Sorry to resurrect but I wanted to thank those who contributed to this thread and share some info. I just upgraded the domes on my Synergy B-3’s with PRV D230ti’s and couldn’t be happier. The bolt to screw on adapters mentioned in this thread are no longer available but Bob Crites over at https://critesspeakers.com/ has an alternative that works, just email him. You still need to drill new holes in the adapter. The crossover on the Synergy B-3 is 2050Hz so the horn driver carries a lot of range. The Eminence driver mentioned in this thread starts at 2500Hz so don't use that driver. The PRV D230 driver starts at 1600Hz and has a suggested crossover of 2000Hz so it works perfect. The PRV is more sensitive than stock but I do not feel that resistors are needed to lower it (sounds great to me on a 2.1 system). The stock driver weighs nothing. The new driver is 2 pounds but the horn and 8 mounting bolts handle the weight fine. My measurements for anyone else with Synergy B-3’s – 5 ¼ inch from the front of the horn to the rear port (total space) 2 ¼ inch horn length without driver (minus the total space gives you 3 inches until you hit the rear port) 1 inch stock driver With the PRV driver and bolt to screw adapter there is a little over an inch of clearance compared to the 2 inches of clearance stock.