Hi JD: Well, I agree with you that there can often be an irrational exuberance for a Steinway. Still, they can be awfully nice pianos, and it is what is before me in my shop as my next project. I make no claim to have any practical experience in deliberately modifying bridge height, at least not yet. But I am aware of the experience of others in doing so, and have long thought about the relationship of bridge height, stiffness, and mass. My query here is to avail myself of the experience and knowledge of others before making deliberate and calculated changes in this piano. Others can tell you if the addition of 4 or 5 mm. along the length of the bridge effects a meaningful change in the tone in areas other than the treble. But, to my ear, that is the area in Steinways that would most benefit from this change. I have long thought Steinways to be lacking in volume and sustain in the treble compared to many other high quality instruments. This is the area of the scale that would likely most benefit from higher bridge stiffness and mass, yet the bridge is shorter and correspondingly less stiff. And the addition of the same amount of bridge thickness will effect a larger percentage of change in the treble compared to lower down in the scale. I have wondered about lowering the inner rim in the grand scheme of things, but have given it no consideration for reasons of practicality. Sohmer added to the effective bridge height in the manner you describe for the Grotrian, at least in their Cupid model, which also had the agraffe bridge. Your comment here is meaningful, because adding stiffness and mass by having an "underbridge" would carry the virtue of not having to disturb existing relationships between the action and the string plane, unless there were other compelling reasons to do so. If the only changes that need to be made in the action to accommodate changes in bridge height on the topside bridge are the hammer bore distance, and there are no other attendant penalties; then it would remain the simplest possible way to effect the desired change. Other than the necessary calculations, you are not really adding much work. You have to cap the bridge anyway, you have to thickness the pinblock anyway, and you have to bore the hammers anyhow, and you have to set plate height at the rim. So I remain most attracted to this methodology. Thank you for your (as always) insightful comments. Will -----Original Message----- From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of John Delacour Sent: Tuesday, March 24, 2009 3:46 AM To: pianotech at ptg.org Subject: Re: [pianotech] Increasing bridge height At 19:13 -0500 23/3/09, Will Truitt wrote: >Well, JD, you certainly are a good salesman for the concept... ... Maybe, but I'm not sure how much improvement you would effect in a Steinway by the modification you envisage except perhaps in the treble. Every few millimetres in total bridge height will make a little difference and, by simple mechanical laws, increase the stiffness by more than the proportion of the added height to the original, but you will not achieve a step change by so small an increase. As Ron says, the string height in the Steinway is likely to be lower at note 88 than in the middle. There's good reason for this in pianos with studs (agraffes), as I explained recently. Why Steinway continued the practice, using the capo bar, heaven knows. Raising the string height is not the only way to increase the effective bridge height. One alternative is to lower the inner rim/soundboard, possibly necessitating cut-outs in the framing to allow the passage of the bars. I've done this a couple of times with experimental models, and it's a lot of work without a good set-up. A simpler way is to do what Grotrian, Rittmüller and others did and add to the bridge height from underneath. I've never been impressed with the result Grotrian achieved with the double bridge, but I think that's because of their actual design rather than a fault in the principle. This way you have a far simpler task and can increase the effective bridge height as much as you like without changing the string heights and getting all the bother that ensues from this. If I were doing this, I would calculate (or get a better engineer to calculate!) what _width_ of under-bridge would be required for a given under-bridge depth (which must be 1/4" greater than the depth of the bars) to produce a structure that is as stiff as a simple 45-50 mm over-bridge. This would almost certainly result in an under-bridge narrower than the over-bridge. I guess that Grotrian's 'mistake', as I would call it, was to over-egg the pudding. One day I must sit down and do the calcs. Rittmüller, by the look of it, put more thought into the matter. As a man with a very limited admiration for Steinway's supposed genius, I myself would start with a better piano! JD
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