EDITOR'S NOTE: This article is part of a series exploring aspects of the Neutral Tension Bridge including: construction details, design theory, and ergonomics. Technology developed by Rick Toone. Patent applied for. John Vereb, patent attorney. Full information access — with licensing included — is available to eLUTHERIE.org members via Design & Technology Exchange.
This design is changing the way I think about building instruments.
I devised the bridge concept in late autumn (2006) and completed the simple prototype pictured below in March, 2007. I filed for patent today (John Vereb, patent attorney) and so am finally able to discuss the idea in public. Breathes deeply, exhales, excited.
Neutral Tension Bridge — a bridge that places zero tension on the soundboard of an instrument.
Why is this important?
EDITOR'S NOTE: I'll bet you're about to tell us.
Every other existing instrument design couples string tension to the soundboard, whether longitudinal, tangential or lateral. Acoustic guitar strings attach to the guitar top. Classical instrument strings (violin, cello, bass, etc.) and archtop instrument strings pull the bridge against the soundboard. Even solid body electrics couple string tension to the soundboard (body).
Two significant problems are associated with conventional designs, especially acoustic instruments:
• Conventional soundboards must be designed to counteract string tension, through the use of bracing. Bracing adds mass (weight) to the soundboard. As strings vibrate, they must push against the combined mass of the soundboard + bracing + string tension in order to transfer energy and amplify sound. This mass slows response time (loss of transient detail & note articulation) and dampens sustain.
• Expansion and contraction of the soundboard due to temperature and humidity changes cause the soundboard — including the bridge — to change orientation angle relative to the neck. As a conventional acoustic guitar swells or shrinks with humidity or temperature, the action changes. String height above the frets is an ever-changing frustrating variable and a constant struggle affecting quality, design and warranty. Bob Taylor (Taylor Guitars) explains the problem in this series of videos.
Both of these issues are eliminated by the Neutral Tension Bridge.
I have absolutely abused this acoustic prototype made from cherry and spruce. It has never been in a case. I have never used a Dampit or any other humidifier. For the past 19 months I have traveled with and played the guitar in climates ranging from the swampy summer humidity of sea level New Jersey to arid (10,000'+) mountain ranges of Santa Fe, New Mexico. Inside. Outside. Winter. Summer. Even stashed inside a (black) pickup truck cab parked in the desert!
The action never appreciably changes.
No splits. No cracks.
A whole world of design posibilities is opening, which I am so excited to explore. The photo below is one simple embodiment of the neutral tension concept. Wait 'til you see what's next...
• Neutral Tension Bridge combined with the Lever Tuning System
• Acoustic instrument with tremolo/vibrato
• Simple realtime at-the-bridge player-adjustable intonation and action
• Alternative neck-to-body joint designs for improved upper fret access
• Easy inclusion of electric guitar pickups in an acoustic instrument
• Asymmetrical ergonomic body shapes
• Use of locally grown sustainable woods for body and neck construction
Wow, Rick, that's brilliant! You've got a real talent for challenging the conventions. Can't wait to see and hear where you're going with this :)
How does it sound?
Posted by: Joachim | October 25, 2008 at 07:00 PM
Once again fascinating, I can't wait to see the complete project!
Posted by: Jesse | October 25, 2008 at 08:33 PM
Congratulations on filing for the patent, Rick. It is gorgeous.
Posted by: Fighting Windmills | October 25, 2008 at 09:57 PM
I think that this will change more than just your way of thinking of building instruments! Awesome! I can't wait to see what's in store from the list of things there.
Posted by: Ola Strandberg | October 26, 2008 at 02:10 PM
It's very interesting to see more work in this area! Ned Steinberger and Steve Grimes did some work on a similar idea (see pat. no. 5,679,910). They include an interesting adjustable neck mechanism (length and tilt) as well as several manifestations of a "stress free" bridge system.
Posted by: Ian L | November 11, 2008 at 06:24 PM
Great job! Nice shape! I'm an industrial designer and I'm without words! Very good innovation!
