I have a pair of M22s and love their sound but wouldn’t recommend them w/o a subwoofer. The only Axiom bookshelf that is IMO designed to be used w/o a subwoofer is the M3 and it’s variants. However, going that route you trade off the flatter frequency response of the M22s. I haven’t seen a frequency response graph for the PSB Alpha but I imagine they play with it a bit like the M3 does to trick you into thinking your hearing more bass.
One problem I’ve noticed in using a speaker with a flat frequency response is that w/o the high end rolling off and/or the low frequencies being manipulated to simulate more bass they will sound “thin” compared to other speakers that do. However, it took me no time at all to appreciate the more accurate sound. But still for most things I would want to use a subwoofer with the M22s and their variants.
