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Double Bass flatback versus carved

1st Bass

1st Bass

May 26, 2005
1,943
4,119
71
Forest Grove, OR
#1
Probably an ignorant-sounding question: Can anyone quantify, or in some way describe the differences in sound, [playability, or something] between a flatback bass and one that has a carved, arched back?

I am not a player, but am building a bass, and was really torn about whether to build one or the other. I have built violins and violas, and have repaired celli and basses, but ALL had the carved backs, so flatback just doesn't look right, to me. But I know they are fine, and that many professional players use them.

If there is a consistent difference, I'd like to know how it manifests itself. I know an archtop guitar and a regular guitar don't sound quite the same...but I could not explain the difference.
 
#2
It's hard to make generalitites about flatback sand roundbacks; it seems like there are too many exceptions to the rule. Most flatbacks (I'm saying most, not all) have a dry, spooky sound to my ear. A little tubby, as well. Roundbacks can be more cello-like, with really rich upper-register tones. But there are roundbacks with incredible rumble, and flatbacks with wonderful mid-range. IMHO, arching, graduation, and the bass bar has more to do with tone than flatback vs. roundback...

However, flatbacks are easier to build and the tonewood costs less. If this is your first bass, my vote is flatback. Post some pics of your work in progress, if you like.
 
#3
Keep in mind that if you are not controlling the humidity in your shop, a carved back will be better. This is an important issue for longevity. The flat back has braces cross grain in 3 or 4 places that cause all kinds of shrinking/cracking problems down the road.

Of course it can be done by waiting for the right day to glue the braces, just as it has been for centuries. But I like to keep the Relative Humidity in my shop 45% when performing cross glue operations.
 
#4
Flatbacks are more comfortable to play seated, but they do seem to have more issues with shrinkage and cracking. I think there are too many variables in bass making to describe any exact tonal differences between a flat and round back. Either one can sound great, obviously. You are going to post pictures, right? It's cool to see someone up here in the NW making a bass...
 
#5
nicklloyd said:
However, flatbacks are easier to build and the tonewood costs less. If this is your first bass, my vote is flatback. Post some pics of your work in progress, if you like.
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Dido on that. This is why I will probably go with a flatback when/if I ever build a double bass. Right now I'm making a violin, and would like to make a viola & 'cello after, but a double bass would be sweet to eventually build, because then I could have my own string quartet! :D
 
#6
Well-- when I have some to post. As I said on another thread, I don't have a digital camera, but I can probably borrow one.

I'm glad to hear the comments on the two types of backs-- I had pretty much been leaning toward a round back, but I had not known about the humidity issues-- and here in northwestern Oregon, it could really be an issue. I think you all have settled it for me.

Thanks. Maybe someday I wil try a flatback, but for now, I am going to try the round.
 
#9
I believe the posters above have said almost everything important about the flatback/roundback difference except one: It's been my experience, and that of my mentor, Lou DiLeone, that it is easier to get a good tone from a flatback. I think this is because the flatback acts much like a secondary soundboard, similar to that of a classical guitar. That said, I think the standard method of bracing a flatback is wrong, and encourages cracking and warping of the back.
 
#12
What are some other bracing types for flat backs? The only two I've seen are the standard cross braces and the X brace setup. From what I've seen with my X braced Shen that doesn't look like the greatest option, and cross bracing causes the back to crack, so what would work better?
 
#13
What about cross braces with an arch in them, or the whole gluing surface of the ribs where the back attatches having an arch in it? Flat-top acoustic guitars (which aren't actually flat) have a slight radius to the back (slightly less on the top). 15' - 20' radii are commonly used. The arching makes them ore stable, and acoustic guitars generally use cross braces on their backs.

When I worked for an acoustic guitar luthier, bracing the tops and backs and attatching them to the frames (side assemblies) was my job. I used a gluing board with the same radius in it to glue the braces on, and used a large motorized sanding board with the radius carved in to shape the frame to fit the radius of the back or top exactly.
 
#14
This is hard to answer honestly for anyone. Unless you make and instrument and Two backs, it's hard to compare. You can't compare different Basses as there are many factors involved. There are many ways to make each Back as well. Don't forget about the Olde American 'X' braced Backs. I have one in repair and we will leave it as-is. It is not original but seems to be fine so not borke = no fixin.

I have played both dark and bright sounding Basses with both types of Backs. I would say if it's your first Bass, try a Flat Back and cut your work down. Listen to Arnold and the others about the Bracing. You don't want the Back (flat or carved) to shrink and Split the Top.

I am lucky to have a 195 year old English Bass with a Round Back and only Rib splits. The Top and Back are almost mint. Ask Arnold, he has seen and played the Bass. That is a great example of building a Bass to hold up in time. Last thing, make sure your wood is well aged and Air Dried before you start building. It's a waste of labour to do things twice, or even more times if you can avoid it.
 
#16
I would imagine that it would be similar to the x-bracing in the front on a steel-string guitar-- but there is a lot of other stuff in there, too, on the guitars.

Ken, I appreciate the counsel--I bought the wood from Tepper Tonewood-- it was supposed to already be aged, seasoned, etc. I guess I just have to hope it really is. He's pretty reputable, I think. I have bought violin and viola wood from him, and it was all very good. (This was his cheapest bass wood. Price was definitely an issue, this time around. If I get good at these things, I'll buy the best wood I can get, but for now, I buy the best I can afford.)

I installed the tuning machines today--that was a satisfying sight--I'll take 'em back off to varnish, I expect, but for the moment, it was good to see them in place.
 
#17
I don't have pictures, but the X brace is just that. The braces are about three inches wide by 5/8 or so thick, and run diagonally from one end to the other. One is cut to make way for the other, and the soundpost sits right on the brace . I think there are also a few cleats on the center seam. I'll try to get some pics of mine tomorrow, but I don't think my camera will do too well.
 
#18
Aaron Noguer said:
Not be a bother but, will you please elaborate. Are you referring to a X or something else?

Also, does anyone have a picture of a X braced back "off" the bass, I have never seen one on ANY site, and that is saying something.
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I'm using a combination of short crossbars and angled length bars. That's all I'm comfortable saying about it...
 
#20
What about cross braces with an arch in them,
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Bingo! That's what we're using for both of our flatbacks, though it has taken some trial and error to get it right. The next time I'm at Ahnold's, I think I'll peek in some f-holes. ;)

As far as round vs flat tone, all I can say is when we switched from round to flat on the 3/4 it made one hail of a difference. Same with the 7/8. Your results are pretty much guaranteed to differ, since there are other variables, like we switched to willow also, and minor mods to the outline. For all I know it sounds better only because the endpin weighs 2 grams less or something. :p
 

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