Double Bass Bass top vibration video

[Matthew Tucker]

It's just a way of measuring flexibility. It means nothing except that the lower the frequency, the more the plate is flexible that way. Inasmuch as you want a top plate to be flexible and responsive to bridge movement, but not so much that it collapses, you can use this measurement , among others, to guide you.

Bass tops twist and vibrate in all dimensions simultaneously. Look here: [Invalid or Expired Link Removed]

I have no idea about the soundpost thing in Traeger's book. I can't really understand the logic and I haven't tried it.

finally ...

 

[Jay VandeKopple]

Another observation I might make is that the modal frequencies of an assembled instrument are quite a bit higher; when you're doing this sort of thing on an assembled bass you need quite a lot of audio energy to get glitter things happening. From a practical standpoint this means a very loud BAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
blasting at the instrument which is quite unpleasant for neighbours to deal with, let alone the luthier!!!

And I was worried about the mess of glitter falling off the assembled instrument. Sounds like you've tried it. You've convinced me not to - my neighbors appreciate the warning.

I quite like the demos on Terry Borman's web site. George Stoppani ran that software on my German carved back bass a year ago (the only bass done so far, I understand) at the VSA/Oberlin Acoustics Workshop, and the animations are very interesting. But we need to learn more and try it on other basses before any conclusions can be drawn.

 

[William Hoffman]

It's just a way of measuring flexibility. It means nothing except that the lower the frequency, the more the plate is flexible that way. Inasmuch as you want a top plate to be flexible and responsive to bridge movement, but not so much that it collapses, you can use this measurement , among others, to guide you.

Bass tops twist and vibrate in all dimensions simultaneously. Look here: [Invalid or Expired Link Removed]

I have no idea about the soundpost thing in Traeger's book. I can't really understand the logic and I haven't tried it.

finally ...

Matt, thanks.

those bormanviolins animations are astonishing. very insightful. of course, a bit exaggerated -- heheh.

the soundpost thing: if the soundpost creates a motionless spot on the twisting top, it stands to reason that a fat soundpost will tend to dampen the top and a smaller diameter SP to free up more area of the top to vibrate. that's how i understood him. what do you not understand on that point?

regards, Bill

 

[MIKMAN]

In his book Traeger claims that a "fat" soundpost usually gives a warmer tone and a smaller diameter one gives a brighter tone. He believes also that the larger diameter creates a nodal point with a surface larger than needed, so he chamfers the perimeter of the soundpost in order to minimize the contact surface, maintaining simoultaneously the "fat" post and the warm tone.
I tried it in each one of my three basses and i have got the impression that he is right. As a general rule, when i have a bass with a bright tone on my bench i use a soundpost with a diameter between 19 mm and 21 mm, chamfered in way that keeps a diameter no less than 16 mm on the contact points. Most of my friends do agree that this little trick (Chuck's trick actually) makes the sound warmer and increases the fundamentals.
Mike

 

[Matthew Tucker]

the two previous posts appear contradictory.

I haven't found that the size or density of the soundpost makes much difference at all compared to its position.

But Mike, as you have tried it and it appears to work for you, can you explain why it might work? it would have to be the extra mass of the SP, as the way you (ex traeger) do it does NOT increase the contact area.

Is a fatter/heavier soundpost more dark? if so I suppose one thing to try would be a 40mm soundpost with the ends chamfered back to standard. that should be REALLY dark.

 

[Jake deVilliers]

the two previous posts appear contradictory.

I haven't found that the size or density of the soundpost makes much difference at all compared to its position.

But Mike, as you have tried it and it appears to work for you, can you explain why it might work? it would have to be the extra mass of the SP, as the way you (ex traeger) do it does NOT increase the contact area.

Is a fatter/heavier soundpost more dark? if so I suppose one thing to try would be a 40mm soundpost with the ends chamfered back to standard. that should be REALLY dark.

I agree about the mass being the difference. I've installed maple soundposts in a few Kays and they definitely changed the sound, albeit very subtly.

 

[MIKMAN]

I've got the impression that the extra mass makes the difference, but there is a specific limit for each bass. During my summer holidays in an Aegean island i found an Italian double bass built with superb tonewoods, about 100 years old and all these years in the possesion of the same family. It needed a thorough set up so i tried my best between ouzo drinks and local dishes. It astonished me that the soundpost was thin, with a diameter of 15 mm, which resulted to a rather bright sound. I ordered some posts from my office and when i experimented i found that the bass delivered its full potential with a post of 19 mm chamfered to 17 mm diemater, giving a thunderous sound with deep and warm funtamendals. A 21 mm post choked the bass, either chamfered or plain and, to my astonishment, a post of 17 mm unchamfered gave inferior results compared to the chamfered 19 mm. Since i had all the time to experiment with it i gathered that the extra mass makes the difference up to some extent and beyond it we have adverse effects.
This excellent bass is in Karpathos, one of the beautiful Aegean islands where the locals honour the traditional Greek hospitality.
Mike

 

[William Hoffman]

In his book Traeger claims that a "fat" soundpost usually gives a warmer tone and a smaller diameter one gives a brighter tone. He believes also that the larger diameter creates a nodal point with a surface larger than needed, so he chamfers the perimeter of the soundpost in order to minimize the contact surface, maintaining simoultaneously the "fat" post and the warm tone.
I tried it in each one of my three basses and i have got the impression that he is right. As a general rule, when i have a bass with a bright tone on my bench i use a soundpost with a diameter between 19 mm and 21 mm, chamfered in way that keeps a diameter no less than 16 mm on the contact points. Most of my friends do agree that this little trick (Chuck's trick actually) makes the sound warmer and increases the fundamentals.
Mike

Mike, have you ever tried a SP with 16mm diameter?

I chamfered an 18mm SP blank to about 16mm across on the top end, and it brightened the sound on my bass too, which is a rather darker sounding bass.

the two previous posts appear contradictory.

I haven't found that the size or density of the soundpost makes much difference at all compared to its position.

But Mike, as you have tried it and it appears to work for you, can you explain why it might work? it would have to be the extra mass of the SP, as the way you (ex traeger) do it does NOT increase the contact area.

Is a fatter/heavier soundpost more dark? if so I suppose one thing to try would be a 40mm soundpost with the ends chamfered back to standard. that should be REALLY dark.

Not sure if there is a contradiction, Matt. Traeger says on page 37 of Setup and Repair that a soundpost that is too "fat" will start to "mute" the sound, and that a narrower SP will tend to "resist the twisting motion" of the top less, giving the bass a brighter sound. "Muting" would be a darker, dampened effect as far as i can tell. "Brighter" to my ear would be a freer ringing of the bass.

 

[MIKMAN]

When i lay hands on a bass constructed with thick plates, which produces a choked sound, i start with a 16 mm soundpost and i examine all the possible positions. If i can't improve the sound and if i am convinced that a new soundpost can make things better i start my experiments with chamfered ones. My limited experience so far is the reason i make all these time consuming approaches, but you have to keep in mind that i am not a professional luthier and i have to examine all the possibilities.

 

[William Hoffman]

When i lay hands on a bass constructed with thick plates, which produces a choked sound, i start with a 16 mm soundpost and i examine all the possible positions. If i can't improve the sound and if i am convinced that a new soundpost can make things better i start my experiments with chamfered ones. My limited experience so far is the reason i make all these time consuming approaches, but you have to keep in mind that i am not a professional luthier and i have to examine all the possibilities.

yes, and if it still doesn't seem to improve that choked sound of that bass with those thick plates, i guess it's just time to get a new bass...