Questions about building my first bass

[PsP]

Hello everyone,

I hope I got my way around the forum correctly and I'm in the right place.

So a brief background - I'm a design student and I've been thinking of a project to do for a while now, and I think I've got a nice, dumb and unnecessary idea that can push my knowledge etc.

So I have seen someone make a sub octave bass, and I think I want to make one. Problem is, with what I've come with, everything is pretty much set when it comes to form of the guitar, electronics, and all that jazz, but I just cant wrap my head around how actually scales and fret distances works. I mostly play stoner/doom metal so we downtune to B standard, but I never really gave the thought to how this works and affects everything. All the setup for me has been done by my friend who's a luthier.
The question I have, and it's not a question of why would I do it, it's a question of how to get there. How to calculate fret spacing, how to get the neck length for what I want. How do I calculate it. It would be a tremendously helpful if you could guide me in the direction of making this dumb dream a reality. 
 

Would a standard scale length and fret spacing work, does it even require reworking? If so what scale length should it be? etc. What would happen to string tension, what strings to have in mind while making this for it to be somewhat playable? I need all the help in the world to wrap my head around this. This a dumb experiment project, I want it to work just about, so I do not care that it's barely audible etc. It's just something I want to make for fun

[curtisa]

7 hours ago, PsP said:

The question I have, and it's not a question of why would I do it, it's a question of how to get there. How to calculate fret spacing, how to get the neck length for what I want. How do I calculate it. It would be a tremendously helpful if you could guide me in the direction of making this dumb dream a reality. 

FretFind2D is pretty good at automatically calculating fret positions based on some basic raw parameters for scale length, plus string spacing at the nut and bridge, and the amount of overhang you want either side of the strings as they pass along the fretboard.

7 hours ago, PsP said:

Would a standard scale length and fret spacing work, does it even require reworking? If so what scale length should it be?

Is there a reason why you wouldn't just take some known parameters from a commercially-made bass and just adapt them to your design? For example, if you essentially play 4-string down-tuned to B, why not just take the specs from an existing 5-string bass and omit the high-G string? The gauge of strings used would then just be a standard 5-string set minus the highest string. Scale length also need not change unless you have a pressing need to do so.

[Bizman62]

9 hours ago, PsP said:

How to calculate fret spacing, how to get the neck length for what I want. How do I calculate it.

@curtisa already answered but let me try to give you an even more simplistic answer:

We're not talking that much about neck length, we're talking about scale length which is the distance from the saddle to the nut. Part of the scale is over the body and the rest over the neck but there's no rules about the proportions. The 12th fret is right in the middle of that distance and the other frets follow a mathematical formula. You don't have to calculate, there's both calculators and tables available for any scale length. Thus you can (in theory) put bass strings on a soprano ukulele or vice versa and if you tune them accordingly you'll get a tiny bass or a huge uke. It's just about how high or low you tune the instrument given that it's strong enough to stand the string pull.

Of course there's reasons why basses usually have a long scale and high pitched instruments like ukes or fiddles are short. The thicker the string the lower you can tune it. But a thicker string will also be stiffer to push against the fretboard accurately enough. Highly exaggerating, think about a wire cable the thickness of your thumb. You can tighten it and tune it to play a note - just think about wire bridges - but you can't make it playable within a standard length. Using the math it would still be possible to make a fretboard for such a cable, maybe for a scale length of a hundred yards...

The material of the strings also matters, there's fretless basses with thick silicone strings that are only half of the length of a standard bass. Stiffness is the key.

So yes, you can choose whichever length you like. For many lengths you can even find readily slotted fretboards.

[PsP]

6 hours ago, curtisa said:

Is there a reason why you wouldn't just take some known parameters from a commercially-made bass and just adapt them to your design? For example, if you essentially play 4-string down-tuned to B, why not just take the specs from an existing 5-string bass and omit the high-G string? The gauge of strings used would then just be a standard 5-string set minus the highest string. Scale length also need not change unless you have a pressing need to do so.

