Now, back to the 4200SE... I measured the crossover settings and slopes and found them to be reasonably accurate and functioning as advertised. If you have never heard the difference between a 12dB/octave to a 24dB/octave crossover, you should. I always prefer the steeper filter slope on a subwoofer to minimize high-frequency output and subwoofer localization. Also, it would be worth noting that if you have a -12dB/octave crossover set at a specific frequency and simply flip the switch to 24dB/octave, the -3dB frequency point changes as well. Bass boost measured 0dB to +18dB maximum, with the frequency of boost adjustable between 20Hz and 80Hz. An enterprising installer may realize that the 30Hz highpass filter setting could double as a subsonic filter as well, creating another way to use the amp's bandpass crossover function.
The amp measured well in all respects and protected as it should when I deliberately shorted the outputs. I did drive the amp to full power into 1 ohm, and although I twice blew the 3 x 40A fusing, the amp made prodigious power into 1 ohm and would most likely not blow the fuses with a dynamic musical input signal.
The 4200SE is also equipped with a balanced input jack in the form of a RJ45 connector, not unlike those used for computer networking. Instructions are provided on how to connect the speaker wires of a source unit directly to these inputs, although no connector or wiring is provided.
Thermal performance was measured, and this is one of the better 4-channel amps from a thermal perspective. It easily passed our usual battery of tests and surpassed the performance of many other 4-channel amps by a wide margin. The fan-assisted cooling system on this amp works, and works well. I did notice that as the test progressed, the illuminated logo would turn from blue to red occasionally, and the hotter the amp got, the more frequently this would happen. I didn't find any definitive explanation as to what this meant, but it occured to me that this could be temperature related.
Manual
The owner's manual is a rather large book, with a total of 14 pages, covering all the models in the Signature Edition line. I found it reasonably complete and it has excellent diagrams to help you understand the uses and settings of the various controls and connections. Features and common adjustments are clearly explained in a common sense, non-technical manner, so those of you who aren't propeller heads will have no trouble getting the amp dialed in properly.
The only notable exclusion in the manual (and I looked for it for a while) was an explanation of the top lighting turning from blue to red during the amp's thermal testing and protection phases. Extremely curious, I contacted Arc for an explanation. They stated that "the lighting on the amplifier starts blue for normal operation and as the amplifier increases in temperature the lighting will change colors. More frequent color changes indicate that the amplifier is operating closer to its thermal limits - peaking a solid red as it goes into protection."
Listening
This is always the most enjoyable phase of my testing, and here I was expecting a very transparent amplifier, with good headroom and dynamics. I was not disappointed.
To be fair, I don't often evaluate the sound quality of an amplifier in my vehicle. I find that the differences between many amplifiers are sometimes subtle, and to give every amp the fairest comparison possible and not lose some of each amp's sonic signature to road noise and the like, I use my very familiar and sometimes painfully accurate reference system in my lab. With that in mind, be aware that the things I mention here are absolutely audible in a prepared listening environment, but how evident they will be for you will depend on your listening environment.