I have owned two pair of the SL6s, and I do believe that the treble is slightly rolled off, but not nearly as much as the copper domed original SL6. Still, it's a smooth non-metallic treble to me. Have you tried experimenting with cables?
Celestion SL6S
Hey all,
I picked up a pair of Celestion SL6S speakers in really good shape. I had a pair of these, back in the early 90’s. I always really enjoyed them and thought, hey, buy another set…
I got them hooked up in my system:
MacBook Pro > Denafrips Ares2 > Rega Elicit-R > Celestion SL6S
what I’m finding is the the treble is really rolled off sounding, more so than I remembered. I’ve put my ear next to each driver and they are all playing.
Anybody have any thoughts on what can be causing the rolled off treble?