Some examples of cubes - real-live measurements from real-live
amplifiers.
First we look at three examples which describes three basic shapes of the
PowerCube measurements, and then we look at three well known brands... and
we're not disclosing any names except one...
The perfect amplifier doesn't care about the load - it's a pure voltage
generator - so the measurement of a theoretically ideal amp would produce a
cube, hence the name "PowerCube".
In popular price ranges you can't really expect to find an amplifier that
will produce a perfect cube, you can see a good example in the last cube on
this page - a very well designed two channel amp from Rotel. Of course, good
Class D amplifiers do exist, just as with any other topology, but you need a
PowerCube system to find them!
If you pay top dollars, you can come very close to a perfect cube.
This is the best cube ever. The Rockford Fosgate T15kW amplifier
uses HT Technology which gives the amplifier unmatched dynamic power
capabilities.
The cube is near perfect, but expect to pay USD 20,000!
Here are some more examples:
Good example
Regardless of the load, this amplifier can produce
an almost equal voltage without clipping. Although you'll see some small
losses when the load decreases, this amplifier will handle any loudspeaker.
Poor Power Supply In this example the output voltage is dramatically reduced into lower
impedances. This amp will
definitely not handle a real-world loudspeaker very well.
Current limiting
This amplifier works into 8, 4 and 2 ohm resistive loads, but any reactive
load will trigger the protection circuits and shut down the amplifier!
This amp is essentially incapable of driving a real-world loudspeaker.
Class D.
Well known brand
Home theatre receiver
Here you can see an off-the-shelf Home Theater receiver with class D output
stages - this one doesn't work at all below 4 ohms.
Class D.
Well known brand
Home theatre receiver
Take a look at this poor example. However, this amplifier doesn't shut down
quite as early into 1 or 2 ohms - so it has a better chance of handling the
dynamic impedance dips of a real-world loudspeaker.
Rotel RB971
Stereo amplifier While you can't really expect to find an amplifier that will produce a
perfect cube, you can see a good example here. This is a very well designed
two channel amplifier from Rotel.
Rockford Fosgate
T15kW The best cube ever. The T15kW amplifier uses HT Technology which gives
the amplifier unmatched dynamic power capabilities.
The cube is near perfect, but expect to pay USD 20,000