Good stuff! Nicely done.
Being a bicyclist myself I do like the comparisons, even do I only ride Reynolds 520 Steel
I was wondering though since the sheet of CF is quite thin, how is the stiffness?
Does it bend easily?
From what I've read the braces are supposed to keep the arm base and platter base at the same distance at all times (something like that?), or am I on the wrong track?.
Allthough I'm sure you've already thought about that
Thanks Troutbum and Etnier!
@ Troutbum: My wife rides the Reynolds 853, while I ride a Dedacciai SAT frame. She always gets the good stuff. Although I preferred a bit more the geometry of my previous Easton Ultralight Alu frame, it was a harsher ride and it was stolen.
CF becomes very difficult to flex at 1/16" or about 1.6mm. I could not bend it perceptibly.
As RoDa says, I think the brace is at least stated to do more than just act as a spacer, it is supposed to provide a rigid mechanical link between bearing and arm. That was one of the ideas I was "testing". The theory is that the forces of rotating the subplatter and platter may lead to arm and platter motion that is not on the same plane or vector, which becomes audible with blurring and timing problems. This is not my theory, I repeat it from reading elsewhere.
If this were true, my hypothesis was that one would expect to hear more cohesiveness and increased resolution with a more rigid material than the somewhat softer mdf plinth covered with phenolic resin. Another hypothesis was that CF is very good at absorbing energy, and therefore would reflect back less energy coming from the arm, and transmit less energy from the plinth. This would likely lead to less blurring effects and more even frequency response.
I still haven't put any other carts on, so I guess I can't say I've proved the hypotheses completely. Because both the SAE and 501 gained resolution, I might say they been partially proved. I'm not sure what to say about cohesiveness, because this is difficult to quantify when the deck was not lacking focus before, AFAIK. I can say that those records with previously boomy or woolly bass are no longer like that. Bass is tight and textured, which may help with a perception of greater extension, because you can actually hear the notes better than before.
And if I don't feel like taking the Shelter away, I guess this is a good result in and of itself? Who knows, but at some point, I will try another cart and report back.
@Etnier: I think what you state about double braces needed to stiffen the plinth is true, based on Rega's description of the DBT as a "stressed beam". Frankly though, I'm not sure (and may be a bit skeptical) how Rega have fabricated the plastic to be a true stressed beam, i.e. flexed prior to clamping, and they don't talk much about the DBT's sonic benefits, only mechanical benefits.
So, in my experiment, even if I had used two braces, it would not be similar to Rega's DBT if in fact they do use a stressed beam approach, as I could not duplicate that in DIY. My "armboard" experiment may only mechanically couple the arm and bearing, and might drain energy better.
WT Simplex, Shelter 501 II, DV20xl, Benz ACE SL > Aleph Ono, Bel Canto PL1/DAC3 > Pass X1 > XA30.5 > DeVore Nines
: Beyond measurements and theory, there's intuition and feeling: