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Mar 23, 2024 - 1:24:53 PM
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4391 posts since 12/3/2008

David Politzer is a professor of theoretical physics at Caltech. Politzer is a winner of the Nobel Prize for physics. Politzer, who is a banjo player, has done extensive research into the physics of the banjo. In his recently published article, Inharmonic Partials and Banjo Ring, Politzer refers numerous times to the Banjo Bolster - an overtone remover/tonal enhancer - calling it an “insanely clever device”.

“Banjo sound is rich in inharmonic partials,” writes Politzer, “i.e., strong frequency components of a plucked note that are not integer multiples of the pitch frequency.”

In other words, the sound of a banjo contains certain frequencies (overtones) that are actually out of tune with the fundamental frequency of any note being played. If my interpretation is correct, it would seem that the banjo has inherent characteristics that result in the instrument fighting itself, in attempting to achieve a fully harmonious sound.

Tom Collins puts it this way in his YouTube video The Banjo Bolster: A Gamechanger: “So let's frame the problem that we're all trying to solve by cramming stuff into the back of our banjos. The banjo is a wild cantankerous beast. And, oftentimes it sounds a little too wild for the context that we're playing it in. Now, we love these overtones. These overtones are what makes the banjo so rich and interesting to listen to. But at the same time these overtones can make the banjo seem unfocused and it can be hard to hear that clear, fundamental pitch that we want to hear.”

“From time immemorial, banjo players have been looking around their environment to try to find to find the next thing to stuff inside their banjo to try to make it sound just a little bit better,” Tom says. “I think I have the answer to all of our banjo prayers today. It’s called the Banjo Bolster.”

Along with a host of others, I, too, am enthusiastic about the Banjo Bolster. Using them in all of my seven banjos, I find that using them is the fastest, most efficient, user-friendly, and unique approach I've ever come across to revive and beautify their sound, to fine-tune and enhance their expressive qualities. Through the many ways I can configure the device - including using two per banjo to go around the full rim circumference - the bolster allows me to achieve the sounds I’ve been chasing for 60+ years. I agree with Professor David Politzer: the Banjo Bolster is an insanely clever device!

Mar 24, 2024 - 5:38:07 AM
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3371 posts since 9/5/2006

Heck yeah, that out of tune sound has been one of the great attractions for me since day one. It is not with the primary notes, unless you are playing a D7 chord in G tuning or a similar dischordant combination (which for me make the banjo a pure joy).  I do not condone using any one thing to attenuate the wild side of a banjo. Each banjo responds differently to being stuffed. 

Back in the days before banjo heads made the big advances they have in the past 40 to 50 years there was a legendary fellow named Big Johnson. He was a big fellow and when he sat down and cradled his banjo, and his prominent belly (i.e. banjo callous) was positioned just so, the tone of that banjo was sublime. He could win a contest on the tone of that combination alone. His playing was also very good.   Years ago Hilaire Burhans showed me that a plastic grocery bag will do the trick as will an old sock, a stress ball, a stuffed animal and any number of things that you don't have to buy. I've got a couple with skin heads and need no stuffing as they actually sound fine without it.

It is certainly heartwarming to have one so enamored of a product to pitch it here.  If the shoe fits wear it.  For me, I've found a job for those socks who's pair partner got lost in the wash.

Mar 24, 2024 - 6:37:26 AM

4992 posts since 9/12/2016

has anybody used one in a masterclone scruggs styling?

Mar 24, 2024 - 6:49:03 AM
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4391 posts since 12/3/2008

Hilarie Burhans, clawhammer banjo

Edited by - Paul Roberts on 03/24/2024 06:52:11

Mar 24, 2024 - 7:00:38 AM
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4391 posts since 12/3/2008

Originally posted by Tractor1

has anybody used one in a masterclone scruggs styling?

