Same watts at 8 and 4 ohms?


I'm in the market for an integrated amp and trying to sort through tech specs. My understanding of the tech aspects of hi-fi gear is limited. Looking for some clarity in regard to watts-per-channel specs.

It is my understanding that wpc at 4 ohms is typically 1.5x -2x the wpc at 8 ohms.

But I'm seeing a number of respectable mid-fi integrateds with the same wpc for both 8 and 4 ohms. The NAD 388 is one and I think this is true for several of the Cambridge Audio units at a similar price point ($1500-$2000).

The NAD features make a point of saying " 4-ohm stable for use with a wide range of speakers". 

Would appreciate any insight to what these specs mean and what 4 ohm stable really means to me. My speakers are 4 ohm speakers.

Thanks,

George
n80

Showing 8 responses by invalid

Danvignau what is your point none of those amps even come close to doubling down when impedance is halved. My krell has a 5kva transformer and 260,000 uf of capacitance and 56 output devices but it even can't technically double down on power with halved impedance.

The bigger the power supply and the bigger the output stage the higher the wattage into 8 ohms. They may spec an amp at 1500 watts into 8ohm but if it's actually measured by a independent 3rd party they always come up with a higher wattage than the spec sheet from the manufacturer says. Take my krell amp for instance it's spec says 300 watts into 8ohm but stereophile measured it at over 330 watts.
I bought my big krell amp because my apogee duetta 2 speakers are very inefficient at 80db/w. 
Cakyol,                                                                                                 those amps are underrated on there 8ohm power specs there isn't any amp that can actually double it's output power, it is impossible. Like Georgehifi says it would be perpetual energy to be able to do that. I have a krell amp that claims that spec but it can't technically do it, it can come close but the lower in resistance the less likely.
I would still think the ML2 would be more than 25 watts into 8ohms. My vintage krell amp is 300 watts and is supposed to double, but it measured higher than 300 into 8ohm, so the manufacturer did underrate the amp to get to that doubling into 2ohm and under.
I doubt any amp can really double it's power with halved impedance. Most of the amps that say they do are actually underrated at the 8ohm impedance.
It does come close, but I need another one to vertically bi-amp my apogee duetta 2 speakers, they are very inefficient but sound great.