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I created the following situation just so I would have the opportunity to do some real comparative tapping and tuning:



What we have here is (left to right)

(1) Romanillos/Bream/GAL plan plantilla and bracing, WRC top, Lutz bracing
(2) same plan, Lutz top from Shane, Lutz bracing
(3) ditto
(4) Romanillos plantilla, Torres SE 114 bracing (GAL/Elliot plan), Lutz top, Lutz bracing.

I went with the Romanillos plantilla for the Torres bracing because this batch is getting built in the Bogdanovich-style form, so no real opportunity for a small change in plantilla.

At this point I've done the basic brace shaping and some cleanup, and I'm trying to figure out what to do next. Of the 4 tops, I like the WRC Romanillos top and the Torrez top the best. The WRC top has a really musical tap note, and I'm not sure I want to mess with it unless I find out that it's tap note corresponds to a string note (?).

The two spruce Romanillos tops sound remarkably alike (reassuring). Their tap note sustains well but does not have the musical quality of the WRC top - more of a thunk. I think the main top note is lower than the WRC, but it seems to have more harmonic activity which makes it hard to get a sense if the main notes are highler or lower than the WRC.

The Torres top's main resonance is lower. This is surprising, as the top is very thick still compared to the SE 114 plan, which has the top taken all the way down to 1.2 - 1.4 mm around the lower bout perimeter. My top is at a fairly uniform 2.2 to 2.3 mm, and it still feels fairly stiff across the lower bout, but the tap note is way down there already.

Here's another picture of Romanillos and Torres side by side. I'm going to see what I can do with my stroboflip in terms of identifying notes, but I don't have a compressor and may have trouble.



Any suggestions on how to proceed are more than welcome.

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Jim Kirby
kirby@udel.edu

I'm interested in the analysis of free plate taps. I'm looking at the spectrum frequencies and how they decay. My goal is to learn how to put numbers to what is listened to while tap tunning. It would be interesting to see if the numbers can show what you hear as



All I need is a wav file of what the ear hears.

Ummm, build the backs and sides??

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Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

Why, Thanks Howard! I was so confused for a second there.

I guess I'm wondering how you go about "adjusting" classical soundboards. I've seen more info on steel strings, but not so much on classical guitars. I've been getting happier with mine (mainly as a result of making them lighter and lighter), but they don't have the sort of treble sparkle that you could hope for. I've left these tops a little tighter feeling than my last few, to give myself more options to play with, but I don't know what a good opening move in the game is.

p.s. I could play a great deal with the two "identical" spruce Romanillos tops, taking them to different places in terms of overall stiffness.
I don't want to mess too much with the WRC top, as it is for someone else. The Torres top is fair game too.

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Jim Kirby
kirby@udel.edu

Jim,
This seems like a lot of work I know but you might consider making a building a very basic guitar (no binding, maybe no finish, etc..) with a removable neck that you can put tops on and off at will. Then build the Torres top to the plan, then one not to the plan. The learning potential of this approach is great as the variable becomes just the top, not the whole box.
Also this is obviously much quicker than building a bunch of guitars.
One thing I can tell you is that just because a thin top doesn't have much of a musical tap tone doesn't mean it can't sound great. On the thin tops when you tap them the edges of the bouts just flap around as they're unsupported, creating a weak tap tone. This of course all changes when it's mounted on a box.
good luck and keep us posted

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Jim Watts
http://jameswattsguitars.com

Can you record some tap sounds wo we can hear?

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Here is what a Parlor Guitar is for!
http://www.youtube.com/watch?v=oEa8PkjO6_I

I agree with Howard !
The top is only one part of the equation!

Couple these tops with B & S !
Then before you finish them -do a fine tuning -by either thinning or
brace shaping!
Then it will be even harder to figure which one you like best!!!
WHY- because the B & S added their own flavor to the sound.

