Neck density

[Keith Newell]

I have two mandolins I am building to spec. Each have an identical top and back. The necks are different. One is much more heavier than the other. One is flamed consistent grain and heavier than the other almost Quilted pattern. The heavier one is going on a body 1/16th thinner than the other body. the thicker gets the almost quilted neck that is less dense.
What are your thoughts you that have had many mando's under your belt? Very slightly thinner body with a more dense neck vs slightly deeper body with a lighter neck?
I myself am very curious and can swap them but the original setting matches the rib patterns.
My gut feels the more dense neck will transfer more vibrations and have more sustain.
The lighter neck will be more warm but less punch. I know this opens a can of worms that right away jumps to tops back etc...I got that down......I'm asking NECK wood responses.
Keith Newell

[Stephen Perry]

Keith, I have a lot to do today and my coffee is just about drunk up, but I'm going to go ahead and pour another cup. Would be more fun to hop on the bike and ride out for afternoon tea, but I think I would need a warp drive motorcycle (something my son and I have been talking about) to make it in time. Of course, the issue being balancing, because the motorcycle doesn't actually go anywhere, space and time just warp around it until I'm there. Probably does horrible things to the road surface.

So anyway, I'm not going to answer your inquiry until I think it through on caffeine and amphetamines. Well. Maybe I'll stick to the caffeine for now.

Two aspects come to mind immediately. Well there's another. I better stop while I am ahead. But before we start, all my work on instruments with necks indicates that necks are extremely important to the final response/tone/sound whatever. More than seems reasonable. Sort of like with pianos, where the felt that stops the keys at the end of a stroke is very important to the sound of the piano because the kinetic energy of the key is absorbed and transmitted to the body of the piano through that felt, and thence into the soundboard and back into the strings and then back into the body and soundboard. A nice reincarnation cycle.

Let's start with B zero. See, e.g., http://www.catgutacoustical.org/research/articles/modetune/ and more specific http://www.catgutacoustical.org/research/articles/modetune/modechrt.html Now don't get me started on this whole concept of mode tuning being everything and so on. The B zero thing works for me, so I'm going with it. Some of the other stuff gets my mind into some kind of Klein bottle universe where I keep looking back at myself. Anyway. Here's what the chart says about B zero (I write it out because of armpit jokes with "B0"):

"First bending of neck and slight bending of body. Nodes across lower bout, at body/neck joint and at nut. A non-radiating mode."

Hutchins matched it to A0 or W, Spears matches it to the "Zaltone" or singing tone, and I took a bunch of fiddles and used clay to weight the scrolls or otherwise worked on the fingerboard/neck combo until I thought I had the response where it was best (clear tone, live in the hands, least noise), and I think Spears is right, although singing into the violin is a bit odd. Regardless, while this match is important, there were other close matches on either side, with the resonance or whatever of the system being more effective at some points that others. I should have figured the frequencies and seen whether they were regular and how they related to all the other parameters like a real scientist, but the N was low and this is expensive work in terms of time.

So what does this have to do with mandolins? Well, during the or one of the sessions with Roscoe Morgan (the originator of the "mandovoodoo" term) -- by the way, he is a FINE musician and mandolinist -- I tried matching B zero on a mandolin, and he really liked it. So did I. I attempted to figure out a reasonable way to do this as a routine step, but the mass needed on the headstock was simply too much. Big lump of clay. A sheet of metal glued on might do it, but a couple of golf weights won't. Of course, a 2 lb tailpiece would.

But stepping away from matching and into my earlier half-baked observation that the B zero resonance changes line up intermittently and possibly with regular intervals with the resonances of the body suggests to me that when one changes the mass or stiffness or whatever of the neck one may be changing how friendly the neck-body system is to acoustic parameters. Which I think was the original query. And the relationship of B zero to various A0 W etc resonances is an aspect of that.

On the operative end of things, I would, were I engaged in matching necks to bodies on mandolins, which I am not (only on violins - at this point), then I would be stringing in the white, adding clay or other weight to see what happens. To see hear ("Listen, smell that" - 10 Internets to those who recognize the quote) whether the instrument likes where the resonance is at now, or whether it might be happier elsewhere. If it likes a bit of mass more than where it is, I would probably take a bit off the neck to reduce stiffness.

The other part of the application I am thinking is that given two necked instruments to compare, which I think is what we are doing, or maybe 4 instruments, we have body 1 & body 2 which are the same, but not really because of the thinness, and neck 1 and neck 2 (wish this caffeine would kick in) so there are lots of permutations. Anyway, we have to assume some consistency in this comparison. So something to think about is whether the mandolins will have a B zero that runs up against a nice resonance elsewhere or not.

