SIX ...

[Beate Ritzert]

... will be my 1st attempt toward archtop basses.
It will be a Bass VI, i.e. tuned like a guitar but an octave deeper, and i try to improve the concept from the experience i have with my converted 4 string. I will dare many things i have never done before. Furthermore my first and only archtop build was more than 30 years ago.

Bass VI means short scale, and in this project it will have a multiscale fretboard. 74.5 cm-77.5 cm, neutral position on the 8th fret. Bass VI also means narrow string spacing and guitar pickups and hence i will need a guitar bridge. After some research on the market situation, there is de facto no alternative to the ABM3210. Tuners will be Schaller M4-2000, pickups a set of minihumbuckers with Alnico magnets. Not potis, just two mini switches to select the pickups and to modifiy the voicing (and to shortcut the output )

Here is my current idea on the shape - it does still require a lot of fine tuning. The shape is based on the final shape of my 1st attempt to build a guitar (but that was a solid body), it is a little bit larger than a typical solid body, but not much, roughly 14.5".



The construction will differ a lot from the usual construction of an archtop guitar, it will be somehow in between an ES335-like semi and a thinline archtop: massive below the neck and also below the bridge, thick ribs and two parallel center bars cut into a solid body slab. The bottom plate will (probably) be arched only on the outside, but the top will be thin fully arched outside the huge end blocks.
I expect the construction to be pretty strong, and i do not plan to use any braces on the top.

The idea is to have a better acoustic response than something ES335-alike. I actually did something similar with my 2nd guitar build, but without the arching, and even after more than 40 years i like the concept.

The neck will be bolt on. I am going to try to have a narrow connection which is inspired by Ken Parker's archtops among others.

Materials:



body: basswood
top: flamed pear
neck: red meranti (from an old window frame)
fingerboard: elsbeere (sorbus torminalis), on of the hardest European woods

[Andy Bounsall]

I really like the design and can't wait to see the finished product. Wondering the reason for having the two pickups fairly close together. Wouldn't you get more tonal variation by moving the neck pickup further forward?

[Beate Ritzert]

That's the "Stingray-Position" and the "Precision-Bass-Position" relative to the average scale length.
Both basses perform very well with just their single pickups. I took these positions from my converted Bass VI where i like them.

Although i do really like more extreme bass sounds like the EB-3 with its mudbucker - this instrument requires a specific playing style where i do not find it useful.

But as this will become a slow build (i am also restoring a house...) i'l have plenty of time to listen to my first Bass VI if i could change the position of the neck pickup a bit. Even as an aftershot it will be easy to swap the minihumbuckers against standard humbuckers if it turns out that i do not like the minis in that instrument. This will bring the center a little bit closer toward the neck, and that little bit will already have a very significant impact on the sound. I do already own 2 pairs of humbuckers - a chinese one with a warm and pretty bassy sound and a pair of Gibson T-Tops (gold plated engraved, i.e. from 1971) which sound pretty aggressive. Maybe also an option. Let's see.

The minis leave more wood, and that's a beautiful top....

[Gordon Bellerose]

Will you post some pictures along the way Beate?
That would be great!

[Beate Ritzert]

The parts of the body are joined (more or better less successful, but in any case a bit better than on my SG bass), and the contours drawn. Here what will become ribs, end blocks and bars:



I am going to work this out with a jigsaw and use a bottom plate cut from the same slab as the wood for the ribs. This is a more work than milling this out, but it will leave me a lot of wood for future work.

The bottom plate will be carved. i am a bit unsure wether also to carve the interior, notably under the sides. The central section will be left thick providing something like a "sustain block".

The top plate will be fully carved outside the contact surfaces of the end blocks.

The idea of this construction is to obtain the stiffness and hence attack and sustain of a solid body guitar but with a bit more "acoustic vibe" than an ES335 like construction has.

[Beate Ritzert]

Now it is really urgent that i define the arching profile. I would like to learn on general guidelines defining the arch, but unfortunately i can hardly find any material. It is my 2nd attempt, when i build my first archtop i simply used parabolas centered in the middle of the center line of the plate. While this basically worked, it led to a "ridge" marking the upper part of the body, and the shape is limited to a convex shape without a recurve (well, i thinned the plate a bit from the interior). I would like to learn about better and more general approaches.

Some questions: how flat is the top along the central line? I hace seen a picture of an Amati violin which was flat in the longitudinal direction over about half the body length. Jahnel shows something similar in his book on luthery, but most achtops are different.

Ho do i deal with the part of the top close to the cutaway(s)?

And ... how do i best define the height profile (along my lines A-D)

Here a 1st sketch; just two contours.

[Beate Ritzert]

Let's continue...

...sawing the top, the bottom and the rib structure:

[Bob Francis]

Looking good

[Jason Rodgers]

Wow, good work with the jigsaw!

[Randolph Rhett]

No kidding! That is either a magic jigsaw, or you are a jigsaw savant.

[Brian Evans]

Your question, how flat is the top along the central line? On archtop guitars in the tradition, not flat. The curve is continuous, quite gradual for the middle half and more extreme for the upper and lower quarters, but always curved.

How to deal with the cutaways? Two schools of thought. Gibson would arch the top somewhat normally towards the cutaway, and use tall bindings to make up for the difference. Almost arched like the cutaway wasn't there, and the top was left thick to meet the sides. I, and others, graduate the top down to the sides so the edge of the top is a constant 3/16" or so thick, and the contours where the cutaways form enhance the shape of the cutaway. You've implied this in your diagram, I think.