Do one at a time and learn all you can from it.
Then change things only slightly-write everything down(keep a log of all braces and thicknesses etc.)
all work- then decide which one you like!
Or like to hear as a guitar!
Mike

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Mike Collins

I just put strings on my pseudo SE 114 Torres - the top is Lutz with the center at 2.5mm and while it does not sound very deep or warm (not to be expected anyway being so young and thick) i can tell you the trebles are *fabulous*. Strong, instant and fast response, harmonics, all the goodies.

I suppose I will get it down to 2.4/2.3 after clean sanding the top and that will mellow things a bit.

Here are some pics of it:
http://s299.photobucket.com/albums/mm30 ... mview=grid

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Build log

Alex - That's great to hear. I've been told that the Romanillos design would just inherently lead to better trebles than I have been finding so far, too. I can't wait to hear. I just bent the sides for the guitar with the WRC top this afternoon.

I couldn't see your pictures, but that could be me. My computer has been funky lately.

Jim

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Jim Kirby
kirby@udel.edu

Thanks Mike. Robbie O'Brien also sent me a separate email and suggested that free plate tapping for classical guitars is an elusive pursuit, because they change a lot when glued to the sides. Guess I'll forge ahead, and see where it leads.

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Jim Kirby
kirby@udel.edu

Actually my bracing is Torres with an open harmonic (but the outer fan braces do not extend in the upper bout). I think the important factors that help getting that nice singing treble are mainly the small shape of the guitar and the use of quality spruce, and the thicker center from hole to bridge - while the arrangement of the fan braces is less important.

I wish I knew what was the actual thickness of SE 114 when it was new. I guess it suffices one repair guy who is zealous about removing dings and nail marks and bang, the top can get thinned from 2mm down to 1.5 with little work. That does not change the general character of the instrument, but it surely dulls the treble edge.

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Build log

Sadly, knowing the wood species of the various tops is not as much help as you might think. Every species shows a lot of variation in density and MOE along and across the grain, and there's a lot of overlap between species. I have a Red Spruce top that has the same density and MOE numbers as a Western Red Cedar top, and those are supposed to be about as different as you can get. It is interesting to note, though, that the lengthwise MOE pretty well tracks the density for all of the soft woods I've tested. If you know the density of the top you can predict the lengthwise stiffness within 10% or so for a given thickness. Density is fairly easy to measure for a top half blank.

It seems to me that treble response has a lot to do with the balance between the bracing and the top stiffness. I look at that using Chladni patterns, but you can get some of the same information from tap tones, and from flexing the top by hand. The Chladni data is a bit easier to teach, IMO, since it takes a while to get the 'feel' for flexing or tapping.

Robbie's right; you don't have as much to work with on a classical top. They can be very sensitive to small changes in bracing; a couple of shavings too many in the wrong place and you can be in trouble. Work slowly, and check often.

It seems likely that a thicker top will tend to give a somewhat stronger treble response, particularly if the wood has low density. At any rate, a low density top will tend to be lighter in weight at a given stiffness, and that's usually a good thing on a classical, where you have only a limited amount of power to work with, and very little in the high frequency range.

I'm a newbie and this is a very controversial topic and I know pea soup about classical guitars...so please take my contribution with a pile of salt.

As I understand him, Somogyi claims that treble responsiveness is determined by the responsiveness of the edges of the soundboard, while bass response is determined more by the center of the soundboard.

"Activation of the perimeter results in treble activity. This makes perfect sense, as the center of the soundboard is the most yielding part and is thus able to support high amplitude, low frequency activity. The edge, being more rigid, is the logical place for high frequency, low amplitude activity to occur."

Quoting from: http://www.esomogyi.com/principles.html

Therefore, I would think, if you want a stronger treble response, build lighter at the edges.

Like I said, I'm a newbie...just thought I'd offer it as another perspective.

Another request for you to record some taps so we can hear them.

For classicals (I also do it for my steel strings) I don't finish the top until after I have glued on the bridge, strung it up and played it for a couple of weeks, I then tune the soundboard edges to get the response I'm after. Only then do I finish the top.

