Rubber Grommets for the Mandolin

[wogster]

Well, since grometts, leather, what have you, eliminate sympathetic vibration by absorbing and re-directing energy, and since energy is at the source of volume, then reducing energy would reduce volume. But the amount of energy is very small in this case, so the overall reduction in volume would probably be noticed only from the player's perspective. And of course, the sympathetic vibrations are part of the overall sound of the instrument, so removing them would affect the 'tone' of the instrument. Whether that affect is desireable or not is another question.

I don't know about on mandolins but on violins they often use a felt doughnut, on the E string, for similar reasons. Even if you use the grommets perhaps they are only needed on some strings, like the E string, has anyone tried using them on some strings, but not others.

[Tim2723]

The grometts or other types of 'supressors' used on the mandolin are intended to stop the vibrations of the short lengths of strings between the bridge and the tailpiece. These can vibrate sympathetically with the main length of string and cause an unwanted extra set of tones. Not exactly the same as the violin, where a string sleeve is often placed on the E string in order to reduce its energy input to the bridge itself. It's not so much a similar reason, but it is a similar technique.

[pickloser]

Where is the empirical research? We know nothing about the effect of any of these items on finishes or sound if there is no carefully controlled double blind testing of these phenomena. I simply cannot accept anecdotal evidence as probative.


Oh, and it's good to see the Joker is back.

[Coffeecup]

I simply cannot accept anecdotal evidence as probative.

I simply cannot accept that somebody requires evidence before forming an opinion.

[Steven Stone]

My personal experience after placing grommets on many instruments during the last seven years is quite different than Tim's.

I have found that grommets actually INCREASE the volume of a mandolin because they eliminate out of phase sympathetic vibrations which reduce overall volume. In some cases grommets also make it easier to accurately tune a mandolin since out of phase sound can fool a tuner and make it more difficult for it to lock in on the actual sound from the string itself.

And although Gibson does use leather and or cork under their stock stamped metal tailpiece, Silencers still reduce the tendency of the strings to vibrate in sympathy.

Also I find that placing grommets in the headstock reduces out of phase sympathetic ringing that can have a negative impact on volume and tone. On some instruments the headstock can actually generate more out of phase sympathetic vibrations than the tailpiece region.

[AlanN]

Also I find that placing grommets in the headstock reduces out of phase sympathetic ringing that can have a negative impact on volume and tone.

For me, the grommets get in the way in this area. I take a small rope-like piece of leather and weave through the strings up there.

[mandroid]

Tonitis takes care of my hearing a lot of tiny overtones..

[MikeEdgerton]

I don't buy the sound increase any more than the sound decrease. It's beyond where it should make a difference and a mandolin isn't a loud speaker and the in phase cancelling concept doesn't fly for me, YMMV.

[Tim2723]

While Steve's explanation of phase cancelling is possible, and even demonstrable, it's not in all likelyhood that probable. True phase cancellation requires very specific manipulation of frequencies that is probably not commonly present in the chaotic environment of string lengths found in mandolins. But I do agree with his observation. He and I are describing different facets the same phenomenon. While I'm talking about undampened strings releasing energy to the air, he's talking about the redirection of that energy to the overall system through a different path.

Honestly though, this is more physics trivia than it is practical application for mandolinists.

[DougC]

I don't buy the sound increase any more than the sound decrease. It's beyond where it should make a difference and a mandolin isn't a loud speaker and the in phase cancelling concept doesn't fly for me, YMMV.

It's the perception that counts here. You'll hear more sound related to the pitch with the odd signals dampened out. The tuner will show the 'improvement'.
Acoustic instruments are very much like speakers because they convert mechanical vibrations into sound. The good news is that a good instrument will be responsive to this level of detail.
Cellists deal with the 'wolftone' problem by dampening the bridge and / or top plate. It's part of a 'design flaw' in the instrument. I've been moving the grommets around to see if there is any difference in dampening effect and I think a mandolin is too small to show any change.

[MikeEdgerton]

Perception becomes reality, but that doesn't make a stringed instrument behave like an audio speaker, they just aren't the same. I do agree though that it is perception. If a person believes it is louder, it will be louder to them. If a person believes it kills to the sound, then it kills the sound in their mind. Harmonic overtones are real and you can kill them with a folded up kleenex or rubber grommets or whatever. That doesn't mean that it affects the rest of the instrument either way.

[DougC]

Has anyone looked at different tailpieces with regard to the string length after the bridge? Some types of mandolins have the string attach at the edge of the instrument and others seem to have a short distance to the tailpiece. I figure if there is more string between the bridge and tailpiece, the more sympathetic vibrations might occur. There are very good instruments of both types so this must be trivial huh?

[jim_n_virginia]

For me, the grommets get in the way in this area. I take a small rope-like piece of leather and weave through the strings up there.

This is what I do also ....
And also you gotta ask yourself WWBD (what would bill do)

Can't help but think ole Bill would choose the leather over the rubber.

[Charley wild]

Usually I jump into these types of threads just ready to go! But this issue is a ho-hummer for me. I've tried them and didn't really hear much if any difference at all. It's nothing I can get to worked up about. I'm not scoffing it's just a non-issue to me.

[AlanN]

O behave

[Philippe Bony]

(again) Bill James tailpiece...

[Mike Bunting]

(again) Bill James tailpiece...

Yes.

[tipptoggy]

Grommits seem to be way over priced on Ebay. I cut up an old windscreen wiper and it works really well, I made easy to fit 1cm sections. It cuts out the harmonics of the strings behind the bridge, not much use in a session but is supposed to be good for recording. It cost me zero and I still have about 1 foot of the rubber left, the windscreen windshield I think in North America) wiper rubber comes with grooves in it and it fits real snug between the strings. Looks cool too, kinda gothic....

[tipptoggy]

It might have an appreciable effect if you have a piezo pick up fitted, the top of the mandolin vibrates and this causes resonance in the free strings behind the bridge, it goes through the amp and builds up energy in the room until it hits a feedback frequency.

Effectively grommits turn the floating bridge into a pin bridge.. but I'd like to see some acoustic evidence to back any of these thoughts up.