Bill-

BTDT..............heavy speakers, drywall wall, no studs to mount to.

Used the MDF "adapter plate method" & a heavy duty speaker mount by
Omni-Mount

OmniMount is the mfr of very heavy duty audio & video mounts

check out

http://www.omnimountpro.com/om.asp

they have a wide variety of mount styles that can handle wide range of
speaker weights.

wall or ceiling mount

IMO plaster w/ metal (or wood lath) can deliver fairly high loads; I
would suggest the use of either SMS screws directly inot the wall (if
wood lath) or molly bolts (not the toggle style), the "epanding cage"
style if metal or gypboard lath

A 15 lb speaker is not all that heavy;
the ratio of the wall to speaker cg distance and the adapter plate
screw center distance will give you an idea of the "force multiplier"
that the screws must resist. Worst case I'd figure 3x. If you get a
4 screw pattern that means your top screws need to deliver about 23 lbs
each in pullout.

www.mcmaster.com
catalog number: 97102A517
Drill Style Hollow-Wall Anchor
10-24 Screw Size, 2-3/8" Length

cheers
Bob