SEAS A26 kit owner here. Purchased the kit in Canada from Solen with the big SEAS T35 tweeter. The cap used in their kit is a Solen Metalized Poly cap and it’s in series with a 10 ohm resistor.
Sounds good to me.
A friend of mine built a birch ply cabinet and it was stained. The cabinet is 'solid'.
The plan was to clone an A35 cabinet with the kit. It did not work out well. But the end result is awesome and I’ll explain why.
We built a 35 litre cabinet instead of the recommended A26 cabinet: the 35 litre cabinet is a bit bigger. You can google A35 cabinet and you’ll find old dynaco drawings.
As the bass was not very good, I decided that this initiative was not a good path to follow.
I removed the internal vent and installed it on the rear cabinet panel. I then punched more holes in the internal mid-section brace, essentially creating an open cabinet of 35 litres with a mid-ship brace. Buttoned everything up.
So how do they sound after the mods? Very good. As a matter of fact, while the bass is not as deep as my Dynaudio Special 40s that I had on hand to compare, they were an enjoyable speaker to listen to for hours on end.
I use an RME ADI-2 DAC and I did some EQ’ing to tune the speaker to my preferences: I benchmarked a harbeth 30.1 for comparison purposes. I added a bass boost of 2.5 db at 120 hz with a Q of 1.5; and a mid-range boost of 2.5 db at 1600 Hz with a Q of 1.3 (if memory serves me well). The mid-range boost was critical to match up with the Harbeth and provide a magical mid-range.
And that is that: a 35 litre cab with a round aperiodic port at the back and a bit of EQ and it’s magic.
The speaker is powered by a Benchmark AHB2. It’s just one of those speaker that you listen to and think, yeah, this is all I need to be happy.