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Mystery of the Weak Gibson ... Solved

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Feb 28, 2020 - 8:58:49 AM
5200 posts since 9/16/2004

... the Vega kicked the Gibson's butt, time and time again. Actually, I should I say, most of the time.

That was the mystery, It was good, then it wasn't. Maybe the Gibson is extra sensitive to the temperatures and humidity. Comparing the Gibson's sound to the daily hygrometer and temp gauges lead nowhere.

Replace the head and strings. Voila! The Gibson sounded like it ought to. The next day, it sounded muted. It wasn't chiming like it did the day before. Tightening the head brought most of it's sound back. The same thing the following day. It was in a downward spiral.

Back apart, and another new head and strings. By the end of the week, it was a repeat of the previous head and string change.

Back apart. Check list:
Rim to neck fit ... check
Tone ring to rim fit... check
Inspect Presto tailpiece for cracks... check

Was just bad wood? The experts offered a variety of possible solutions, including the ever ubiquitous bridge change (it was already on it eighth or ninth bridge change.)

Clue:
From day one, the drum (head) tone was slightly different from front to back, side to side, despite equal tension on each of the twenty-four hooks. The original tension hoop wasn't perfectly round or flat. But I've seen worse on other banjos, and they sounded fine

Back apart for another head and string replacement, but this time with a new Prucha tension hoop.

That was the fix.  I was ready to change every part of this banjo, piece by piece.  As it turned out, it didn't need a several hundred dollar rim, a more expensive tone ring, or a much more expensive neck... no, it turned out to be a relatively low cost tension hoop. 

In retrospect, it made sense that the head replacements worked fine until the mylar relaxed. Flathead tone rings seem to require a more precise tension hoop than other tone ring types.  Live and learn.

Finally, I want to thank all who contributed to helping me find the solution to this banjo mystery.

...as the current ad jingle goes, "not quite right, isn't good enough."


 

Feb 28, 2020 - 2:59:37 PM

12709 posts since 6/29/2005

Interesting—what do you think was different about the tension hoop that made such a big difference?

Feb 29, 2020 - 7:34:37 AM

5200 posts since 9/16/2004

quote:
Originally posted by Ken LeVan

Interesting—what do you think was different about the tension hoop that made such a big difference?


All I know is the results, and aside from the obvious,  I can only guess at the reason for the results.

The obvious part was there was a minor distortion of the bottom side of the tension hoop.   It was out about 3/32" on a surface plate.  Since I'd seen much worst on well performing banjos, I didn't regard it as a serious problem.  I thought the stretch in the mylar would easily compensate for that irregularity.

Here's the goofy part;  I'd R&R the head and the banjo would come alive.  Then, by the next day, the chimes were weaker and the volume had dropped off.  But everyone knows that mylar stretches and retightening is normal.  The problem was, the banjo never sounded as good as it did that first day.  After a week or so, the tap tones around the head became irregular... like a flaw in the mylar. Since I bought several heads at a time, I mistakenly believed that this was a bad batch of heads. 

The more I write, the dumber I sound.  It's the classic sign of insanity, repeating the same thing over and over again, expecting a different result. 

Apparently tension hoops need to be completely flat... at least when applied to flathead tonerings

Feb 29, 2020 - 1:14:42 PM

12709 posts since 6/29/2005

Quite a mystery.  How much of the circumference of the tension hoop was up 3/32"?   Was it  just a short blip where the tension hoop didn't make contact with the flesh hoop?

How tight did you have the head tightened?

Mar 1, 2020 - 7:21:34 AM

5200 posts since 9/16/2004

quote:
Originally posted by Ken LeVan

Quite a mystery.  How much of the circumference of the tension hoop was up 3/32"?   Was it  just a short blip where the tension hoop didn't make contact with the flesh hoop?

How tight did you have the head tightened?


The tension hoop had a gentle arc front front to back when viewed on a granite surface plate.

The new heads were tuned to G - A as measured with an audio tuner.

As I've already said, after a few days the tap tones became flat or "thumpy" up towards the neck.  A more accomplished player / builder, probably would have realized the problem from the beginning.

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