Last night I did my serious listening test playing Side 2 of Blood On The Tracks by Bob Dylan in the Mobile Fidelity Sound Labs audiophile 200g pressing, which I've used in every tonearm test since the Linn was fixed last month.
The bass, while musically fine now, isn't any "stronger" in fact it might be a very little bit less. The higher mass kept the vertical resonance centered at 12 Hz, the new lighter mass only keeps it down to 13 Hz. I suspect the effect of these resonances is to absorb and reduce frequencies up to about twice the frequency. So I'd predict a resonance of 13 Hz to cause reductions as high as 26 Hz. That's not ideal, and a vertical resonance at 12 Hz or less would be better. By extrapolation I can see the resonance moving up to 16 Hz with with a stock Ittok with no tape on it at all and my Dynavector 17D3, which would cause bass reduction up to 32 Hz, and at that point it's musically deadly, at least in the bass.
But something else has happened that I just wasn't thinking about, though I've long worried about.
By far and away the biggest change from "optimizing" the mass at 1.7g "added" (this probably means almost 3 g more than a stock Ittok arm, because just the damping tape all over including the headshell itself probably raised the effective mass by about 1g) is that the transparency and resolution has improved enormously.
I'd always thought my recent turntable playback had a bit of obscurity compared with digital inputs. I noticed this especially listening to Purple Rain earlier this year and it inspired me to do a whole new wave of adjustments to the midrange EQ, then the Bass EQ, and ultimately the Bass Limiting as well.
But this didn't entirely fix the slight opacity in vinyl playback. I was beginning to just accept it, after all the rest of the sound was sumptuous and wonderful with recent adjustments.
Now, finally, with the optimized effective mass, I have reduced that opacity. And I believe that change results from moving the horizontal resonance above 8 Hz. When the horizontal Resonance is centered at 8 Hz, and reaches down a bit to 7 Hz and below as well, it's then picking up and resonating in response to all the physical imperfections of the vinyl. And all that resonating is not so audible in itself as in how it's constantly modulating the signal, adding an opacity to the sound.
Now I could take this improvement all the way by going back to a stock Ittok arm with no tape added to it anywhere, then the horizontal resonance would probably be centered at 11-12 Hz with not a bit at 8 Hz and below. That would be even better, except for one thing. It would push the Vertical Resonance up to 16 Hz, leading to loss of audible bass up to 32 Hz and higher, and making it sound "thin" (and "metallic" as well...with the stock undamped Ittok).
That was the sound I originally had with the stock Ittok and pretty much hated after awhile. Way too thin. I presumed then that the remarkable transparency (which was remarkably good in revealing tonearm metallic resonances in particular) was caused by the lack of bass. Rolling off the bass often gives and artificial clarity...but it's a clarity that can quickly become tiresome.
Then the year or so I listened with the huge 6.1g extra rolled mass gave nice extended and even luxuriant bass, but lack of clarity. I did not know how to fix that, but now I do.
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