Open D vibration

MollyKay · #1 08-06-2010, 09:31 AM

I need help understanding an annoying vibration that has developed on my open D string. Vintage plywood bass that plays very well, good volume, the bass actually pushes air out the FF holes to the point where you can feel it with your hand (strong playing bass). It has developed an annoying vibration on the open D string only. It does not sound like a wolf tone, but rather a buzzing. All other strings are fine and do not produce the noise.

The source of the vibration has been pin pointed to the top of the bass, running directly down the bass bar. If you place your finger/hand over the bass bar almost at the bottom of the bass the vibration stops. Our two guesses so far are loose plywood laminates (the bass does have some very minor vertical cracking on the outside of top plate) on the top of the bass that stop vibrating when you hold your finger on it or <GULP> a loose bass bar. If the bass bar is loose you can not see it with careful inspection. The bass bar looks good at both end and has not sprung loose from the top plate…unless there is a slight gap between the bass bar and the top plate that can not to be seen with careful inspection.

The vibration is an annoying bugger that we can literally put our finger on, but can not detect if it is top down or bass bar up. It takes very little pressure on the top plate with one finger to make the noise stop. Any suggestion on how to diagnosis and fix the concern? I’m all ears.

davpal · #2 08-06-2010, 10:25 AM

My guess is that the plys are delaminating. If the glue holding the bass bar on appears to be intact then the glue holding the ply together is letting go. This happened on my Kay - it was quite clear upon inspecting with a mirror that the top (bottom?) layer of wood was still glued to the bass bar but it was pulled off the layers below it. I believe this was due to using steel strings and the tension was too much. Maybe it was a bad batch of plywood... maybe it due to some conditions it was stored under sometime during it's life? I think you'll have to take the top off to fix it properly. Can it be fixed and not start delaminating somewhere else? That's a good question...
I bought a new bass and put the Kay in the closet.
Sorry I'm not more encouraging about the prospects.

CPike · #3 08-06-2010, 01:28 PM

Be careful with your assumptions. Pressing down on the top along the bass bar doesn't automatically mean the culprit involves the bass bar or even that area of the bass. I know this sounds counter-intuitive, but my experience has shown me that one can often silence a buzz by pressure along the bass bar - even if it's an open seam causing it. I've witnessed the same phenomenon in chasing down buzzes with violins, violas and cellos as well. Sometimes it can be as simple as a dried drop of glue that's worked its way loose somewhere, or even something in the pegbox - oddly enough. Pressing on the bass bar just seems to alter the intensity/trajectory of the vibrations that are fueling the buzz.

cdp

MollyKay · #4 08-06-2010, 02:27 PM

Thanks for the replies. Chasing down a buzz or vibration can be maddening. We have been successful in the past with simple fixes like a loose screw on the tuner, ill fitting end pin or an open seam.

When you are chasing down a noise, is there a systematic way to approach this task?

davpal · #5 08-06-2010, 02:41 PM

A stethoscope might help find the area that's buzzing.

CPike · #6 08-06-2010, 03:15 PM

Quote:

Originally Posted by MollyKay

When you are chasing down a noise, is there a systematic way to approach this task?

I'm sure everyone has a different strategy. I just have a checklist:

External - knock around for open seams, check fingerboard/neck joint, nut height, examine hardware (endpin/tailwire, adjusters, tuning machines, string ends in pegbox, pickups, etc.)

Internal - with mirror and flashlight, inspect bass bar, soundpost, linings, blocks, braces if any...

If nothing is obviously out of whack, sometimes the buzz will go away on its own.

cdp

bigolbassguy · #7 08-06-2010, 03:57 PM

Since your buzz is on an open string, you could use a length of rubber hose. Stick one end in your ear, and use the other end to search for the location of the buzz. Sounds goofy, but it works like a charm.

MollyKay · #8 08-07-2010, 06:34 PM

This is crazy…our weather has changed and today in lower humidity the bass does not buzz. <Sigh>

If we can point to any one thing there may be some slight delimitation on the top plate right around the bass bar area. This stuff will drive you nuts. Those that do this for a living don’t get paid enough. This will drive me to drink.

forester · #9 08-07-2010, 07:35 PM

no choice but to get rid of it..at the least,get it away from your other basses before it spreads,...i have truck w/cap.

MollyKay · #10 08-08-2010, 11:15 AM

I like you forester…you’re a funny guy. Nice too!