Posted recently on another thread:

Mar 12, 2024 - 10:43 AM

Players Union Member

Laurence Diehl

Laurence Diehl
Seattle, WA, USA

5991 posts since 3/6/2006

Okay, consider me convinced!
I was a bit skeptical at first. I play resonator banjo and stuffing doesn't work very well. But this is not about stuffing. What I like most about the bolster is that you can dial in the suppression of overtones with a high degree of granularity. I spent years wrestling with tones with my Stratocaster so I am familiar with notching/boosting, Parametrics etc. I was experiencing an over-ring from my fifth string and I was able to just make it go away with the bolster. The configurations are limitless and I may never be done experimenting, but at some point you have to call it good. And $28 for a handmade item? I spend more than that on a thumb pick. Any tool that gets you closer to the sound that you love is well worth the price, and is well worth 28 bucks just to find out (okay, it's refundable).
Thanks Ric!

Mar 24, 2024 - 10:51:13 AM

682 posts since 2/21/2005

I wonder if an example of inharmonic overtones is that harsh, hollow sound that I hear when I pick the banjo without anchoring my ring and little finger on the head. When I anchor my fingers, that unpleasant tone disappears and I really like the sound. I also question whether those of us who pick 3 finger style need any enhancements inside the pot because anchoring fingers on the head eliminates those harsh tones. I notice that most players who do use something to stuff in the pot are clawhammer players, a style in which fingers don’t anchor. Therefore they would need something inside the pot to accomplish the same thing that anchoring does.

Mar 24, 2024 - 11:11:49 AM
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1669 posts since 1/9/2012

Bronx banjo -- I had a seasoned pro try out the Banjo Bolster, and he said more or less the same thing about anchoring. Zero, one, or two fingers anchored where and how he chooses offer a range of head mode damping that is inaccessible with the bolster installed. It does a pretty complete job by itself.

One aspect I thought "insanely clever" is that adding yet more fiberfill (the actual secret sauce) does relatively little more than what the BanjoBolster provides.

I figure that "what sounds better" is a personal choice and not physics. But a question that has driven me for years is: What is it about banjos that makes people say that they ring? And what's the banjo physics that produces that sound?

By the way, the other strings, no matter how tuned and/or fretted, provide another set of inharmonic partials that can't be eliminated in normal playing.

Mar 24, 2024 - 3:13:38 PM

13121 posts since 10/27/2006

No thanks.

Mar 24, 2024 - 4:03:16 PM

1669 posts since 1/9/2012

I like to hear 'em ring, and I'm pretty sure that it's the head "inharmonic partials" that do that. They provide anything between the “ping” of a taut mylar head and the “boing” of a looser skin head with each note.

Mar 24, 2024 - 11:11:16 PM

Alex Z


5769 posts since 12/7/2006

"I like to hear 'em ring, and I'm pretty sure that it's the head "inharmonic partials" that do that."


You take your 9 foot Steinway Model D concert grand for $200k in perfect piano tuning, you got inharmonic partials coming out all over the place.  Nothing wrong with that.  That's why it sounds like it does.

As Mr. davidppp says, preferred sound is a matter of personal choice.  Not all banjos need dampening to sound good to the player.  

A question I have on stuffing material, is "How does the material know it is capturing only the inharmonic partials, and letting the harmonic partials through?   Or are all the partials -- by the design,materials, and tuning of the instrument -- somewhat inharmonic, and the material simply filters out higher frequencies?"

Mar 25, 2024 - 3:32:10 AM

4391 posts since 12/3/2008

Mar 25, 2024 - 4:24:19 AM
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229 posts since 10/25/2007

When I first saw references to the banjo bolster I was reminded of this video, and similar information, that took me a while to dig up again.
The relevant part is from 6:20 onward.
Basically, the practice of taping the edge of a bodhran (Irish drum) creates an edge loading effect, reducing the reflections of vibrations travelling from the center of the head, outward, and reflecting back inward by the hard edge of the rim/head contact. I suspect the banjo bolster does the exact same thing. Reducing the hard, mechanical impedance mismatch that tone rings create.

