False Beats

[Richard Brekne]

Ron, Ron, David, and others..

I aggree... most interesting..so far we are dealing with one particular kind of false beats. I hear these as very clear sounding, almost pleasing to the ear from time to time taken by themselves.. however badly they sound when listened to withing a tuning situation. There are other kinds of falsness I'd like to get a bit into as well,, but for now I'd like to keep to this bridge pin related type.

Ron Overs... you make a great case for the offset angle, I do have one quiestion relating to this tho.. the necessity for a particular degree of sidebearing to avoid this kind of falseness... is this because of the use of bridge pins to secure the string to the bridge to begin with ? Or is it (the side bearing)  necessary in the effective transmision of string vibration to the bride, hence dictating the use of the bridge pin configuration ?

I think back to that wreck of a piano I saw a while back with the brass clamps.. not a good example to judge by for sure... but the sound there was... well.. better for sure then the surrounding area on the bridge... Also one thinks of the bridge aggraffe system.. I have never had a chance to check one of these out so I dont know how they sound.. yet as some were in production for quite some time I suppose the solution was workable from an acoustic point of view. These would indicate (to me anyways) that side bearing in itself would not necessarilly be essential.

If on the otherhand, these configurations have inherent falsness of this type, and the employment of the appropriate amount of side bearing is the way to get around it, then I sure would like to know a bit more about the mechanics involved.

Ron Overs wrote:

> David, Ron, Richard and list,
>
>
> So often these makers use bridge pin inclinations which are insufficient and a string offset angle which is often below 10 degrees.
>
> I learned a lesson the hard way a recently. Ten degrees of string offset angle and twenty degrees of pin inclination certainly works well.
>

Grin... ( below) this sounds kinda neat... its not any kinda process you can make available to the technical community is it ??

>  For the second take, the bridge pin positions were transferred from the spreadsheet to a CAD drawing of the piano. The drawing scale was adjusted to produce an accurate 100% print out on our Epson inkjet. The print out was placed on the blank bridge caps, which allowed us to punch the marks through to the bridge cap. Using this system we were able to get the highest bridge pin location accuracy we have had to date.

>
>
> >  I have a 1870 or so, factory rebuilt, Bechstein grand that has some
> >of the worst falseness in the treble...5 beats a second if you can believe
> >it.
>
> Typical of Bechsteins of the period. Is the bridge pin group parallel to the capo bar?
> Bechsteins usually do not comply - a highly suspect practice.

I have a similar old Bechstein.. a 9 footer... horrible falsness.. yet I suspect we are talking about falsness related to other problem areas then the bridge pin alone.. And in any case on mine there is no capo bar.. (common to Bechstein ??) only agraffes. Here I wonder if things like lack of crown / insufficient downbearing, worn agraffes, old strings, etc are the major problems. In anycase the kinda falsness I hear on this piano is entirely different then that I hear from the Petrof piano I describe when starting this thread. Here the falseness is very unclear.. wangy, string noise-ish, long unstable meeeowww-ish like.

>
> Ron Ns post was very interesting.
>

Aggreed... and I have to concure with his experience. False beats annoy us all, and more then a  few of us have dinked around trying to figure out if we can improve the situation. I have seated strings.. changed strings.. turned bridge pins, tapped them further in and all the rest with basically the same experience that Ron N reports.. tho I have never thought to much about the depth of the hole. The few epoxy fills I have done have cleaned things up pretty well as a rule, but sometimes this is accompanied by a slight "deadening" of the sound as a whole. I havent tried CA in this regard yet.

My best results with cleaning up falsness in general have always come from cleaning up the front termination point. But this is more that kind I described in the Bechstein example. I have always figured I wouldnt be able to really do much about bridge related falsness untill I learned how to re-cap or build a new bridge, and notch it. (For some reason this really intimidates me... grin)  But like I said, I have had some limited success with epoxy and re-notching.

>
>
> Interesting posts guys.
>
> Ron O
>
> Overs Pianos, Sydney Australia
> -------------------------------
> Email:   sec@overspianos.com.au
> Website: www.overspianos.com.au
> -------------------------------

--
Richard Brekne
RPT, N.P.T.F.
Bergen, Norway