Acoustic bass specs

[Dominic]

Hey, was talking with craig about an acoustic bass he is planning on building and it got me thinking about the design. conventional 'wisdom' says an acoustic bass should have a large deep body, extra bracing and a thicker top. But more recently I have read that 4 string bass guitars can be built a lot lighter and on smaller bodies and create better guitars. Volume would be one main consideration to help project the bass notes. Now volume is a function of mass and stiffness suggesting smaller bodies can be closer to the sweet spot for spruce tops. Trevor talks about this in section 3.1. So perhaps smaller bodies may well be better for ABGs. I'm also not impressed with the look. Many are blobby and fat, obese even, and don't look slick like they could. So I think there is plenty of scope to work on asthetics.
The really deep body is about creating a lower air res which could be achieved with a smaller soundhole. Its all balance but some of the monsters I have seen would be difficult to play unless you were of monster proportions yourself.
Anyone made a decent ABG? We have enough equations in the book to work out a comparison between the tension of 6 guitar strings and 4 bass string and then calculate the required brace heights to give us a decent angle of rotation and high monopole mobility.
The 3 main resonances could be shifted down somewhat but there would be limitations to how low while maintaining structural integrity.
Cheers
Dom

[kiwigeo]

Dom, there are a few acoustic bass articles in the GAL Big Red Books...Ill have a sift through my copies tonight and let you know if I find anything useful.

[Phil Mailloux]

There's a reason why good sounding ABG's all have huge bodies, they need that to pump out the air required to get the volume necessary. I can say from having tried a few ABG's that the majority just isn't loud enough to do anything decent acoustically with someone playing a Dreadnought next to you.

That being said, what do I know? I haven't built any acoustics yet but I've been researching ABG's for a while since I'd like to offer one for sale as part of my range of basses at some point in the future. The only production ABG's out there that seem to be getting decent feedback are Tacoma Thunderchiefs and Warwick Aliens. I haven't tried any of these but right now I'm almost to the point of breaking down and buying a Thunderchief to reverse engineer it. I'd like to get an ABG done within the next year but honestly, I have no time or energy to try to engineer something from scratch that *maybe* will sound good... or maybe will sound like crap... I've also thought of maybe getting a Mexican guitarron and checking it out, way too big a body for an ABG but it could be interesting to see whats under the hood, bracing wise

But hey, I'm signing up for this thread if you're going to go ahead with this as I want to see the results and hear how this ends up sounding

[graham mcdonald]

Back a long time ago myself, Gerard Gilet and Jim Williams all got orders for acoustic bass guitars, and we all took a similar if differing approach to making them. A couple of things to keep in mind. You are not going to get much grunt on the bottom E string. There is just not the air volume, but this is not so important as the ear can be tricked into thinking it is there if the upper harmonics are happening. The string tension is around 80kg, around the same as a medium/light guitar set so you don't need massive bracing. I suspect there is a belief out there that bass tension is much greater than it actually is. I think I still have some notes I made (some ideas for a GAL article which never happened) on all three instruments which I can dig out, but you will have to wait a couple of weeks as we are in Italy

Caio

G

[Dominic]

Thanks Phil, I am more along for the intellectual stimulation but like everyone, an acoustic bass is on my list somewhere.

The article I read about them said basically what you said, most of these basses are not very good. And whoever it was said they were having good results using lighter braced smaller basses. The implication was that ABG were made by factories who didn’t think about the design but it has stuck as the norm. I wish I had the article. I probably do somewhere but the key point was that there was scope to improve the design.

So here are my thoughts out loud. As always I am happy to be informed that I am wrong.
My understanding is that if it just about moving air, the amount of air in the box is less important than the area of the oscillators which do the pumping.

And the freq of the coupled air res can be controlled by soundhole size. I picture a violin and a cello. Cello has much bigger body but the f holes are not proportionally larger than a violin.

So a decent area of top and back but as the area of the top increases, we would be adding increasing mass in order to maintain stiffness over a larger area and efficiency declines.

I’ll do all the calcs and work it out. As you said, no point rushing into it and making a guitar that does not work. And no point copying all the other guitars out there which also don’t seem to work.

Perhaps Craig will chip in as he is the one committed to make one. Apologies if I’ve dumped you in it Craig.

Cheers
Dom

[Dominic]

Cool thanks Graham. I'd love to see your notes at some stage.
Still a bit cold here in Canberra so I would not be rushing home from Italy just yet.

