robedney

I realize that this is an old thread -- and I haven't been on Maestronet in a long while now -- but we've had an inquiry about carbon fiber sound posts specifically referencing this thread. I thought I'd answer here and share what we've found: We make carbon fiber violins, so you might assume that we'd fit carbon fiber posts. As a general rule, we don't. The reason -- as suggested in some of the replies above -- is entirely pragmatic. Luthiers are well equipped and experienced in fitting/adjusting spruce posts, not so much carbon fiber. As sound post adjustment is a key component in any good setup, it makes no sense to put an obstacle in anyone's way. It's basically the same reason we use ebony nuts and maple bridges. When it comes to the real difference between spruce and CF, in my experience there isn't any -- not that I can hear or measure. Here's my pet theory: The use of the sound post in violins may very well have had to do with simply keeping the top plate intact -- maintaining the arch and avoiding cracks under the treble foot of the bridge. This is an evolutionary thing. It turns out that the sound post -- when well fitted and placed -- also has a significant desirable impact on sound, so the adaptation persisted. In my own experience (and testing) the primary (other than structural) impact of the sound post is to mechanically link the top and bottom plates. Any effect of the sound post itself transmitting sound is drowned out by the activity of the plates. So, so long as you make the thing out of something structurally suitable the material doesn't much matter, although the diameter does have some impact. The fitting does matter however -- and quite a lot. We do -- upon request -- fit CF posts, just as we will pressure permeate an already cut and fitted bridge with epoxy resin. The reason here is to create an instrument that can tolerate really adverse conditions, like ridiculously high humidity, extreme temperatures/variations, or even the possibility of full immersion. As a side not, if someone wants to mess around with CF posts on a wooden instrument I do suggest veneer on the sound post area of the top plate, which in my book is good standard practice anyway -- regardless of the material there is still significant point loading in that area. Cheers!

Very nice indeed!

I can do that (measuring and adjusting the resistance in the area of the bass bar) -- good thought. I've had the same thought (as you, above) about adding damping. My latest prototype is somewhat thicker with more mass. I was looking for a more focused sound, and I thought it worked. The pros I've had play the two I'm working with at the moment like the thinner, lighter instrument better, in fact asking me to make something as thin and light as possible to try on the next round. They felt I was pretty darned close with the lighter instrument. I'm listening to them. So, I'm back to where I was at one point -- building as light as I can while still producing a highly durable instrument -- and adding damping if and where needed. I'm moving my shop right now to gain space. As soon as I'm done with that I'm going to work on the next one. I'm going to take some time while doing that to develop some version of an adjustable post, and perhaps a CF bridge. I'm a little reluctant to take on the bridge right now because it is such a critical component and there is so much territory to explore. We'll see. John, I will definitely send you the next one to have a look at (once I've gotten some feedback from the aforementioned pros).

A perfectly fair statement. Part of the inventiveness involved in creating any sort of "upgrade" is taking what you're talking about into consideration. I've learned to monitor myself when it comes to becoming too attached to an idea, and I actually sort of enjoy scrapping something that's not proving out. That takes me one step closer to something that works. Also, I should clarify: I wasn't saying that anyone's views here were wrong. Someone who is very skilled at setting and adjusting wooden posts would appropriately have little interest in such gizmo.

And that's where I think I have something of an advantage. Anyone looking at a CF violin is already demonstrating an open mind. What we've seen here is that many respectable folks have a negative reaction even before any sort of design is finalized. It is not at all a complex gizmo, but the tendency is to decide that it is. In truth it's a rather simple and sensible gizmo. We've also seen that those who have experience successfully installing traditional posts don't see what the big deal is. And, I assume that there is some resistance to making what is traditionally the task of a luthier less complex and daunting. On the other hand -- how many of us would be able to avoid tweaking the sound post tension if we could do so with an allen wrench from the back of the instrument? We're a lot of tweakers on this forum And how much more likely might we be to vary the position of the top of the post if it were easy and safe (safe from knocking the post over) to do so? Much of this same sort of discussion happened when people starting bolting guitar necks on. It was a simple, sensible solution that stirred many to the defense of tradition. It's also now a common place practice for many reputable makers.

