Banjo Bridges by Bart
|I got busy with my soundlevel meter one afternoon to get an idea how a
bunch of different bridges I had made would behave. I took the readings in
my living room, not in any kind of acoustic lab room or anything like it,
so I had to figure a way I did them all the same to make sure I would come
up with [hopefully] unbiased numbers. Keep in mind also, the numbers are
all relative: they are as they applied *that* afternoon to *my* fingers
playing *my* banjos. Here's what I did:
1) Digital sound level meter set for A Scale weighting, Fast sampling, all numbers in dBA
2) "Facing" sound volume - the meter pointed directly at the banjo at a 1 meter (=3 ft + 1 beer) distance
3) "Away" sound volume - the meter pointed away from the banjo into a large open concept kitchen, also @ 1 meter. This measurement is really the most important number as it determines how a banjo's sound will project/carry and this is how your audience hears your banjo, check the last table on this page to see what I mean
4) "B2E" = banjo-to-ear distance. The meter pointed horizontally towards the player's ear, 50 cm (about 20") away from the center of the banjo's head. It should really have been 40 cm but the tripod the meter was mounted on didn't want to get that close to my chair. The point of this exersize was to show how many decibels the banjo shoots directly into the player's ears.
5) Peaks and Averages measured over a 60 second period (includes grab-the-banjo and push the start button time)
6) Wearing finger picks while playing 3 finger style down the neck, up the neck (both X and Y positions), digging into the strings pretty good as if playing a break
7) Patient 1: Fender Leo, equiped with light gauge strings, ugly see-thru clear head - decent banjo, decent volume
8) Patient 2: Framus Nashville, fyberskin head, medium gauge strings, (heavy gauge 4th string), Saga neck - lower end of the scale in the banjo world, tends to get drowned out in jam sessions (although a bit of tinkering will make a huge difference...)
9) Patient 3: Ode D, thin head, light gauge strings - kick-butt top of the line banjo
10) Patient 4: Stelling Bellflower, light gauge strings, a powerhouse banjo
Here's the "map" for the bridges
Fender Leo - dBA
Framus Nashville - dBA
The numbers for this Framus increased dramatically after I installed a custom hardwood rim in it, it now sounds every bit as loud & proud as any decent mastertone/clone banjo.
Ode, Model D - dBA
It's hard to come up with any kind of interpretation of these numbers except that a change up/down of 3 dBA means twice or half the volume. The Stelling banjo won the overall decibel race but it was very close volume wise, to the Ode as most banjos of this caliber would be. A couple of things are clear though: you can improve on volume by choosing something other than a no-frill standard bridge that comes with most banjos. In particular, the way the sound carries at a jam distance is of great of interest. The charts also show that bridges produce different volume levels on different banjos. Keep in mind too that these charts only show volume, not tone. In fact, louder does not automatically mean better tone although the more volume available, the more tone and dynamics you have available to exploit as a musician. My personal overall favourite for tone and clarity was the XEA3. Well, that afternoon anyways...
Just to be sure: these numbers cannot be compared to any other numbers unless they are measured during the same picking session, using the same banjo(s) played by the same musician else you'll come up with incorrect and/or unfair numbers.
In case you're concerned about your hearing and the high number of decibels some banjos produce - put your banjo down for a minute and click here.
"Away" volume continued
This afternoon (Feb 2005) I stumbled across the perfect example to illustrate the importance of the "away" volume. Someone brought a Gibson RB-3 to see if I could squeeze out some more horse power. It was a marvelous instrument and everything was set up real nice and tight. The banjo was totally responsive and sounding great, it was equiped with an excellent after-market bridge (0.656" or 21/32" height). I picked my way through a handful of different bridges and the mystery topped teak bridge (5/8" - yup, that's lower than the original bridge) put this banjo right in the magic zone - totally crisp and clear all the way up and down the neck with perfect intonation. The sound level meter showed identical volume levels for both the original bridge and this new one. Yet, the teak/mystery jobbie made this banjo sound decidedly "bigger," the banjo barked big time. Spinning the meter around, having it point away from the banjo clearly illustrated why and how:
Like I said, the "away" volume level is hugely important as it is shows how well a banjo projects its sound - the way your audience hears it. In this case the the "away" volume was only 1 dBA less (for both peak & average) than the "facing" volume. Yup, this RB-3 rocked!
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