Mar 25, 2024 - 5:58:07 AM

4992 posts since 9/12/2016

when I built my master clone the poplar lined resonator softened the tone- another one with harder wood was harsh--
however on my baritone it didn't seem to matter--
John hatrford mentioned lining them with velvet

Mar 25, 2024 - 7:12:29 AM

1669 posts since 1/9/2012

Alex Z --
The material (i.e., the fiberfill inside the bolster) simply does what it's good at. It damps air vibrations. Interestingly, at the densities used, it pretty much fails at that above 4000 Hz. The key to its selectivity below that frequency is that the air inside the pot couples strongly to the head and very weakly to the strings. (Note that even though the strings and head are coupled, to succeed as a musical instrument, their combined modes must be "mostly string" and "mostly head" so that you can hear the notes of the strings.) So, the bolster damps the head directly and the strings only indirectly.

In the write-up linked by the OP, I explain that behavior by analogy to two weakly coupled oscillators with only one directly damped.

I also describe an experiment that supports that conclusion. I record a series of plucks on the 1st string with a series of head tensions, going from 80 to 91 on a DrumDial. Spectrograms show that the bolster is most effective at reducing the strength of the partials whose frequencies increase with head tension and leave the partials that are independent of head tension pretty much alone.

You also have to damp all the unplucked strings to eliminate all inharmonic partials -- approximately, i.e., to the extent that an acoustic guitar does naturally. The resulting sound is still clearly a banjo rather than a wood-topped instrument because of the sound distribution among the harmonic partials.

Another experiment and set of recordings identify the difference in sound output between the bolster and a sponge stuffed under the co-rod at the neck joint. Sponge or sock stuffing in much more indiscriminate at reducing all the highs. That can be understood, too, in terms of the physics...

Mar 25, 2024 - 8:53:07 AM

Alex Z


5769 posts since 12/7/2006

"Spectrograms show that the bolster is most effective at reducing the strength of the partials whose frequencies increase with head tension and leave the partials that are independent of head tension pretty much alone."

Thanks.   Figure 9 now makes sense to me.  And the difference from guitars.  Will go back and reread section VII.

Mar 25, 2024 - 9:28:29 AM
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1676 posts since 11/10/2022

I dont think Im going to listen to a business trying to convince me my banjos have a problem so that I will then listen for a problem. I get creepy snake oil jitters everytime I see these thread-ads.  Yeah, dampening does change how an instrument sounds...but Life has enough real problems. 

I like harsh loud banjos and if I didnt, Id do like my Grammy said....put a sock in it!  Earl didnt need one...and now Grammy's advice mum.

Mar 25, 2024 - 11:20:55 AM

4992 posts since 9/12/2016

I don't see much elsewhere--on the mentioned (in one of the links) --di-pole cancellation--google calls it out as an electrical engineering subject--not any mention of wave travel-
wave travel on a molecular level is still un explained completely -- not to say others don't understand and have complete knowledge on it--and definitely cudos to those'' including David'' that have captured and explained so much --
We have a note leaving the bridge at differing times and hitting the rim at various times for that reason --along with the differing distances between the --bridge and rim that also differs in time--then we have reflection-angle of incidence etc.--what about the whispering? gallery note -- what goes on in the tone ring molecules--exactly --then the energy flow from ring to rim--why a slip fit or a tight fit matters --grain orientation in the rim--I would love to see the actual molecules
I did notice the j-pegs showed a rounded off attack on first few milliseconds-

Mar 25, 2024 - 12:24:12 PM

6047 posts since 3/6/2006

I know we're all suspicious of anything that looks like a sales pitch. After all, we are bombarded with them 24 hours a day. I frankly don't care if anybody on here buys a Banjo Bolster or not. This is America, you have the freedom to NOT buy something if you don't want to. But we are banjo players. We tinker with things. This is one of those things. It might work for you, it might not. But if you reject it without trying it then you won't know what you're talking about because you have to try it to know - then you can reject it. Not that I care either way.

