Double Bass Sound Post Free Design

[gbaker]

That's good data GB.

Do you like the new sound well enough to consider boring a hole in the top and supporting the G foot on the top of the sound post? Or not yet?

I think its a GREAT experiment!

Not yet Jake. I have a few things to try (after the holidays) before I decide to drill or not. Like try it on a different bass I know better.

I have started searching for a grommet or such to support and center the SP but let the top move free. And not offend the eye.

Thanks for the questions. If you can think of any more or other things to try let me know.


Matthew and Pentabass, thanks for the info, very interesting.

 

[gbaker]

What about putting the bridge foot down on the top like normal, but raising the saddle a lot to reduce down-pressure on the top? Having a saddle boot of 2/3 or 3/4 of the bridge height...?

LF, hope I didn't miss your point:

Raising the saddle reduces string tension and generally less tension = less loudness. Right?

You could raise it (not that you should) to a point where there is no pressure at all on the bridge (or set any pressure you want between normal and none).

But, you need to keep enough pressure to keep it all together: string-bridge-top-sound post (one side) or it would rattle. So the pivot foot would always have to clamp the top to the SP and not allow the top to vibrate as freely as it could.

Or if your objective is to get rid of the SP then the violin bridge family rocking action is lost and I don't know what you have. Maybe something like the two BBar design mentioned earlier in this thread.

BTW I think the Dobro type guitar has a string-suspended bridge, and that there was such a bass on the market.

 

[PB+J]

I think this is fascinating--kudos to you for trying. I love the DB and always will, but who ever said instrument design had to stop? You can have a bass with no sound posts, and basses with sound posts, in the same universe, and nothing bad happens!

I'm a pretty fair jazz guitar player, and I think as Arnold said the interesting comparison is to the archtop guitar, which has a carved top and back and no soundpost. The archtop guitar was an attempt to get more volume by getting more of the string's energy into the top. It sort of worked but the original acoustic archtops were played with heavy strings and a pick. They had a tight, focused sound with lots of mids and none of those jangly acoustic flat-top overtones. Great sound for cutting through the mix in a band, or for making complex chords sound clear. Lousy for the old cowboy chords with lots of repeat notes. The envelope of the note is totally different on the archtop

I'm sure, absolutely sure, you could make a DB with no soundpost and an excellent pizz tone, but it would not sound like a traditional double bass. Might have real advantages. I doubt it'd sound good with a bow. I would think that you would want less of a neck angle, get the saddles closer to the top, because as mentioned yhou would have a different kind of bridge motion than the rocking motion. The Selmer/Macafferi guitars are really interesting to look at--they have a very interesting sound, very different from an acoustic flatop

 

[Jeff Kissell]

Jeff,
This was never intended to be a finished product just a test device to avoid having to do irreversible alteration to the top, (which makes it look pretty darn good to me).

What if I added purfling?

Perfling won't save it... lipstick on a pig... etc... Excellent point though regarding a hack job in the name of science.

I'm very curious how this turns out, hopefully form and function will be equally successful. Kudos for the effort and for sharing your work with the rest of us!

-J

 

[wayne holmes]

You might try changing the sound post from time to time, but not having a sound post is like living without a heart, or something. You could probably so something like the guitar makers do to prevent having a sound post- This is just a guess, since I am no expert on guitar tops. I have experimented with the with and without sound post- If you remove it- you are going to have to do something to replace its functions. I have no idea as to what and really don't want to think about it. Nice work with your test-interesting.IME-IMO

 

[gbaker]

I just wanted to close this out. I removed the temporary cross bridge and released the bass to its natural habitat so everyone can relax, no basses were harmed in this experiment.

One last thing: I wondered what the thing sounded like with the sound post back in, but with the cross bridge still supporting the treble foot of the bridge but I could not get the SP set, the cross bridge was in the way. So to simulate the SP in place I put a little external wedge between the cross bridge and the top at the point where the sound post would be internally. This was to stop or dampened the top vibration (like the SP). The result was hardly noticeable.

I concluded that this bass with a completely free top preformed about the same as with a sound post.

However, the experimental setup STILL seemed louder in low end than when I reassembled the bass as normal. I think it was because of a higher pivot point on the bridge leg that provided mechanical advantage to the lower strings at the expense of the higher strings.

See you in the library.

 

[Matthew Tucker]

The top and back vibrate in many twisting/pumping/flexing ways. A free plate vibrates in a symmetrical manner, more or less. Addition of an offset sound post has been shown to add and allow assymetrical modes of flexion, without removing the flexible ones. So, simplistically, with a soundpost the plate has more ways it can resonate. I've a detailed thesis somewhere here I'll send you if I can find it. Quite a good read.

 

[gbaker]

The top and back vibrate in many twisting/pumping/flexing ways. A free plate vibrates in a symmetrical manner, more or less. Addition of an offset sound post has been shown to add and allow assymetrical modes of flexion, without removing the flexible ones. So, simplistically, with a soundpost the plate has more ways it can resonate. I've a detailed thesis somewhere here I'll send you if I can find it. Quite a good read.

Matthew, if you find it send it, I would like to read it.

 

[drurb]

So to simulate the SP in place I put a little external wedge between the cross bridge and the top at the point where the sound post would be internally. This was to stop or dampened the top vibration (like the SP). The result was hardly noticeable.

FWIW, as explained so well by Matthew, the wedge really would not simulate what a soundpost actually does:

The top and back vibrate in many twisting/pumping/flexing ways. A free plate vibrates in a symmetrical manner, more or less. Addition of an offset sound post has been shown to add and allow assymetrical modes of flexion, without removing the flexible ones. So, simplistically, with a soundpost the plate has more ways it can resonate.