So from talking with my friends, and my own experience, what I've realised and know is that - my bass downtuned to B standard and having a standard fender scale length of 34'' makes standard strings pretty floppy, so I use a set of .135 (I don't really remember, but I think these are what is on my bass) to compensate for the slack with string thickness. Maybe I haven't worded my question well enough, but I do get that part. The lower you go, the less tension there is, so you have to use thicker strings, but at a certain point it becomes unplayable. I don't want to use a ridiculous set of strings that are .3000 thick for it to somewhat work, and so to barely achieve playability i have to make the neck longer so it kind of balances out. At least that's how I understand this has to go. 

And this is where I get lost really. If I were to use a 5 string bass scale length it would come out to be just 35'', and I don't think that will work for E0 (I'm not actually sure, at least not with reasonably thick strings, might be wrong about it), so I think it would need to be longer, but how long actually. Is there a way to get the needed scale length in relation to string tension needed to play it, and what kind of strings would work the best? I'm lost on this part. I want it somewhat playable, but just enough. I don't think there would even be an amp, or a speaker that could produce such low notes but, I believe its still a fun and silly project to do.
Also my friend that I've mentioned earlier suggested that it possibly would have to have a scale length of over 40'' for it to be feasible, don't actually quote me on that.

[PsP]

4 hours ago, Bizman62 said:

@curtisa already answered but let me try to give you an even more simplistic answer:

We're not talking that much about neck length, we're talking about scale length which is the distance from the saddle to the nut. Part of the scale is over the body and the rest over the neck but there's no rules about the proportions. The 12th fret is right in the middle of that distance and the other frets follow a mathematical formula. You don't have to calculate, there's both calculators and tables available for any scale length. Thus you can (in theory) put bass strings on a soprano ukulele or vice versa and if you tune them accordingly you'll get a tiny bass or a huge uke. It's just about how high or low you tune the instrument given that it's strong enough to stand the string pull.

Of course there's reasons why basses usually have a long scale and high pitched instruments like ukes or fiddles are short. The thicker the string the lower you can tune it. But a thicker string will also be stiffer to push against the fretboard accurately enough. Highly exaggerating, think about a wire cable the thickness of your thumb. You can tighten it and tune it to play a note - just think about wire bridges - but you can't make it playable within a standard length. Using the math it would still be possible to make a fretboard for such a cable, maybe for a scale length of a hundred yards...

The material of the strings also matters, there's fretless basses with thick silicone strings that are only half of the length of a standard bass. Stiffness is the key.

So yes, you can choose whichever length you like. For many lengths you can even find readily slotted fretboards.

Yes exactly, and this is my problem. Sure I could use construction rebar thickness strings but that's unplayable. And I understand that it's a balance of scale length, string tension and string thickness, and I want to make it have reasonably thick strings, so it actually can be somewhat played. I understand that a standard scale of 34'' wouldn't work at E0, not without extremely thick strings, because that would be unplayable, and this is what I want to avoid. I want to get to E0, with the ability to actually pull the strings. And what I understand about scales that yes, the 12th fret is the halfway point, and the lower you go, the lower the tension is, so you make up for it with longer and thicker strings, and this is what I basically got stuck on. I understand the neck and the whole scale actually would probably have to be much longer, but how long? What strings to use? You have mentioned that there are tables available for any scale length, is there even one for something so stupid as an electric bass tuned to E0?

[henrim]

Have you already seen this video of a 42” scale length sub octave bass that was posted yesterday?

 

[Bizman62]

3 hours ago, PsP said:

You have mentioned that there are tables available for any scale length, is there even one for something so stupid as an electric bass tuned to E0?

In my understanding any string can be tuned to E0 but will it work is another question. The longer the string the lower it can be tuned. Also the thicker the string the lower it can be tuned. Based by your answer I figure you already know all that...

You know how using a capo makes the scale shorter by removing frets that can be used. What if you could add  a bunch of frets? A 5 string bass starting at B has a scale length of 35". The first fret is a little short of 2" long (wide?). If you make a 46" scale bass, the 6th fret would be of about the same length (width???) and the first one would be about 2.6" (toyed with https://www.stewmac.com/fret-calculator/ ). Those extra frets would take your B down to F if I counted right. And you'd want to use the thickest strings available, I guess...

