Fostex FE208E/168E & Sub

[DarkOne]

I'm going to build speakers using Fostex drivers, FE168E or FE208E powered by Aleph amps. I'd like to put them to closed enclosure and support low frequencies by active sub made with Beyma 12BR70 powered by class-d amp.
My first question to some of you (experts) is about Xmax of Fostex drivers, it's low and I don't know if I should use it without highpass filter (I'd like to use no filter).
Second question is about sound, does anybody have some real experience with these drivers?
And finally third - are these drivers able to kick out 110-115dB SPL with so small Xmax without being highpassed?

[Nelson Pass]

1) Are you using the FE208E (older) Sigmas or the newer
banana fiber cones?

2) If you're using an active sub, think about a single pole high
pass on the Fostex.

3) I have real experience, and so do a lot of others.

4) Yes, barely, and depending on which you've got, the
frequency, the enclosure, and peak or average.

There's a white paper which includes Fostex FE208E Sigmas,
old and new to be posted on www.firstwatt.com before the
end of the week. Until then check out Dick Olsher at
www.blackdahlia.com

[LageB]

I have been in the same line of thoughts as you, but with the older FE168S Sigma driver. Namley, sealed enclosure and supporting woofer. I tried different sealed enclosure volumes with Q=0.5-0.7and my observation (by eye) is that the Xmax is exceeded even at moderate volumes.

After research here at this forum and elsewhere, the advise by most people has been to using active XO, or a passive line-level crossover.

Good luck

LageB

[DarkOne]

Thanks for ypur replies,
I've been thinking about using the Sigmas with "banana" cone. But it looks more like midrange-tweeter driver than bass/mid-tweeter. I'd like to avoid sigle pole high pass filter, so now I'm thinking about classical two way system supported by sub. Anyway these drivers are specialized for horn system, I think, so I'll better go two way. It was quite interesting to me to use sigle driver for everything. Maybe the upcoming event on www.passdiy.com will give more light to this problem.