[Randolph Rhett]

Now it is really urgent that i define the arching profile. I would like to learn on general guidelines defining the arch, but unfortunately i can hardly find any material. It is my 2nd attempt, when i build my first archtop i simply used parabolas centered in the middle of the center line of the plate. While this basically worked, it led to a "ridge" marking the upper part of the body, and the shape is limited to a convex shape without a recurve (well, i thinned the plate a bit from the interior). I would like to learn about better and more general approaches.

Some questions: how flat is the top along the central line? I hace seen a picture of an Amati violin which was flat in the longitudinal direction over about half the body length. Jahnel shows something similar in his book on luthery, but most achtops are different.

Ho do i deal with the part of the top close to the cutaway(s)?

And ... how do i best define the height profile (along my lines A-D)

Arching profiles on acoustic instruments have historically used a "curtate cycloid", not a parabola. It is related to a sine wave. But this is not going to be an acoustic instrument, so it is purely an esthetic consideration. No?

Gibson carved a symmetrical non-cutaway plate and then literally cut away the cutaway with a band saw. They made up for the gap with a support block inside the cutaway and tall bindings. I am not a Gibson historian, but I know at some point they also graduated the area of the cutaway. However, like so much to do with Gibson, there are people who absolutely INSIST on the hacked up look of the tall binding. That is how Gibson did it in the 50's, so that is what they want now. Gibson being masters of profiting from their own brand mojo still make guitars this way.

[Beate Ritzert]

No kidding! That is either a magic jigsaw, or you are a jigsaw savant.

The deviations are just as usual, especially those at depth ( i am still looking for a trick to avoid sideward breakout of the blade). I admittedly attempted to cut relatively precise and smooth, just in order to have a basis to mark the height of the plate at the outer edge.

As to the profile: i just read the article of RM. Mottola on various profile vs. measured data.
And i saw the profile of an Amati violin which was nearly flat in the centre of it longitudinal profile (flat is practically impossible after sanding by hand). And that's something i'l try.

That instrument is not intended to become a fully acoustic archtop, but some acoustic properties is desired, ideally usability as an unamplified practice instrument. Otherwise it would be wise to leave the plates flat on their inner sides. But actually the top between those two huge end blocks will be arched and it will even be able to move freely (4-5 mm thickness, no bars attached to the top, but two pickups as additional masses).

[Beate Ritzert]

Arching profiles on acoustic instruments have historically used a "curtate cycloid", not a parabola. It is related to a sine wave. But this is not going to be an acoustic instrument, so it is purely an esthetic consideration. No?

It would really interesting to learn about acoustic differences. Parabolic profiles do work. (and hence circular arcs or even third order polynomial profiles, the deviation is really small in the dimensions of typical archtop guitars (35 years ago i did an estimate)). The archtop i build that time really meets its design goals - the more i dig into the topic the more i see how much, and it sounds as an archtop with thick top and large parallel bars should sound, but not too loud (which was a design goal).

Gibson carved a symmetrical non-cutaway plate and then literally cut away the cutaway with a band saw.

Which even has its own beauty. 35 years ago i also decided to to it this way, but mainly because arching was a lot easier to achieve with my limited and inadequate tools. But there are tons of other examples - archtops with laminated tops cannot be built this way, at least not without a huge effort.

Gibson historian, but I know at some point they also graduated the area of the cutaway.

as i just wrote, more or less inevitable if You're doing laminated tops.

Thanks for the hint with the curtate cycloids. As i have not cut any jigs i have the freedom to try this out.

[Brian Evans]

Laminated top guitars are very often built with the "Gibson arch". It's way easier. I personally believe that Gibson did this because they didn't want to have to make new masters for their copy routers and presses, so they just made a top and cut out the cutaway, as Randolph describes. The gap is filled with a filler piece and covered with wide binding. With laminated tops and backs, you just need the mold to be what you want, the wood doesn't care at all.

[Bill Raymond]

What Brian said: Laminating vs. carving does not dictate which style of arching at the cutaway. Personally, for aesthetic reasons I prefer the symmetrical arch with the cutaway rather than carving (or otherwise shaping) what looks to me like an unsightly "bubble" over the cutaway. Of course, others have different preferences. It's not what is right or wrong, just what you happen to like.

[Beate Ritzert]

Well, i just decided to make the profiles along the lines A, B, C and D as circular sections. I am still undecided on the two horns - but that will follow when the shape of the rest of the body is visible. As a curtate cycloid curve or something similar will always fall below these circle lines, i can convert to such a shape at any time. Actually, profile D is a candidate for such a shape (that would be a similar approach as in the ES 335).
BTW: my 1st build of that shape was a flat top with very gently rounded corners, and i liked that, too.

[Nathan Dodd]

Hi Beate, I understand the bass VI has regular guitar tuners. you have decided to use bass tuners for this build. Why is this? Do you envisage there being an issue with ratio or the side of the holes through the tuning shafts themselves? Are you making purchase decisions based on measurements of a certain weight of string? I have literally zero bass experience.

[Beate Ritzert]

The slot width of a guitar tuner might be too narrow for especially the E string (it is, and i do not want to widen it....).

Moreover, and actually more important, i want people to recognize the instrument as a bass, not as a guitar. Otherwise i could mount the smaller knobs of Schaller M6 tuners which AFAIK fit onto the M4 tuners.

BTW. the Bass VI has custom tuners with axes that can be used with bass strings. At least the old instruments had.

[Jason Rodgers]

For future reference, Hipshot drills out the low string tuners on their 7- and 8-string sets to accommodate a .08", if memory serves. I have an 8-string on the bench that will eventually be tuned E-B-E-A-D-G-B-E with a D'Addario XL140-8 set (.010-.074). This is nice, since I'd be very nervous attempting that drilling task myself.