expression

• easy and mobile set up

New Issues

• The part has to be printed in one unity

• It works but it is super instable

Future improvements:

• I would problably make the tube connector a bit longer (In this version was 3cm , mabe I should do 6cm)

• I would also consider to add some sort of belt on the floor that hold the feats in a stable place

• Maybe To add some chamfers

Nicolo has designed an

Solved

• Expression

• easy and mobile set up

New Issues

• The part has to be printed in one unity

• It works but it is super instable

Future improvements:

• I would problably make the tube connector a bit longer (In this version was 3cm , mabe I should do 6cm)

• I would also consider to add some sort of belt on the floor that hold the feats in a stable place

• Maybe To add some chamfers

Nicolo has designed an

Solved

• Expression

• easy and mobile set up

New Issues

• The part has to be printed in one unity

• It works but it is super instable

Future improvements:

• I would problably make the tube connector a bit longer (In this version was 3cm , mabe I should do 6cm)

• I would also consider to add some sort of belt on the floor that hold the feats in a stable place

• Maybe To add some chamfers

Nicolo has designed an

Solved

• Expression

• easy and mobile set up

New Issues

• The part has to be printed in one unity

• It works but it is super instable

Future improvements:

• I would problably make the tube connector a bit longer (In this version was 3cm , mabe I should do 6cm)

• I would also consider to add some sort of belt on the floor that hold the feats in a stable place

• Maybe To add some chamfers

I have been thinking if instead of we try to find stability on the knees of the performer, we use the stabilibity of the floor. There has been a lot of people curious and encouraging me for making a cello to play standing, we loose to much of performance expression sitting on a chair!

Solved

• Expression

• easy and mobile set up

New Issues

• The part has to be printed in one unity

• It works but it is super instable

Future improvements:

• I would problably make the tube connector a bit longer (In this version was 3cm , mabe I should do 6cm)

• I would also consider to add some sort of belt on the floor that hold the feats in a stable place

• Maybe To add some chamfers

Playing with a bow already gives you drone sound, so why not playing with rhythm instead of ? In end of April I designed

Solved

• The design of the mics work pretty well

New Issues

• Making the tuning system wise, the strings aren't aligned so well with each tuning peg. It is necessary to rethink in the distribution of it

• 
  

Future improvements:

• The case can be reprint again to stabilize the endpin completely inside the case, The usb slot and audio out can be place a bit higher to facilitate maintenance

Solved

• The ring avoids feedback between the speakers and mic

• The snap slots are easier to assemble instead of the scrolls

New Issues

• .

Future improvements:

• Maybe trying thicker could help even more

Few tests and iterations were necessary to offer the best stability to the instrument but also effectivity

Solved

• The design of the mics work pretty well

• The tuners head were removed for an aesthetical purpose

• The underbridge and the the tuning case were printed together, its diameter has increased to avoid breaking points. The strings slot are around the

• An 16mm tube guides the end pin into the carbon fiber tube. The belacase is fixed to it, avoiding the excessive amount of set up if you need to open the case for check up

New Issues

• Making the tuning system wise, the strings aren't aligned so well with each tuning peg. It is necessary to rethink in the distribution of it

• The mic needs some kind of support, I will design it attached to a certain vein inside the end of the fingerboard.

• The first iteration of the tuning case was to thin again, I changed the shell to 1.3 cm and the cover thickness to 1.07 cm

Future improvements:

• The case can be reprint again to stabilize the endpin completely inside the case, The usb slot and audio out can be place a bit higher to facilitate maintenance

Look, is this a cello ? Is this a Hurdy-gurdy? Is this a viola da gamba? No! This is Knurl!

Inspired by the possibility to have long sustaining strings with easy access and control, I decide to give a try to a motorized circular system around Knurl. Mihalis joined the team with me, Nicolo and Tim by designing this mechanism with 3d printing.

Solved

• The system was designed with great precision, the upperpart can rotate freely by inner balls supporting it

New Issues

• The part is to big to be removed or assembled into the waist of the instrument.

Future improvements:

• To use multiple tiny rotation system around the instrument

This is the second prototype of this part. Evaluating the previous one, Our main goal was to avoid extra noises and to distribute the balance equally. Nicoló has solved them already in the first tests, even without using the ball bearings. The after work was dedicated to make the design fit to Knurls general design

Solved

• Loud noises

• Weight distribution

New Issues

• The system needs some sort of support in the knees

• The TPU carpet needs to follow the pattern shape of the wheels

Future improvements:

• To be verified

The case in the previous prototypes made me design a new format where the instrument doesn't need supports to stand but meanwhile matches with the Fingerboard design and width.

Solved

• Trapezian slots worked! Thanks Nicoló!

Still not Solved

• The bela place needs to be safe far from the spike

New Issues

Future improvements:

• Should the case interior be more accessible

Reflecting about the previous prototype, I designed a button which its position can be visualized by the performer without to much effort. I made them big and longer but slightly curved its body.