OK, after pondering overnight and reading the additions above, I'm thinking that step one (working experimentally) is to significantly lower the profile of the existing bar in a prototype. Thanks for the floor joist example John, that helped me with the mass vs. stiffness issue. I have one prototype with a zip off top (it's glued on with black high temp silicone). It also happens to be the variation with the thinnest plates. So, I can record some open strings and spectral analysis before, then again after re-profiling the bar. That ought to demonstrate something. One thing that's occurred to me is that it's easy to put mass back if needed, so I'll judge the new profile based on my sense of how the plate handles loading on the bass side and take it down as far as I'm comfortable with.

I'm quite certain that John's response to you was in good humor.

A _careful_ reading of the gizmo discussed on this thread will reveal that it allows for a great deal of adjustment, very likely with the same results as a wooden post. Part of the design parameters as discussed make it easier to install and adjust -- not just for amateurs but also pros. One thing you can't do with a traditional post is adjust the tension easily. One gizmo version (above) makes that very simple. It's not for everyone, anymore than Peghead tuners or composite tail pieces, but it's far from running in leg irons.

Interesting. Do you remember where? I'm more or less convince that a spring loaded post on its own isn't going to do the trick -- the spring will introduce way too much damping in the linkage. What seems to work is a more or less rigid connection (just how rigid being open to debate). John seemed to suggest the possibility of a spring to hold the thing in place when the string tension is removed, but solid contact when under tension. That might work. And please everyone, don't take offense. We're just throwing ideas around here. Sometimes good stuff comes out of that.

I wouldn't worry about the luthier business -- carbon fiber is unlikely to replace wood in large numbers. Moreover, it I start to sell these things -- instead of just investing in them -- I'll have more expendable income, and the most likely expenditures will be on wooden instruments from contemporary American makers I'd like to own (and Manfio, of course). Edit: I think I need to include the Aussies in that too -- and maybe the Brits. You can see where this is going...

Hah! So right you are (about the speculation). I think maybe you've got a point. The bass bar may prove to be redundant, but I do agree that if you eliminate the sound post you both stray too far from the violin sound (been there, done that) and you remove an important adjustment point. I've found that if you go sans sound post you lose much of the focus of the mids and highs (although you get a richer low end). I'm guessing that this is because the top and bottom plates are no longer mechanically linked, and the bridge behaves very differently without the post in its vicinity. So, I'll do that (just try it) and report back. If that proves confusing, I'll maybe take John up on his very kind offer with Abacus, although I'm not sure I'm up for the learning curve. I started this whole project from a theoretical/analytical perspective and ultimately concluded that the empirical approach is not only more direct but -- for me at least -- faster. I seem capable of learning new tricks (in regards to the analytical approach) but lack the sort of background that, for example, John and Don have to fit it all into and make sense of it.

Actually, I'm thinking that it might amplify movement. If the bass bar does indeed rock, beyond some measure of initial resistance it might rock more with more weight on the ends of the beam. This is pure speculation -- and very possibly wrong.

Hey J, only the foot of the post is fixed in position (in one imaginary version, at least). The top of the post can be tapped around to your heart's content. The nice thing is that you could de-tension it just enough to make said tapping easy, than re-tension to whatever degree you wanted.

I hear what you're saying, and I might even agree. In part the question is "simpler for whom?" Such a post would certainly be simpler for the end user -- the player, much in the same way that a modern, well engineered car is simpler to own and more economical to drive than something from the sixties, even though is far more complex to initially make. It's simple for an experienced set-up person to adjust a post, but far from simple for anyone else. I understand any reservations regarding having players messing around with things, but some would be skilled enough to make adjustments and perhaps improve sound for themselves or their students. And who knows? Would a post that was very easy to re-tension/position improve sound at times? Clearly this is a niche sort of thing -- not everyone would want one. The question is are there not advantages for those who would?

And John, I think your idea for a patented adjustable post may have real potential. Despite the way we tend to think here, most of the violins in the world are student level instruments and many of them in schools. Such a patented post could be installed and adjusted in a matter of a few minutes with even minimal practice. Any adjusting tool could be cheap and included with the post. A video on YouTube could demonstrate the process and the results. Many string teachers would be adept enough to do it on their own. Not to put an luthiers out of business, but the schools need all the help they can get these days -- particularly strings programs (in other words, instruments that don't normally appear on a football field). Not to mention the fact that I'd be happy to buy such a thing from you and skip the development process on my own