So back to the question. Were I building these things I would dry fit the necks on each body, listen to the singing tone of the box, see the comparison to B zero, and guess at which one lines up most nicely with the resonances. I don't know that the system lends itself to simple comparisons. My gut is thinner body with - well, there I go, thought experiment out of control, with too many variables.

Anyway, this is how I would start into thinking about it. I have dry fit necks and strung up. I have put on different tops on violins with glue stick and strung up. Hey, it holds for a little while!!!!

Where are we? Oh, the second point. Wood resonance itself. There's a really key variable. I had a chat with a reasonably well known feller who makes banjos and designs production instruments etc. He indicated that experiments at XYZ big guitar company that has changed hands and morphed now showed clearly that wood with lots of resonance made a much better neck. So I would be looking at the resonance of the wood, too. How that plays into selecting one neck over another, I don't know. but worth thinking about. I keep thinking I should get some a) sunken maple from up north, b) cooked maple, c) deep cryo treat some maple, d) [insert some other half-baked concept] for violin necks.

OK. Now I will move on to three. http://www.lafavre.us/tuning-marimba.htm Don't yell at me!! I don't really do all this to everything, but the general way of thinking, if not application, works on a few of the pieces of wood in an instrument to make that piece happier (see, I'm going to get yelled at already) and improve the sound. A maker therefore (in my observation) is best served by making sure that piece of wood X is acting as much like piece of wood Y in the form it will be in to allow comparison. On necks, I just use four points, one on each side at the heel-shaft junction, and two on the sides near the nut. I get those points matching in tap pitch (see, I will get yelled at for sure - you know what I mean, tap the point and compare to the other points, it isn't rocket science, but there are lots of pitches excited and I'm looking for the one that varies with a light scrape). Then the neck is happier. And the instrument is happier.

So those are variables I would be attempting to normalize in comparing two necks. As to the original thought experiment, I don't know. However, I tend to put the neck that looks best on an instrument and then do all the other stuff I can to get it working!!!

Have fun, and if you want more discussion, Keith, we can chat sometime via gchat or skype or something. We have actually met at some point, in the distant past.

Peace guys, off to write legal stuff and get the weed wacker working.

Oh, and the four point thing is really cool to do on bridges. I do the -- how do I describe? Look directly down to the top so you just see the planform view of the bridge. Eight areas. The four edge segments that are north and south of the posts on the saddle. The four edge segments on the base that are outboard of the posts. That's an easy thing to mess with. Light scrape with a razor blade or pocket knife or piece of broken obsidian (depending on one's technological setting).

[peter.coombe]

Well I know little about violins, but there is a "neck/body" mode on a mandolin. One node is close to the nut and if you hold it at the nut and tap at the neck join you will hear it. My experience is if the frequency of this mode matches the main air mode (A0) then the mandolin will have a huge sustain. The difficulty is in adjusting the frequency. There is not a lot you can do about it since there is limit on how much you can shave the neck down. Apart from that the only other thing I have noticed about necks is that if the neck is lighter then the mandolin seems to be a bit louder and more responsive. Personally I don't think the neck has a huge impact on the sound of mandolins, so to answer the original question, I think you are probably exaggerating the influence of the neck. I would not worry about it. If the mandolin with the heavy neck turns out to be less responsive, that is the laws of physics working.

[multidon]

Say Stephen, I was sure I read on that other thread that you don't lecture at the drop of a hat! ;)

[sunburst]

I know that Dave Cohen has started doing some research into the effects of neck stiffness and mass. From one (or so) brief conversations with him, I gathered that necks in the normal range of mass don't have much effect on the sound or the measurable behavior of the mandolin if they weigh a few grams more or less. Dave has a mandolin with a hollow tube-constructed neck of carbon fiber. That's about as stiff and light as a neck can get with relatively normal technology. His conclusion, as I understand it: louder but harsh sounding and not what he considered an improvement.
It should be possible (perhaps) to adjust neck stiffness and mass to bring the whole body bending mode closer in frequency to the lower frequency body modes, and that should increase coupling and thereby increase lower frequency response (bass response) in the mandolin.
OK, I'm already in over my head here, so I'll leave it there before I get even farther into stuff I don't understand.

[Stephen Perry]

I really think other things play more into making the instrument what we like than the B zero match or whatever!

The highly resonant wood is what gets me thinking.

Per earlier comment, caffeine fueled blather isn't lecturing!

I went ahead and started designing a mandolin bridge that should allow the adjustments I'm used to on violin bridges. Proves difficult in the stretched out mandolin bridge world!! If I come up with a suitable outline, I'll drill and shape a piece of maple and then slab it at a range of thicknesses. Will give different mass out of the same wood.