Dunlavy 4 or 8 ohms for Audio Research VT-100 amp?

Andy, it won't hurt the amp or the speakers hooking your speakers to either the 4 or 8 ohm tap. Try both and listen for which sounds the best. If the speakers are between 4 and 8 across the frequency range, you may not hear an appreciable difference with the VT100.

This is one of the easiest tweeks to try, and I would encourage others to experiment as well. It costs you nothing, and could make a dramatic difference in the amps ability to deliver power to the speakers, especially in the low end. Remember the "nominal" impedance may be quite a bit higher than the "lowest" impedance, and unless you have a plot from the manufacturer, it is impossible to know what you are dealing with.

It is interesting to know that Robert Lee of Acoustic Zen has recently developed the "Adagio", a speaker which has an almost totally flat 5 ohm impedance from 100 to 10K Hz. This is very rare in the speaker business.