Double Bass home built DB (warning carbon fibre content)

[David Jayne]

Needs whiskers.

 

[El Thumpo]

Please don't take the whole Giant Rabbit thing as a disparagement of your skills and creativity, both of which are impressive. It's just that it's clear you've approached the project from an EB perspective (hence the horn/ears), and the DB is another beast entirely. An acoustic instrument is essentially a sound pump, which is why degree of top flexibility and size of interior chamber make such a difference in volume and tone.

Taking an EB shape, making it larger and hollowing it out--well, it's likely to produce exactly the kind of sound you're getting. Which is why I would pronounce the experiment a success, and move on to Project 2.0.

I certainly hope you feel encouraged to keep experimenting. The damn thing EXISTS, which makes it infinitely better than any similar product of my imagination.

 

[richtea]

Needs whiskers.

here ya go

 

[richtea]

Richtea, you've got skills and guts. You made an upright guitar. But without holes in the belly (top), it would probably work better electrically than acoustically. Your top is too stiff to project low fundamentals There are several U Tube videos on carbon fiber string instrument construction, and DB setup. Make another bass; get it right; start a second career/hobby. The best Jazz basses are amplified, so you might thumb thru the hundreds of pickups. Start with the Soundpost.

I think with 15 years of hindsight I must agree with your appraisal of the project. I have just realised that this was the first instrument that I ever built and I am an Electric player of some 30 odd years. That experience is the sole basis of my knowledge. With that in mind it is always natural to “go to what you know” so during the numerous design decisions I would naturally err towards the EB solution. So a thousand small decisions add up to a large EB with a limited acoustic capability. One must also take into consideration that at the time the InterWeb was not what it is today, solutions and information that today are at our finger tips required days even months of research. I will perhaps look at another DB project in the future but currently my spare time is taken up with building Eb’s more than I really have time for. It was a fun project which pushed my abilities and was not a complete disaster, and I have a playable ornament and talking point in the corner of my lounge, so its not all bad.

 

[richtea]

Please don't take the whole Giant Rabbit thing as a disparagement of your skills and creativity, both of which are impressive. It's just that it's clear you've approached the project from an EB perspective (hence the horn/ears), and the DB is another beast entirely. An acoustic instrument is essentially a sound pump, which is why degree of top flexibility and size of interior chamber make such a difference in volume and tone.

Taking an EB shape, making it larger and hollowing it out--well, it's likely to produce exactly the kind of sound you're getting. Which is why I would pronounce the experiment a success, and move on to Project 2.0.

I certainly hope you feel encouraged to keep experimenting. The damn thing EXISTS, which makes it infinitely better than any similar product of my imagination.

No, I really don't take the Giant Rabbit thing the wrong way at all, I do see it. It's very funny. You guys have named my bass. To accept criticism gracefully is to quickest route to growth, I am not at all precious with the things that I do creatively. I will continue to mess around with “Da Wabbit”, as it’s there and see if I can make any improvements. It all adds to the knowledge. I expected a certain amount of “resistance” to this project on the DB side of this forum. But frankly you guys have been quite gentle, logical and constructive for that I thank-you. I have seen much worse on the “other” side. I really only posted this bass on the off chance that I had missed something simple and obvious. As it turns out it appears that I have, I built the wrong instrument. It was a fun project and a now have a name for my bass. Would I do it again the same way, not a chance. Am I glad I did it, for sure. So its all good as they say. For those of you that do wander over to the other side I think I have unintentionaly built the "best DB for metal".

 

[james condino]

THAT THING IS COOOOOOLLLLLL!!!!!!

Disregard any and all of the crusty comments from the overwhelming majority of folks who have never built an instrument and never will but love to jump all over someone else's work. The first instrument you build is generally the hardest one you'll ever tackle, and yours is bold, dynamic, and not afraid to step up in a crowd. My highest honors and respect go out to you for the vision to attempt it, the tenacity to complete it, and even more bravery to put it out for public comment here!

So the sound isn't 100% of what you were after...pretty similar to almost every first "outside of the box" build. I've seen many firsts built by what a lot of us consider some of the finest builders in the world and quite a lot of them were basically wall art. My second one ended up in the fireplace...Yours has lasted this long.