Cheers
Dom

[Clancy]

Thanks Dom, I was going to start a "help me" thread anyway.

My client is a professional musician, a product of the Australian School of Music here in Canberra, but is based in Sydney earning a living gigging & teaching. He's a true bassman, being just as accomplished on the Doubble Bass as on a Fender.

I'm lucky in that he recognises the natural short-comings of an acoustic bass guitar.
So his requirements are
- that he can use it acoustically when practising or composing by himself
- that it is amplified for accompanying other musicians
- that it is not too large a reach over it to play

I was discussing these with Dom and how all my research revealed custom built abg's were around 5" deep & 18" lower bout.
This is probably too large for his requirements
On the other hand factory models tend to be just a bass neck stuck on a standard jumbo body. And sound completely shit acoustically.

Obviously I'd like to provide the best acoustic response, tone & volume possible - without having to build a bus sized instrument.
Obviosusly I can't have it both ways.
This is the point that we briefly started throwing around our thoughts.
And now we are here.
Thanks for all and any input.

[Bob Connor]

What about doing a Manzer wedge to make it a little more comfortable to play?

Regards.

[Clancy]

Thanks Bob, the wedge has certainly been in my thoughts.
Could any of you bass players here consider how your wrist position would be with an angled top & let me know what you think. Would it make a difference? good/bad?
I've also been thinking along the lines of an archtop, where around 5" can be ahieved at the center with the sides only 3" deep. But he doesn't want the "archtop" sound....

[Clancy]

Another approach I saw was to extend the upper bout further up the bass side of the fretboard.
this looked a little odd, but not too bad & added some volume to the body without increasing the lower bout dimensions.

[slowlearner]

Lots of great points here. The point about the E lacking fundamental is especially true. It's also true for lots of smaller uprights. I'm no expert, but I'm just reflecting on two things. Firstly, I don't think there's a replacement for body volume (but there are lots of crazy ideas to help this throughout guitar history). Secondly, lots of people are starting to put flatwounds on ABGs. Again different sound, but then I guess you realise the the ABG is a vastly different instrument from both electric bass and upright. Jonas Hellborg is one of the few people to get that. Christopher Hale is another one pushing the boundaries. Be worth checking out both their basses.

[Nick]

I only ever played a thin electric bass and not acoustic but I'm in Bob's camp & would use a wedge to reduce the width on the player's side (I'm with your customer on that one!). I don't think there's much you can do to 'alleviate' playing position or make hand position easier, remember it's constantly changing depending on the sound you want to produce,i.e anywhere from up on the neck to back near the bridge. Something like a Jumbo shape or SJ where it has the larger lower bout (& hence larger vibrating soundboard area for monopole activity) with the narrow waist could be worth considering Craig.

[Dominic]

So while everyone seems to agree that a large air cavity is good for a bass, can anyone explain why?

What are the attributes of a large air cavity that helps support the lower notes and that can not be gained by reducing the relative sound hole radius.

Using the Gore framework I can't see how this could improve a bass sound. Perhaps that is what's wrong with most/all of the current models.
Actually, I'll try doing that in the 4DOF model and see what it does to the peaks.

[kiwigeo]

What about doing a Manzer wedge to make it a little more comfortable to play?

Regards.

A comment on Manzer's wedge. Manzer states on her website that she's happy for others to use her idea but makes a request that acknowledgement be included in the form of a note on the instrument label or associated documentation.

Graham Caldersmith I believe has made bass classicals and the build has been documented in GAL journal. Might be worth reading same for clues on sound hole size/body volume

[graham mcdonald]

Air volume/Helmholtz frequency/bass response - all related

Smaller soundhole, lower Helmholtz, but there is a limit when the air movement becomes audible according to Graham C.

Craig, I have a body outline template for a ABG in the shed if you want to have a look whenI get back
Cheers
G

[jeffhigh]

I have not made an acoustic bass guitar, but I have just initially strung my classical size seven stringer this morning.
Using a 58 thou D'Addario 7th, the low string is no slouch on B or A

Seems like a stronger B than my Baritone SS with a big dreadnought body.(with large soundhole and about 115 air resonance)

This one has a main air at 87Hz with a 84mm soundhole, will probably bind the soundhole and bring that down to 85

Looking around, I see that Savarez has classical bass guitar strings, that sounds like an interesting way to go, with a light high mobility top, and a small soundhole

[Clancy]

Thanks Graham, I'll take you up on that offer.
Just got to find the time to drop around. (Having a day job again really sucks!)