Seas A26 - Anyone heard them?

Ask at DIYaudio.com and do a search.

Someone there suggested adding a second pole to the tweeter high pass filter, it seemed like a good idea.

I did both. Bought the Madisound cabinets and built them exactly to spec with the MUndorf Silver/Oil Capacitor. I also had a pair of cabinets built from 1" Baltic Birch, no port and a much more sophisticated crossover as used in the World Designs WD26 which uses the same woofer and a less expensive SEAS tweeter. The birch pair with the crossover outperformed the simpler A26 by a large margin. 

delphin could you provide me a link to the wd26? I've been looking but can't get there. I also found a wd25ex that I'd love to try. Maybe that is what you are calling the 26?