While many of us would admit that you can make a number of small changes to the basic character of the voice and response of an instrument, you generally don't have drastic makeovers in it without drastic measures. In simple terms, a small box, a small scale, and a stiff construction generally equate to a smaller stiff sound; a large box, a log scale, and light construction generally give a lot of deep sound with volume. I'd still experiment a bit with this one, but I'd encourage you to take the lessons learned here and go for number two. Rather than using a generic public forum, I'd also suggest a private visit to several different established builders whose work you admire and respect for a more intensive private session where the two of you can try out a few ideas towards your goals. If need be, pay for the time and seek out a second opinion; look at it as educational. Don't go to a conservative traditionalist for advice on a modernist piece, unless you just want something speculative. There are plenty of people available that push the envelope and have experience with modern approaches. Even after close to 350 instruments, I still do the same thing and visit both my peers and elders for advice on a regular basis.

In the short run, take a bit of masking tape and cover up the soundhole farthest from your ears completely to see if you lower the resoant frequency of the box. Acousticians may have a different vocabulary for this concept, but the basic (bass-ic?) idea is that as you make the soundhole apertures smaller, generally you'll increase the percieved bass response of the instrument. I'd also give a try to experimenting with a "Hemholtz tube" to see what effect that has.

can you give us more details about the construction and possibly a few more photos?

Again, that is incredibly cool for a first build!!!!

(I also dig the painting behind you!)

j.

 

[powerbass]

Pretty impressive materials and use of technology. I was looking into using honeycomb combined with wood veneer for UB construction. Since you have so much experience with this process I think you should start building another bass this time use wood instead of CF. I'll see how you do it, get some tips before I give it a go

 

[lucas vigor]

You should get rid of the horns and market it as an Oud-Bass or Bass Lute!

 

[lunarpollen]

Are those two black teardrops holes?

I think a soundpost should help immensely!

 

[richtea]

THAT THING IS COOOOOOLLLLLL!!!!!!


In the short run, take a bit of masking tape and cover up the soundhole farthest from your ears completely to see if you lower the resoant frequency of the box. Acousticians may have a different vocabulary for this concept, but the basic (bass-ic?) idea is that as you make the soundhole apertures smaller, generally you'll increase the percieved bass response of the instrument. I'd also give a try to experimenting with a "Hemholtz tube" to see what effect that has.

can you give us more details about the construction and possibly a few more photos?

Again, that is incredibly cool for a first build!!!!

(I also dig the painting behind you!)

j.

Thanks James,
I realized that I was being brave posting here, I actually expected a lot worse than I got. Classical lutherers are a bit thin on the ground in Cape Town. At the time I did get in touch with one (possibly only) classical respected lutherer who’s workshop was within walking distance of my house. I gave him a call and explained that I was building a 3/4 DB, he was quite enthusiastic (with a heavy Italian accent) until he heard the words carbon fibre, he went quiet for a few seconds and put the phone down. I thought it was quite funny, It’s his life, he can spend it talking to who he likes, or not.

I intentionally made the teardrop sound holes large, thinking it would give better volume, I had always assumed that the small f holes on a DB were as a compromise between sound and material strength. I had no idea that the shape and size would play a role in the tonal response. I will try the tape thing. Experimenting with a resonation tube could be fun as well, I hadn't even considered that. No drawings exist of this bass, any that did are long gone. I will try and sketch something up on the pc later and post it.
Thanks for the comp on the painting, I did it about the same time as I built the Bass. Its oil on canvas, a fake of a painting by Tamara de Lempika one of my fav artists, a real wild child for her time. I used to paint them to order. I havent painted since they took the lead out of artists oils, Its just not the same.

 

[richtea]

Are those two black teardrops holes?

Yep

 

[richtea]

Pretty impressive materials and use of technology. I was looking into using honeycomb combined with wood veneer for UB construction. Since you have so much experience with this process I think you should start building another bass this time use wood instead of CF. I'll see how you do it, get some tips before I give it a go

An interesting idea, practically I don't know how you would press the veneer around the compound curved surface of the top. If you moulded the core first, then glued very accurately cut strips on to the face of the core, perhaps. The effect could be that of a the bowl back of a lute. You could go to town with contrasting woods, checker board, or harlequin might be fun. Sound wise, I just don’t know. Get some small samples and try it. Just make sure you speak to someone at a high tech composites supplier who is knowledgeable and willing to spend a bit of time with you. There are hundreds of types of epoxy, all with different properties ( and cost, unfortunatly).

 

[Andrew McGregor]

You could use thin balsa, steam it thoroughly before vacuum bagging it into the layup. That's done frequently with RC glider wings, which have pretty tight curves in places (and crazy tolerances... they use CNC aluminium molds because nothing else will give the precision).

