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Double Bass Soundpost Question (for a washtub bass)

zeytoun

zeytoun

Dec 19, 2008
478
12
Portland, Oregon
www.facebook.com
#1
(FYI: I've read the newbie links about soundpost placement.)

My question is this: Other than the obvious issues with moving the soundpost, would there be any acoustical disadvantages to gluing a soundpost in place? (or, re-phrased: If you had a bass with an easily removable soundboard, would you consider gluing the soundpost in any way?)

The reason I ask is that in my A/EUB build, I'm putting on a removable soundboard. I was considering using hide glue to fix the soundpost to the soundboard once I have good placement/fit. My reasoning is that it will 1) prevent slippage 2) make for a simpler fitting process (I can glue the soundpost to the soundboard, and then install the soundboard, instead of fumbling through the f-holes). Bad idea?

*The reason I posted in this forum, is because I wanted opinions from an acoustical point-of-view (as in, will glue affect the acoustics). If a mod thinks that this would be better off in the EUB section, that's fine.
 
#4
Bad idea.

Sometimes the instrument's age or a change in location/climate can affect the gap where the soundpost sits. An example, f you go to a dryer/colder climate your top might sink a little and the soundpost will be too long. This can force the post to crack the top of your instrument if left unchecked. A luthier can simply remove the soundpost, shorten it, and put it back in. This is an inexpensive fix. If the soundpost was glued in, that presents a world of problems which might warrant taking the top off your instrument just to do a soundpost adjustment. This can get really expensive really quick.

If you're afraid of the soundpost falling, you might look into buying a soundpost setter tool to have on hand and learn the basics of setting one up. They aren't terribly expensive. This way you could at least get your bass functional in between visits to your luthier..
 
#5
1) (to Mr. Tucker) re: why a removable soundboard? Because it's equally easy to make a removable one as a non-removable one, and having that ability could make some things easier. I don't have pictures yet, but I'm drilling holes around the perimeter of the washtub, near the lip. I am using wood blocks (with hardware) as a sort of nut, to a bolt that will go through the hole in the tub. The soundboard will be glued to those blocks. So it should be pretty easy to remove the soundboard.

I just figured it would be easy to fit a soundpost to the removed soundboard, then put a bit of hide glue to hold it, and fit the soundboard into place.

I figured it would be pretty easy to remove the soundboard and reposition the soundpost to find the optimal spot. But from reading around hear, it seems that some luthiers believe that a better fit is more important than a milimeter-sized adjustment of the placement of the post. So I was focusing more on how to get a perfect fit.

2) (to 1st bass and Dallas Strings): sorry, I should have specified clearly: the soundboard is plywood, and the back and sides are metal, so I'm not sure that seasonal concerns are as much of an issue (although I definitely see the issue with a carved double bass, as you both bring up).

*side note to all. This is for a weird EUB build. I would have posted in the EUB area, but thought maybe the point was better addressed in this subforum.
 
#8
lol.

I probably should just shut my mouth until I have the thing built, then people can say "oy that sounds like ****!" or "Wow, that sounds less ***** than I was expecting."

It's not a washtub bass in the classic sense. It's a hybrid, with the washtub acting as the back and sides. So it needs the soundpost for the same reasons a double bass does: to support the top against the tension of the strings, and to transmit vibrations to the back. The same acoustical principles apply.

It's a silly project. There are probably better things to do with my time and money, but I can't resist the pull of building something unique, of learning the acoustics of double basses by transferring the principles over to a completely idiotic instrument.

(Here's an example of one similar to my design, with a sound clip. I'm using an oval tub, and attempting an arched top, and using an Englehardt replacement neck and FB)
Link Removed

I'm here to (1) learn from experts about some principles of acoustics and luthier concepts and (2) share details of my build in case anyone is interested or curious.

I do expect to get a lot of guff for the project. But I'm here sincerely.

It's really a simple question: is there any acoustical disadvantage to hide glue between the soundpost and the soundboard?
 
