exactly what i'm thinkin lol. from what i've gathered, the impedance goes up when you stick it in a box. the only thing i could think of that would do that is if the sub, being semi enclosed or even completely sealed, gets hotter, so the resistance of the coil(s) goes up. but that's a completely uneducated guess. where's MS?
That amp may be ok, but i really wouldnt recommend it. Thats already a 'dirty' amp, Its a decent budget amp but running it lower would only complicate things. Also, its kinda overrated.
Do you already have the PA amp? What subs are they? Whats your amp budget?
Yes musical ohm load is something entirely different. Plus with amplifier parts especially cheap ones the values of the electronics can impact this significantly. Most cheap made amplifier components are + or - 10%. The high end stuff is 2% tolerances and the mid grade is 5%. So in short your ohm load on your amplifier will actually vary. Rockford fosgate printed a big article about this in crutchfield way back when the 3 subwoofer boxes came in. So you can actually push an amp rated at 4 ohms mono with 10% tolerances at 3.6 ohms
Another note for Toyotaduder what kinda amp are you wiring them up too? Most amplifiers that run 4 ohm standard will stiil push the same power to an 8 ohm sub as a 4 ohm sub because the amplifier isn't made to push the light 8 ohm loads.That is why manufactures don't give 8 ohm load ratings.