You have to work fast with that technique, and have all the parts pre-cut. The vacuum will get the water vapour out.

It's a lot of trouble though...

 

[richtea]

You could use thin balsa, steam it thoroughly before vacuum bagging it into the layup. That's done frequently with RC glider wings, which have pretty tight curves in places (and crazy tolerances... they use CNC aluminium molds because nothing else will give the precision).

You have to work fast with that technique, and have all the parts pre-cut. The vacuum will get the water vapour out.

It's a lot of trouble though...

Balsa probably would do it physicaly, not sure about the wear and tear propreties as the outer face for a bass though. Its pretty soft, fairly devoid of any tone too, it's also a bit plain visualy.
After thinking this through if I were going to try somthing experimental in the DB department again, I think I would maybe look at a hybrid. Make the top in a traditional manner from tone wood. Then a one piece moulding for the neck back and sides and bond the two togeather. Bond on the finger board, hey presto! A very speedy method of production. Again how it would sound, who knows. I alot of effort in mould/ pattern making for a dud.

 

[Andrew McGregor]

Oh, the balsa thing is usually done between some layers of whatever fiber is being used in the layup; if there's a couple of plys of carbon over the top, it's pretty durable.

 

[richtea]

Oh, the balsa thing is usually done between some layers of whatever fiber is being used in the layup; if there's a couple of plys of carbon over the top, it's pretty durable.

Hi Andrew,
Sure, I totally agree, in that application the balsa does a similar structural job to the honeycomb core. It works really well in most applications which need maximum strength and minimal weight, like racing hulls, where cores need to be 20 and 30mm thick. I don't have any aviation experience, (R/C or otherwise) so I bow to your superior knowledge in this area.

Tonally, If you were to use a vac infusion system then I would think that a lot of the "air" in the balsa is replaced with epoxy so the result would probably be pretty similar to a honey comb. It may be possible to vac infuse the outer skin of C/F,(for aesthetics, ie. a smooth air free surface), then lay up the balsa, in pre-shaped pieces and back layer of C/F by hand, as you would with fibreglass. Some of the timber properties may be retained. There would be a slight in-balance in material properties, in this application I don’t think that it is an issue. Never done it, so I’m just hypothesising, I don't know for sure.

But I think POWERBASS, is looking for a wooden outer surface, for aesthetics. I could be wrong, but that's how I read it. Some of the new wood grain printed surface tissues are quite convincing these days, that could be an option. Some how it feels dishonest though. To me, wood should look like wood and C/F should look like C/F. It would feel as if you are ashamed of the materials used. Just my opinion.
Richard.

 

[powerbass]

I started a thread a while back about using Nomex honeycomb and wood veneer for a bass top plate. I'd been reading about "double top" acoustic guitars which many players and some guitar builders rave about for it's acoustic properties since it is so thin and stiff. I also watched a video of the Louis & Clark CF basses being made. I have extensive experience with vacuum forming wood parts though not compound shapes such as a top plate - I have yet to pursue this idea since it would require a fair amount of work, wood, epoxy, time etc. My idea was to carve a male mold out of dense foam and glue veneer to the inside/outside of a honeycomb core. I expect the veneer would have to be made very soft via flattening solutions and the shape would have gentle curves.

 

[richtea]

Powerbass, I would be interested to see that production video, do you have a link?

 

[powerbass]

Here's the link to the CF cello being formed

 

[richtea]

Thanks, The cello is pretty much 100% how I would have done it. The only thing I couldn’t work out was how they deal with the inner cavity of the peg box. I assumed that I would need to make a separate moulding and bond it into the outer, requiring really accurate trimming of both pieces to avoid ugly bonding lines, right at eye level too. A classic opportunity to screw up .

I post-cured my bass in a card board box with an electic oil radiator, in the mould. It took about a week though due to the lower temperatures.

The double top stuff was interesting. To achive a double top DB with the customary profiles a possible route mat be tp pre thickness then really steaming your wood tops and vacuuming them over a former allowing them to set in form. Before Proceeding as the video except for bonding up the whole thing in one shot and suffering the small amount of glue run back. It’s all experimental though, you could end up going through allot of different former designs until you get to a reliable compromise between desired curvatures and wood failure in the form splits. tears and creasing.
You’re wetting my appetite to attempt a C/F semi acoustic EUB with a double top. It’s ALOT time and heaps of money to invest in tooling and pattern making though.