This might be of interest: https://www.bassox.com/lowest-bass-tuning-possible/

And this might give you some idea about the measurements trying to reach the lowest possible notes on a stringed instrument: https://www.ludwig-van.com/toronto/2015/05/20/cool-stuff-8-the-octobass-an-instrument-capable-of-playing-below-human-hearing-range/

 

[curtisa]

18 hours ago, PsP said:

And I understand that it's a balance of scale length, string tension and string thickness, and I want to make it have reasonably thick strings, so it actually can be somewhat played. I understand that a standard scale of 34'' wouldn't work at E0, not without extremely thick strings, because that would be unplayable, and this is what I want to avoid. I want to get to E0, with the ability to actually pull the strings.

D'Addario provide tension data on all their strings, plus also provide the basic tension math behind the data.

If you assume you go for the .135" string for the lowest pitch, D'Addario indicate that at 34" scale length a B'' (aka, low-B) will have a tension of 36.1lb (see page 10 of the PDF):

But you want to tune down to E'' which isn't provided by the charts. So, say you stick with the .135" string and keep tension the same at 36.1lb, you can rearrange the formula provided on page 4 of the PDF in terms of scale length:

Becomes (rather messily):

So with the known values of tension = 36.1lb, unit weight (for a string gauge of 0.135") = 0.00315944 and your required tuning pitch = E'' = 20.6Hz, you get a suggested scale length of 51" (yikes!).

So you'll probably have to either increase your string gauge and/or reduce your expected tension to get scale length back down to something more reasonable. If you use D'Addario's 0.145" string and reduce tension to 29lb the scale length becomes 42.6". That's getting similar to the specs for that sub bass in the video that @henrim posted. Note that the above calculations become a lot easier if you set up a spreadsheet to do the math for you, so you only have to feed in frequency, unit weight, scale length and tension.

The other thing to weigh up is whether strings at such long lengths are easily obtainable. Don't forget that many large gauge bass strings are made taperwound to make it easier to wrap around the tuning post. They're typically sold under the assumption that they fit certain scale lengths, and that the taperwound portion falls behind the nut. If you make a bass with a super long scale length the taperwound section of these strings may sit within the fretted area of the neck. At the very least this will feel odd to play at the lower frets; I don't know how it might affect the sound. Consider whether or not the strings are only available as some kind of custom wound item or from a boutique manufacturer for your project.

There are other factors to consider when making an extended range instrument of this size beyond the choice of scale length and string gauge. The video also touched on these - things like frequency response of the electronics, the ergonomics of a long neck and how to work around it etc

[curtisa]

11 hours ago, Bizman62 said:

This might be of interest: https://www.bassox.com/lowest-bass-tuning-possible/

The article is misleading, as it implies that the thicker strings used in extreme drop-tuning exert more tension on the neck than standard strings tuned normally and may result in permanent damage to the bass if not set up correctly. It fails to mention what scale length or the degree of detuning is being used to make that claim.

I can't find data on the .200" bass string mentioned in the article, but the relationship between D'Addario's quoted Unit Weight change relative to string gauge change in their PDF appears to be fairly linear. If you extrapolate the Unit Weight up to a theoretical .200" string gauge, on a scale length of 34" a drop-tuned E'' exerts a tension of about 31lb. That's 16% less tension than a .100" tuned to E on a standard 4-string bass set over the same scale length.

[Bizman62]

6 hours ago, curtisa said:

The article is misleading, as it implies that the thicker strings used in extreme drop-tuning exert more tension on the neck than standard strings tuned normally

Thanks for bringing that up, I didn't read it that thoroughly. Not to mention that my understanding in physics is not at a scientific level.

Supposing this is a down-to-earth approach to tension: https://youtu.be/N46HGv0ehuQ

This seems quite interesting as well: https://stringjoy.com/guitar-scale-length-explained/ . What puzzles me is this: It's a fact that the longer the scale the more tension is needed to tune a string to pitch. Obviously that means that if a string of a certain gauge is tuned to a certain tension on different scales, the longer one will be tuned to a lower pitch. But how long can you go before that string gauge stops working properly? I mean things like the string hitting the fretboard on the video @henrim linked to. Doesn't this mean that the shorter the scale the thicker gauge you'd need?

Actually, thinking how mallet instruments work, the lower the tune the longer and thinner the bar is.

