A low mass arm and a low compliance cartridge is not a good match. That is the reason why you did not have woofer pumping with the higher compliant Ortofon. Return the cartridge for one with a higher compliance or you will have woofer pumping until the cows come home!
Is the at 150mlx a bad match on the jmw9 tonearm
I am asking because I just installed the at150mlx on my vpi scout 1.1 and am getting woofer pumping. I had a ortofon 2m blue before this and had no pumping. The table is on a flexy style stand with 4 butcher block shelves and a laminated top shelf of 1/2" acrylic ,1/2" aluminum, 1/2" acrylic. The table sits on the top shelf on top of a sand box. The stand is spiked into carpet on a concrete slab. It is located about 12' away from the right speaker behind the listening position. I am not sure what other information would be helpful but it seems to happen at normal listening levels( slightly louder than conversation).If it is a bad match I would like to figure it out ASAP and return it for something else. Thank you for any help.