1 ohm is not very hard to stay stable at....u do go down in efficiency but stable? no anything under 1 u will loose stability if u dont kno what ur doing
almost everyone on here runs 1 ohm daily.......
This^..The on/off high speed switching design of the class D facilitates a much more efficient and stable transfer of high current at lower output voltages in those amps that are designed to be ran at 1 ohm, which is why most Class D bass amps are 1 ohm stable. Companies rate an amp to the lowest impedance they will warranty that amp design to be ran at. The Alpine is rated at 2 ohms minimum impedance. It is obviously designed to operate at a higher output voltage for 2 ohm stable operation. Running that amp at 1 ohm could cause it to overheat from low output (rail) voltage and fail(they have been known to do this).
On the flip side, the Class D American Bass VFL80.1 from my previous post (and quite possibly the best built amp in this thread, aside from the Mmats mentioned), is designed to operate at extreme low output voltages without overheating. It is rated at 1 ohm minimum operation for warranty purposes, but I have heard of people running them at 1/2 ohm loads without issue on proper electrical for daily use and 1/4 ohm loads for competition use in very skilled hands for short durations...that is almost a dead short...lol.
Class D amps are most efficient at rated output..80%+ is not uncommon at 1 ohm operation.
The Class A/B amps, by design, generate more heat at lower ohm loads and are far, far less efficient. The effects of efficiency loss and heat generated dramatically affect performance not only on the internal parts, but on your car's electrical as well.
Class A/B has a theoretical max efficiency of 75%(IIRC)... 55%(or less) is not uncommon at 1 ohm operation.
check this out:
A 2 ch 1 ohm stable class A/B rated at 250 watts/ch rms at 4 ohms @ 14.4v should produce 2000 watts rms (ignoring losses and rail voltage sag for the sake of simplicty) bridged mono at 2 ohms (1 ohm/ch)
2000w/.55(55% efficiency)= 3636 watts required to produce the rated 2000w rms
3636/14.4v = 253 amps required to produce the rated 2000w rms
A 1 ohm stable class D monoblock rated at 2000w @14.4v and 80% efficiency.
2000/80% = 2500watts required to produce the rated 2000w rms
2500/14.4v = 174 amps required to produce the rated 2000w rms
Keep in mind, all current that does not make it to the speaker outputs is dissipated through the heatsinks. 79 amps in the above comparison dissipated as heat for the same rms wattage..that could be the difference between having to buy a $500 H.O. alt or not, depending on the vehicle.
I understand you are not choosing between Class A/B and Class D (well, kinda, the Class G/H is supposedly a hybrid of the two..A/B SQ and D efficiency), but I feel this is where the question of stability at low ohm loads derives from in folks who have learned through trial and error. I have smoked a prized amp and burnt a coil or two from weak electrical and pure ignorance...It su
cks.