We THINK we have the problem solved for now.

It indeed was loose plies on the top plate the size of your thumb print. My husbands creative, non-luthier approved solution was to drill three very small (jeweler size drill bits) holes down into the effect area only penetrating the first or second layer of plywood. He injected hot hide glue into the area with a syringe and then laid a warm, heavy bag on the area and let it dry over night. This morning the noise is gone. While this may have fixed this spot, I agree with Forester it will spread with time. This is one of the down sides of vintage plywood basses.

I play in loud acoustic jam’s, I imagine the only person that would actually hear the noise is me in my quiet music room….good thing I stopped at a half of a bottle of wine last night.

bassics1975 · #11 08-08-2010, 08:21 PM

I have a century old instrument that had developed an almost identical buzz. The reason it sounds with the D-string (like mine) is because whatever is loose has that same resonant frequency. A buzz is never that easy to locate and just when you think you had found the location, it turns up to be something else in a different area of the bass.

Seeing as it is a plywood bass and cracks aren`t an issue, start by checking the seams for tightness. If this doesn`t work, I would pay the luthier a visit. I have had several buzzes and devoted countless hours tapping and checking the inside with a mirror and pen light but have never actually found the source myself. Good luck!

wineaux · #12 08-09-2010, 06:01 PM

I know a really good luthier near Gettysburg!!! If you want, I can send you a referral!

MollyKay · #13 08-09-2010, 07:56 PM

I heard he works for home brewed wine…same guy???

William Hoffman · #14 08-10-2010, 01:52 AM

Quote:

Originally Posted by MollyKay

I need help understanding an annoying vibration that has developed on my open D string. Vintage plywood bass that plays very well, good volume, the bass actually pushes air out the FF holes to the point where you can feel it with your hand (strong playing bass). It has developed an annoying vibration on the open D string only. It does not sound like a wolf tone, but rather a buzzing. All other strings are fine and do not produce the noise.

The source of the vibration has been pin pointed to the top of the bass, running directly down the bass bar. If you place your finger/hand over the bass bar almost at the bottom of the bass the vibration stops. Our two guesses so far are loose plywood laminates (the bass does have some very minor vertical cracking on the outside of top plate) on the top of the bass that stop vibrating when you hold your finger on it or <GULP> a loose bass bar. If the bass bar is loose you can not see it with careful inspection. The bass bar looks good at both end and has not sprung loose from the top plate…unless there is a slight gap between the bass bar and the top plate that can not to be seen with careful inspection.

The vibration is an annoying bugger that we can literally put our finger on, but can not detect if it is top down or bass bar up. It takes very little pressure on the top plate with one finger to make the noise stop. Any suggestion on how to diagnosis and fix the concern? I’m all ears.

ahh, the mystery buzz! i've got one too, and jumping to conclusions can be risky and costly. mine is on a carved bass, but it sounds like your description only on the open A. i did everything (new SP, new bridge, changing out strings, checking for cracks). but it's still there, depending on the weather. just a faint buzzing when the open string is plucked real hard.

like you, i've tried to pin-point its whereabouts. it sometimes sounds like it's coming off the top in the left upper bout region. other times it's sounds like it's just the string. but oddly, if i place my left knee against the back at the lower C bout, it stops.

i did succeed in almost eliminating it a few times. every time i tinker with the set up (new bridge, new SP), it goes away until the bass settles in. then, by moving the sound post slightly inwards, it really went away for a long while. also, when i swapped in a lower tension G string, the buzz was gone and at that point i thought the tension balance of strings across the set had contributed to the buzz somehow.

i asked Arnold and others here on TB what it might be and they gave me the insight that it may have to do with the natural resonances of the wood being at about A. like a wolf tone, that frequency is quite loud (and you mentioned this also in your OP). if my experience matches your mystery buzz, you might try shifting the SP just a tad inward or outward an see if that changes the buzz in some way.

MollyKay · #15 08-10-2010, 08:17 AM

For now we have quieted the vibration with our not so high tech approach.

But I very much agree about the resonate frequency. My 1937 Kay M-4 is a loud bass, the open A string makes the ductwork vibrate (not the bass, but the ductwork). While some of our other basses resonate on different open strings that bass consistently makes the metal duct work rattle.

Funny, funny thing…the more I understand how these big beasts perform the more I love them. Each bass has a personality and it mood swings.

Thanks all!