Help. System sounds thin and bright or harsh

@cymivka I have not reread everything, so I am going from memory if I write something already mentioned.  

First, try another pair of speakers before hauling your amp off for repairs.  From what I have read pass gear is fairly bulletproof.  We're not talking testing for sonic nuisances here, were testing if something is big time wrong and your Harbeths or amp are not functioning properly.

I would try changing the speaker connections on one of the speakers only, so the negative black speaker wire is attached to the red positive connector on the speaker.  This will tell you if a whole speaker was wired out of phase.

Last, I would try @peter_s post to verify that individual drivers within a speaker have not been hooked up out of phase.  As he mentions, definitely research the test first to make sure you don't accidentally mess anything up with the battery.  I have done it but only on lesser cost speakers.

Have you ever gotten good bass from the Harbeths? The specs says they only dip down to about 50hz so not much deep bass will show up. I know it’s a completely different animal but I’m running Martin Logan Impresions with a Parasound A31 and its a beautiful relationship. Very good balance in all octaves and never harsh. Solving your issue through a forum is nearly impossible because whatever scientific recommendation given doesn’t change your ears. Until now you’ve done it all right. I haven’t read all the responses but by now you may have figured out your next move is to keep adjusting speaker placement, properly treat your space, and maybe try other cables. I’ve found cardas to be naturally bright (for my ears in my system) Happy listening.

@ejspain2020 The OP didn't complain about not getting deep bass his issue is "System sounds thin and bright or harsh".

The 50Hz spec is correct but that doesn't account for the room. As an example the 'heartbeat' in Breathe sounds remarkably good from a 50Hz midrange driver - even my local dealer was surprised - (I brought a 1979 MOFI issue in as one of my test records) 

If you want REALLY full, deep bass with the 30.1 / 30.2 you'd need subs as others have mentioned. I use 2 REL T/9x, but turning them off doesn't make my system sound bright/harsh nor does it sound like they are suddenly lacking good bass.

Adding 2 RELs was way less than going up to the 40.2's, which was my calculus but most people buy Harbeth's for it's mid-range performance and their overall range is where most of the music is, depending on what kind of music you listen to.

E.g. an open E on a bass guitar is 41Hz 

@macg19 great points. Hope he gets it figured out. Completely understand how this can be frustrating. I'm about to go down the rabbit whole of adding a new processor so hopefully I don't lose more hair integrating...I'm already bald😉