Room Acoustics, minimal treatment and measurements

Normally, I say to leave a speaker be and not to try to hack it very much.  Either love it as is or get something else.  In this case though I feel you have a number of approaches which could be really worthwhile for you and your dad.

Compared to a traditional multi-way speaker, the Legacy focus seems to be "missing" the crossover between the 7" and woofers.  While we can argue about the end result, two things are happening:  The lack of a crossover = 2 Ohm minimum load, and there's some interference between the woofer and mid-woofs(7"). 

Based on that, I think in the future there are a number of ways to deal with it which improve the bass performance significantly:

I.  Passive bi-amping. The reason this is an excellent idea here is that the lack of a crossover means you have a very low minimum impedance in the bass range. Less capable amps can handle just the bass or the mid-treble section but not both. Separate the two sections and each has ~ 4 Ohms minimum.

II. Active bi-amping. Put a miniDSP in front of your two amplifiers. This will give you excellent EQ capabilities, and you’ll be able to add the "missing" filters. Again, you end up with 2 x 4 Ohm sections instead of one 2 Ohm section.

III. Low impedance capable amp, like a stiff Krell or Sanders or Coda. Something that will handle the 2 Ohm or lower load in the bass section.

Yea closer to wall or even corners will boost bass but could also negatively impact imaging. Try it and see. If not then this may be a job for a proper powered sub or two. Gotta get that bass for best results.  Could be the speakers are just not fully up to the job  for a room that size. 

Are these older speakers that have been around prior to your involvement? Always possible woofers are damaged say detached from voice coil. Hopefully not. If you apply some pressure to woof near center while playing does it suddenly pop to life? That’s an indicator of a detached voice coil.

@mapman I really think his system would benefit most from two subs like you noted.  That way he could enhance low level listening, get proper music reproduction, and NOT introduce issue while maintaining all the better aspects.  He's very old school that 'subs are of the devil' and totally useless, but there are so many aspects of the music he loves, that he has no idea he is missing out on.  My understanding was that these speakers were made and shipped during the very early stages of Covid, so it took awhile to build.  I did some basic phase testing and the woofers are working and moving in the right direction, they are just at a much lower level in comparison to the mids-highs. 

@erik_squires I was wondering myself if this is one of those rooms/spaces, speakers and systems that would be perfect for using Bi-Amping?  I honestly never knew of "active or passive bi-amping"?  My step father had given me his old Adcom GFA-555 (modified) that I bet would be PERFECT to be used just for the woofer end, and leaving the Rega Illicit for the mid-high which that amp excels at in general (details). 
As we noted, honestly a couple moderate subs would really change the whole presentation, while keeping the amazing staging and details.  Alas, that likely aint gonna happen!  But at least I learned a TON from all of this, and it has made me appreciate my baby system in my own house, that sounds just as good as this does (just NO WHERE near the same staging!)  😆

Yes if teh speakers are operating properly then your measurements indicate teh speakers need help with the lowest octaves in a room that size.  Also yes he probably does not realize what he is missing.  Adding a powered sub or two properly almost always helps complete the entire musical experience even in scenarios less bass deprived than this one.  Cheers!.

I was wrong btw, I found I think a polish sight that says the min impedance is 4 Ohms, but still, with bi-amping you can set levels independently. 

The site also noted poor off-axis integration, a potential sign of the effects of the overlapping woofer/mid-woofs, so I really think at the very least, bi-amped with an EQ in front of the woofer amps is going to give you everything you need.