Beautiful Speakers, I can see why you want to keep them,
IMO, it ain’t the equipment, it’s the speakers. I’m no fan of ports, but you have already stuffed them with insufficient improvement. And you certainly have tried them far enough away from walls to know the problem is from the speaker, not the room reflections.
I suspect it’s the magnet/surround/cone that is not working together harmoniously.
How old are they?
Did they sound better when new, for a few years?
Did you perhaps buy them used? If so, any info regarding age from the seller? Serial # clue?
IOW, perhaps the surrounds are not as much in control as they should/could be? Or the cones themselves have lost stiffness?
Have you asked the maker for advice?
Or, perhaps something in the crossover needs correcting/improving, however once the crossover has divided frequencies, it’s up to the drivers to sound good themselves. I’m no crossover expert, just thinking what part of the speaker is not working properly.
from a review:
" The crossover sports just 4 components, with 1st order high-pass (tweeter) and 2nd order low-pass (woofer) filters. Parts quality - Solen metallized polypropylene capacitors, a generic-looking wirewound resistor and an air-core inductor - is solid but hardly fancy, a deliberate decision by Alan who isn’t much of a believer in expensive boutique parts. Based on the results he’s achieved here, it’s hard to argue."
https://taww.co/post/183853254737/silverline-sr17-supreme-loudspeaker-review" It has sufficient body and power down to 60Hz or so to give music real foundation, with meaningful output down to 40Hz. I think Silverline’s quoted 32Hz bottom limit is a bit optimistic (or perhaps you just need the right room), and I preferred the speaker with my REL T-9 subwoofer providing a little extra oomph. But for a great many listeners in moderately-sized spaces, this will be all the speaker you ever need. Listening to “The Elephant” from Saint-Saëns Carnival of the Animals [
Tidal,
Qobuz,
Spotify], a track I’ve heard on some very full-range speakers (e.g. Focal Grande Utopia EM Evo), the double bass is big and present, lacking a bit of rumble that was easily provided by flipping on the REL sub. Piano left hand similarly has nice weight, never sounding diminished in scale as typically happens on small monitors. Debussy’s Ariettes oubliées song cycle from the album
Paysages by soprano Susanna Phillips and pianist Myra Huang [
Tidal,
Spotify] is a lovely test of colors, with ethereal vocals floating above dark undertones from the piano’s lower register. The Silverline possesses suficient extension and body to bring out these contrasts with depth and balance."
