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?

I have a pair of A26s with the Madisound-supplied cabinets (actually they’re built by Source Technologies out of CT) I deviated from the original design some by lining the insides with No-Rez material from GR Research, and used brass machine screws and inserts instead of the supplied wood screws for the driver mounting. I chose the mid-level Mundorf caps per the advice of Madisound and find the 15ohm resistors sound the most balanced to my ears.

For the price they are excellent speakers. The tweeters are some of the best available at any price and that’s backed up by measurements:
http://www.troelsgravesen.dk/large_domes.htm

Where they’re most lacking is bass depth. Definitely need a sub with them but otherwise they’re a killer value. With No-Rez and an additional inch of foam between the woofer and rear cabinet wall, the midrange near rivals that of Spendor and Harbeth. But also keep in mind I didn’t mount the woofers with wood screws, and IME, driver mounting method plays a significant role in a speaker’s overall sound quality.