Shape of Acoustic Lap Guitars

[Frank Sellors]

It would a lot easier to built a acoustic lap guitar with a rectangular box shaped body - but would it sound dreadful - i.e are those curved sides necessary for a great sound?

[Alan Brookes]

The shapes are purely cosmetic. A plank with a pickup sounds the same. I've built all sorts of lap steels over the years. The only things that affect tone are type and location of pickups, strings, type of wood, pressure on the bridge and nut. After that you can cut the wood to any shape, varnish it, paint it, leave it unfinished, even glue a toilet seat to it.

I once made a lap steel out of a piece of 2"x4" in a weekend. It sounded just as good as any of the fancy shapes I've made.



I even fitted a tremolo unit as an experiment.

[Frank Sellors]

Thanks for the reply Alan, but I did say acoustic lap steel.

[Chris Drew]

The acoustics are kinda complicated, and the interpretation subjective... Let's just say it would sound different.

I saw a guy ( on this forum I think ) who's got a travel-sized acoustic twin-neck which is basically box-shaped, by all accounts it sounds pretty sweet...

I can see coffin-shaped acoustic steel being quite a talking point, you'd have to busk morbid blues with it, wearing full-on antique funereal garb, top-hat with plume, etc...

[John Kavanagh]

Roy Thompson has made at least one acoustic steel with a rectangular body - though the one I've heard was a resonator instrument, where the body isn't so crucial to the sound. It sounded great.

I think the only problem with a rectangular box might be that the response wouldn't be even. A shape that regular might reinforce certain notes at the expense of others. It's assumed that the curves of the figure-8 shape equalises things by bouncing the sound around inside.

There is another shape, though, that's been used succesfully for the soundbox of violins and might work well: the trapezoid. Imagine a long triangle with the top point cut off. It would be almost as easy to build, though the corners aren't right angles - just a box with one of the short sides quite a bit shorter than the other (you'd put the tuners at the narrow end.)

Even some fairly stuffy and traditional violin-builders (Heron-Allen, Dolmetsch)have admitted that this shape can make a fiddle that, other things being equal, sounds pretty nearly as good as the standard one. Acoustically, it wouldn't be that different for the hollow-neck Weissenborn design, and would give you an even bigger internal volume.

I have a semi-acoustic upright bass with a coffin-shaped sound box. When we designed it, I was thinking of it as kite-shaped (with the bridge at the widest point), but the luthier who made it for me said it was quite disturbing to come down to work in the mornings and see what looked like a child's coffin on his bench.

[Alan Brookes]

Thanks for the reply Alan, but I did say acoustic lap steel.

Oops, I didn't read it properly...

So now let's answer the original question.

Yes, the shape of the soundchamber can make an enormous difference to the sound, otherwise a guitar would sound the same as a lute. That doesn't mean a rectangular body wouldn't produce a good sound. I built this one a while ago, to be played electrically or acoustically, and it sounds okay without amplification, but it doesn't sound as good as my Dobro or my National Tricone...

[Kurt Schoen]

Frank -

I am just a new guy here, so take it with a grain of salt, but yes I think the acoustic instrument shape is very important. The profiles of acoustic instruments, in all dimensions, affect the development of sound waves emanating from the instrument. The traditional dual-bout instruments, with their two chambers with alternating convex and concave panels, must surely cause the wave forms to become complex and rounded. Layer upon layer of waves are reflected, absorbed, and recombined into more complex waveforms before they finally escape the instrument. There are also all kinds of acoustic filtering affects going on, which I do not fully understand, that affect what we hear.

One of the most important affects is the elimination of standing waves. The tilting of the top and back portions of the acoustic guitar helps to minimize the affects of standing waves. This is one reason I have oriented the panels and baffles of my Turbo Steel guitar to have no parallel surfaces. It is not as complex surely as the inside of a guitar or viola, but it helps a bit.

Anyway, just my 2 cents.

Kurt Schoen

[Kurt Schoen]

This is a picture of the Turbo Steel I refered to in th e prior post.

Kurt

[Keith Cordell]

Here is a guy who makes square dobros. http://www.myspace.com/oldlowe and they seem to be pretty cool. Don't forget the pineapple ukeleles that have been around for about a century.

[Frank Sellors]

Thanks for all the replies. Kurt, your Turbo Steel certainly looks very interesting.

[Frank Sellors]

Kurt, could you tell us about the woods you used, and the resonator - and about the sound, volume etc of the Turbo Steel, And, anything else you feel would be interesting to know! Just in case I have a go at doing something along the same lines.

Cheers

[Frank Sellors]

Kurt, I've just been browsing the forum and I've found out that you make the Turbo Steels commercially. Ignore my previous post!

[Steve Norman]

The curves where put there for spanish style playing, resting on the knee as it where. The "guitar shape" stuck in the squareneck dobro designs. The sound is really from the cone and associated chambers. Listen to weissenborns and mountain dulcimers, different shapes from standard guitars, Square dulcimers dont sound all that different from the pretty ones. Type of wood I think plays a bigger roll. Also more wood = more weight, so rectangular may weigh more than a paired down instrument.
I think........

[Harrison Withers]

Here is a guy who makes square dobros. http://www.myspace.com/oldlowe and they seem to be pretty cool. Don't forget the pineapple ukeleles that have been around for about a century.