This is an interesting thread!

 

[curtisa]

1 hour ago, Bizman62 said:

Doesn't this mean that the shorter the scale the thicker gauge you'd need?

Yes. And the formula provided by D'Addario bears this out:

If frequency goes up, tension goes up. If scale length goes up, tension goes up. If unit weight (gauge) goes up, tension goes up. Conversely, if your aim is to reduce the scale length but you want to maintain the pitch and tension, then yes, the string gauge needs to be thicker.

There are practical limits though. You can't have a 0.5 inch gauge string tuned to E' over a 1 foot scale length. Mathematically it might work according to the formula, but it will sound like crap. Likewise, expecting a 0.010" plain steel string to sound good tuned down to E' over a 3 metre scale length is unrealistic. Guitar strings tend to have a window where tuning, scale length and tension all work nicely to give harmonic results, but either side the inharmonicity of the string becomes an issue.

Case in point - I used to have an Ibanez 7-string guitar with a 25.5" scale length, essentially based on Steve Vai's Universe model. Using a 0.052" string for the low B I had to routinely tune it slightly flat, as the low-ish tension of the B when used within chords made it appear ever so slightly sharp due to the inharmonicty causing the string's natural overtones to 'bunch up'. Switching to a .056" or a .058" made the tuning issue more manageable, at the expense of a slightly stiffer string compared to the rest of the set.

Piano tuners come up against a similar situation and have to implement 'stretch tuning' to account for the overtones of the bass strings clashing with the fundamental tones of the treble strings. The bass strings tend to be tuned slightly flat and treble slightly sharp to compensate.

[Bizman62]

Thanks @curtisa! You answered even to the questions I didn't dare to ask in fear of sounding even dummier than I am: I was thinking exactly about a 0.010 plain steel over a looong scale length, just didn't do any math to calculate it.

I've learned a lot from this thread, previously I didn't even know this question existed! Goes to show that asking questions is a thing that can educate more people than just the one asking.

Thanks also for the inharmonicity link which explained how elasticity or the lack of it affects to (in)harmonics - another unasked question. That explained why the Ashbory bass works.

And all this makes me ask a silly question: If a thin string can be tuned lower than a thick one, why are high pitched strings thinner in all stringed instruments? Is it because of balancing the tension? I guess tuning the 0.046" to E4 and a 0.010" to E2 could easily warp any neck!

[Bizman62]

And back to the original question through a side track: A bass ukulele has a scale length of 20-25" and it's tuned similarly to a bass guitar.  Now if we take a 20" bass uke and add extra 12 frets to extend the neck we'd get a 38" scale length. The Ashbory has an 18" scale length so using the same math we'd be at 34" which is common.

The issue with uke or Ashbory strings is that they aren't magnetic so they can't be used on a standard electric bass. But for building a sub-octave bass with piezo pickups... Would they work?  And are they available at the lengths needed? At least the u-bass strings have a simple knot and a stopper at the end so it might be possible to negotiate with the manufacturer for special lengths. And there's metal coated versions which may tune more precisely.

[edit] Further thinking and studying the string materials, it seems that  polyurethane and nylon are commonly used for u-bass strings and they only have a knot and a washer to keep them from sliding off the bridge. Bot PU and nylon cords are available at the string thicknesses which commonly are from 2 to 5 mm.

[mistermikev]

On 1/14/2023 at 5:27 AM, henrim said:

Have you already seen this video of a 42” scale length sub octave bass that was posted yesterday?

 

I immediately was thinking of this too.  is a cool video.  my initial impression was that - on the one hand... very cool... on the other - that low string is literally so low I can't really hear it and my ears are attuned to 5 string bass so... it's too low imo.  You see in the video he doesn't spend much time w the stuff below a normal basses range.  all this... just my observations... ymmv.

a standup bass is typically 42" as well and the lowest note is a B.  I can see going a little lower than that but not quite as low as this bass in order to make the lower range more useable.

all that said a 42 scale is fine... just not sure I'd tune it that low.  

assuming a 42" scale... I see some unique challenges here.  that is one long stick that is unsupported.  I'm thinking you'd want some carbin fiber reinforcement or at the least some rock maple and a fairly thick profile... or perhaps a single cut with more support on the lower range of that neck... maybe a multi lam neck with some wenge or other super rigid wood in there.

the other consideration is truss rod.  24" truss rod is going to be about the max you'll find for std truss rods.  this type of neck is probably going to require a custom rod in the 28"+ range.  lots of folks will make those (lmii or allied luthier for ex) but it is probably going to be expensive for a truss rod ($50?)... just something to consider.  

