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
@georgehifi I have a Levinson, well, Madrigal, dual monaural amp
I would keep it, just have it serviced up to factory spec. Which model BTW?

Cheers George
@georgehifi,
Get an amp like I said for your Aerial 7T’s and you’ll be happy. Your 7T at 84db and 4ohm "nominal" you need 100w-8ohm and close to 200w into 4ohms because you can bet they dive to 3ohm or less with epdr somewhere.
The OP's new speakers are Aerial 6T’s;
manufacturer’s specs are 90dB sens, 4 ohm nominal with a 3 ohm low.
I couldn’t find independent testing or impedance curve. So, possibly sensitivity could be 88-89 dB. The amps being considered could drive these speakers.



While it is true that 'speaker sensitivity plays a role in required amplifier power, it is also true that amplifier power capability plays a role in distortion.  An amplifier will exhibit lower distortion at low output levels than at high output levels.  Distortion will often rapidly increase as the amp's rated power is approached.  Linearity is usually much better at small signal levels, hence lower distortion. This means that at a given output power level, well-designed high-power amplifiers typically exhibit lower distortion than lower-powered ones.

I run two channels of four Harmon Kardon Citation II tube amps each that, on the bench, deliver over 500 watts/channel with 0.05% THD at 1 kHz if line voltage is held at 120VAC.  This means at normal listening levels, each amp is operating at or close to small-signal operation.  Since the 'speakers driven by these amps are B&W 802Ds, I am glad I have the high-power capability.
Normally, solid state amps will deliver twice the power to 4-ohm than to 8-ohm loads.  However, power supply limitations can limit 4-ohm output.  Tube amps generally deliver the same power at 4- or 8-ohms provided the secondary winding of the output transformer has a tap to match the 'speaker's impedance.
By the way, at age 77, it is getting to be a big burden to carry a 60-pound tube amp from the first-floor listening room to the second floor test bench every time I have to change a tube.  I do so because I set the output tube balance for lowest THD.  If anyone wants to make an offer for 10 Citation IIs (I have four spares but want to keep a pair for other use), please let me know.

Norm
George, the amp I was referring to is the Proceed HPA2. It is functioning fine and is in my primary system with an AR tube pre and Areial Acoustics 7B speakers. I'm keeping all of that as long as it keeps running.

The 6Ts are for a secondary system in my living room, primarily casual listening. The reason I'm looking for an integrated with DAC is that it all needs to be as small and discrete as possible to make my wife happy and integrate with Sonos Connect (so coax or optical-in are important).
Most amps you've mentioned are class D so George will do what he does bash class D using a Behringer PA amp as his usual suspect for all class D. If you want boat anchors you're all set but with your criteria of placement and price  most small discrete integrated amps will be class D. There are a few AB the Micromega M100 is class AB in a small package as well as a few others. The NAD C388 should work fine with your speakers. The little 316Bee you mentioned measures 4 and 8 Ohm the same, it's the way they use their power supply with the modified Ncore amps. McIntosh uses autoformers on some integrateds they measure the same watts into 2,4,and 8 Ohms. George won't like the McIntosh either. Here's specs on the 316Bee notice the same 40w at 4 and 8 Ohm. 

  • Continuous output power into 8 ohms and 4 ohms
    40W (ref. 20 Hz-20 kHz at rated THD, both channels driven)
  • THD (20 Hz – 20 kHz)

<0.03 % (250 mW to 40 W, 8 ohms and 4 ohms)

  • Signal-to-Noise Ratio
  • >95 dB (A-weighted, 500 mV input, ref. 1 W out in 8 ohms)
    >97 dB (A-weighted, 500 mV input, unity gain in 32 ohms)
  • Clipping power (at 1 kHz 0.1 % THD)
  • >45 W in 8 ohms
    >60 W in 4 ohms
  • IHF dynamic power
  • 8 ohms: 90 W
    4 ohms: 120 W
    2 ohms: 170 W