Colin

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

Colin,

Based on your comments and what others have said, this seems like the way to go. I'm so much happier with the idea of accidentally wrecking a free plate than wrecking a finished guitar, though. How did you first get an idea of where to start making adjustments first?
(I read a description by Tom Blackshear once, of going inside and taking a little off of this brace here, and that brace there, and it sounded downright mystical. How do you know where to start?)

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Jim Kirby
kirby@udel.edu

Great info....and great question Jim...........
big John

@Tom B., that was a bit mystical for me too, especially since i spent a lot of time trying to improve a guitar by shaving the fan braces. I must have missed all the sweetspots, or maybe it was completely unbalanced to start with, that i never noticed huge improvements or degrading in tone. It seemed to be all very slow, subtle and gradual, never a revolution.

But back on the question of tuning the completed guitar, I would say that once the bridge is on, your options become limited, and there are roughly 3 main areas:

1. between rosette and bridge, and a little behind it
2. outer zones left and right of the bridge
3. outer zone at the tail

Since (1) is sort of a spine of the top you try to avoid it at first, especially if you are reasonably happy with the sound.

According to Al Carruth (2) will bring out trebles and (3) will round/warm up the tone. But if the top is already too thin, I could not tell if it works still like that. In any case, if you do both, just make sure you do not overlap sand the two zones and get double thinning at 4:30 and 7:30h on the lower bout circle.

If the tone is unquestionably tight to start with, I guess you must remove a layer from the entire top. I know I will do that considering the 2.6mm thick Lutz top I work now. I like the strong trebles plus good clarity and power it has so i won't remove too much at all though.

I would build two guitars in parallel. Lutz with both Torres and Romanillos bracing. Since volume wise the two fans are very similar, I would graduate the tops the same. Leave aside the other Romanillos Lutz, an use the cedar as shop wall deco (:D) Build the third Romanillos Lutz considering experience gain from the first two.

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Build log

Alex, the cedar one is the one that already has a future owner, so of course it's getting done first - it's in the form now, waiting for lining blocks to get cut.

Thanks for your suggestions. I'll meditate on them for a while. I will be doing one Lutz Romanillos and the Lutz Torres next - I have more time to spend with them.

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Jim Kirby
kirby@udel.edu

Interesting comparision Jim.

I've built a WRC honduran rosewood and a Spruce EIR with essentially the same geometry. I tapped along the way, (however I have to admit I'm sort-of in the Cumpiano school on tap tuning) and had a similar experience, the WRC always had more ring and was more defined. When finished, the WRC was noteably louder and there were no particular notes that dropped off, also very nice tone although a little more on the nasal side than the spruce. I built another WRC-honduran, also same geometry, same result very similar sound. That being said, I still much prefer spruce-EIR, I love the appearance and tradition of spruce on classicals.

I use the spruce-EIR when I play, although I often find myself reaching for the WRC-HRW, I like the volume.

I'm building another spruce-EIR now, I'm hoping it ends up sounding as vibrant as the WRC-HRW combination.

I'll be intereted to see how your final comparison turns out.

Jim, there is no accounting for taste in tops. It's not your fault that your client's taste is suspect! You build what they want, right?

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

Well, at the course last summer, Jose' Romanillos inspected the tops as we worked them down to the specified thicknesses (2.5mm above the lower harmonic bar, and ranging from 2.2-2.5 at the bridge location and 2.2-1.8 around the perimeter). Unbraced, he wanted to hear a dull thud when tapped. I don't think I saw him tap test anything after the tops were braced. This was an affirming experience for me as I've never found tap tones particularly useful. My experience relates far more to the mass and relative flexibilty of the top in the hands as you work it.
I think as long as a braced top is well worked thickness wise (I prefer spruce, it's what I'm experienced with but if cedar is your choice go with it) flexible and of good quality, well quartered, stiff and hard (the more aged the better here) you'll get good results regardless of your particular bracing pattern. Witness all the fine instruments which differ from one another.
I think major differences can be had from working with the overall mass of the back and sides as well as the structure of things like neck blocks and end blocks etc. Building on your own experience is key here........