Try fitting a thin card tornavoz.

[John Cadd]

I recently read that a violin soundhole should not be too thin edged or tapered as that will reduce the resonance.I applied that idea to a classical guitar and it ran away with me.I made a bigger rim of 11mm ---.Better!   Then I went to 18mm ---Better again.All with thin plastic and card.Next stop 65mm .Really good sound.Better high and low notes.
      This is all attached with masking tape and it really works.I saw that Domingo Esteso made a guitar with air resonance about 75Hz.That`s D below bottom E.It works like a dream. One "failure" with a full bodied Spanish guitar seemed dull.Then I realised you cannot just measure and fit.You need to work out what the air resonance note will be.I trimmed off one centimetre of card at the bottom and Bingo it was spot on with really warm resonance on all strings.You can fit it from the outside as a small reduction of hole width will not reduce the air resonance nearly as much as the depth of the tornavoz.
  The Tornavoz will reduce air resonance frequency,give great deep bass notes and makes the high notes very sweet.Once the sizes and sounds are worked out the card or plastic can be replaced with thin balsa wood.Maintenance is not a problem as balsa wood is easily replaced.That`s usually the main worry with fitting them.  Well worth a try.
     The air in the "tube " acts like the plug of air in the neck of a bottle.       That gives it the ------------------Resonance.))))))))))))))))))))))).

[John Cadd]

Sorry about the capitals Ned. Funny story about that . On another site where players of another string instrument ( no names , no pack drill ) had a disagreement going back some months,they had a real go at each other.It finished with abuse in red letters an inch high.Next day the topic had been deleted. My latest way is to leave extra space either side of the word.
The size of tube I am using has now reduced to about one and a half inches. It seemed balanced too much to the bass side. But it was never boomy. Even though there is a lot of room on a fretboard for several frets between the lowest two frets the tone of each tube position (to your ears) is much more specific.So just avoiding the exact fret position is not enough for your ears.There are a number of positions that will sound good.You have the fun a picking your own.

[Ned Knepp]

Sorry John (Cadd) I was responding to John (Smith) because he seems to feel that any use of all cap words is out of line. I was just letting him know that how he is use all caps is acceptable.

I've been involved in a few forums that had threads that ended in flame wars. No one wins.

Ned

[john smith]

I never said anything about using caps so I am confused by your comment. The only thing I did was to say I am interested in the idea and to provide dimension conversion in the hopes that others will try it and give some feedback.

[Ned Knepp]

Hi John Smith.
I was referring to CAPITOL letters. You apologized twice in your last post and I was just wanting to let you know that your use of them is appropriate. I'm an old computer guy and "caps" has become such a part of my vocabulary that I forget that it is a truncation of the word "capitol". Sorry for the confusion.

Ned

[John Cadd]

Well not so bad , you got my funny story out of it. The part about measurements got me thinking. What sort of rulers do Americans have? Don`t they have inches and millimetres as well? What`s on the other side of the rulers? When I went to school we had all sorts of old fashioned things to learn . Bushells and pecks. Florins and farthings. Inches and millimetres.We used inches and feet but still learned all the others. But we also did Latin and the school week finished 12 o`clock mid day Saturday. Very odd that.

[Ned Knepp]

The problem is that it's hard to envision something in our minds that is measured in millimeters unless we have worked with metric measurements a lot. I would guess that it's the same reason you used millimeters instead of inches. BTW, not all rulers in America have both on them. I've got several measuring tapes around the place and I think about half have metric scales too.

It's our quarter of a dollar that throws english as a second language people. Our paper money has 1, 5, 10, 20, 50 and 100 dollar bill but our coinage uses 1, 5, 10, 25, 50 and 100 cent coins. It seems to be hard for people that don't grow up with it to understand the 25 cent coin until they understand what a "quarter" is. (Just to mess up the paper bills, we also have a, not very popular, 2 dollar bill. Business don't like them much because most cash register trays don't have a slot for them.)

Ned

[John Cadd]

Ned We have lots of timber suppliers that give metric sizes for thickness and then want to know how many feet you want.That really messes me up.But timber people talk about "nominal" sizes so you never really know what `s coming. My son thinks in metric ( in conversation ) where I have to make a mental gear change. When he was small a "normal "clock with a dial would confuse him.The school had the flop-over numbers 60s style. We met a nice American couple in Cumbria once who asked " Is your " lorry " the same as our " truck"? That was nice. It gives a charm to the difference. Any newcomer to guitars heads for the dictionary when the word "plantilla " comes up. Ehh??

[Ned Knepp]

That's funny, John. I got a chuckle out of it and, of course, I had to look it up too.

I recently read a book that my daughter recommend to me. It is about the English language and it evolution. I can't remember the title right now but it was a fun read. According to the author, an American in England, there something like 2000 or more words that don't match up in usage or definition between British English and American English. Some of them can lead to some very awkward misunderstandings. I once heard a very funny, from our point of view, story concerning a "W.C." that hinged on this sort of misunderstanding. We all speak the same language except when we don't.

Ned