I did a tweak to my BOSE 901's that made them sound soooo much better !!
I put two coats of Elmer's Carpenter's wood glue on all the paper cones and dust caps of my speaker drivers.
I put one coat of wood glue and let it dry good for 24 hours and then put another coat of wood glue and let it dry good for another 24 hours before playing music.
My 901's sound like different speakers now!! I'm hearing a more extended top end more realistic and a more extended bottom end and the mid-range is cleaner more 3-D more realistic....WOW!!
This AMAZING SOUND was there all these years, you just had to tweak it out of them !...