MIMF

The idea is actually a few years old...

... making an acoustic / electric archtop bass. Just a counterpart to my Jazzlady which also turned out to be fully acoustically usable. If this project idea turns out to be useful the actual start of the build will probably next summer after a thorough planning phase and after finishing my present projects.

Such instruments a rare, but there are a few makers who do such archtop basses. While that alone is encouraging i would like to understand why these instruments are rare before i start planning. Is it just the cost of a good archtop compared to a flattop or are there technical or acoustical aspects of the archtop concept which make it inferior for a bass guitar?

It has design challenges. The neck must be quite long in order to put the bridge in the best place for good tone. A bass scale is quite long, and for the bridge to be placed where it belongs that means the neck must really stick out.

I would probably move the bridge back a bit to help in that regard. The neck will still be pretty long, so will need a bit of planning for the balance. Lighter neck (Hah!) and heavier tail piece can help.

I made an 8 string archtop guitar that used three bass strings and five guitar strings, and fanned frets to accommodate the 29" (near 725mm) bass string, and the 25" (near 625mm) small 'e' string. It works well as an acoustic but really is better amplified.

A beautiful carved arch top acoustic bass guitar (fretless as I recall) was posted here quite a few years ago. I can't remember the builder and I'm not sure it's still available in the archives. It was posted well before the change over to the current forum software. In any event, it appeared to be a successful instrument and forum members responded to it very enthusiastically. I see no reason why such an instrument couldn't be built as an acoustic/electric.

Michael Lewis wrote:I would probably move the bridge back a bit to help in that regard. The neck will still be pretty long, so will need a bit of planning for the balance. Lighter neck (Hah!) and heavier tail piece can help..

The neck will probably become quite light ... i do not plan to use an *adjustable* trussrod. Let finderboard and central stripe form a stiff T-bar instead. Works really well in my 5 string.

BTW: where is the acoustically optimal position for the bridge? Really that close to the narrowest part of the body as we usually see in archtops? I always considered that a reminescence to the bowed string instruments where such a construction is essential for bowing flexibility.

Patrick Hanna wrote:... and I'm not sure it's still available in the archives. It was posted well before the change over to the current forum software. ....

Thanks very much for the hint into the archives. I found plenty of information there and did already learn a lot.

Construction wise i am still a bit uncertain: Bill Moll's beautiful bass is probably a bit large for me, but i found some hints to different designs including a bass by one of the German luthiers with good reputation on archtop building with 16 cm high sides (!), pretty large length and just 17" width. I am actually looking for a compromise between playability and potential for sound.
Maybe even my own old guitar shape will work (it is about 16.5") if i increase the height of the sides by a reasonable amount (10cm, 4"?) and use a thinner top.

Looks like you're finding the box size to be a challenge, but big volume is what you'll need. There's a reason the double bass has so much oomph: big volume, tall bridge. And it takes a lot of energy just to make that work pitzacato. I once saw jazz tenor saxophonist Joshua Redman at my alma mater, Lewis & Clark College, and his bass player borrowed a college orchestra bass. The guy was handed the bass on stage as they were setting up, and he started plunking around on it, shook his head, and probably raised the bridge another inch! I used to go see jazz bassist Leroy Vinegar here in Portland (got his start in Chicago) toward the end of his life, when he was on oxygen. It was a really big deal for him to lower the action on his bass and use an amp to be balanced in a trio, because the high action he built his career on was too taxing for his heart!

Then there's the Mexican guitarron. Those things have really big, arched back bodies, and are played almost exclusively with octaves with a claw-like slapping pull, so two strings are putting energy into the soundboard.

RM Mattola had an article in American Lutherie documenting his build of a bass mandolin. It was ginormous and looked absurd, but he reported it sounding like a pitz double bass.

At this year's GAL conference, Harry Fleishman had a huge acoustic bass guitar that was really a sight to behold. I got a picture of it, but I'll have to go find it and reduce it for posting here. It was a very large instrument, with an arched back and extended upper bass-side bout with soundholes. It was still in the works, and I didn't hear it played, but it sure looked like it had potential to thump.

Good luck, and of course we'll be looking forward to seeing your solution posted here!

Yes, indeed i am aware of the volume issue/necessity - and the most powerful instruments among the bass guitars prove this, of course both as flattops as well as archtops. As You pointed out even these instruments are still compromises.

At present, in the earliest stage of my planning, i will basically follow more than on e lines of thought:
a) the most consequent
b) is it possible to build a "reasonably" sounding instrument which fits into the case of my archtop guitar?

To b): i actually own such a tiny AGB and have the impression that its sound could be improved a lot by simply reducing material strengths to its optimum.