#9
the soundpost carries vibrations from the top table to the bottom table. Anything extra in the way (like glue) will inhibit those vibrations.
Scenario: ( you get the soundpost fit the way you want on the top and bottom. You find a sweet spot where it resonates perfectly. You take the soundpost out and put some glue on it and put it back in. Suddenly it's not in the same place anymore, but it's locked in place with the glue. You try to remove it to change position, but it rips off little bits of the top and bottom. Back to square one..:crying:)
 
#11
Hi zeytoun
if it was me, making an unconventional bass such as you are, I'd install a captive nut in the washtub. Where the post will go. Then I'd use a threaded rod with a screwdriver slot on one end as the sound post. Now it's adjustable for tension, and fits perfect. Rod can be metal or wood. Sound post acoustics is more about proper tension, and perfect fit between surfaces, less so about where it is exactly. My two cents.
What ever floats your boat, though. I wouldn't count a drop of glue on a sound post as any kind of factor in tone. It is made out of a washtub and plywood, after all. ;)

have fun with your project
 
#14
;) I got a wild hair and build a similar upright washtub about 5 years ago. I took it to one old-time fest and it drew a crowd, people asked if they could take video's of me playing it, and it wasn't because I played well. I wanted something to play I didn't have to plug in, however it was a little too outrageous for me so I build a wooden bass after that.

Guys, please keep in mind this is not a strat. It is tin, and a novelty.

I followed DENNIS HAVLENA's design mostly:
Invalid Link Removed


OK, here are some things I remember about building it:

Soundpost - remember the primary purpose (among other things) is to stabilize the treble foot of the bridge, this causes the bridge to rock sideways when driven by the string causing the bass foot to vibrate the top plate.

I fit a hardwood block about 1 1/2" sq X 1/2" thick to the back end of the sound post. It had a hole drilled half through to hold the post. I experimented some, moving it around. Ended up with a point about 3/8" down from the bridge and in-line with the treb foot, projected it to the back and to the tub tin. The soundpost is installed just barely tight, fit it, then glue it, the string pressure will later hold it in place.

Super-structure - Make the main support that runs under the top plate from bottom to top of the tub and holds the neck very robust. I tried a 1.5" x 2.5" spruce piece flatways and it bent. Go for at least 2" square.

Top plywood - Make the top plate 3/8" larger than the tub all around. Split a 3/16" clear plastic hose and use it for a gasket between the tub rim and the top plate. I increased the size of the holes and got more sound out of it.

Neck - The neck is relative thin and looong for the string tension. Mine was a soft hardwood (cherry) but I had to go to weed whacker string on the g because it was starting to bend under the pressure from steel strings. You could use hard maple or a truss rod.

Working metal - You can cut the tub after drilling corner holes with a hammer on a flat screwdriver (worked better than a saber saw).

Hope this helps, good luck and have fun.
 
#17
"Why a soundpost at all?" is not a silly question. I presume your soundboard is flat, and that you are not intending to BOW the thing(!) and you are playing Pizz. In which case, why not just brace the soundboard like a guitar, or with two bassbars? Not a new idea. Much simpler. Probably louder.

What do you hope a soundpost will bring you? The tone of a Montagnana?
 
#18
I saw this Hillbilly music / Bluegrass band over the summer at a car / tattoo / music festival where the bass player had a huge washtub bass.

The bass was made from a large oval washtub, had a regular double bass neck / bridge and tailpiece, f-holes and all.

The bass sounded really fat and, well, tubby! :D The big fat thump it made was perfect for the music they played and I liked their sound quite a bit.

He had it amplified with a Rev Solo II actually.
 
#19
Who said it was a silly question? I answered it directly.

Yes, I am attempting an arched top. Yes I am going to make it Arco-capable. No I don't know what it will sound like. No, I don't imagine that it will sound as good as a luthier-made double bass.

I doubt that guitar construction will stand up to 250+ pounds of string pressure without a very thick top. Plus, flat-top guitar construction, while louder in some respects, tends to increase treble sustain at the expense of a punchy percussive thump.

Besides, as an experiment, I'm trying to transfer over as many of the construction details of a double bass that I reasonably can.

(Anyone who assumes that I am operating under delusions about the final tone of said "instrument" (I am not), am imagining that I will upstage 500 years of craftsmanship (I am not), or that it is a waste of time because they would not find it rewarding (I do find it rewarding, even if it results in an abysmal failure), will get the wrath of the raspberry from me. (:spit:).)

:)
 
#20
I say go for it, Z.

Have fun and be sure to post pics and sound clips. ;)

I think glueing in the soundpost would be fine, hide glue is not a flexible vibration-dampening glue, this is one reason why it's used to construct musical instruments.
 

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