Official Luthiers Forum!

In Robert O'Brien's latest video dealing with steel string back braces, he mentions that some luthiers build their backs so they will be stiff and reflexive rather than responsive. I found that interesting, and so I tried to find some more information, but was unsuccessful. So after searching the forums a little and not finding anything, I thought I'd just ask.

What are your thoughts on reflexive back bracing? Are there any distinct advantages, and are there any luthiers you know of that prefer that style?

Thanks for your patience and for your input. The answer to the question will influence my approach to my current project. Thanks also to Robert O'Brien for these incredible videos. I get really excited every time a new one comes out!

http://www.youtube.com/watch?v=ismWy-GFvEk

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David Morris

the little I know about this is, you basicly have two schools of thought on guitar backs, one I call the stiff back . where the back basicly reflects the vibrations of the top, and you have what I call the flexible back, where the back vibrates sympatheticly with the top. great sounding guitars can be nade either way. I built one guitar with a master biulder, the back was ( relativly) thick and the braces ( relativly) stout by design . the guitar sounds great. on the mahogany dread i just built I used the loose back method, my braces were much smaller and the back much thinner. this guitar sounds very nice also. I cannot make a fair tonal comparison since the first guitar has a smaller body , and except for the neck I used completely different woods for the back, top, sides,linings , bridge,bridge plate , braces and fingerboard,of each, so a different sound would probably be expected simply on the use of differing woods. . Jody

Hi David,

You might try searching here (including the archives) using "reflective" rather than "reflexive", and I bet you'll find some discussion.

Rick Turner is a big proponent of a rigid, reflective back, throwing the sound of the guitar deeply out into the audience. Other luthiers (Al Carruth comes to mind) talk about the flexibility of the back plate and top plate working together as a pump.

One thing that struck me from the discussions was that this may be an area of players preference: some (maybe even most?) players may like the sense of intimacy of having a flexible back moving and vibrating against their body - the sensation of the instrument being "alive." Some players may even judge a stiff-backed instrument as quieter or somehow inferior unless they are educated as to the purpose of a stiff back, or maybe until they stand at the back of the recital hall and do A-B comparisons of instruments with stiff and flexible backs.

Me personally: I feel like throwing the sound far is easily accomplished with a pickup and an amplifier, and so I'm thinking more in terms of a flexible back for intimacy. Of course, that doesn't mean I'm right, and especially if the guitar is custom built as a commission, you may want to consult with the player and let them know you could provide either, depending on their preference.

Dennis

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Dennis Leahy
Duluth, MN, USA
7th Sense Multimedia

Ok, I feel really dumb. Thank you for that patient response. There's tons of information here that I would have found quickly had I realized that "reflexive" is not actually a word.

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David Morris