Official Luthiers Forum!
http://luthiersforum.com/forum/

Acoustic guitar engineering and design decisions.
http://luthiersforum.com/forum/viewtopic.php?f=10101&t=47135		 Page 1 of 1
Author:  MrBing [ Sun Jan 24, 2016 12:46 pm ]
Post subject:  Acoustic guitar engineering and design decisions.
I am needing some advice or help finding information regarding wood choice and dimension considerations for small parlor or Martin LX1 size guitars.
I want to build myself a small travel sized guitar. It is important to me that I reduce the intonation problems I create for myself when I press too hard and from a strange angle on the frets of a short scale guitar. (I will keep working to correct this bad habit). I of course could use a 25.4 scale length on a small body. However, I do not encounter this problem with the Martin LX1 which has a short 23 inch scale length and is built to handle medium gauge strings.

I have the sides bent for the Martin size 2 parlor.
1. Should I make a neck block and tail block with the same dimensions used for a 00?
2. Any advice on choosing a scale length?.
3. Are there detailed plans available for a Martin size 2 or the Martin LX1?
4. Is their a good source of information I can use regarding these types of engineering and design decisions?

Thanks for any help and advice

John
Author:  Joe Beaver [ Mon Jan 25, 2016 12:15 am ]
Post subject:  Re: Acoustic guitar engineering and design decisions.
Hi John,

Wish I could be of help but I have never built a Parlor or other small body guitar. As far as intonation problems with short scales go, it seems to me a good setup will mitigate most of your troubles. I am thinking that has something to do with 'no problem' with the Martin 23". Other than that, this will bump you post up to where one of the experts might take notice.

Good luck.
Author:  Hesh [ Mon Jan 25, 2016 7:41 am ]
Post subject:  Re: Acoustic guitar engineering and design decisions.
What Joe said.

We set-up over a thousand guitars annually as well as many other sorts of repairs, the full gambit so-to-speak and the intonation issues that you describe almost always go away when the instrument is properly set-up. Specifically the nut is absolutely key here and rarely, very rarely are nuts set-up well IME.

If it were me I would select the size, style, and scale of the guitar that you want and then be sure it's set-up well and I strongly suspect that this will take the vast majority if not all of your issues with intonation away. If not a guitar was never a perfect temperament instrument anyway and there are some things such as this that we just have to live with. It also never stopped about 100 million guitar players from having a good time either...:)

As for plans they are available and I would simply select a plan that others have had success with. This forum is your friend for finding out the experiences of others.
Author:  Mike OMelia [ Mon Jan 25, 2016 12:56 pm ]
Post subject:  Re: Acoustic guitar engineering and design decisions.
I saw a post somewhere (YouTube?) where a guy attached a neck to a concrete block, a bridge to that and an acoustic pickup under the saddle. Sounded pretty good.

https://youtu.be/hFyQXy74xz4
Author:  Ruby50 [ Mon Jan 25, 2016 9:53 pm ]
Post subject:  Re: Acoustic guitar engineering and design decisions.
Mike

Great video and the comments are what the internet is all about!!

Ed
Author:  Terence Kennedy [ Mon Jan 25, 2016 10:15 pm ]
Post subject:  Re: Acoustic guitar engineering and design decisions.
The Scott Antes small parlor plans are close to a size 2. 24.9 scale. I've built a bunch. It's a nice little travel or couch guitar.

Use 1/4" bracing and be aware that the top bracing is shown from the top on the plan not the bottom. A bunch of us have glued the lower face brace off the wrong side of the X because of that.

Good luck.
Author:  Jim Kirby [ Wed Jan 27, 2016 8:20 am ]
Post subject:  Re: Acoustic guitar engineering and design decisions.
Terence Kennedy wrote:
A bunch of us have glued the lower face brace off the wrong side of the X because of that.

Good luck.


A little off topic, but I've asked a number of times and never seem to get a conclusive answer. Does reversing the tone bar brace(s) make any difference? My guess is that it wouldn't, but that is based on the notion that the forcing of the top is localized in the center and so a mirror image wouldn't matter (i.e., string spread much less than top width). However, I don't know how small the ratio of string spread/top width has to be before it is effectively small (another engineer here), so I need to defer to folks with feet on the ground.

My question is somewhat urgent as I am getting ready to convert an unfinished OM built righty to a lefty for one of my sons. Of course, he is just learning to play so it probably wouldn't matter anyway, but it's not a bad guitar and could serve him for a long time if he sticks with it.

