Hi Col,
I found this exact same problem with my Walstein Tenor - but then this was my first tenor, having played only alto for 18 months or so. I could play all the low notes no problem but to play them quietly was a real struggle. Over the first three months I tried everything from different reeds and reed strengths, to all sorts of strange embouchures but could not get those quiet low notes to stay still. I was convinced it was me but....
Then started to get other professionals to try it and they agreed it was more difficult than might be expected and to my joy, I also heard them warbling horribly as well. This suggested a real problem to me, so I returned it for them to check out. Their technician made some minor tweaks and suggested it may have taken a very slight knock in transit but it came back wth all the same problems on the low end.
I went back last week though, in the expectation of exchanging it for one of a new batch which, to his credit, Martin at Walstein was only too happy to do - even after three months of me having it. Their techinician happened to be present and sure enough he was thoroughly testing all the new imports ready for sale - Steve Howard was a fine chap, great to talk to (and occassionally contributes to this forum

). He took it from me and blew it like nothing I had ever heard, instantly proving that there wasn't anything wrong with the sax at all - though this was with his own aged Vandoren Mouthpiece, which was indeed a much easier blow. With the stock mouthpiece he did admit that it was more difficult to control.
I was there for some time, with another more experienced sax-playing friend of mine and we quickly came to the conclusion that I should persevere but with a more suitable moutpiece. After trying a few I came away with a Yamaha 5C (it just felt slighlty more free-blowing and controllable than the 4C for me), which I'm hoping will get me on the way but I admit to still really struggling down there. I'm just trying to play as much as possible to get to know the instrument's foibles and try and tease those low buggers out, slowly but surely.
Both Steve and my friend agreed that the Walstein plays more like a vintage Selmer, than a modern Yamaha, and the low end is harder work for it. I haven't a clue what they are talking about, not having that experience, but having heard Steve play it like some sax-God and coax those low notes with a deliciously warm, breathy sub-tone 'til they were almost inaudible, I am wholly convinced that I just need to knuckle down and keep working at it. :cry:
I'd be really interested to hear how you progress with this though - keep us up to date, please!
🙂
EDIT: Oops, after all that I hadn't read your penultimate post thoroughly enough - was that definitely the cause? Is she good now?