<!doctype html public "-//W3C//DTD W3 HTML//EN"> <html><head><style type="text/css"></style><title>Re: rear string lengths</title></head><body> <div>Hi Dale,</div> <div><br></div> <div>As usual, I get around to replying to a topic by the time you've probably forgotten that you wrote it.</div> <div><br></div> <div>At 10:22 PM -0500 24/11/02, Erwinspiano@aol.com wrote:</div> <blockquote type="cite" cite><font face="Times New Roman">Although there are many reasons for the usually generous sustain times heard on Mason &Hamlins</font></blockquote> <div><br></div> <div>Indeed the heavier rim construction and thicker plate webbing (at least when compared to the slightly built S&S instruments, and the later offerings from Kawai and Yamaha) would also contribute to sustaining qualities. I was quite impressed with these aspects of the M&H B I saw at Reno.</div> <div><br></div> <blockquote type="cite" cite><font face="Times New Roman"> all this talk of rear duplexes got my attention the other day as I tuned one of my recently bellied Mason A's. All the backscale lenths in the plain wire are generous. I found the sustain very good in the K- ovtave as is usual for these pianos with decent boards.  I also note that the first 9 notes of the first capo section had  tuned duplexes corresponding to a 6th partial and the rest of the section double octaves. . . .the rear string lengths of the first nine notes were quite long. Starting at about 4 inches down to about three then back up to longer lengths again.</font></blockquote> <div><br></div> <div>The ultra short back scales used by some makers would seem to be effective in reducing sound board panel response (since the short back-scale lengths would function like a group of small bars, holding on the bridge - I just imagine them controlling the panel - don't move).</div> <div><br></div> <blockquote type="cite" cite><font face="Times New Roman">Although these segments were fairly well in tune the greater attributing factor I believe is the long backscale lengths.</font></blockquote> <div><br></div> <div>Yes I suspect that it is important also. Although they can to be too long also, which causes terrible back scale noise problems (the Yamaha CFs of the mid '70s had high noise trebles which were shockers in this regard). When we rebuilt a KG6 Kawai (a piano known for its intrusive back scale noise) in '99, we relocated the hitch pins and set the bearing blocks to a shorter tuned layout (filling the original pin holes with car body filler). The new hitches were located 20 mm (which is a standard figure we use) behind the revised block locations. The outcome was very pleasing indeed.</div> <div><br></div> <blockquote type="cite" cite><font face="Times New Roman">Other contributing factors would be wide cases/board</font></blockquote> <div><br></div> <div>What do you mean by wide cases/board ?</div> <div><br></div> <blockquote type="cite" cite><font face="Times New Roman"> good scales (mostly)</font></blockquote> <div><br></div> <div>The M&H cross over is somewhat old worldy, complete with diving-tension-syndrome as the treble bridge approaches the crossover - like so many other makers, some of whom consider that they are modern piano manufacturers.</div> <div><br></div> <blockquote type="cite" cite><font face="Times New Roman">, good bridge location in the center of the board etc.) (As a side noteRecent discussions on Mason a's very short bass backscale lengths didn't however in this case render the tone unacceptable by any means. Tail thinning helps greatly on these pianos with conventional belly's)</font></blockquote> <div><br></div> <div>Indeed, but if it had a longer back scale it might have been even more impressive.</div> <div><br></div> <blockquote type="cite" cite><font face="Times New Roman">  Finally the question. What are adequate backscale lengths  capable of giving  increased freedom/sustain. The lengths in this case are much longer than the average stwy. It seems like 3 to five inches on any piano(in the capo) would allow more bridge and board freedom.</font></blockquote> <div><br></div> <div>Agreed, but five inches or 125 mm would be getting towards the longer length which might be appropriate for the rear duplex - any longer and there is some risk of intrusive back scale noise.</div> <div><br></div> <blockquote type="cite" cite><font face="Times New Roman">  If I removed the duplex on the average stwyL and changed nothing but the string lengths.(forget the tuning) what would happen?</font></blockquote> <div><br></div> <div>You'd probably get some improvement. But I suspect also that the smallish bridge dimensions could be a likely factor in the less than impressive sustain of many Steinways. Back in 1990 I re-bridged a circ. 1925 New York D which had amazing board crown, but the bridges were shot<font color="#0000FF"> (a well known Australian piano maker had previously 'rebuilt' this piano by inserting shortened balance rail pins into the split treble bridge, presumably in an attempt to gain a tighter fit between the 'bridge pins' and the split bridges - the outcome seemed to be somewhat less than impressive)</font>. Furthermore, I suspect that this piano might have been one which the belly man built while he was thinking about lunch, since there was virtually no bearing but substantial board crown. There we also major disagreement between the bearing on bass bridge relative to that of the long bridge. Since the board appeared to be relatively undistorted with age, I could only conclude that it had been poorly assembled.</div> <div><br></div> <div>So I took the opportunity to rectify the down bearing by building taller bridges instead of lowering the plate, since already I had begun to suspect that tall bridges helped sustaining qualities. When the bearing was finally set this piano ended up with a nearly 40 mm high treble bridge in the mid section<font color="#0000FF"> (with an unstrung down bearing setting of 6 mm - 4 of which typically sinks out during the stringing)</font>. The sustain of this piano is very good. One old timer local tech<font color="#0000FF"> (John Rocks)</font>, who has - since rest his soul - graduated to harp tuning, claimed that I'd transformed the piano into a European style singing piano which had a slightly smaller upper dynamic range. I agreed. It was an important lesson for me on the importance of bridge rigidity, since nothing else on the piano was altered (apart from reshaped capo and duplex bars - which were unhardened since we only started this practice in '94-95).</div> <div><br></div> <blockquote type="cite" cite><font face="Times New Roman">     I'm looking for suggestions and expeience from whomever.</font></blockquote> <div><font face="Times New Roman"><br></font></div> <div>I that while I still feel somewhat unsure about this topic, I have developed hunches. I feel that the back scale length should mirror the requirement for the excursions necessary to produce the lowest harmonic of the adjacent notes. In other words, in the bass where a significant ' board displacement is required to generate effective sound pressure level of the fundamental, the board must be at its most moveable. This doesn't necessarily mean floppy, since we do want the board to move as a homogenous whole as much as possible. But the edges or perimeter of the board should be very flexible. As the frequency of the fundamental frequency increases as we move up the scale, the sound board should become progressively stiffer. If the back-scale lengths gradually shorten they will work with the stiffening sound board panel to help raise the impedance of the board for the higher notes. But I do not think we should use 30 mm back-scales unless we are looking for less sound pressure level in the treble. Of course, this might be a legitimate goal when designing a small grand for the home environment.</div> <div><br></div> <div>Interestingly, while still on this matter of appropriate sound pressure level for the environment, the buyer of our piano no. 001 has it housed in a largish music room at his home. This piano produces so much volume that it sounds somewhat like it is trapped in a biscuit tin. I suspect that 225 cm is too large for a home environment piano. So it may be that a suitable design for a 200 cm grand might incorporate slightly shorter back scale lengths to reduce the sound pressure level to more acceptable levels for the home.</div> <div><br></div> <div>Just a couple of thoughts from down under.</div> <div><br></div> <div>Best,</div> <div>Ron O.</div> <x-sigsep><pre>-- </pre></x-sigsep> <div>_______________________<br> <br> OVERS PIANOS - SYDNEY<br> Grand Piano Manufacturers<br> <br> Web: http://overspianos.com.au<br> mailto:info@overspianos.com.au<br> _______________________</div> </body> </html>