PS I thought the science was mildly interesting, but I still just rely on my ears, just like always.

Mar 27, 2024 - 4:02:53 AM
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Players Union Member



17511 posts since 8/30/2006

Um...You might wish to take another look at the game changer promotional photo.  It's tacky and looks like something organic instead of a helpful friend. 


This photo demonstrates an interdependence between optics, hydraulics, and acoustics.

I think there is much more going on inside the rim that can be harnessed for pleasing musical contributions for band members as well as soloists.


Edited by - Helix on 03/27/2024 04:08:01

Mar 27, 2024 - 7:34:43 AM



36 posts since 10/4/2004

What people look for and like in tone varies widely of course, but it's clear that players have stuffed their banjos for a long time and there's plenty of discussion to be found on what works best. Since so many people stuff, that would indicate to me that there's a reason to do so and folks are trying to improve on something they think can be better. In my experience the bolster helps me adjust my tone effectively and in a way that nothing else i had tried did. The science supports the results, but my ears are the reason i use it. I've bought plenty of other accessories that didn't work for me. This is not one of them.

Mar 28, 2024 - 12:22:47 PM
Players Union Member

Lew H


2948 posts since 3/10/2008

I'm still puzzled! I've never understood why people take up the banjo if they don't like the sound of it. I have several banjos that have different tones ranging from a simple Kay to a Vega style M tuba phone conversion, to a Gibson RB175 to a Deering Sierra open back. They all have different tones and I like the tone of every one. CONFESSION: I have friends--fellow oldtime jammers--who stuff their banjos. I have begun stuffing some to reduce the volume of my banjo: "Too loud" they tell me. I don't think my banjos sound as good when they are stuffed.

Mar 28, 2024 - 1:54:54 PM
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15008 posts since 6/5/2011
Online Now

Tongue-in-cheek, I'm reminded of a joke (?) about a taxidermist ... with a twist:

You stuff banjos?!?!?!   

... Stuff this one where yer granny can't see it.


[P.S. Don't mind me ...  I'm harmless. wink  Now back to regular programming.]

Mar 29, 2024 - 4:19:52 PM

4391 posts since 12/3/2008

Mar 29, 2024 - 11:30:19 PM
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515 posts since 3/24/2020

We have been stuffing all sorts of dampeners/filters into our banjos for years. The way I construct banjos the only way in is to remove the head. To restrict the amount of sound bouncing around inside the pot I rough sand the entire inside, apply finish coats and rough sand again. Makes a big difference it transforms it from a bathroom kind of sound to something more like the kitchen.

Apr 25, 2024 - 9:38:56 PM
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12376 posts since 2/7/2008

Wasn't there a book or an expression, "That Half Barbaric Twang"?

Isn't that why we play banjos, because we like that sound? If we wanted clean sounding notes with less overtones, we'd play tuning forks, keyboards or electric guitars set to clean mode. The banjo spoke to me listening to two guys frailing an RB100 and a Framus, neither were stuffed with anything.

Apr 26, 2024 - 4:28:56 AM


Czech Republic

26 posts since 11/22/2022

For me it's still unconvincing gimmick, maybe useful for some extreme cases. Like one videos in post above where it's somehow mellows sound one of the fretless banjos strung with nylon strings.
But in my amateur opinion there is plenty variables which could matter: pot material, drum head (top/bottom frosted/fybreskin/clear/real skin etc.); bridge (plain/ebony top/bone inserts (y/n)) two/three footed, Seeger type bridge...
Neck wood and most importantly are of contact where neck meets pot.
Strings winding material and string age.
List could me mile long I believe.
IMHO most important is players technique. Main question for me is: Why I should stuff something in to my banjo? If I need to play somehow quieter I would use mute and softer pick. JS

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