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640 mm scale for classical
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=28716		 Page 1 of 1
Author:  RonaldD [ Sat Aug 21, 2010 9:00 pm ]
Post subject:  640 mm scale for classical
I want to reduce a standard 650mm scale to a 640mm on a Hauser classical.
Does anyone know of or has a proven 640mm scale ( hard tension strings).
Also other then the scale do we add the same saddle compensation as on a 650mm
Ronald
Author:  WaddyThomson [ Sat Aug 21, 2010 10:29 pm ]
Post subject:  Re: 640 mm scale for classical
I don't think you have to use HT strings on a 640. Maybe on one shorter than that. My 640 was built without changing anything but the neck length and the bridge location (Romanillos style build), and I had no problems. It sounds great, and except for the high E, all the strings are normal tension. If you use a bridge patch, you'll certainly have to move that, otherwise, just build it. The difference in the bridge location is only about 6 mm. 6 because the compensation is a bit less at 640 than 650.
Author:  Mike Collins [ Sun Aug 22, 2010 7:06 am ]
Post subject:  Re: 640 mm scale for classical
I just finished 2- 640mm guitars.
One a Hauser & the other a raised f.b. larger body guitar.
I remove 1mm from the 1st fret for comp. and set the saddle back
1.5mm -High e
2mm -b
2.5mm -g
1mm-d
2mm -a
2.3mm- e
They play intune and I use med. high tensions.
Labellas.
The new owner loves them !

Mike
Author:  RonaldD [ Sun Aug 22, 2010 7:54 am ]
Post subject:  Re: 640 mm scale for classical
Mike,
I don't understand the millimeters adjacent to your individual strings.
Ronald
Author:  WaddyThomson [ Sun Aug 22, 2010 9:07 am ]
Post subject:  Re: 640 mm scale for classical
Mike is using a double compensated saddle on his bridge. I have tried it on my two most recent, and got good results too.k Not hard to do when you are making the saddle. David La Plante uses this process too. His was the first I had seen.
Author:  Bailey [ Sun Aug 22, 2010 9:56 am ]
Post subject:  Re: 640 mm scale for classical
I love a 640 scale Hauser. I built one with no compensation other than the saddle. I don't know why 650 became the standard in the industry. Older Classicals commonly had 630-640 scale lengths. Some of the Mangore arrangements like: Choro Da Saudade" open tuning demand 5 fret finger stretches and nearly impossible with a 650 even with big hands. Certain compositions work great with a 630-640 and others prefer the 650. So...I feel the 640 hits a good compromise for most demanding, versitile players.
Just finished a 640-655 fan fret Hauser and all intonation adjustments were at the saddle. I use med Composites and plays in tune nicely.

I'm speaking more from a players opinion here...as I've only built 6 guitars...but know plenty about what feels, plays and sounds right.
Kent
Author:  RonaldD [ Sun Aug 22, 2010 10:41 am ]
Post subject:  Re: 640 mm scale for classical
No compensation other then the saddle, does that mean that the frets are at the same place as a 650?
Because I am trying hard to build one and I really want a 640 scale
Ronald
Author:  WendyW [ Sun Aug 22, 2010 10:57 am ]
Post subject:  Re: 640 mm scale for classical
I just assembled 2 Torres with 640 scale length. I used fingerboards that were preslotted for 640mm from LMI. I haven't gotten to the bridges yet, and I didn't realize that the saddle compensation would be different than a 650. Since I'm not doing a double compensated saddle, how much compensation should there be overall for the saddle position? I'm also in the process of building a Torres with a 24.9 or 632.5 scale length as requested by a friend. So I guess that one will need high tension strings? And how much compensation will that saddle need? Is there a formula for figuring compensation in the saddle? Thanks, Wendy
Author:  WaddyThomson [ Sun Aug 22, 2010 2:22 pm ]
Post subject:  Re: 640 mm scale for classical
Here is a picture of my double compensated saddle on my current build.
Attachment:
P1040206 (Large).JPG
Author:  Jim Kirby [ Mon Aug 23, 2010 8:25 am ]
Post subject:  Re: 640 mm scale for classical
Waddy - How wide is your saddle slot, i.e., thickness of saddle blank?
Author:  Stephen Boone [ Mon Aug 23, 2010 8:51 am ]
Post subject:  Re: 640 mm scale for classical
Ronald said,

Quote:
No compensation other then the saddle, does that mean that the frets are at the same place as a 650?
Because I am trying hard to build one and I really want a 640 scale
Ronald


Ronald,

The frets are going to be in different places for different open string lengths or scales. The 650 or 640 number reflects the length of the vibrating string in millimeters. The fret placements are derived from applying a mathematical formula to the open string length. You do not have to worry about the math because fret placement tables are readily available. The fret placement via the mathematics is theoretically perfect, however, the actual playing of the instrument stretches the strings behind the fret as it is played and it causes notes to sound sharp. This sharpness is more pronounced as you move up the fret board. This phenomenon is much more noticeable on steel string and it is why the saddle is placed into the bridge at a slant. This slanting idea leads me to what is known as compensation. If you place the frets perfectly but add a mm or two to the actual string length then the notes on the fret board would play flat except that this extra length compensates for the sharpness incurred through actual play. The end result is a compromise. I would recommend for your first build to have a scale length of 640, use the 640 fret placement numbers, but place the bridge so that the actual saddle location makes the strings 641.5 mm in real length. If you want to be extra picky and make each individual string have a different amount of compensation that would be fine but there probably is already enough to worry about.
Author:  WaddyThomson [ Mon Aug 23, 2010 9:12 am ]
Post subject:  Re: 640 mm scale for classical
Jim Kirby wrote:
Waddy - How wide is your saddle slot, i.e., thickness of saddle blank?


Jim, it's exactly the thickness of a Freud 10" blade. About 2.5mm.
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