Solved

• Easier set up

• Perfect position and size for all the types of people and their fingers

New Issues

• This type of filament is quite conductive, I have to isolate the buttons better because I am having a short circuit on bela

Future improvements:

• Maybe to use a wire better isolated

• Print with TPU

This prototype had a lot of iterations during 3 weeks. I was not sure if it was stable enough. After a lot of testings and days tuning 24 strings, I realize the main problem wasnt in this prototype

Solved

• The weight is lighter

• Long heads

• Absurdly weak printing settings but strong enough for it! (so happy when things like this works :))

New Issues

• Issues were solved

Future improvements:

• Maybe I could experiment a bit wider later on

• Bigger head could give a bigger torque

The biggest nightmare of knurl: where 24 tuning pegs are installed. The top base has a prefect match with the bridge part, the strings holes are fine and the general design works. But it is very important to distribute the tension with the scroll part that goes around the . I took a long time to realize that this was an issue.

07/03 - Due poor strength material, the part has collapsed. I reprint this part designing a more solid and wider structure.

Solved

• I can have 24 strings in the same ratio!

• The string curvature doesn't damage the string

New Issues

• The slot in the bottom between the caped isn't not well adjusted yet, I have to remake (04.03 - done)

• I am going to make my life way easier if I decrease the height of the second cape!

Future improvements:

• Fix that part, Adding a bit more thickness to the wall

• Redesign the case around it

This is the easiest part to design on knurl, this time I made the head a bigger longer since the whole body has increased

Solved

• Easier set up

• Perfect height on the tuning

New Issues

• not discovered yet

Future improvements:

• Maybe I could experiment a bit smaller later on

New bridge, new speakers

Solved

• Acoustic and electronic sound has more space now, The strings are in direct contact with the body

New Issues

• The speakers for this prototype aren't good enough.

Future improvements:

• I have to find a rectangular speaker model for the size of the cavities

The Fingerboard is now combined with the Bridge. That was possible due a slow transition to an appetite for electrodynamic pick up system.

This prototype offers 4 sets of 6 strings (24), which each string is tuned by 24-TET equal temperament. It means more tension on its body, does it going to influence its sound production

Solved

• The new mic system allow me to have more space

• The design allows to verify other materials

• A trapezium slot is ideal for all the types of enclosure

• The new thumb position gives a better reference of hand position

New Issues

• A new tuning system has to be design for 24 strings. Besides it, 24 tuning pegs are considerably heavy!

• The desired un-bow system can't be place 'in between the bridge body, a sort of parallel gear mechanism has to be produced.

• The position of the mic wasn't design correctly. The mic doesn't fit in the inner structure

Future improvements:

• A 3D tuning head for the tuning pegs

• Un bow

• Rotation system

• PCB

In January, I planned to dedicate sometime thinking about a future case. I got the format that I want, but I need some extra time to make it really safe.

Solved

• I have a way to transport Knurl

New Issues

• Strength of the joins and snap for the arm belt

Future improvements:

• Redesign the correct middle size

• Create a better snap shot system for the middle

There is one thing which makes me play conventional cello still, which is related to string spacing: The strings are very far from each other. Each fingerboard set had a very huge distance between each string. I a short visit, the luthier Tim Duerick asked me once in Ghent: Why not more strings then? :)

Well, If I would do that, I would destroy my idea of using the circle of harmonics in the cello. But, wait a second.... why do I have to use this system ? There is so much to explore in different temperaments! There is so many temperaments of different cultures to explore, and to divide your 5ths in a same proportion is to lose the opportunity to explore color, expression and cultural heritage.

Most musician doesn't dare to come in this barrier: Music temperament

It sounds cheesy, but it is a great shift. That requires a whole different way of listening, and that is a lot for a musician! Besides it, you wouldn't be playing with conventional instruments that often. That requires also a lot practice, listening, prototypes, design and a lot of passion for research.

Microtonality has been always present in cultural music but it seems during the development of our civizalitions that the pitagorean system took it over to make music education accessible and understandable to everyone. We are nowadays not educated to listen difference between halftone. That is such a revelation!

The influence of Turkish music through the wonderful work of Tolgahan, with its microtonal guitar, was a great start point for me.

When I started Knurl, I had a lot of things that I wanted in a new format of a cello and one of them was the access to different tonalities and multiphonics, it never came in my mind to explore better microtonality, until the end of december 2021 by a specific physical reason:

Using 32 faces gives me the exact possibility to work the standard string spacing of a cello with the body ratio that I am currently working on ( 0.73 in the head, 1.6 in the bridge).

This sometimes, seems not enough to change for this design: More costs will be included on it and I have to find a solution for lighter bass tuners. Maybe I can design my own?

Knurl will have a microtonal version in 2021.

This is such a small thing, but such a good idea! It came up the idea to add an string block inside the head, so that I could organize the strings better.

Results: failed, the circles of each string is usually bigger and different from each other.