To a): the two basses i mentioned in my previous post seem to be similar in volume. The Moll gets it by a larger area of the top, the Sonntag archtop gets it from its large thickness, and the Stoll flattop bass possibly from both.
I actually need to figure out if i can play such a large beast, and which concept is the preferable - large top and relatively flat body or somewhat smaller top and thicker body.

In this context different question might arise: cutaway. It is desirable for playability (i need to be able to reach fret 20 easily) but will take away body volume. Will it be useful to restrict it just to the top in order to minimize volume loss - both ergonomically as well as soundwise?

In regard to the "optimum position for the bridge", I suggest carving the top so the place the bridge sits is the apex of the arch. That then becomes the optimum position.

Find a case for the instrument and make the instrument to fit the case.

Make it as big as you can comfortably play, then optimize all elements as best you can. It should be good.

Piezo under saddle pick up should work well, or electromagnetic coil and magnet type. They each give different kind of sound.

Michael Lewis wrote:In regard to the "optimum position for the bridge", I suggest carving the top so the place the bridge sits is the apex of the arch. That then becomes the optimum position.

Thanks. Important hint.

Piezo under saddle pick up should work well, or electromagnetic coil and magnet type. They each give different kind of sound.

I thought of making a floating pickup myself and put it roughly in the position used by Gibson in their "Les Paul Signature" bass or its Epiphone clone (It must aslo be pretty close the positon of the pickup in the P-Bass...). Maybe a 2nd one closer to the bridge. Using a LowZ-design would enable me to retain a lot of its acoustic sound. I am unsure if i sqeeze the electronics under a detachable pickguard like i did with my archtop or if i use a symmetrical microphone level output to a breakout box.

The photo below shows some of the relations: it is really promising. I think might actually simply use the old shape and just increase the thickness of the ribs to something like 10-12 cm in oder to obtain an instrument which is at least usable. For an even larger volume i will probably just need to enlarge length of the lower part of the body of the shape of my archtop and increase its width accordingly, use a shortscale neck or - if i am really adventurous - fanned frets and will end up in an instrument that will remain (optically) balanced and playable.
BTW: i also tested if a partial cutaway will be sufficient to reach the high frets - it would. Maybe i should actually try and design a less traditional looking guitar...

[quote] RM Mattola had an article in American Lutherie documenting his build of a bass mandolin. It was ginormous and looked absurd, but he reported it sounding like a pitz double bass.
/quote]

I was going to suggest taking a look at his "Canotto". IMO, it's probably the only way that you can get a box physically big enough for purely acoustic use, but I'm open to being corrected on that. Most ABG's I've seen commercially have pickups and are played through amps or PA's, in which case it might as well be a solidbody or semi-hollow and much smaller.

Up to a couple months ago, I'd been working up drawings in Rhino for a fanned fret based on the Canotto, but I've since shelved that. The only times I'd be playing it would be amplified, so it would make more sense for me to just go the EUB route.

Indeed, L. Mottola has lots of unconventional and really interesting ideas - great sources of inspiration. And he appears to be fully aware of ergonomic aspects of his instruments.

An upright like the Cannotto would be an interesting project, but it would definitely be a project of its own. Unfortunately i do not have not enough space for such a large instrument. Actually also the tiny SX ABG will need someone else respecting it when the Archtop is done.

BTW: after hearing recordings from a Ribbecke Halfling bass i am a bit unsure on the sound i should aim at. But time will tell, and there is still a lot to learn before i actually start with hte project.

Hey, Beate, here is that picture from the the GAL Convention of Harry Fleishman's latest take on the acoustic bass guitar. This thing was massive, as can be seen in comparison with the fairly standard sized guitar to the left. The back, if I remember correctly, was arched with large staves, not unlike the guitarron.

I built two to Bill Moll's dimensions. They sound great but are about as big a guitar as you'd want to play before you considered standing them up.

Wow, 5 years later. But there is too much going on around me, more than i can handle. And too many other ideas were waiting to be realized "quickly".
Although my other archtop bass is still on the bench, not even fully carved.... But there is something going on.: next spring a challange will start in a German (mostly) hobby builder's forum - and that should be a good project to participate. That contest is something like a kick in the ass - and i hope no further catastrophe will happen that prevents me from starting the build.

Jason Rodgers wrote:Hey, Beate, here is that picture from the the GAL Convention of Harry Fleishman's latest take on the acoustic bass guitar. This thing was massive, as can be seen in comparison with the fairly standard sized guitar to the left. The back, if I remember correctly, was arched with large staves, not unlike the guitarron.

