Bar below the bridge

[John Underhill]

 In his article on guitar bridges, Sinier de Ridder writes that Pons and Lacote added a bar below the bridge (i.e. between the bridge and the lower block) 'with quite a special design' which 'allowed a better sound production'.

What was special about the design of this bar, and in what way might it improve the sound?

[Michael. N.]

It was scalloped, similar in manner to the way that some steel string makers shape their bracing. It's low in the centre, rising towards each end before the usual 'end scoops' drop into the linings.

I've done both, with and without this Bar. Not nearly enough to say with any certainty which is better. There are just so many variables. I suspect the stiffer soundboard might make for a different treble response but perhaps at some small expense of the bass. Just a guess!

[Scot Tremblay]

I've worked with this bar as well and in my experience the tone was more evenly controled across the range and there seemed to be more projection and percieved volume with a bar below the bridge than without that bar. However, I think I'd be hard pressed to claim a significant difference between the scalloped version and other versions one sees; tapered or equal height from bass to treble. And as Michael says, there's also a lot of variables to take into consideration. I think one would have to experiment a fair bit to be certain which is preferable.

 

I've had a couple instruments come through my shop where the lower brace showed convincing signs of being carved, through the sound hole, after the instrument was together. Both were by the prolific French builder "Anon" from early to mid 19th century. So it seems early on that there was the knowledge that by shaping this bar the sound would improve.

[Michael Schreiner]

I agree that that this bar increases projection and evens out the sound. It can also cause problems. The first Lacote I built after  the Edinburgh plans calls for a 14mm high unscalloped bar. I did that and found that I had a nasty  "wolf tone". Somehow, I decided that the lower bridge bar was the culprit and putting a sanding stick through the soundhole I was able to lower the bar bit by bit, tuning the strings back up each time and noticing that the "wolf" was diminishing. I got rid on 90% of it.

[Lars Hedelius-Strikkertsen]

Exciting discussion though I know nothing about building guitars. I'm curious to know what a "wolftone" is, Michael can You please explain.

[John Underhill]

Thank you all for your replies.

Michael Schreiner - I recently bought the plans for the Edinburgh Lacote. Michael N. told me (on another forum) that the soundboard thicknesses on the plan are untypically heavy for a Lacote, being 3mm or just over everywhere. I would be interested to know what you did in your copy.

I like your blog, by the way - very informative. I built a number of lutes myself, many years ago, and have recently returned to instrument making - but now it's guitars.

[Michael Schreiner]

Hi John,  I stick right at 3mm in the bridge area and then a little less elsewhere. A thickness of 3mm or over seems to be the norm for guitars from that era. I have the measurements of a Stauffer (cira 1830) in GNM, Nuremburg that is over 3mm, likewise a 1828 Panormo and a 1822 Fabricatore (Edinburgh). Interestingly, an undated Panormo in Edinburgh is around 2 mm but it has 7 fan bars. His 1828 model has a diagonal and a below bridge bar.

Thanks for your comment on my blog. I enjoy writing it.

[Scot Tremblay]

"His 1828 model has a diagonal and a below bridge bar."

 

That's interesting. I've examined a slightly earlier Panormo (1826) that only has the two bars on either side of the soundhole and the diagonal between the soundhole and bridge but no below the bridge bar. Always experimenting.

 

The soundboard on that one struck me as on the thin side at around 2mm but I'm thinking it didn't start out that way. There had been a fair bit of work done over the years that may have thinned things out a bit.

[Scot Tremblay]

Sorry, wrong info. I just checked my notes and its a 1828 Panormo that has the thin top and only one bar. The 1826 has same bar configuration but thicker top, ca. 3mm.

[Michael. N.]

I suspect that 2 mm on a Panormo might be thin but it wouldn't surprise me if that was the original intended thickness. Generally speaking I think Panormo's are on the thin side, especially those being built in the  'Spanish style'. I've very little knowledge on the 'fecit' models.

James Westbrook in 'The century that changed the Guitar' gives a single soundboard thickness for the Guitars featured in his book.

Fabricatore is given as 3.0 mm, Lacote 2.5 mm, Panormo 2.5 mm. Soundboard measured in the bridge area.

I think that the Edinburgh Plan for the Panormo shows the soundboard going down to 1.7 mm, perhaps a touch thinner.

[Jelma van Amersfoort]

Hi Lars 

A wolftone is when on an instrument one frequency/pitch/tone (or two) is very much louder than the rest. That is something instrument makers try to avoid :-) J.

[Lars Hedelius-Strikkertsen]

ok. Thanks for telling me

[Michael Schreiner]

Hi Lars, Jelma is right about that type of wolftone, but there are others. The problem I had was with a  barely audible high harmonic buzz that pervaded the guitar. Although I thought I was pretty successful in eliminating it, a recording engineer picked it out during a recording session.