Jim
Author:  Alan Carruth [ Wed Jan 27, 2016 1:38 pm ]
Post subject:  Re: Acoustic guitar engineering and design decisions.
My opinion is that the fact of asymmetry in the bracing is more important than the direction. Asymmetric bracing does make the top end to vibrate in an asymmetric way, and this has consequences for the tone. However, the top doesn't really have 'bass' and 'treble' sound producing areas: lowest notes tend to be produced by the whole top, and as you go up in pitch it breaks up into smaller areas that are distributed around in different ways depending on the bracing, the wood, the phase of the moon, the state of the stock market, and the wholesale price of coffee; all the usual variables. ;) Changing a right handed OM to left handed won't make a lot of difference in the tone. It's far more important to get the saddle right so that the intonation is good.
Author:  Terence Kennedy [ Wed Jan 27, 2016 3:36 pm ]
Post subject:  Re: Acoustic guitar engineering and design decisions.
I glued the first guitar wrong. I've built about 10 more size 2's since with the brace on the proper side.

Quite honestly I didn't notice a big difference.
Author:  Jim Kirby [ Thu Jan 28, 2016 8:53 am ]
Post subject:  Re: Acoustic guitar engineering and design decisions.
Alan, your comments pretty much mirror what I was expecting to hear.

Luckily, there is no permanently attached bridge yet :^)
Author:  SteveSmith [ Thu Jan 28, 2016 10:32 am ]
Post subject:  Re: Acoustic guitar engineering and design decisions.
Terence Kennedy wrote:
I glued the first guitar wrong. I've built about 10 more size 2's since with the brace on the proper side.

Quite honestly I didn't notice a big difference.


Yep, did my first one backwards too - didn't seem to make any difference as I could tell either.
Author:  Pat Foster [ Thu Jan 28, 2016 12:59 pm ]
Post subject:  Re: Acoustic guitar engineering and design decisions.
Alan Carruth wrote:
My opinion is that the fact of asymmetry in the bracing is more important than the direction. Asymmetric bracing does make the top end to vibrate in an asymmetric way, and this has consequences for the tone. However, the top doesn't really have 'bass' and 'treble' sound producing areas: lowest notes tend to be produced by the whole top, and as you go up in pitch it breaks up into smaller areas that are distributed around in different ways depending on the bracing, the wood, the phase of the moon, the state of the stock market, and the wholesale price of coffee; all the usual variables. ;) Changing a right handed OM to left handed won't make a lot of difference in the tone. It's far more important to get the saddle right so that the intonation is good.


'Course there are people who say there's a bass side and a treble side of the top, and that diagonal tone bars let the top vibrate more on the bass side.

But I am not one of those people.

Pat
Author:  DennisK [ Thu Jan 28, 2016 6:55 pm ]
Post subject:  Re: Acoustic guitar engineering and design decisions.
Pat Foster wrote:
'Course there are people who say there's a bass side and a treble side of the top, and that diagonal tone bars let the top vibrate more on the bass side.

But I am not one of those people.

Pat

Yeah, I use bass side and treble side in a similar way to left side and right side. They're more meaningful since left and right change depending on whether you're looking at the outer face of the soundboard or the bracing, and whether the guitar is left or right handed. But as far as sound production goes, I wouldn't expect any significant difference from mirroring the bracing.
Author:  Jim Kirby [ Thu Jan 28, 2016 9:32 pm ]
Post subject:  Re: Acoustic guitar engineering and design decisions.
Thanks everyone. It's what I expected to hear but it's good to hear it. I will proceed with my incorrect lefty without fear!
Author:  Alan Carruth [ Fri Jan 29, 2016 12:37 pm ]
Post subject:  Re: Acoustic guitar engineering and design decisions.
There is a standard nomenclature in organology for talking about the parts of the guitar, or any similar instrument. It's based on the notion that there's a body with a neck and head. The part that the bridge and strings are attached to is the 'belly', with the 'back' in the usual relationship. The back and belly are connected by 'ribs'. The 'left' and 'right' sides of the instrument are as you'd expect from that. We normally have the treble strings on the left side, and the bass to the right, but that's not the case on all instruments. Mountain dulcimers (which don't have much of a 'neck' admittedly, but still use the same nomenclature) have the bass strings on the left. Referring to the 'left' and 'right' sides, rather than 'treble' and 'bass', thus helps avoid confusion when you're talking about different sorts of instruments. The whole scheme goes back at least to Bessabarov's inventory of the instruments in the collection of the Museum of Fine Arts in Boston.
Page 1 of 1 All times are UTC - 5 hours
Powered by phpBB® Forum Software © phpBB Group
http://www.phpbb.com/