I have a pair of Linkwitz LX521 Dipole Woofer cabinets with two Dayton Audio RSS265HF-8 10" drivers in each cabinet. The Dayton Audio drivers are better than the Linkwitz specified SEAS drivers and can handle more power. The cabinets are Madisound's outstanding dove-tailed birch veneer plywood and have been assembled without any fasteners and are unfinished - you can easily stain or paint and finish these to your desired appearance. I used these to develop my Little Dipole Woofers (LDW) for the Maggie LRS panel speakers.
They are available for $450 each or for $900 for the pair plus shipping from St. Louis, MO. I also have a miniDSP 2x4 crossover for programming the EQ, if desired. These are great starting point for anyone wanting to build the wonderful LX521 speakers - all you need is the upper baffle board and the high frequency SEAS drivers - all available from Madisound. Photos to follow.