Nice Stewie! Glad it worked for you, but i knew it would . Here's the thing: There are both output and input impedance as you clearly understand. However, the input or "nominal impedance figure" [4 or 8 ohm in your case] of an certain speaker is not really the impedance of the speaker itself. It's actually the DC resistance of the speaker's coil. Therefore, it's really looking at the worst case that an amplifier can handle in regard to power [remember Ohm's Law, I=V/R and the converses V=IR and R=V/I. i.e., for an amplifier's or output source's output measured in *volts a 4 ohm load would draw twice as much current as an 8 ohm load. So the problem is more in battery drain rather than blowing the speaker cone unless you somehow managed to crank the vol up to 200% an' rip the knob off so to speak... or so i've heard . I really think the concern is more for the output source than the speaker itself when you use a higher impedance speaker than that specified as optimal.