MRX 300/500/700 DSP has around the same amount of number crunching ability as anything in the price range, which is around half as much as AVM/D prepros using ARC (and PBK for that matter), which have as much as pro systems in the five figures. This means that MRX 300/500/700 corrected response usually does not meet target response as closely as AVM/D, thought it's also usually not too far off.
The other difference is that correction range not only defaults to 5 kHz but cannot be made to go higher. Correction above 5 kHz is not normally recommended regardless.
Another difference not dependent on ARC is that MRX DSP uses crossover frequencies of 60, 80, 100, 120, and 150 whereas AVM/D allows 25-160 in 5 Hz steps. It relates because ARC selects the crossover frequencies based on in-room measured response.
The practical difference depends on the amount of correction the room speaker/combo needs, and this varies greatly. MRX-ARC still improves things regardless, using the same principles as the other ARC.
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