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You know what I mean. Strum a full chord and hold it and then with the palm or full spread out hand touch the guitar top under the bridge in the lower bout and remove your hand and repeat and you can hear that wha wha sort of effect right?

Lately I've been giving this some thought. I've always considered this to be a sign of a responsive guitar, at least one of the signs. About a year ago I acquired, under unique and special circumstances, a nice luthier built dred with Sitka top and BRW back and sides. Basically it's a D-35 copy and was sold as the luthiers 'traditional series' guitars. It's like a really good luthier built a Martin guitar. So it sounds way better than or in some cases perhaps just as good as the best Martin guitars out there of this breed.

Now, back on point, this Dred sounds absolutely fantastic. A big full sound that sounds equally good strumming and picking with a hard flat pick or playing with the fingers only. When I do the touch test on this guitar there is hardly a detectable woomp or wha sound.

So I guess it begs the question, is this test meaningful in any way? If it is then what is the meaning? If that wha sound is pronounced then does it actually perhaps mean that the guitar was under built?

Or perhaps we are just talking about different end goals in the design of the guitar. The dread was built to be loud and bold for example so the top is stiffer.

Like I said it got me to thinking...

My guess is that the bracing/top is stiffer and thus responds differently to being touched.

There's a guitar for sale in my shop with a ludicrously thin top. Even with one note being played and the top being touched it immediately kills the vibration. There's a McPherson in my shop too, top being touched has little to no effect on the tone unless you lay your hand on the whole top behind the bridge. Different build styles on both. The McPherson is ludicrously stiff built with laminated braces and a heavy radius to the top with a thick bridge.

Hmmm I guess I thought this would have generated more discussion here but it's not. It seems to me that this trait has a lot to say about guitars but I just don't know what it is. All my guitars are very responsive to this touch test.

I am interested. I just don't have anything useful to add. I was under the same impression, that the more difference there is when you damp it out with your hand, the more responsive the soundboard must be. Maybe all this tells us is that responsiveness and pleasing tone are two separate things.

Same as Dennis, interested but nothing i can contribute really. I have worked on guitars I thought were overbuilt but that also sounded good. Now that you mentioned it I will try damping the lower bout with my hand when I'm evaluating them.

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Steve Smith
"Music is what feelings sound like"

This is interesting to me as well. My Jumbo guitars do this just by rocking your strumming arm toward and away from the body after hitting a chord. In one respect this makes me anxious, but these guitars also sound much more rich than a production instrument that does not respond as much to this same action.

If the world were a perfect place, I would like to get the same sound I have now without having the top interference being as much of an issue. Of course, I think we all have to agree that damping the top in any way "has to" affect the sound, but the extent to which it does could be a fascinating study.

Ultimately, I think we have to be talking about the same ol' mass and stiffness. I wonder which one contributes more to the interference of an arm or hand on the top? Imho, placing my hand on the top behind the bridge is not a factor. No player would ever do that while playing. But, the amount and consistency of contact with their arm while strumming... now that is a key to a guitar's playability. I've had very good players play my jumbo models and not notice it at all. I suspect this is because they are using their wrist more than their arm while playing (which I understand as a better technique). Then some lesser players (like me) do notice the effect as the guitar is strummed, because my arm moves a decent amount and that changes that contact with that body enough to hear if you are listening for it.

I would speculate that when you're placing your hands like that you're inhibiting one of the main modes, either cross or long dipole, which would explain why it's a wha sound, as it's the mids....

Yeah, I think what I am getting at is... Is this some sort of test to show that a guitar is responsive or not, or even underbraced or the top is too thin and so on. I Know it's subjective, if the guitar sounds good to you then who cares, kind of thing. And then again in comparison to this dred that I have which is the very best dred I've ever played (and again I do realize that it is my conception of what the best sounbding dred is), it is one of those things that gets my head thinking differently again.

It could be the bracing and top thickness are heavier in the middle and thinned out at the edges, rather than consistent like we would expect. Maybe try the same test, but instead of touching the center of the lower bought, rock your playing arm toward and away from the top and see if you get that similar tone change you are used to hearing on the typical responsive guitar.

I think it was David Newton who said " the Sound is in the Wood". I have taken that to heart over the years and make my tops a little thicker and my braces a little lighter. I use my fingerstips to feel for the responsiveness of the top, but I no longer try to make the top excessively responsive under them. I don't believe I have perfected this technique, and I can understand why Torres said it was not something he could easily pass on.
I think you have reached that point where you are questioning if responsiveness is the final measure of a great guitar, and will be going beyond that.

Yeah that's more in line with what I am thinking. I have found that my deflection method actaully matches up almost spot on with Trevor's acoustic testing for determining the thickness of the top. So I've been doing it this way for a long time without even realizing it. And when I build with these methods the top is VERY sensitive to touch.

I also have Hans's book on building Larson type guitars and those tops are hugely thick and the bracing is laminated. So I'm looking forward to some day when I have time to build one like that. I did play a vintage Larson once and the thing sounded great!

I still want to get that book. Feel like I could learn a lot from it.

With this discussion I was thinking that this whole thing might be a good way to sort of test where a guitar is responding and where it isn't. But with the variety of guitar build styles and techniques I'm not sure there's any real correlation to build style and tone.

I've started to notice with the massive variety of guitars you see in repair work that a super responsive top doesn't always equal the same level of tone. Good example is Guild guitars in the 70s. Heavy build with heavy bracing and thick tops. But the 12 strings of that era to my ears at least tend to sound fantastic and powerful.

Flip to the Gibson small bodies of the late 20s and early 30s. Unbelievably thin bracing and thin tops on some models. And they also sound fantastic. I had a Kel Kroydon in the shop recently for a bridge reglue and that thing barely weighed 2 pounds. Cheap guitar for the time period but it sounded fantastic. Also had a 38 J35 on the bench last year. It was one of the 3 tone bar versions (overbraced by some standards) and the bracing was a bit tall by other standards. But that thing had a tone that made you just want to keep playing it. Good guitar too just a different sound but not bad in any way.

All that to say, I think it's just evidence that there's more than one way to make a guitar. Is there a wrong way? Maybe maybe not. I think as long as your end result is that your guitar sounds good to yours or someone else ears then that's really what's important.