Graham:
I own a few Alembics, and I've played lots of them over the years. I also own a Wal Mach III, and I can tell you that the low end of most Alembics is at least equal to the low end of my Wal, and is probably better, to my subjective ears.
A couple of observations: generally speaking, all things being equal a neck through bass will produce noticably more sustain than a bass with a bolt-on neck. The increase in sustain will often manifest itself as an increase in the first fundamental of each note, or what we call low end. All Alembics except Orions and Excels are neck-throughs. Wals are bolt-ons, like your beloved Stingrays. Don't get me wrong: bolt-ons produce a very pleasing tone that lots of musicians really love, but I don't think that you can say that those basses are stronger in their low frequency response when compared to neck through instruments.
I think that when people say that Alembics are lacking low end response what they are really mean is that Alembic electronics are capable of producing more high end than they are used to hearing. Alembic electronics produce a very flat frequency response way up to about 6khz, and there are very few basses that can do that. So, when people say that a XXX bass has a strong low end what they really mean is that the highs are missing, which accentuates what is left. It you want to produce that tone with an Alembic, all you need to do is roll off some of the high end with the filters. But, as Greg Allman once said, you can't lose what you never had, and if the high end isn't there in the first place you can't roll it off. Alembic's whole design philosophy is to let the player make tonal decisions as opposed to forcing them upon him or her.
As others have said, if you are really into a sound with less high end you would probably prefer an Alembic with a mahagony, walnut or cherry core. Steer clear of maple. If you can afford it, adding ebony neck laminates to a maple neck will give you more low end than is legal in some states. The top wood makes some difference as well, but as long as you stay away from flame maple you will be fine.
Last point: I really hate to say bad things about people as life is far too short for that, but the truth is the truth: Wal's customer service is horrible. I mean the WORST. Basically, there is no customer service. The neck on my Mark III bowed terribly after about 6 months, probably because the wood wasn't properly dried. Hey, it happens. However, this should never happen: it took me 18 months to get a new neck for the bass. It took me 6 months to contact Pete. I must have left him 20 phone messages (and I live in the US!) without a return call. Finally, and in desperation, I complained about the whole sad story on a Wal forum, and some kind soul in England actually went to the Wal shop and told Pete to call me back. At his direction I sent him the neck from my bass, and he didn't send me a new one for a year. Caveat emptor.
(Message edited by s_wood on May 27, 2006)