Interesting responses thus far. Except Ernie's. He missed the obvious: this is a hardware problem and I only do software. Actually, we used to work together and I've come to expect such shennanigans from him. ;-)
The ideas on using nuts and washers actually came to mind, but a more elegant solution is desired. My thoughts on using a regular nut are that finger access to it would be restricted by the cone making a wrench necessary to for adjustments.
Washers are an interesting consideration and might be worth a try. They'll have to be *exactly* the right ID and thickness or Marsh will be correct. He may be anyway.
Either of the above solutions would be cumbersome as these speakers weigh 100 lbs. each. They're easy to tilt, but that ties up one hand which is why I'm tooking for a "one-handed" solution. I'd hate to drop one while futzing around!
The idea of teflon tape is interesting. If the threads on the inserts were cut to a closer tolerance, as Marsh suggests, there wouldn't be a problem. They're most likely made as they are for a reason. Otherwise it would be harder to install the cones due to a greater likelihood for cross-threading the shaft into the insert.
When initially pondering the problem (ok, I actually do hardware on a limited basis) what came to mind was not a nut, but a threaded thumbwheel. Something that would be run up against the bottom of the speaker after it was leveled. Since posting I have found that knurled brass nuts of the appropriate size are probably available at the local hardware store. Eight of these and an equal number of longer threaded shafts (which are actually allen head set screws) should fix the problem.
Nonetheless, thanks for the suggestions.
As an aside, larger spikes would still be nice. The stock ones are 1" in diameter and 1.5" tall. My seating position is higher than a normal couch or chair and raising the speakers a bit probably wouldn't hurt things.
