Hi Duke, an old thread, but I am about to try this tweak disadvantage by zero technical knowledge, but I do at least have a soldering iron!
I have stacked Quads, in parallel, connected to the one amp.
I have found a suitable, 8ohm one inch tweeter, and assume that the fact that it is rated at 91DB will probably make it about equivalent to the 88DB efficiency you had in mind for an average tweeter, given I have two pairs.
What I am wondering is what the different impedance of the tweeter circuit does to the way that the amplifier drives the different speakers, given that all speakers are connected in parallel, and driven by the same amp.
IE, why doesn't the power just go to whichever circuit (be that tweeter, or the two Quads) is easier to drive for the amp, at the particular point in time of the music?
I know this question betrays a fundamental lack of understanding of things electrical. I hope, however, that it is comprehensible as a question!
Happy to hear an answer from anyone who has one.