Thanks, Ron, for bearing with us. Your post is perhaps one of the most succinct and easy to understand descriptions of what is going on that I've seen. Please keep stoking. >>The bass works well when the assembly is light >>and flexible down there. The purpose of floating the bass in >>small grands, and moving the bridge to increase back scale >>length, is to add flexibility and amplitude of movement. If I consider a woofer speaker, it is designed to be very rigid/stiff to produce a large area pressure pulse without deflecting/deforming the cone, otherwise the pressure pulse would disintegrate. The cone is also very low mass so that it can accelerate quickly back and forth with large amplitudes. It is very flexible around the edges but not the cone. This is what I would like to see a little clarification on. You and others speak of the need for increased flexibility in the bass section. When you say you need increased flexibility in the bass for amplitude of movement, aren't you really saying you need the flexibility around the edges, or even a floated edge? The panel itself needs to remain rigid or stiff, but for it to move it has to be able to give around the perimeter. Dean Dean May cell 812.239.3359 PianoRebuilders.com 812.235.5272 Terre Haute IN 47802 -----Original Message----- From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of Ron Nossaman Sent: Saturday, February 02, 2008 11:05 AM To: Pianotech List Subject: Re: Compression ridges was :Do you dry the ribs, along with the board,prior to gluing ? You quit stoking the fire for a minute, and the darkness creeps back in. A flexible treble goes "dink". The treble needs to be stiff, which is what the fish is for. The bass cutoff diminishes unwanted spurious resonances and makes the ribs shorter in the killer octave - to stiffen them. Too stiff a treble shrieks, which adding mass cures. So an overly stiff treble that's mass loaded is highly functional while still being well above minimally adequate stiffness. That's a built in safety margin for future climatic aging and deterioration. Too stiff a bass is thin and lacks fundamental. Too heavy a bass clangs. The bass works well when the assembly is light and flexible down there. The purpose of floating the bass in small grands, and moving the bridge to increase back scale length, is to add flexibility and amplitude of movement. The use of mass loads on the low tenor or high bass bridge is an after the fact attempt to blend any existing tonality mismatch across the break if the builder didn't get exactly what he wanted with the design. Nobody's perfect, so there's make up. Ron N
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