Not quite a "Thread from the Dead", but from the dormant, perhaps...
I'm tearing my hair out with this. Having spent a couple of hours playing around with the bias again, I got to the point where I could detect no actual difference, better or worse, on the sibilance issue regardless of how I set it. There was, however, a benefit in clarity and (to a lesser extent) focus when backing it off a little, making it easier to hear into the mix.
I reduced the VTA by a quarter of a turn, i.e. giving a very slightly tail-down attitude on the arm and found much improved bass, both in quality and quantity. Again, there was improvement in the imaging, as though I'd put a squirt of Windowlene across it and given it a polish, removing a sense of "haze". The image width also seemed improved, as if the performers weren't squashed together so much. However... still no improvement in sibilance.
I decided to re-check the basic cartridge alignment, having convinced myself that I'd not got the protractor properly aligned first time. To my surprise and a little shock, I realised that the stylus wasn't actually fully pushed home into the body of the cartridge! There was a couple of fag-paper's gap between the two parts. How that happened I don't know, must have been ham-fisted when I fitted the cart to the new arm. Additionally, I think I was right that I'd not quite managed to align the protractor correctly to the centre of the arm pivot, it was a fraction out I think.
Considering these two problems I ended up moving the cartridge forward very slightly in the arm slots, so it's now not pushed fully back "against the stops", as it were. I think it's now better aligned than before.
I re-checked the setup with the HFN test disc for bias, taking into consideration the advice above (so using it as a start point rather than an absolute). I backed off the bias to as little as I could, and gradually increased it a fraction at a time until it would track the +16dB (second to last) track OK, although it won't do the +18dB track. I decided not to increase bias any further, but to use that as my start point for fine-tuning by ear. I also re-checked the horizontal and vertical resonance - vertical looks to be around 11Hz, horizontal begins at 10Hz and peaks at 9Hz down to 8Hz. Is that too low?
Anyway, putting on a brand new (but cleaned) LP afterwards (Years & Years "Palo Santo"), I noticed that the treble in general seemed a little "hot". And as for that sibilance? The very first track on each side (it's a double album) seemed OK, but from about the middle of track 2 onwards it seemed rear it's ugly head again, although I wouldn't necessarily say that it got continually worse. It just seemed to appear.... and stay at a level.
Swapping to an older pressing - Fleetwood Mac "Mirage" still displayed that slightly hot treble - not quite sure exactly how to describe it but perhaps "feathery" might be appropriate? It's not cut-your-ears-off bad but I can imagine that many people on this forum with an aversion to brightness would run from the room. Dynamics seemed particularly good on the opener "Love in Store", the drums having real impact and tonality, and the imaging was also very good, with that hear-through ability I value so much. The sibilance issue didn't seem quite so bad on this recording, but it was definitely still there, especially towards the end of each side.
Texas "The Conversation" (which is an awful recording and abundant in sibilance anyway, even the CD version suffers) did sound better than it had before, but still had a splashy top end and of course, the dreaded sssssss-word was there for all to hear.
So I've made some improvements overall, but not in the one thing I'm trying to fix! What on earth could still be the issue? I'm too scared to adjust that damned bias again!
And on the evidence of earlier, it didn't really make much difference anyway. Bringing the VTA down improved the bass and imaging, but didn't really make any difference otherwise... unless it's responsible for that brighter top end too? I was of the understanding that lowering the VTA tended to favour bass over treble, and that raising it would brighten things.
I've been wondering about azimuth. It's one of the potential causes listed on the
Soundsmith website and is something that's non-adjustable (well, not user-adjustable) on the OL arm. I was wondering about trying one of the OL cartridge enablers to allow some adjustment to be made - thoughts on this one please?
Am I just going to have to accept that I'm perhaps particularly attuned to sibilance and that I'm never going to get rid of it completely? It does make me wince sometimes, and despite your reassurances, David, I'm still paranoid about the records!