I own one and enjoy it quite a bit. You can't beat the built-in beer holder. It has good volume and a nice reverb-e sound, sustain is not it's strong suit. Fun.

Harrison

[Steve Norman]

Oh Man, That guy kicks ass. I love the modified picture of a trailer on the moon in his myspace pics. Im gonna get me a lobro too!

[Harrison Withers]

I don't know any theory behind it, but I make these:



I call it the ghettoborn. It's uneven, rough, made from laminated pine and masonite, and it sounds good.

You can hear sound samples of a lowebro and the ghettoborn on my myspace page:

http://www.myspace.com/hcw3stringguitars

"a new day" is on the ghettoborn. the lowebro medly is obviously the lowebro. "a new low" is on one of my 3 stringers and 'reach in" is done on a jim farris 4 string reso.

Harrison

[Kurt Schoen]

Hi Frank -

Well, just because I am selling them doesn't mean I can't share!

I took into consideration the Weissenborn design, which was what drove the long hollow body concept. The Weissenborns are so light, yet relatively robust with the monococque shell. And they fit so nicely on the lap. So I spent many evenings thinking about how to take some of teh essence of that design without just copying the shape.

Of course, I wanted to employ my small 7 inch cones, which would keep the profile narrow like a lap steel. One thing that I think is so funny is the prevailing concept that a small cone must be low in volume, or very narrow in its ability to reproduce frequencies. If that were the case, the National company, with its three tiny cones, would never have gotten off the ground. It just is a simple fact that thin, springy aluminum absorbs much less energy than relatively soft, spongy wood. So because of that, you can get an amazing amount of sound out of a small area. The energy contained in a plucked string is a constant - what you do to transform that energy into sound waves is where the game is played.

The long Turbo Steel lap steel box has been a very interesting study, because of the relatively large ratio of vibrating cone area to the internal volume. It responds with more bass than the instruments with smaller boxes, and is a cleaner sound overall. The long box kind of has a reverb sound to it, that the musicians notice right away - undoubtedly from the out of phase frequencies coming from the back side of the cone. But the bottom line is that it is cool to see how one cone can sound so different in three different applications.

I've chosen douglas fir for the sides because it is strong, light, and transmits sound very well. Plus, since I like to use recycled wood as much as possible, it is plentiful in my neck of the woods here in Washington state. I'd love to use it for the tops and backs too, but veneered plywood is just a more practical choice.

On my workbench right now is a concrete version. I'm making it from concrete tile board, and glued together with thinset. Identical dimensions otherwise. It will be interesting to string it up and compare it to the wooden guitar - to see what the volume is, tone, etcetera.I wonder what the best finish will be - Saltillo tile, or stucco?


Kurt

[Kurt Schoen]

That ghettoborne is so cool! It looks like a Nate Daniels design! Very cool, pulling together the Weissenborne influence, the Danelectro thing, and a sweet paint job!

Kurt

[Jon Light]

Ever since I saw this on ebay a few years ago I've really come to appreciate guitars with simple form. It doesn't try to be sexy or alluring. It is a sound box with strings. Cool. I love the beauty of a luthier's masterwork. But I dig this baby and I appreciate the instruments being discussed and displayed here too.

[Roman Sonnleitner]

That ghettoborne is so cool! It looks like a Nate Daniels design! Very cool, pulling together the Weissenborne influence, the Danelectro thing, and a sweet paint job!

Kurt

+1 - I love the design - just misses a lipstick pickup or two...

[Harrison Withers]

That ghettoborne is so cool! It looks like a Nate Daniels design! Very cool, pulling together the Weissenborne influence, the Danelectro thing, and a sweet paint job!

Kurt

Kurt, as a longtime fan of yours, that means a lot to me. I will have a turbo one of these days. I used to frequent an open mic in ypsilanti that rollie would play and or host. But that was before his turbo days.

I've got another ghettoborn on the bench with a cigtone p90 slated, but I always intended to use lipsticks. I just need to find a good re:cheap source.

harrison

[Roman Sonnleitner]

Well, don't know how good they are, but www.guitarfetish.com has some affordable GFS lipsticks...

[Harrison Withers]

^^^^good source, Thanks!

[Alan Brookes]

The curves were put there for spanish style playing, resting on the knee as it were....

You're absolutely right, Norman. A lot is talked nowadays about the upper and lower bouts being the size that they are in order to give balance to the strings, but in reality the guitar has a flat back because the round back of a lute makes it difficult to hold, and the waist is there to rest it on the knee. If you don't believe this, try playing the cittern, which has the same shape as a guitar but no waist. The waist on the other side was made so that the instrument was symmetrical. That being so, there is absolutely no reason why a guitar which is not rested on the knee should have a waist. It's just become a tradition. Indeed, you don't want the back of an Hawaiian guitar to rest on anything, as it just deadens the tone. I build my acoustic lap instruments, which includes dulcimers, etc., with little rubber feet to keep the backs off the surface of the table, and I recommend that they be played on a table.

[Loni Specter]

Alan,
You've given me an idea! Why not incorporate a 2nd back that is isolated from the real back, allowing the inner back to resonate without interference?