Cast Frames rather than stamped steel frames.
Yes and terminated, That mean all the cut corners are curled to add strength, stop ringing and lower basket flex. Lower distortion!!
Get a product like black hole, SR71, or just one sided sticky dampening material. I've done a lot of VMPS drivers which are punched baskets with shark shin. A woven carbon fiber you can see through. Super strong, Super fast. You apply it to all the outside of the basket and wrap the magnet too.
You cut it to fit and make sure there is enough to just fold over the outside edge to the underside edge. THAT is the real trick to distortion, slightly over the edge and pinched it tight all the way around, every edge. It use to take me just about an hour to do 4 12" drivers. 2 subs, 2 mid bass couplers all WCF sharkskin.
You tap on driver before and after, It's night and day..
Just because it's a stamped basket doesn't make it a so so driver. It's actually one of the best sounding bass drivers I've heard. 3-500 watt drivers. 110db, clear as a bell. Very light weight super strong cones. They also use tuned/trimmed chassis mount fixed phase plugs. The sub PP is shorter and has a flat face. The MB couplers PP is 3/4" longer and has a tapered face. Now the second wave coming back can't distort the cone moving forward or backward.
Mortite has always worked for me, whether for damping turntables, metal cabinets, speaker frames, or- whatever.
Never falls off, when applied to a clean, smooth surface and: easy to remove, without leaving anything behind.
Funny I use Mortite to adjust the mass on passive radiators when I do the initial set up. Seal drivers and it doubles for plumbers putty in a pinch.
Now you know what they forgot on Apollo 13, the Mortite. I know they had duct tape. Maybe if they would have used the Mortite they wouldn’t have had to use the duct tape to get back. I’m pretty sure Mortite will be in Heaven too. LOL
I still use his RM30s, and have STII SE, and QSO 808s.
Planars and ribbons, I been using them over 40 years.
The 808s are used every day with a MX110z and a MC225. It all looks like it just came off the the show room floor. The room though looks like Dr. Frankenstein's Lab.