The base is also super thick and it makes the strings not properly

Reflecting on the exposed thought of prototype n.26, I need more space for a speaker enclosure and more resistance on the un bridge.

I came back to my digital fusion sketches to recreate this part a bit longer and larger.

Results : Pretty stable, but heavy like hell. My intention to make it dense was to damp a bit the sound induction to the electronic area. But perhaps I can decrease a bit and add some soft material.

Coming version: Less infill

I have been receiving very often the question: Are you going to create a bow for Knurl? Since it has 16 strings, of course anyone wont be satisfied only with the rotatable system, but also with a mechanism that could reach multiple strings.

A bow is such a simple an unique mechanism that has been for centuries used in worldwide cultures and their practices. It has been never my intention to transmute or improve such a simple and multi approach tool.

Today, Bows arent the only mechanisms of string instruments: we do have ebows, magnetic wheels, motos that can pich strings. The question I've been asking myself, as composer, was: What of those mechanisms could bring the amount of strokes, accents, phrases, such as a bow does?

In all my cello classes, I had to learn precisely to perceive all the variations that our wirst, fingers, shoulders, could bring for the sound generation of a cello. I wouldn't never be able to forget this experience building such a intended mechanism. All of these new mechanisms offer some purpose pretty specific. As a performer and composer, If I wouldnt be able to be satisfied with such a thing.

Knurl is an aspiring instrument for polyphony. I would love to be able to trigger strings independely of its geographical space that they are placed. This gestalt looking for an opposite pression remembered me the gesture of a scissors..

One of my design goals is to have a self-contained cello, However, I know I have to do some sacrifices during the symbiose of the parts. I designed to have speakers in the bottom that are place towards the audience. Playing Knurl I started to realize how difficult is to perceive sound balance if you are not anymore a speaker listener, but a speaker producer. I was out of the speaker ratio. I would have to somehow design a speaker enclosure that is still in the knurls body but its direction allow me to have an balanced perception about the sound levels. Perhaps they could be design to reflect and expand its sound?

And even better, they could help the enhance the sound pression of the f holes not touching the component itself, but towards its direction! Eureca!

This is one prototype I didn't like the shape at all. That is why I call lunatic :) But l I had to try to get the most space as possible from this part for it. The volume necessary for the speakers that I choose demands it.

This autumn I have been meeting a luthier of composites cello (Tim Duerick) online. We discussed about the efficiency of some designs, making me excited to investigate :

1. A thickness of 1.8 mm on the finger board

2. A bridge more flexible

3. A finger board bigger and longer

4. The f holes smaller an directional

5. The offset adjusted for each string (0.10 m of difference)

The body, as you can see in the picture, gets visually more bright. The cavities aren't curve anymore (it is beautiful, but it doesn't help the stability of the structure)

In the way of assembling/design it, I started to doubt about the space that I was losing by having a 2.2 cm tube in the middle. Wouldn't the be bridge structure be able to hold the tension of the body itself ? In that way I would have way more space for a speaker enclosure. I had to try that.

In October 26th, I got my Prusa mk3s finally assembled. Prototyping ha never been so easy with it. My first test was a better fourth head model.

Having a time to breath in the autumn holidays of 2020, I had a click to . I learned a couple of weeks ago that my bridge has to be more flexible in other to induce better sound. I realize touching the arms with my fingers was actually helping the resonation of the body. So I made 3 bridges connected to the arm.

It looks silly, but it a small improvement for:

• sound loudness

Things to consider next time:

• the bridges are very fragile, The line socket in the arm has to be thinner

The aim to make Knurl a rotatable cello was always into my main goals of its design. Previously I manage to rotate using my legs during the performance, the problem is, as playing barroc cello, it is not a healthy practice for your lower back and legs. You get exhausted after playing 1 hour.

I start to sketch a adjustable support where I can hold the instrument and rotate it.

Thanks to new design of prototype n.20.b, I was able to design a smaller bottom part. I always state on my sketches that the bottom part is where the electronic sound of this instrument would be placed, while the arm produces and welcome its acoustic sound.

• Solved issues still applied:

Speakers design, fine tuning while playing and stability

• Issues

1. The space is limited for the battery charge

2. For a future performer that is not used to electronics, it can be a big challenge even to tune the instrument because you have to take the microcontroller out of its box. I am not sure if I should solve that at this moment.

3. After months of reflection, I decide to change my silly idea of solar panels into the instrument. I personally love the idea to have inside of Knurl, but indeed it is not practical. I will be placing the solar panels into the case of the instrument, which is easier for maintenance and to use for other purposes (charge the phone, computer, speakers, etc).

• Improvements

4. When the bottom part is smaller, it is easier to rotate a bigger angle of the instrument.

5. The case is very well fixed in the bottom.

• Future considerations

6. A did hole for usb cabel for now, I hope in the future to add wifi connection on Knurl so that I don't need to connect Knurl on my computer by usb

7. I will place the battery in the support itself. I think it is easier to manipulate

This prototype was produced thanks again to the support of: Reflow (Emerald filament)