Hey, It's fun when an old thread comes back to life!
I found that dual chamber site later and the plans on the Fostex web site. Thanks KW
It is for a smaller (and less efficient driver) then we are using. I'm sure I could have scaled it up but Pascal and I have been keeping in touch, and we have gone the route of the big bass driver with 8" Fostex and maybe a tweeter.
I found out about that concept from the Basszilla plans, which I bought. As you can see from the pictures Pascal posted, a full range with big woofer and a tweeter was a common idea in France. The open baffle too.
For the bass driver I bought two 15" Selenium wpu1505 from Parts Express on sale for $100ea. They have a pretty smooth curve but a peak a little above the crossover that I want to chop off.
Pascal got the Eminence Delta 12LF I believe. Both claim to put out 97dB but I'm pretty sure they at least put out 95.
I'm using the passive crossover that Dick Olsher recommends for the Basszilla but at 180 hz instead of 200. This is about the lower limit that you can use a passive but it seems like it will barely work
I am using a steel core inductor from Erse that Zylatron sells. A cored inducter is the only kind that seems to work in this size(around 14Mh, 14 Ga wire) Nelson Pass says it will handle 6 amps DC in an amp. It should handle more AC amps in a speaker.
Since my Son of Zen will put out 25 watts max, I think I'll be OK.
Of course an active crossover is optimal, but I would want to spend the time and money to make a good one and the passive
approach is pretty reasonably priced. Also I need to make another amp to use it or I could fix the bad channel in my Adcom
Another project.....
The full range choice of the week changes weakly
As you noticed I'm sure, Pascal and I got a little worried about the FF225's xmax. - half what the FE 208 has. I'm sure it would work, but might get stressed in an open baffle. The Fe 208 is what Dick uses in the Basszilla but it is reputed to be best for horns also. It definatly needsa notch filter to tame it.
There is some question if one can actually get a FF225 anyway.
Madisound seems to be the new Fostex distributer and they don't have it.
Pascal and I decided on the Fe 204 because it has more travel and is highly recommended- also cheaper than the 208!!
So when we went to order we discover that the 204 has been discontinued. They have a new driver- the Fe 206 This has the big magnet from the FF225 for more damping, which makes it very much like the Fe208, but the xmax of the old 204,which is double that of the 208 and 4 times that of the 225. Also it only costs $94
(it has a pressed frame-but heavy)
It does have a whizzer, which I had not wanted, but what the hell I'll give it a try. It also has that yummy banana pulp cone paper!!!
The response curve is as awful as the 208, but lots of people like the 208.It seems to not have the 2 huge peaks the 208 has so might be OK I might need to design a notch filter or try to talk Dick into buying a pair and testing them and developing a notch filter. He is somewhat interested in a half price Basszilla and has measurement software and mics.
It will be interesting to try out the new driver: It might be horrible-you guys hear anything about it?
PAscal is assembling his cabinet, I will start mine in 2 weeks.
Some have told me a tweeter with a first order filter might have phase problems with the tweeter. Planet 10: have you had much luck with a tweeter with a full range with whizzer cone or haven't you tried it?
(Fostex reeommends a single 1 mfd cap for addding a tweeter to the Fe 208 which I believe will roll off 6 db/octive starting at 19000 hz! ) so we are talking about just the very top end here.
We'll keep you informed, please tell me of any rumors regarding the fe206
