Responsive Bracing for Flat-back Basses
Flatback basses, unless constructed lightly and assembled with great care in a very dry environment, nearly always suffer from problems relating to the movement of wood due to humidity changes. The traditional 90 degree "ladder bracing" constrains the wood's natural movement, and inevitably ends up in cupping or swelling in dry or humid conditions, and eventually cracks open up between the braces. The ailment is VERY common on older flatback basses and is also found on many new instruments.
Of course this is not an issue if the bass is built and kept in the same humidity all its life, but these days this is just not likely.
The sudden changes in humidity due to air-conditioning, travel etc result in wide cracks, distortions, and significant internal stresses on ribs, tops and other components. Trying to regulate humidity with wet sponges inserted in the f holes is, in my opinion, ineffective and causes other problems.
Some luthiers are addressing the problem by using various "X" style braces with varying degrees of success. However these still constrain the wood to a degree, and are typically quite heavy.
After a lot of careful thought, I've invented a new curved bracing system using modern composite laminating techniques to make braces that work with the wood rather than against it.
As the wood expands and contracts with changes in humidity, the "responsive" braces flex also, in a lateral direction, while still providing adequate support for the sound post.
I believe flat backs braced this way will be much more stable than with other systems, both now and in the long term. This approach also generally lighter than most other systems, and leaves the edges of the back plate free.
The system, which is also now being adopted by luthiers in other countries, can be used in both new and old basses and is affixed with traditional hide glues.
Is it right for my bass?
Maybe. If you have an instrument with a cracked or distorted back, its not going to get better on its own. We know that ladder bracing is the cause.
This new system is not traditional, but it is non-invasive, innovative, and it works ...
Have a look at the video on the right to see the result of humidity changes on a couple of test panels I made up for demo purposes. Its pretty eye-opening to see the degree of wood movement in a traditionally braced system!
But how does it sound?
The basses in which I have installed this system all sound great.
I - and several other luthiers now - have retro-fitted the responsive system in basses that previously had X or conventional ladder bracing. Without exception, the consensus from luthiers and owners is that this system results in an improvement in both sound and structural integrity. Resonance and bottom end is noticeably better.
Andrew Hassel of Chicago Bassworks writes "Had a Romanian bass that had ripped and warped around the center seam. I had previously removed the ladder bracing, repaired the crack and warp, and rebraced with replacement ladder bracing. Surprise, it didn't work. Second time I tried this new bracing system and it's been almost two years now and no issues at all! The owner says that the bass has really opened up, and his teacher says it responds similarly to Christian McBride's bass"
If you'd like to discuss what re-bracing with this new system can do for the your instrument, or get a quote, please get in touch. You might be interested to listen to an interview I did with Jason Heath for Contrabass Conversations where I discuss the system, among other things.
For luthiers: The system is not patented and you may use it as you wish. I wrote a technical article on this system for the magazine of the Violin Society of America (VSA) which you can preview below. If you are interested to discuss this system or read the full article please contact me directly, or click the link below.