. It also begs the question: If the treatments work to some extent, are they permanent and is the effect cumulative?
Assuming the same effects are occurring as those which occur during regular playing time, they should be cumulative and permanent.
Here's what I noticed between my 2 dreadnoughts:
BOTH of 'em started to open up after about 200 hours of playing.
The D25 had a "Big Moment" I never would have believed in if I hadn't been there playing it when it happened.
Literally felt the neck vibrating in my hand and was thinking to myself "Wow it's never sounded so full, yet airy at the same time, before" and thinking that somehow the neck vibration was feeding back into the top, either through the heelblock or the fretboard extension or both in a kind of acoustic feedback loop.
With the D40 it was a long slow gradual improvement.
Because I was underwhelmed with the D40's volume when it was new, I devised a test to compare 'em that I could repeat at intervals:
I just strike a full 6-string harmonic at the 12th fret using as much force as I can without any buzz or muted strings. It's a little tricky and I actually do it with bare fingers in a clawhammer technique so I can get 'em all to sound simultaneously and equal volume.
I figured that's getting the max out of the soundbox. Then holding it carefully by the endpin and the heel so the body doesn't get muted by contact, I bring the soundhole up close to my ear and count seconds until the very last of the decaying overtones becomes inaudible.
So it's basically a "decay time" test.
The D25 was already at way past the 250 hours mark when I first tried it and I forget where the D40 was but it definitely was pretty young like I think under 100 hours.
It didn't get as much play time as the D25 for the first 3 or 4 years. I didn't track time "religiously" but knew in any given week if I spent an hour with one of 'em it equated to at last 45 minutes of actual playing and just kept rough track.
Anyway, the D40 was WAY quicker to decay than the D25, which could be attributed to the natural difference between arch and flatbacks, but it also wasn't much louder than the F65ce which has a significantly smaller soundbox.
I forget the exact times but something like 13 seconds for the D25 to 7 seconds to the D40 seem to be the figures? ( I kept notes in the D25's case, it's at home)
A couple of years later after I'd been dedicating bonding time to the '40 it was up by a couple of seconds.
About 4 or 5 years ago when it was finally getting into that 200 hour territory I realized one night "Wow this thing has finally found its voice". I think it was up to 11 seconds that night I think the D25 was up to 15 by then.
But I haven't done the test between all 3 of 'em since then.
Both D's were always strung with the same strings that had similar amounts of playing time when I first tested, and usually tested right after string changes, to eliminate that variable.
Curiously the F65ce seems to have gained the least over time, as if it was already near its peak when it was built.
On the other hand I never tracked the time on that one like I did the D25 and the '40, and only just started really giving it most of my playing time in the last year or so. It might not even be at 200 hours yet, the way my playing has fallen off.
For quality of build and materials it was in the D55 class, just a different body type.
Anyway, my suggestion would be try the test and start tracking actual playing hours on it and see if it evolves.
Or even do the test, give it another treatment, and see if it actually picks up time to complete decay.
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