Very interesting instruments - although one needs to get used to the looks. And it encourages me to try a design with a large bass side. Thank You for pointing me to that.

My two cents....

I'm not sure box volume is as important as top area. The 'Violin Octet' is very successful acoustically, and the basses are long and broad, but not deep. They started out making them deep, but cut the depth down significantly later, which helped a lot with clarity: the deep ones tend to be 'woofy'. It reminds me of something my voice teacher said: "The way to make your bass notes sound good is to work on the high notes".

I built several archtop classical guitars before I got one right. The key insight was that the arch height scales with the top thickness rather than the box length. You figure out the thickness you're going to use based on the down load of the strings, and work out the arch from there. Making a thin top with a high arch to keep the weight down made the timbre too 'harsh'.

It really helps to keep the down load as low as you can: use overstand and bridge height to keep the break angle to no more than 6-8 degrees. More break angle doesn't transmit more energy to the top: the actual string forces on the bridge are well defined, and so long as the string remains in contact throughout it's excursion it will transmit all of the signal to the top. In one experiment I found that at some point as I increased the break angle the sound died; too much down bearing overloads the top.

From what I can see, the limit to how wide you can make an archtop guitar is ergonomic. As you make a flat top wider and longer you have to beef up the structure to withstand the torque, and weight goes up faster than surface area. This actually cuts down on sound power. With an arch top you're using the vault of the top and thickness instead of bracing, for the most part, so there seems to be no structural/acoustic limit to the size.

I have made long and narrow arched instruments a few times, and they work out pretty well. I suspect I'd do better these days since (I hope) I understand things a bit better now than I did 25-30 years ago. Scale the box length as much as possible relative to the string pitch: if you're going to tune a fifth low, then the length should be 50% longer. I'd keep the width to no more than 19" (48.25cm), which is about as wide as they went with unamplified archtops in the big band days.

You can use F-holes if you keep them small to keep the 'main air' pitch down. Moving the hole up into the upper corner as Harry did keeps that pitch low and allows you to use larger holes. See Allen's article on air resonances in AL #1.

I'd go with 'curtate cycloid' cross arches with the low point over the edge of the liners. This seems to resist sinking over time better than schemes with a wider recurve.

Thank You very much for those hints.

Today i drew the 1st sketches on paper. My idea is trying to transfer the ideas of the Sharkfin bass to the archtop context. Which means multiscale 78/76 cm and a asymmetrical shape in order to get the position of the bass lying on the right leg comfortable. Width is asymmetric - the upper half at around 24-24.5 cm, ideally with a bevel for the right arm - width of the top itself 23 cm, and 23 cm on the lower half. the smallest width has been taken from a classical guitar - 12.5 cm each side but asymmetrical. Sound holes in the upper corner as You suggested. Length of upper body 65 cm - i.e. i'm going to use tops and bottom for a cello.

Regarding arching and string angle i'll follow Your hints - thanks very much for that.
I'm a bit unsure regarding the height. Somewhere between 8 and 10 cm, as usual?

I think i'll scan the sketch and post it this night.

Well, here is a 1st rough sketch of the idea as a starting point of thinking.
I'm still trying to enlarge the lower part a bit, but i do not see many possibilities. BTW - the lenth of that part is that of a 16.5" or 17" archtop guitar.

Sound idea: more like a deep baritone guitar - double bass imitation is not intended. The harshness of tpical ABGs is not desired at all. And it should mean X bracing instead of parallel bracing, shouldn't it?

That also means strings like LaBella Gold oder Copper White Tapewound or GHS Pressurewound Gold. And two firebird like minihumbuckers (i.e with Alnico blades) or thunderbuckers as freely floating as possible. Or a wide bandwidth pickup with a current transformer in order to get the acoustic sound.

If you can, try and test drive a Taylor GS Mini bass. Its a departure from everything normal. The short scale is functional due to the unique strings manufactured by D'Addario. Unfortunately, there is no ferrous alloy in the strings and you can't employ magnetic pickups. However, the tonal response and intonation is true without the typical side effects of a short scale. There is no reason why a 25" scale archtop wouldn't work as long as you could find a way to employ a piezo pickup effectively. I have successfully modified an Epiphone SG using these unique string and a piezo undersaddle pickup. They will tune to a 24-5/8" scale and have been installed at this pitch for over a year. I just don't have a quality preamp. The instrument would be outstanding if I employed a compressor as the dynamic response is difficult to control with my bass playing skill level.

Various people measure the arch height in different ways. I'm used to just taking the height of the peak of the top above the bench, so a normal violin top would be about 15mm. If you're taking the difference between the low point of the channel and the high point, it's 12 or so. That's for a nominal 3 mm thick top.