Originally Posted By: JohnK
Mike, you appear to have a concern about lower speaker impedance that isn't justified by either principles of audio technology or real world experience. There's no brick wall that amplifiers run into when speaker impedance drops below some critical number. As Alex(dakkon)pointed out, amplifiers output voltage. When the voltage meets an impedance in the speaker, a certain current results(following Ohm's Law)and the product of the voltage and current is power in watts used. As the impedance gets lower with a given voltage output from the amplifier, the current gets higher and the heating effect on the amplifier increases. If this heating effect was high enough and continued long enough, the protective circuits in the amplifier would shut it down until it cooled. This just doesn't happen with typical quality receivers in the 100-150 watt range and they have no problem with M80s(as many of our members have reported)or similar speakers operating at safe(to your hearing)sound levels. As an extreme example for your information and/or amusement, I'll cite Mojo's heroic surgery done on the 2 watt amplifier in his wife's Sony boombox and resulting M80 blind listening results here .

You also seem to have partially misinterpreted Richard's(Socketman)measurement results. There's no increase in M80 impedance with the top and bottom inputs separated by removing the connecting links. As I noted previously, the high and low frequency sections of the crossover always have to be separate for there to be a crossover. The graphs in Richard's fine measurements simply are showing the different driver combinations which are being measured through the separated top and bottom terminals, with the big impedance increase a little over 2KHz reflecting the tweeter crossover(the Axiom spec is 2.3KHz) and the impedance hike above 100Hz reflecting the woofer crossover(160Hz Axiom spec). This is the way the M80 crossover works and removing the connecting links can't change it. The graphs would be the same with the links still on if the measurements were made inside the enclosure at the beginning of the crossover circuitry where the wiring normally splits for the separate crossover sections.

John I hole heartedly agree. Most if not all quality modern receivers will have no trouble drivining the m80.My Pondering revolved around a vintage yamaha amp refered to as the m70 rated at 200watts into 8 ohms 20hz to 20khz freq. that clips at 250 watts 1khz 4 ohms. A very different amp then say the m80 which has dynamic power to 640 watts 4 ohms.The m70 still has lots of power but is limited compared to its newer brother. Anyway, all my ideas are a bust but it is good to aquire accurate knowledgeWhen you talked about the high frequency part of the crossover network having influence over the low frequency resistance that the amp sees I kinda knew my biamping ideas were shot.(if I read what you said correctly in your previous post)Answer me this so i get it right.Does the high frequency section of the crossover raise or lower the low freq.resistance the amp sees?