Same watts at 8 and 4 ohms?

Hi George,

Take a look at any speaker review on Stereophile and they will plot the speaker impedance.

This impedance is never a flat line at 4 or 8 Ohms and in fact take quite complicated shapes.

The lower the impedance, the more current the amp has to produce to maintain a stable output, otherwise it starts to drop.  If you think of a wall wart, 12V, 2 Amps.  If you try to draw more than 2 amps, it no longer produces 12 V but instead the voltage sags until it overheats.  Amps do the same thing.

An ideal amp maintains the voltage output regardless of speaker impedance, which is synonymous with saying it doubles the wattage as the impedance is cut in half.

You may not need an ideal amp or like how it sounds matched to your speakers though, so keep this in mind.  The C 388 uses a hybrid Class D designed by Bruno Putzeys (or nCore?) which is a pretty sweet little thing. It puts a linear amp in the middle of the Class D.  I have another NAD integrated with it and I like the sound a lot.  It's not as fun to listen to as my Luxman, but nothing wrong with it either. 

Nice lesson ,to pass the time ...higher efficient speakers less power.To each his own.

n80 OP

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. 

From Keith Howards Measurement Labs https://ibb.co/7JrRXX8

This is the Wilson Alexia 90db and Wilson spec 4ohm nominal. You would think that just about any amp could drive it. But no.
The Wilson Alexia is said to be one of the hardest speakers ever to drive. And that because just in a small band of the low to mid bass it has an EPDR (combination of low impedance and high - phase angle) which to the amplifier seems like .9ohm!! and it sucks the life out of an amp.

And a 3000watt Behringer amp won't do it justice, but 25w ML2 will, to a certain volume level because they can double down to 1ohm, , it's all about the current, being able to double wattage 8ohm to 4ohm and 4ohm to 2ohm if you can do it for speakers like the Alexia and there are many like it.

Cheers George      

The NAD C388 will drive your speakers just fine if you don't play your music at rock concert levels.

But since you own/like a Levinson amp, which I think are all Class A/B, the NAD's Class D module may not make your speakers sing a tune you like.

Safer to buy a Class A/B amp like the Cambridge CXA81 (which has a decent DAC), which is 80/140 watts into 8/4 ohms, and is within your budget. I have heard that amp make a pair of Monitor Audio Gold 100 5Gs sing, which are only 86 db sensitive and dip at various points under 4 ohms. 

@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