With older amp, yes! With most newer Crown amplifiers, Bridge mode analog circuits do not include (bypass) the Ch2 input and level circuitry. The XLS amp has this flexibility set in its DSP. Furthermore, using the 'Ch1 + Ch2' feature ensures that the full range of sound from both channels is summed before using the Bridge mode operation.
The XTI series (and most of other Crown products) can have up to three different speaker connections : Speakon, binding posts (bare wire) and terminals (bana plugs).
Note : Ch1 Speakon also has connections for Mono (+1,-1) and for Bridge mode operations (+1, +2).
So yes, you should be all right at 4 ohms.
Note : for the Crown XTI series, lowest Z (impedance) is 2 ohms Dual mode or 4 ohms Bridge.
You are so welcome! Wouldn't want you to blow the amp at two ohms Bridge!
BTW, when specs say that the XLS HPF starts at 50Hz, your 20Hz information is just [about] an 'octave' away from this frequency. Because of the Linkwitz-Riley 24db per octave filter, you may not have enough information down to 20Hz to have a successful listening.
However, you may want to use the 'LPF' (low pass filter) instead. The 'LPF' and the 'HPF' feature are both assigned to Ch1 and Ch2. Note : When the 'Crossover' feature is selected, Ch1 has the LF information and Ch2 has the HF. If you bring the full range information into the XLS LPF circuit, it will send to your speakers all LF information up to 50Hz. This could be an alternative to the HPF configuration. Of course, as you mention, the XLS doesn't go low enough at the crossover point and you may now have too much VLF (very low frequency) bass info. Adjust levels according to taste!
Note : 20Hz information is not a [perceived] 'frequency', it feels more like a rush of air; However, when well applied, feels like a punch to the stomach. Much of the perceived sound is above 40Hz and you will have great bass at 60Hz! Also, for ultra low frequencies, it would be important to have a 'big' room, to avoid standing waves.
Yes, the XTI1002, can handle the signal. It is 500W at 4 ohms and is configurable. It is also twice the price!
Coo, coo, cool!
CTS4200A failures are usually caused by a failing LVPS (low voltage power supply). If you see bulging caps or failed LVPS voltages, just order a new LVPS from your neighborly authorized Crown service center.
You don't mention if the issue was cleared...