Also going to require some seriously long range strings and likely some thick guages which may present issues with the tuning machine holes (idk).  getting long scale strings for my current 35" scale basses opened my eyes to the idea that getting strings for 36" scale is expensive and only a few sources.  something to think about.

the other day I saw a thread about ibanez and the new "electric stand up" they came out with... it instantly made me think about a long range bass altho the ibanez is only 35" scale.  Carl Thompson does 36" scale as the standard if I'm not mistaken and swears by it.   Def adding a 37-40" scale to my 'someday' build bucket list.

[henrim]

I’m not even thinking about building a bass let alone sub-octave one but this thread is a good read nonetheless! Thanks!

(I do have one bass in the closet which  has a broken headstock. I may attempt to fix it at some point but the other option is to build a new neck. In which case all this info becomes valuable).

[curtisa]

8 hours ago, Bizman62 said:

If a thin string can be tuned lower than a thick one, why are high pitched strings thinner in all stringed instruments? Is it because of balancing the tension?

It's because of inharmonicty. From the wiki page:

Quote

...a stiff string under low tension (such as those found in the bass notes of small upright pianos) exhibits a high degree of inharmonicity, while a thinner string under higher tension (such as a treble string in a piano) or a more flexible string (such as a gut or nylon string used on a guitar or harp) will exhibit less inharmonicity. A wound string generally exhibits less inharmonicity than the equivalent solid string, and for that reason wound strings are often preferred.

You could have a plain steel 0.042" for a low E on a guitar if you really wanted, but it would be extremely stiff and hence sound pretty awful when played. Using a small core, but wrapping it in an outer helical winding allows the string to be more elastic while simultaneously boosting its unit weight, both perfect criteria for a string that can be tuned to a low pitch while still sounding good.

Getting back to @PsP's original query, as we're definitely straying well off the mark now, I'd personally get my hands on a few super-long scale strings of different gauges, a pickup and make a simple one-string test bed on a plank of wood. Install a bridge and a tuner at each end, fit the pickup, try out the strings over various long scale lengths tuned to E'' and test empirically to find out what works best, and where the compromises need to be made. The trouble with building such a left-of-field instrument is that there are few examples out there to base your own work off. You're probably better off experimenting with the physics of the strings, tuning and scale lengths before building the instrument, instead of building something and hoping it will work out in the end.

[curtisa]

6 hours ago, mistermikev said:

the other consideration is truss rod.  24" truss rod is going to be about the max you'll find for std truss rods.

If you watch the 'making of' video on the Lignum Youtube channel, they make their own truss rod from scratch. There's also no extra reinforcement being added to the neck, so it appears that the neck is probably OK with the long scale length. I'd be suspicious that it is pretty 'bendy' though, but maybe when you're dealing with such low pitches the amount of pitch variance when flexing the neck is generally undetectable.

[mistermikev]

15 minutes ago, curtisa said:

If you watch the 'making of' video on the Lignum Youtube channel, they make their own truss rod from scratch. There's also no extra reinforcement being added to the neck, so it appears that the neck is probably OK with the long scale length. I'd be suspicious that it is pretty 'bendy' though, but maybe when you're dealing with such low pitches the amount of pitch variance when flexing the neck is generally undetectable.

I didn't see that vid... and if you have a great piece of maple perhaps it'd be fine... either way... could be great today... tomorrow... I wouldn't wager my fur lined bathtub on that one!  

[PsP]

Thank you everyone so much for replies!

I've been busy because of midterms, but with all of your help I feel like I can get the project out of just the concept phase and get to slowly working on it!

I'll make sure to follow up on this thread when I get to working on my unbelievably useless bass

(and yes, that sub octave bass was partially my inspiration, I've been thinking about making a longer scale bass anyway)

Cheers