Good vibrations???

[Matthew Tucker]

guys and gals ...

For the fun of it, I'm trying to map some chladni patterns on the cornerless bass top i am graduating now, and annoying the neighbours with loud sweeping tones when all good citizens are tucked up on the sofa watching the footy ...

but it seems to make a big difference where I place the speaker, and how I suspend the plate.

So far I have suspended the plate with strings either end and the speaker directly under the bridge point. But if I change either of these, the patterns and response changes! So i changed the suspension system to foam pads under the shoulders. Seems better.

This is what I have so far. Not really sure what it means. They're not very good patterns

96Hz -This one could be a mode 1 or 3 I suppose?

134 Hz - not sure what this one is ...


170 Hz - this could be a mode 6??


hell, the neighbours are complaining of the noise. I'll have to do some more tomorrow in the daytime ...

[ctregan]

What are you using for a vibrating medium?

[Matthew Tucker]

software called sinegen and a small 15watt guitar amp under the plate. Not really powerful enough for these low freq I think

[ctregan]

and the black particles on the plate?

[arnoldschnitzer]

Do I see a Klingon warship in that third pattern?

[Matthew Tucker]

yeah it brings a whole new meaning to reading the tea-leaves!

I see a diving shark in the second pattern and someone dancing the tarantella in the first.

But actually, I think all it's telling me is I have some more work to do on the plate. It's great to watch when you hit a resonant peak but it takes a lot of volume to get the tea-leaves moving.

[toman]

Cool photos; I feel bad for the neighbors though. heheh... and, uh, "footy"?

[Matthew Tucker]

Its a man's game. But these men aren't interested in doublebass.

[Matthew Tucker]

Here are some better results by using my 180W roland amp. Seems I need a lot of power to get the thing moving. My daughters complain of painful ears ...


66Hz: 71Hz: 91Hz:

93Hz: 96Hz: 98hz: 133Hz:

They don't really seem to conform with any conventional violin plate modes except maybe Klingon mode 6 at 96Hz.

At 71 Hz I thought the plate was going to take off!

The lines indicate antinodes, or points of least vibration. Anyone give me an idea of where I remove wood to "move" the antinode? My instinct would be to remove wood from the side of the antinode I want it to travel to ... is that right?

(By the way i'm prepared to accept that this is all bullsh1t but I'm giving it a go )

[arnoldschnitzer]

I personally think there is more to learn from tapping, rubbing and flexing the plates. The pattern tuning methods cause you to carve symmetrically to achieve the "correct" patterns. Who says symmetry is good for bass tone? There are so many factors involved (shape, size, f-holes, wood stiffness, weight, grain width, moisture content, etc.) that I believe the maker's brain has to wrap around the whole process and make it work as a sort of Gestalt. I understand the desire to reduce the process to a bunch of numbers, but I don't personally think that's the way the finest instruments are born.

That said, there's something cool about that Klingon warship pattern...

[Matthew Tucker]

Arnold I agree with what you're saying but I'm experimenting nonetheless.

Ken McKay has suggested that rather than using it to slavishly guide plate carving, it is maybe one way to "document" the plate flexibility before gluing on the bassbar and fixiing it to the top, when of course everything changes. Especially if I am using the same or similar wood each time, it may enable me to understand in another way what is going on. Flexing and tapping is one way, but this is another. Both are probably as valid as the other. I'm not looking for symmetry, I'm looking for a way to understand what the wood is doing.

for example, I'm interested to kn ow what is different between the left and right half of the lower bout here. I'll do some more thickness readings and see if that tells me anything. I may not respond by moving more wood, but if for example it reveals that the RHS is 1mm thicker all over ... I might.

The 71Hz shake was such a visual surprise when the plate started oscillating wildly. I think a stroboscope might reveal some interesting things too. But I don't have one of those.

[Bob Branstetter]

Originally Posted by arnoldschnitzer

... but I don't personally think that's the way the finest instruments are born.

That may very well be true. However, proponents of plate tuning are looking for a methodology to achieve consistently good instruments, not necessarily making a master class instrument every time (if such a thing is even possible). IMO,this is particular beneficial for beginning bass makers who may lack the experience to know by feel what is desirable resistance and/or twisting of the plates in their hands.

[KSB - Ken Smith]

Since we listen to Music with our Ears, maybe one (or two ears) should be used to make instruments and not Machines. After all, can we hear what the machines can measure?