Mrcl
Posted by: Marcel Roy | December 06, 2008 at 04:41 PM
Elegant design I have to say. I've sketched on a similar design myself. Although, in my sketches, it was kept within the looks of an ordinary bridge. Of course mechanical principles in action are the same. I came up with the idea when trying to figure out what Babicz had in mind with their bridge design. Your design takes away the forces on the soundboard. In contrary I guess the Babicz solution answers a question that nobody have asked.
I find your work very inspiring. Both asesthetically and in terms of technical solutions.
I'm going to build my first acoustic guitar at Totnes School of Guitarmaking early next year. I'm fascinated with acoustic instruments in particular. And I would like to design and build more ergonomic and still elegant guitars in the future. I'm also interested in improving the guitars efficiency in transforming sting vibration to sound. Your bridge design could be a key element in such guitars.
As a mechanical engineer I find the complexity in the function of traditional sound board brazing a bit confusing. Taking away the torque and stress of the soundboard should give room for more optimal sound transducer designs.
I wish you good luck with your work Rick
Posted by: Gorm Sverre Bruland | December 12, 2008 at 12:19 PM
How do you deal with intonation compensation? Do you have a way around this?
By the way, I think Bob Taylor wishes he was as clever as you are.
Posted by: Tyler | December 29, 2008 at 08:18 AM
Thanks, Tyler.
I've owned Taylor acoustics and they are fine production guitars. I have a lot of respect for Bob and the excellent work he's done both in advancing lutherie and associated ecological issues. Perhaps at some point we'll have an opportunity to work together.
Intonation is approximate on the prototype pictured above, equivalent to a production acoustic. Compensation for the B was simply a matter of filing the cross-member.
This prototype was only to test the concept. More advanced bridge designs — with intonation compensation — are under development in prototype form. I will be publishing additional information as I have time.
Posted by: Rick Toone | December 29, 2008 at 12:56 PM
This is really good, nice job!
I'm assuming that there has to be no appreciable break-angle in order to ensure zero-pressure on the top? I'm asking because I was wondering if this style of bridge could be retro-fitted to a vintage instrument with a delicate top?
Regards, John Maddock.
Posted by: John Maddock | January 15, 2009 at 12:14 PM
Beautiful design! Are the strings pulling up on the center crosspiece, as well as resting on the outer crosspieces? Love that tailpiece too!
Posted by: Jeff Wewers | April 08, 2009 at 12:48 PM
This is a brilliant idea, not to mention stylishly executed, but there is very little that is new in the guitar world.
Take a look at the bridge on this guitar:
LINK | http://www.harpguitars.net/history/org_images/form1/lacote_9-stg-mfa_dangerous_curves.jpg
...Interesting, huh? That was built by Rene Lacote in 1827. He made at least one other (a seven string) with the same bridge. I assume he used this design to relieve the tension from the extra bass strings.
On a different note (no pun intended), your use of native woods is fantastic. It’s always nice to see someone making great instruments without using bits of what precious little rainforest we have left. Besides, cherry and walnut are easier to work and they don’t give you lung cancer. ;-)
Posted by: Rob Johnson | May 23, 2009 at 04:36 PM
That is truly genius Rick.
Posted by: Rick Canton | June 23, 2009 at 12:04 AM
i really like your idea for the neutral tension bridge, yet im curious about the tone and projection of the instrument.
where i work, we put a lot of time and effort in to shaping all of the braces so the top resonates at a tone that sounds beautiful, but what really drives that is the tension from the strings, which also increases the projection and volume of the guitar.
it seems to me youd be trading one dragon for another, then again i havent heard your prototype. much respect.
Posted by: Jake Powers | June 24, 2009 at 08:53 PM
Jake — thanks for commenting.
You can actually hear the prototype on my website. It is a small test instrument, slightly larger than a Martin backpacker. I built it just to test the concept — prove that it works — before applying for the patent.
LINK | http://www.ricktoone.com/2009/02/neutral-tension-bridge-recording.html
I'm currently building a full size guitar using this technology. It will sound much bigger and deeper, of course. It will also feature a (very) different embodiment of the Neutral Tension Bridge concept, along with a body mounted (headless) tuning system that I've had machined.
Unlike current acoustic guitars with centuries of bracing refinement, I think of this idea as ripe for exploration. It is the beginning of a new branch on the tree of acoustic instruments.
Posted by: Rick Toone | June 24, 2009 at 09:41 PM