Flat or Round Back?

Google search the acoustical study between the two. Round backs take all that carving so I would venture they are much more labor intensive.

 

I have read that flatbacks experience more problems late in life due primarily to the way they have to be braced. The sound study from Germany shows there are differences in sound to microphones and sound analysis software, but to human ears there were not as much difference. There are probably 1,000s of things that influence the sound, primarily the player.

 

Steve, this doesn't make sense. It either has a flat back or a round, swelled back. Looks round to me in the pics. There is nothing unusual about ply basses, round or flat back.

 

You can lay up plywood in a form and mold it at that time. My cheap Cremona SB-2 has a round plywood back and front.

 

So far as I know, virtually all plywood basses are round backed. Now I'll go out on a limb and speculate as to the reason, given that both flat and round backs are equally respectable for basses. My guess is that making a round back out of plywood doesn't cost much more since the layers have to be pressed together in either case. And a round plywood back eliminates the need for bracing.

Oh, and is this your first descent into the dark side? If so, welcome, and enjoy your new bass!

 

More to the point, you can make your plywood top and your plywood back in the same mould!

 

I was wondering about that. Do they have the same amount of bulge? I can't tell from looking at my Kay, because the belly is certainly not its original shape.

 

I've never made profile gauges and confirmed but my eye says they're the same - and my eye's very good!

 

Just get one of these:
http://www.parktool.com/product/wheel-alignment-gauge-wag-4

 

That'll just show the depth - I could do that easily enough if I cared but...

 

When ordering my Upton plywood bass my choices were the Standard model which has a round back, and the slightly more expensive Bohemian which has a flat back. The nice folks at Upton said that the flat back Bohemian produces a sound closer to a solid wood (carved?) bass. It's also my understanding that flat back basses are a bit more punchy. The bass is being built and will delivered in January.

 

As for flat backs and bracing. The traditional ladder bracing is problematic since the wood of the braces is 90 degrees to the back/top plate wood. This wood orientation traps the seasonal movement of the back, eventually leading to some type of failure either in the glue, ribs or back center seam. Maybe a luthier will chime in w/more detail about this. An older bass experiences less seasonal wood movement and may be more stable. There are other types of bracing currently used for FBs, some call it propeller bracing or diagonal bracing, try doing a TB search, you'll find pictures.

 

Indeed, it would be good for luthiers to chime in. I'm not sure how much more seasonal movement goes on in newer basses if they are constructed of properly dried wood. Also, any movement is greatly reduced when we're talking about a ply back. Indeed, there are alternatives to the older forms of bracing and I believe that Upton uses more modern methods. Finally, while I trust Upton's description of the differences in sonic qualities across their own roundback and flatback basses, reading the comprehensive discussions here suggests that one cannot necessarily validly generalize.

 

"Compression set" is a term used to describe the action of how wood will expand and contract to relatively the same dimensions, if the wood is trapped it will not return to it's original width as in "compressed and set". I think this also happens with older wood, it may loose its' ability to expand/contract to a large degree

 

Mr Rogers makes a plywood bass:



Louis