If this is the case, then someone go measure my 'ex-Riccardi' Storioni and see what makes that thing tick. It is one of the best sounding Basses I have heard in my life. If a Machine can help you to match the sound of that Bass, then I will change my opinions.

In the mean time, tone tapping with a good ear seems to have worked just fine for the last 400 years or so.

[Matthew Tucker]

I bet Storioni turned out a few duds too. You are lucky that a nice one survived this long.

In your second paragraph ... you are just being a smartarse, aren't you? You're not really going to let anyone pull your Storioni apart and do chladni pattern analysis on it. So you're just thumbing your nose at anyone who has an alternative view to yours.

Since you seem to be an expert on everything, why not teach me a little about the 400 year old tone-tapping that's worked so well? How do you do it? Or at least, show me evidence that Storioni did it? Or is this just speculation?

Otherwise, if you will just defer this to the real luthiers to explain to me, why not just let them do so instead of weighing into every thread you have an opinion on and throwing a wet blanket over it?

Sorry this is how your comments appear to me. I'm not a complete beginner and I'm not stupid. I'm here for some friendly pointers on Chladni analysis and double basses. Maybe I'm in the wrong forum?

[KSB - Ken Smith]

Can't I have my own opinion? Do you have any idea how many great Basses I have played in my life?

I have also done work on Basses so enough with the name calling. I am not going there. Besides, I never made a Lute and never plan to so becoming a Luthier is not something I want to do.

My point is that using machines and listening with your ears may not be the same. As far as Storioni turning out some bad ones (attributed or certified) that is some bit of guess work.

Old Italian basses usually sound great. They were also made with out any Electric, light bulbs or running water as we know it today.

I have had many restorations and alterations done on old Basses of mine with good results, often beyond my expectations, Not a single machine was used to make these changes or repairs as far as the tone goes.

Have fun, I am not here to burst any bubbles. I am just voicing my opinion. In the future where you are concerned, I will refrain from posting anything in your direction. Also, if you want only specific people/Luthiers to respond to your questions, then call or email them directly and don't go public with it.

[Matthew Tucker]

Originally Posted by KSB - Ken Smith

Can't I have my own opinion? Do you have any idea how many great Basses I have played in my life?

Of course you can have your opinion. I was just wondering how much the wiser I am on Chladni patterns as a result of your post?

[Darren Molnar]

Looks like fun Mathew.I find it interesting that at every frequency so far, the center line remains immobilized.I don't have experience in this feild, but I have some questions.
Aren't chladni paterns measured after the f-holes are cut?
at What hz. is the open e string vibrating at? And what notes are corresponding to the hz you're measuring?
How much higher in hz are you able to go with you're set up?

[Matthew Tucker]

The centre line I think is simply the result of gravity pulling the tea leaves to the lowest point!! They'd all end up there if you left the thing vibrating too long.

Chladni patterns can be measured at any time. All they do is show the antinodes at various frequencies, ie: the rest of the plate is oscillating as a standing wave, the black parts are where the plate is not vibrating. I suppose if you are using them to guide your final graduations you want to do it with ffs cut and bassbar glued. I am somewhat sceptical of the usefulness of this approach, however I am experimenting because i can and because its fun and costs nothing.

I don't think there's any correspondence with real notes and I'm not sure there would be any advantage. I can go real high, supersonic so only my teenagers can hear it, but the returns in terms of patterns diminish if I go much higher than I did. The plate isn't flexible enough to demonstrate the standing waves at higher freq.

[Darren Molnar]

It is interesting. I've always wondered if these patterns are affected by the outline and the archings even more so than thickness variation. I think a lot of the emphasis gets put on the thickness. An area that would be fun to look into would be to measure these patterns, varying only arch shapes, and leaving the rest consistent.Tuff experiment to set up, though.

Oh, and careful to not let the sound devils loose in you're shop at night. You might want to turn the speakers off, so you don't wake up to these!
http://www.youtube.com/watch?v=WnDKO...eature=related

[Matthew Tucker]

I have finally (almost) figured out what they mean:

1. witch on broomstick
2. ballet dancer leaping
3. sad face?
4. dog lying on its side
5. klingon warship
6. no idea
7. I think this one is on the way to being a prehistoric "white horse"

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