Advice needed: replacing tweeter in PSB Image 4T

On a lark I purchased a pair of PSB Image 4Ts for my brother in law who is using bookshelves in a 25 foot ceiling room, thinking these would be more enjoyable to use until his budget allows him to get what he wants.  They are in pristine exterior condition, but just don’t sound right to either of us.  At first I attributed this to comparing them to the Imagine Ts I have, which I really enjoy.  The sound coming from the tweeters is markedly off, almost tinny and somewhat faint, leading me to conclude the tweeters are not working as they should rather than the inherent performance of this speaker, which seems to have pretty good reviews.  This was reinforced by online references to some PSB speakers being prone to having tweeter issues.

A couple of sources recommended replacement with Peerless by Tymphany BC25SC06-04 1” textile dome tweeter as a perfect match (different material notwithstanding), just “swap and done”.  However, others stated that the differences in specs for impedance (6 ohms vs 4 ohms) and sensitivity (89db/2.83V/m vs 96.2db/2.83V/m) between the PSB and replacement part respectively needed to be compensated for with modifications way above my knowledge level to understand or implement.  On the plus side the tech support guy where I purchased the replacements (only $35/pair) said put them in and if I don’t like the sound just return them, which is what my plan is right now, fingers crossed.

Any advice/thoughts is greatly appreciated!

Replace the tweeters with the stock replacements. Play some music with your ear next to the tweeters on the speaker before and after you replace them. They should sound a little weird but you'll hear the difference between good tweeters and broken tweeters. 
Unless this was a really poorly designed tweeter, would be quite unusual for both to go bad at the same time.  Even with prior abuse, tweeters usually burn out instead of "going bad".

Yes the specs are way off. Surprised anyone would suggest these as drop in replacements. Even with close specs, swapping different tweeters will always be a complete crap shoot.  Are stock tweeters available?  

But, hey, if you can return the Peerless tweeters, what have you got to lose?  Sounds like a fun way to spend a few hours.
Thanks so much for the responses, especially the crapshoot analogy!  Yes, multiple posts saying this particular PSB series prone to tweeter problems/failure so I’m guessing that may be the case with this pair.   Parts arrive tomorrow, I’ll try contacting PSB if I strike out.  I’ve decided to be happy that I can still hear the difference at my age (65) no matter the outcome.  Thanks again.

My replacement tweeter had the same DC resistance, same impedance at 1kHz, same efficiency and the same build (short horn), but result was strange.  I verified phase using small battery and magnifying glass.  New tweeter had more pronounced very high frequencies, but there was suck-out at lower treble.  I tried them in opposite phase, just in case, and suddenly everything is fine.  They sound little louder and cleaner and that was my objective.  I've done it before to Paradigm Studio 60 and I failed in spite of extensive changes to xover .  It is not as simple as it seems and perhaps in your case it is just dried ferrofluid, if speakers are over 10 years old (or less if played very loud).  You can find ferrofluid at Parts Express, but have to be very careful separating voice coil.  Best to find somebody who does it.

to MGM424 -- did you ever install the Peerless BC25SC06-04's and if so, what kind of results? Did you keep them or return for something else?  I'm in the exact same boat ... but I need 4 tweeters for my two Image towers and 2 back channels. Any info would be appreciated. 

Hello Jaybird5619:

Yes I did, and the results far exceeded expectations, the speakers came to life.  Yes, a bit more forward in high end vs my Imagine Ts but for my ears a joy to listen to, and matched the reviews for the Image 4Ts.  I was pleasantly shocked.  Hope this helps.