Another,very inexpensive method is,providing the speakers have slots in their backs for them,is to just get some long wood screws or sheetrock screws & just mount them in a stud in the wall & hang the speakers off them.If you leave enough of the screw exposed,you can slide the speaker out to the end of it & it will be angled down.As Shinerman said,this is provided that the speakers are not real heavy,& I'm betting they're not,& you're not too particular of the aesthetics. This is not what I would do with a pricey speaker AT ALL,but I have done it with cheapies & it worked fine.Wasn't enough juice to worry about vibration or anything along those lines.Temp solution anyway.
Of course,if the slots are right in the middle of the rear of the speaker,not near the top,it won't work as the speaker will not brace itself against the wall.